Precast Concrete and Readymix

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2008-02-28T00:49:00.000-08:00

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Interactive Design of Semirigid Steel Frames

2007-12-23T23:33:00.000-08:00

By : Balaur S. Dhillon, Fellow,ASCE, and James W. O'Malley III, Associate Member, ASCE

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Inelastic Design of Infilled Frames

2007-12-23T23:26:00.000-08:00

By : Abolghasem Saneinejad and Brian Hobbs

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FINITE ELEMENT ANALYSIS OF REINFORCED CONCRETE BEAMS

2007-12-23T23:22:00.000-08:00

By : D. NGO and A.C. Scordelis

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Self-Compacting Concrete

2007-12-23T22:17:00.000-08:00

By : Hajime Okamura and Masahiro Ouchi

Abstract :
Self-compacting concrete was first developed in 1988 to achieve durable concrete structures. Since then, various investigations have been carried out and this type of concrete has been used in practical structures in Japan, mainly by large construction companies. Investigations for establishing a rational mix-design method and self-compactability testing methods have been carried out from the viewpoint of making self-compacting concrete a standard concrete.

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AERODYNAMIC STABILITY ANALYSIS OF CABLE-STAYED BRIDGES

2007-12-23T21:52:00.000-08:00

By : M.S. Pfeil and R.C. Batista
Abstract : Cable-stayed bridges under wind loading exhibit dynamic behaviors that depended on the aeroelastic forces and coupling among vibration modes.

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WIND-INDUCED NONLINEAR LATERAL-TORSIONAL BUCKLING OF CABLE-STAYED BRIDGES

2007-12-05T20:02:00.000-08:00

By Virote Boonyapinyo, Hitoshi Yamada, and Toshio Miyata

ABSTRACT: A finite element approach to calculate directly the critical wind velocity for the nonlinear lateral-torsional buckling instability of long-span cable stayed bridges under the displacement-dependent wind loads is presented. An analytical modeling of wind-induced lateral-torsional buckling is formulated taking into account the three components of displacement-dependent wind loads as well as geometric nonlinearity. A combination of the eigenvalue analysis and the updated bound algorithm for wind velocity is applied to automatically calculate the critical wind velocity. The results show that the incorporation of the three components of displacement-dependent wind loads as well as the geometric nonlinearity in the analytical modeling of the lateral-torsional buckling instability results in significant reduction in the critical wind velocity compared with both the conventional non-linear torsional divergence and linearized lateral-torsional buckling.

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Structural Analysis with Finite Elements

2007-11-09T19:28:00.000-08:00

The finite element method has become an indispensible tool in structural analysis, and tells an unparalleled success story. With success, however, came criticism, because it was noticeable that knowledge of the method among practitioners did not keep up with success. Reviewing engineers complain that the method is increasingly applied without an understanding of structural behavior.

Often a critical evaluation of computed results is missing, and frequently a basic understanding of the limitations and possibilities of the method are nonexistent. But a working knowledge of the fundamentals of the finite element method and classical structural mechanics is a prerequisite for any sound finite element analysis. Only a well trained engineer will have the skills to critically examine the computed results.

Finite element modeling is more than preparing a mesh connecting the elements at the nodes and replacing the load by nodal forces. This is a popular model but this model downgrades the complex structural reality in such a way that—instead of being helpful—it misleads an engineer who is not well acquainted with finite element techniques.

The object of this book is therefore to provide a foundation for the finite element method from the standpoint of structural analysis, and to discuss questions that arise in modeling structures with finite elements. What encouraged us in writing this book was that—thanks to the intensive
research that is still going on in the finite element community—we can explain the principles of finite element methods in a new way and from a new perspective by making ample use of influence functions. This approach should appeal in particular to structural engineers, because influence functions are a genuine engineering concept and are thus deeply rooted in classical structural mechanics, so that the structural engineer can use his engineering knowledge and insight to assess the accuracy of finite element results or to discuss the modeling of structures with finite elements.

Just as a change in the elastic properties of a structure changes the Green’s functions or influence functions of the structure so a finite element mesh effects a shift of the Green’s functions. We have tried to concentrate on ideas, because we considered these and not necessarily the technical details to be important. The emphasis should be on structural mechanics and not on programming the finite elements, and therefore we have also provided many illustrative examples.

Finite element technology was not developed by mathematicians, but by engineers (Argyris, Clough, Zienkiewicz). They relied on heuristics, their intuition and their engineering expertise, when in the tradition of medieval craftsmen they designed and tested elements without fully understanding the exact background. The results were empirically useful and engineers were grateful because they could suddenly tackle questions which were previously unanswerable. After these early achievements self-confidence grew, and a second epoch followed that could be called baroque: the elements became more and more complex (some finite element programs offered 50 or more elements) and enthusiasm prevailed. In the third phase, the epoch of “enlightment” mathematicians became interested in the method and tried to analyze the method with mathematical rigor. To some extent their efforts were futile or extremely difficult, because engineers employed “techniques” (reduced integration, nonconforming elements, discrete Kirchhoff elements) which had no analogy in the calculus of variations. But little by little knowledge increased, the gap closed, and mathematicians felt secure enough with the method that they could provide reliable estimates about the behavior of some elements.

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REINFORCED CONCRETE DEEP BEAMS

2007-10-29T21:32:00.000-07:00

This book is designed as an international reference work on the behaviour, design and analysis of reinforced concrete deep beams. It is intended to meet the needs of practising civil and structural engineers, consulting engineering and contracting firms, research institutes, universities and colleges.

Reinforced concrete deep beams have many useful applications, particularly in tall buildings, foundations and offshore structures. However, their design is not covered adequately by national codes of practice: for example the current British Code BS 8110, explicitly states that for design of deep beams, reference should be made to specialist literature. The major codes and manuals that contain some discussion of deep beams include the American ACI Building Code, the draft Eurocode EC/2, the Canadian Code, the CIRIA Guide No. 2, and Reynolds and Steedmans Reinforced Concrete Designers Handbook. Of these, the CIRIA Guide No. 2: Design of Deep Beams in Reinforced Concrete, published by the Construction Industry Research and Information Association in London, gives the most comprehensive recommendations.

The contents of the book have been chosen with the following main aims: (i) to review the coverage of the main design codes and the CIRIA Guide, and to explain the fundamental behaviour of deep beams; (ii) to provide information on design topics which are inadequately covered by the current codes and design manuals: deep beams with web openings, continuous deep beams, flanged deep beams, deep beams under top and bottom loadings and buckling and stability of slender deep beams; (iii) to give authoritative reviews of some powerful concepts and techniques for the design and analysis of deep beams such as the softened-truss model, the plastic method and the finite element method.

The contributing authors of this book are so eminent in the field of structural concrete that they stand on their own reputation and I feel privileged to have had the opportunity to work with them. I only wish to thank them for their high quality contributions and for the thoroughness with which their chapters were prepared.

I wish to thank Mr A.Stevens, Mr J.Blanchard and Mr E.Booth of Ove Arup and Partners for valuable discussions, and to thank Emeritus Professor R.H.Evans, C.B.E., of the University of Leeds for his guidance over the years. Finally, I wish to thank Mrs Diane Baty for the much valued secretarial support throughout the preparation of this volume.

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Discussion of “Unloading and Reloading Stress-Strain Model for Confined Concrete” by Junichi Sakai and Kazuhiko Kawashima

2007-10-29T21:24:00.000-07:00

by Asad Esmaeily, A.M.ASCE; Steven D. Hart; and`Brandy Gaitan

In this paper, the authors, Sakai and Kawashima, propose a “comprehensive . . . model . . . that takes into account the effect of repeated unloading and reloading and partial loading.” This model was evaluated by conducting several tests on concrete cylinders confined by carbon-fiber-reinforced polymer CFRP material.

Three standard 150 mm300 mm 6 in.12 in. concrete cylinders were cast and cured for 28 days in a moist curing room. Two strain gauges with a length of 50 mm 2 in. were placed
longitudinally on the central part of the specimens on opposite sides. The unconfined compressive strength of the specimens was 40.7 MPa 5.9 ksi at the time of testing. Confinement was provided by two layers of CFRP attached by an epoxy adhesive, which is different from conventional confinement by steel as used in the authors’ original research. Testing was conducted by using a closed loop servocontrolled material testing system with a maximum capacity of 667 kN 150 kips. Since the envelope for CFRP confined concrete does not have the descending branch after a peak point as observed for conventionally reinforced cases, all specimens were initially loaded to 614 kN 138 kips at a rate of 62 kN 14 kips per minute to achieve sufficient plastic strain for a reasonable evaluation of the unloading/reloading paths.

There was a creep-hold of 108 min at 133 kN30 kip load level for one of the specimens. At the load level of 614 kN 138 k, the specimen with a creep-hold was subjected to three complete unloading and reloading cycles at a rate of 124 kN 28 kips per minute, the next specimen had similar cycles but at a rate of 186 kN 42 kips per minute, and the last one was loaded monotonically to 614 kN 150 kips to establish the envelope curve.

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Analytical Sensitivity of Plastic Rotations in Beam-Column Elements

2007-10-29T21:13:00.000-07:00

by Michael H. Scott

Abstract: Analytical sensitivity equations for the plastic rotation of beam-column finite elements are derived for reliability and optimization algorithms in structural engineering and for the assessment of plastic rotation sensitivity to uncertain design parameters and modeling assumptions. The plastic rotation is defined by elastic unloading of element forces in a basic system, which makes the corresponding sensitivity computations applicable to most material nonlinear beam-column formulations available in the literature. The analytical response sensitivity is verified by finite differences then applied to a first-order reliability analysis of a steel subassemblage where the performance function places a limit on plastic rotation.

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Controlling All Interstory Displacements in Highly Nonlinear Steel Buildings Using Optimal Viscous Damping

2007-10-04T19:05:00.000-07:00

by T. L. Attard, M.ASCE

Abstract:
A gradient-based optimization algorithm is used to simultaneously control all interstory displacements in nonlinearly degrading steel buildings using optimal viscous dampers. Optimal damping ratios are computed in each mode of vibration such that the sum of the errors between the interstory displacements and the “just-yielded” performance objectives is minimized. A representative damping formulation is used to determine the sizes and locations of the damper devices. The members of the buildings are assumed to degrade smoothly according to a constitutive rule that was developed to model the behavior of kinematically strain-hardened materials. Numerical examples are used to demonstrate the ability of the algorithm to control potential damages in a 10-story building and also in an 8-story building responding at significant higher modes of vibration. It is found that the interstory displacements in the 10-story building are very adequately controlled. Although demands in the 8-story building are significantly reduced, some modes remain overdamped and not all performance levels are exactly met as some stories remain marginally damaged. Finally, the algorithm is applied in a 20-story benchmark building, and it is shown that the interstory displacements, postyield curvatures, and plastic damages are very adequately controlled.

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Classification and Seismic Safety Evaluation of Existing Reinforced Concrete Columns

2007-10-04T19:04:00.000-07:00

by L. Zhu; K. J. Elwood; and T. Haukaas

Abstract:
This study contributes to the critical need for safety assessment tools for existing reinforced concrete structures. Of particular concern is the possibility of collapse due to shear failure followed by axial failure of columns supporting gravity loads. This is a potential threat to a number of existing buildings in seismically active regions. Due to unavoidable uncertainties, drift capacity predictions can only be made in a probabilistic manner. This is addressed by the development of probabilistic drift capacity models at two performance levels:
lateral strength degradation and axial load failure. First, a classification method is proposed to approximately distinguish between shear-dominated columns and flexure-dominated columns. Second, for each type of column, a probabilistic shear capacity model is developed by applying an existing Bayesian methodology to an experimental database. The focus of the presentation is on the physical insight gained from the model development. Third, a probabilistic model is developed for the drift capacity at axial load failure. Finally, the probabilistic drift capacity models are employed to develop fragility curves—with confidence bounds—that are utilized to assess the probability of failure implied by current seismic rehabilitation guidelines.

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Long-Term Behavior of Wood-Concrete Composite Floor/Deck Systems with Shear Key Connection Detail

2007-09-29T09:32:00.000-07:00

by M. Fragiacomo; R. M. Gutkowski; J. Balogh; and R. S. Fast

Abstract:
The paper investigates the long-term behavior of wood-concrete composite beams with notched connection detail. The experimental program comprised the characterization of the component materials wood, concrete, and connection detail and long-term tests on beam specimens. The beam specimens were monitored during the construction process, and for an overall period of 133 days after the application of the service load. The experimental results have then been extended to the entire service life of the structure using a
one-dimensional finite-element model. It was found that the increase in moisture content due to the bleeding of the fresh concrete is not an issue for the durability of the wood deck, and the type of construction shored or unshored does not significantly affect the structural performance. The rheological phenomena experienced by the component materials lead to quite large deflections over the entire service life, whereas the variation in stress is not significant. If the limitation of the deflection is required for serviceability considerations, the use of concrete with reduced shrinkage and the precambering of the wood deck are to be recommended. A simplified approach based on closed form solutions for composite beams with smeared flexible connectors is finally proposed for the prediction of the long-term
behavior.

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Deterioration of Strength of RC Beams due to Corrosion and Its Influence on Beam Reliability

2007-09-29T09:29:00.000-07:00

by Dimitri V. Val

Abstract: This paper examines the effect of corrosion of reinforcing steel on flexural and shear strength, and subsequently on reliability, of reinforced concrete beams. Two types of corrosion—general and pitting—are considered, with particular emphasis on the influence of pitting corrosion of stirrups on the performance of beams in shear. Variability of pitting corrosion along a beam is considered and the possibility of failure at a number of the beam cross sections is taken into account. Probabilities of failure are evaluated using Monte Carlo simulation. Uncertainties in material properties, geometry, loads, and corrosion modeling are taken into account. Results show that corrosion of stirrups, especially pitting corrosion, has a significant influence on the reliability of reinforced concrete beams.

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Confinement Model of Concrete with Externally Bonded FRP Jackets or Posttensioned FRP Shells

2007-09-29T09:26:00.000-07:00

by Chris P. Pantelides, M.ASCE; and Zihan Yan

Abstract: A design-oriented confinement model for square and rectangular columns confined with bonded fiber-reinforced polymer FRP jackets, and shape-modified square and rectangular sections confined with posttensioned FRP shells is developed. The proposed design model for FRP-confined concrete columns is based on the bilinear four-parameter formulation by Richard and Abbott. The axial compressive strength of FRP-confined concrete is obtained using concrete plasticity theory based on the five parameter Willam and Warnke model. The ultimate axial strain of FRP-confined concrete is obtained from a strain-based approach depending on either passive or active confinement; the ultimate axial strain is based on the concepts of secant concrete modulus and strain dependent stiffness established by Pantazopoulou and Mills. Comparisons of the proposed stress-strain model with uniaxial compression experiments for columns with bonded FRP jackets or posttensioned FRP shells, performed by the writers and other researchers, show satisfactory
agreement for the entire stress-strain curve.

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Static Strength of Thick-Walled CHS X-Joints Subjected to Brace Moment Loadings

2007-09-29T08:33:00.000-07:00

by X. D. Qian; Y. S. Choo; J. Y. R. Liew; and J. Wardenier

Abstract:
This paper presents results from a systematic finite-element FE study on the static strength of moment loaded thick-walled circular hollow section CHS X-joints, and compares the results with CIDECT and ISO/CD 13819-2 recommendations. For thick-walled joints subjected to brace out-of-plane bending, the CIDECT formulation excludes the dependency in the joint strength, which is different from the ISO equation and the present FE observations. The current study compares the different load paths mobilized in the X-joint under various brace loading conditions, through a detailed three-dimensional finite-element study. The numerical results reveal the significance of the joint geometric parameters and the tensile chord stress effect on the ultimate joint strength. Based on the present detailed study, a new chord stress function which incorporates the geometric dependency and the tensile chord stress effect is proposed.

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Determination of Composite Slab Strength Using a New Elemental Test Method

2007-09-29T08:30:00.000-07:00

by Redzuan Abdullah and W. Samuel Easterling, F.ASCE

Abstract:
Composite slabs utilizing cold-formed profiled steel decks are commonly used for floor systems in steel framed buildings. The behavior and strength of composite slabs are normally controlled by the horizontal shear bond between the steel deck and the concrete. The strength of the horizontal shear bond depends on many factors and it is not possible to provide representative design values that can be applied to all slab conditions a priori. Thus, present design standards require that the design parameters be obtained from full-size bending tests, which are typically one or two deck panels wide and a single span. However, because these full-size tests can be expensive and time consuming, smaller size specimens, referred to as elemental tests, are desirable and have been the subject of a great deal of research. Details for a new elemental test method for composite slab specimens under bending are presented. Test results consisting of maximum applied load, end slips, and failure modes are presented and compared with the results of full-size specimens with similar end details, spans, etc. It is shown that the performance of the elemental test developed in this study is in good agreement with the performance of the full-size specimens. Application of test data to current design specifications is also presented.

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Vibration-Based Detection of Small-Scale Damage on a Bridge Deck

2007-09-29T08:28:00.000-07:00

by Zhengjie Zhou; Leon D. Wegner; and Bruce F. Sparling

Abstract:
Vibration-based damage detection VBDD methods use damage-induced changes to the dynamic properties of a structure to detect, locate, and sometimes quantify the extent of damage. This paper describes a laboratory-based experimental and finite element analysis study conducted to evaluate the ability of five different VBDD methods to detect and localize low levels of damage on the deck slab of a two-girder, simply supported bridge, with a focus on using a small number of sensors and only the fundamental mode of vibration. It is demonstrated that damage can be detected and localized longitudinally within a distance equivalent to the spacing between measurement points using data for only the fundamental mode shape before and after damage, defined by as few as five evenly spaced measurement points. The localization resolution declines by approximately 50% near supports. Increasing the number of measurement points improves the localization resolution of the techniques, although not always in proportion to the resulting decrease in measurement point spacing. Incorporating data from two additional modes was not found to significantly improve the localization performance.

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Possibilistic Approach for Damage Detection in Structural Health Monitoring

2007-09-29T08:25:00.000-07:00

by E. Altunok; M. M. Reda Taha, M.ASCE; and T. J. Ross, F.ASCE

Abstract:
This article suggests the process of structural health monitoring SHM in the context of a nonstatistical damage detection paradigm. We particularly focus on applying the theory of possibility to the damage detection problem. The basic idea behind the proposed approach is that the application of possibility theory does not require probabilistic knowledge or assumptions on the damage feature and thus encompasses aleatoric and epistemic types of uncertainties. The approach is not damage feature dependent and thus is generic for use in many SHM systems. Additionally, two new damage metrics are introduced. These metrics extract information concerning damage evidence from observations performed at unknown health states of structures. Damage detection with the aid of the proposed approach is demonstrated by means of a case study.

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Assessment of Improved Nonlinear Static Procedures in FEMA-440

2007-09-29T08:22:00.000-07:00

by Sinan Akkar and Asli Metin

Abstract:
Nonlinear static procedures NSPs presented in the FEMA-440 document are evaluated for nondegrading three- to nine-story reinforced concrete moment-resisting frame systems. Evaluations are based on peak single-degree-of-freedom displacement, peak roof, and interstory drifts estimations. A total of 78 soil site records and 24 buildings with fundamental periods varying between 0.3 s–1.3 s are used in 2,832 linear and nonlinear response-history analyses to derive the descriptive statistics. The moment magnitude of the ground motions varies between 5.7 and 7.6. All records are within 23 km of the causative fault representing near-fault ground motions with and without pulse signals. The statistics presented suggest that lateral loading patterns used in pushover analysis to idealize the building systems play a role in the accuracy of NSPs investigated. Both procedures yield fairly good deformation demand estimations on the median. Displacement coefficient method DCM tends to overestimate the global deformation demands with respect to the capacity spectrum method CSM. The conservative deformation demand estimations of DCM are correlated with the normalized lateral strength ratio, R. The CSM tends to overestimate the deformation demands for the increasing displacement ductility.

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Vertical Stiffness of Elastomeric and Lead–Rubber Seismic Isolation Bearings

2007-09-29T08:17:00.000-07:00

by Gordon P. Warn; Andrew S. Whittaker, M.ASCE; and Michael C. Constantinou, M.ASCE

Abstract: An experimental study investigating the influence of lateral displacement on the vertical stiffness of elastomeric and lead–rubber seismic isolation bearings is summarized. Two identically constructed low-damping rubber and lead–rubber seismic isolation bearings were subjected to a series of tests with varying levels of combined lateral displacement and axial compressive loading to study this relationship. The results of these tests showed the vertical stiffness decreases with increasing lateral displacement for each bearing tested. Additionally, the vertical stiffness data are used to evaluate four formulations for the estimation of the vertical stiffness as a function of the lateral displacement. From this comparison, two formulations, one based on the Koh–Kelly two-spring model and the other on a piecewise linear relationship, showed good agreement with the experimental data over the wide range of lateral displacements considered in this study.

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Testing of a Full-Scale Unreinforced Masonry Building Following Seismic Strengthening

2007-09-29T08:12:00.000-07:00

by Franklin L. Moon; Tianyi Yi; Roberto T. Leon; and Lawrence F. Kahn

Abstract:
To investigate the effectiveness of several seismic strengthening techniques, a full-scale unreinforced masonry URM structure was subjected to slowly applied lateral load reversals after the application of fiber reinforced plastic overlays, near surface mounted rods, and vertical posttensioning. Results showed that all techniques were effective for improving the seismic resistance of the previously tested URM building structure. Each system either increased the lateral in-plane strength and/or provided continuity of pier and spandrel elements over increased lateral displacements. In addition, the response of the test structure overall height to base ratio of approximately one showed that global issues such as flange effects, the effects of overturning moment, and global rocking can be substantial and must be considered.

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Experimental Evaluation of a Large-Scale Buckling-Restrained Braced Frame

2007-09-29T08:07:00.000-07:00

by Larry A. Fahnestock, P.E., M.ASCE; James M. Ricles, P.E., M.ASCE; and Richard Sause, P.E., M.ASCE

Abstract:
As buckling-restrained braced frames BRBFs have been used increasingly in the United States, the need for knowledge about BRBF behavior has grown. In particular, large-scale experimental evaluations of BRBFs are necessary to demonstrate the seismic performance of the system. Although tests of buckling-restrained braces BRBs have demonstrated their ability to withstand significant ductility demands, large-scale BRBF tests have exhibited poor performance at story drifts between 0.02 and 0.025 rad. These tests indicate that the large stiffness of the typical beam-column-brace connection detail leads to large flexural demands that cause undesirable failure modes. As part of a research program composed of numerical and experimental simulations, a large-scale BRBF with improved connection details was tested at the ATLSS Center, Lehigh University. During multiple earthquake simulations, which were conducted using a hybrid pseudodynamic testing method, the test frame sustained story drifts of close to 0.05 rad and BRB maximum ductility demands of
over 25 with minimal damage and no stiffness or strength degradation. The testing program demonstrated that a properly detailed BRBF can withstand severe seismic input and maintain its full load-carrying capacity.

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Seismic Response and Performance of Buckling-Restrained Braced Frames

2007-09-29T07:22:00.000-07:00

by Larry A. Fahnestock, P.E., M.ASCE; Richard Sause, P.E., M.ASCE; and James M. Ricles, P.E., M.ASCE

Abstract:
As the use of buckling-restrained braced frames BRBFs has increased in the United States, the need has grown for knowledge about member and system behavior under seismic loads and for implementing this knowledge into design provisions. In particular, methods for designing BRBFs and predicting seismic response require validation. To address this need, along with the need for experiments demonstrating system-level BRBF performance, a research program composed of numerical and large-scale experimental simulations was initiated at the ATLSS Center, Lehigh University. This paper describes the nonlinear dynamic analyses that were conducted as part of this research program. Numerical simulations of BRBF response were conducted using ground motion records scaled
to two seismic hazard levels. The performance of the prototype BRBF was acceptable and performance objectives were met in terms of structural damage. It is shown that the currently accepted deflection amplification factor underestimates mean inelastic lateral displacements under design-level earthquakes and the system overstrength factor may be unconservative. The current method for predicting BRB maximum ductility demands is also shown to be unconservative and a more rigorous method for predicting BRB maximum ductility demands is provided.

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PILE DESIGN AND CONSTRUCTION PRACTICE

2007-09-29T07:15:00.000-07:00

Piles are columnar elements in a foundation which have the function of transferring load from the superstructure through weak compressible strata or through water, onto stiffer or more compact and less compressible soils or onto rock. They may be required to carry uplift loads when used to support tall structures subjected to overturning forces from winds or waves.

Piles used in marine structures are subjected to lateral loads from the impact of berthing ships and from waves. Combinations of vertical and horizontal loads are carried where piles are used to support retaining walls, bridge piers and abutments, and machinery foundations.

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THE MODIFIED COMPRESSION-FIED THEORY FOR REINFORCED CONCRETE ELEMENT SUBJECTED TO SHEAR

2007-09-29T07:04:00.000-07:00

ACI Journal
Title no. 83-22
by Frank J. Vecchio and Michael P. Collins

Abstract
An analytical model is presented that is capable of predicing the load-deformation response of reinforced element subjected to in plane shear and normal stress. In the model, cracked concrete is treated as a new material with its own stress-strain characteristics. Equilibrium, compatibility, and stress-strain relationships are formulated in term of average stress and average strain. Consideration is also given to local stress conditional at crack location.

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HANDBOOK OF CIVIL ENGINEERING CALCULATION

2007-09-28T06:47:00.000-07:00

This handbook presents a comprehensive collection of civil engineering calculation procedures useful to practicing civil engineers, surveyors, structural designers, drafters, candidates for professional engineering licenses, and students. Engineers in other disciplines—mechanical, electrical, chemical, environmental, etc.—will also find this handbook useful for making occasional calculations outside their normal field of specialty.

Each calculation procedure presented in this handbook gives numbered steps for performing the calculation, along with a numerical example illustrating the important concepts in the procedure. Many procedures include "Related Calculations" comments which expand the application of the computation method presented. All calculation procedures in this handbook use both the USCS (United States Customary System) and the SI (System International) for numerical units. Hence, the calculation procedures presented are useful to engineers throughout the world.

Major calculation procedures presented in this handbook include stress and strain, flexural analysis, deflection of beams, statically indeterminate structures, steel beams and olumns, riveted and welded connections, composite members, plate girders, load and resistance factor design method (LRFD) for structural steel design, plastic design of steel structures, reinforced and prestressed concrete engineering and design, surveying, route design, highway bridges, timber engineering, soil mechanics, fluid mechanics, pumps, piping, water supply and water treatment, wastewater treatment and disposal, hydro power, and engineering economics.

Each section of this handbook is designed to furnish comprehensive coverage of the topics in it. Where there are major subtopics within a section, the section is divided into parts to permit in-depth coverage of each subtopic. Civil engineers design buildings, bridges, highways, airports, water supply, sewage treatment, and a variety of other key structures and facilities throughout the world. Because of the importance of such structures and facilities to the civilized world, civil engineers have long needed a handbook which would simplify and speed their daily design calculations. This handbook provides an answer to that need.

While there are computer programs that help the civil engineer with a variety of engineering calculations, such programs are highly specialized and do not have the breadth of coverage this handbook provides. Further, such computer programs are usually expensive. Because of their high cost, these computer programs can be justified only when a civil engineer makes a number of repetitive calculations on almost a daily basis. In contrast, this handbook can be used in the office, field, drafting room, or laboratory. It provides industry-wide coverage in a convenient and affordable package. As such, this handbook fills a long-existing need felt by civil engineers worldwide.

In contrast, civil engineers using civil-engineering computer programs often find dataentry time requirements are excessive for quick one-off-type calculations. When one-offtype calculations are needed, most civil engineers today turn to their electronic calculator, desktop or laptop computer and perform the necessary steps to obtain the solution desired. But where repetitive calculations are required, a purchased computer program will save time and energy in the usual medium-size or large civil-engineering design office. Small civil-engineering offices generally resort to manual calculation for even repetitive procedures because the investment for one or more major calculation programs is difficult to justify in economic terms.

Even when purchased computer programs are extensively used, careful civil engineers still insist on manually checking results on a random basis to be certain the program is accurate. This checking can be speeded by any of the calculation procedures given in this handbook. Many civil engineers remark to the author that they feel safer, knowing they have manually verified the computer results on a spot-check basis. With liability for civilengineering designs extending beyond the lifetime of the designer, every civil engineer seeks the "security blanket" provided by manual verification of the results furnished by a computer program run on a desktop, laptop, or workstation computer. This handbook gives the tools needed for manual verification of some 2,000 civil-engineering calculation procedures.

Each section in this handbook is written by one or more experienced professional engineers who is a specialist in the field covered. The contributors draw on their wide experience in their field to give each calculation procedure an in-depth coverage of its topic. So the person using the procedure gets step-by-step instructions for making the calculation plus background information on the subject which is the topic of the procedure. And since the handbook is designed for worldwide use, both earlier, and more modern topics, are covered. For example, the handbook includes concise coverage of riveted girders, columns, and connections. While today's civil engineer may say that riveted construction is a method long past its prime, there are millions of existing structures worldwide that were built using rivets. So when a civil engineer is called on to expand, rehabilitate, or tear down such a structure, he or she must be able to analyze the riveted portions of the structure. This handbook provides that capability in a convenient and concise form.

In the realm of modern design techniques, the load and resistance factor method (LRFD) is covered with more than ten calculation procedures showing its use in various design situations. The LRFD method is ultimately expected to replace the well-known and widely used allowable stress design (ASD) method for structural steel building frameworks. In today's design world many civil engineers are learning the advantages of the LRFD method and growing to prefer it over the ASD method.

Also included in this handbook is a comprehensive section titled "How to Use This Handbook." It details the variety of ways a civil engineer can use this handbook in his or her daily engineering work. Included as part of this section are steps showing the civil engineer how to construct a private list of SI conversion factors for the specific work the engineer specializes in.

The step-by-step practical and applied calculation procedures in this handbook are arranged so they can be followed by anyone with an engineering or scientific background. Each worked-out procedure presents fully explained and illustrated steps for solving similar problems in civil-engineering design, research, field, academic, or license-examination situations. For any applied problem, all the civil engineer need do is place his or her calculation sheets alongside this handbook and follow the step-by-step procedure line for line to obtain the desired solution for the actual real-life problem. By following the calculation procedures in this handbook, the civil engineer, scientist, or technician will obtain accurate results in minimum time with least effort. And the approaches and solutions presented are modern throughout.

The editor hopes this handbook is helpful to civil engineers worldwide. If the handbook user finds procedures which belong in the book but have been left out, he urges the engineer to send the title of the procedure to him, in care of the publisher. If the procedure is useful, the editor will ask for the entire text. And if the text is publishable, the editor will include the calculation procedure in the next edition of the handbook. Full credit will be given to the person sending the procedure to the editor. And if users find any errors in the handbook, the editor will be grateful for having these called to his attention. Such errors will be corrected in the next printing of the handbook. In closing, the editor hopes that civil engineers worldwide find this handbook helpful in their daily work.

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CONCRETE FORMWORK SYSTEM

2007-09-28T03:33:00.000-07:00

Formwork development has paralleled the growth of concrete construction throughout the 20th century. In the last several decades formwork technology has become increasingly important in reducing overall costs, since the structural frame constitutes a large portion of the cost of a formwork system.

This book has three objectives. The first is to provide technical descriptions and evaluations of ten formwork systems that are currently used in concrete construction. The second is to serve as a tool to assist contractors in selecting the optimal formwork system. The third is to present the design criteria for conventional formwork for slabs and walls using the stress and the stress modification factors provided by the National Design Specifications (NDS) and the American Plywood Association (APA).

Following a comprehensive introductory chapter, five types of formwork systems for concrete slabs are presented in chapters 2–5. These are conventional wood forms, conventional metal forms, flying forms, the column-mounted shoring system, and tunnel forms. The last four chapters describe five types of formwork systems for concrete columns and walls: conventional wood forms, ganged forms, jump forms, slip forms, and self-raising forms. Particular consideration is given to topics such as system components, typical work cycles, productivity, and the advantages and disadvantages associated with the use of various systems.

The selection of a formwork system is a critical decision with very serious implications. Due consideration must be given to such factors as the system’s productivity, safety, durability, and many other variables that may be specific to the site or job at hand. Chapters 5 and 9 provide a comparative analysis of forming systems for horizontal and vertical concrete work to facilitate the selection of the optimal forming system.

Existing formwork design literature is inconsistent with the design criteria for wood provided by the NDS and the APA. Chapters 3 and 7 provide a systematic approach for formwork design using the criteria of the American Concrete Institute committee 347-94, the NDS, and the APA. For international readers, metric conversion is provided in the Appendix.

This book is directed mainly toward construction management, construction engineering and management students, and concrete contractors. It may also serve as a useful text for a graduate course on concrete formwork, and should be useful for practicing engineers, architects,
and researchers.

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BRIDGE ENGINEERING SUBSTRUCTURE DESIGN

2007-09-28T03:22:00.000-07:00

The Bridge Engineering Handbook is a unique, comprehensive, and the state-of-the-art reference work and resource book covering the major areas of bridge engineering with the theme “bridge to the 21st century.” It has been written with practicing bridge and structural engineers in mind. The ideal readers will be M.S.-level structural and bridge engineers with a need for a single reference source to keep abreast of new developments and the state-of-the-practice, as well as to review standard practices.

The areas of bridge engineering include planning, analysis and design, construction, maintenance, and rehabilitation. To provide engineers a well-organized and user-friendly, easy to follow resource, the Handbook is divided into four volumes: I, Superstructure Design II, Substructure Design III, Seismic Design, and IV, Construction and Maintenance.

Volume II: Substructure Design addresses the various substructure components: bearings, piers and columns, towers, abutments and retaining structures, geotechnical considerations, footing and foundations, vessel collisions, and bridge hydraulics.

The Handbook stresses professional applications and practical solutions. Emphasis has been placed on ready-to-use materials. It contains many formulas and tables that give immediate answers to questions arising from practical work. It describes the basic concepts and assumptions omitting the derivations of formulas and theories. It covers traditional and new, innovative practices. An overview of the structure, organization, and content of the book can be seen by examining the table of contents presented at the beginning of the book while an in-depth view of a particular subject can be seen by examining the individual table of contents preceding each chapter. References at the end of each chapter can be consulted for more detailed studies.

The chapters have been written by many internationally known authors from different countries covering bridge engineering practices and research and development in North America, Europe, and the Pacific Rim. This Handbook may provide a glimpse of a rapid global economy trend in recent years toward international outsourcing of practice and competition in all dimensions of engineering. In general, the Handbook is aimed toward the needs of practicing engineers, but materials may be reorganized to accommodate undergraduate and graduate level bridge courses. The book may also be used as a survey of the practice of bridge engineering around the world.

The authors acknowledge with thanks the comments, suggestions, and recommendations during the development of the Handbook, by Fritz Leonhardt, Professor Emeritus, Stuttgart University, Germany; Shouji Toma, Professor, Horrai-Gakuen University, Japan; Gerard F. Fox, Consulting Engineer; Jackson L. Kurkee, Consulting Engineer; Michael J. Abrahams, Senior Vice President; Parsons Brinckerhoff Quade & Douglas, Inc.; Ben C. Gerwick Jr., Professor Emeritus, University of California at Berkeley; Gregory F. Fenves, Professor, University of California at Berkeley; John M. Kulicki, President and Chief Engineer, Modjeski and Masters; James Chai, Supervising Transportation Engineer, California Department of Transportation; Jinron Wang, Senior Bridge Engineer, California Department of Transportation; and David W. Liu, Principal, Imbsen & Associates, Inc.

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BASIC TOOLS OF REINFORCED CONCRETE BEAM DESIGN

2007-09-24T07:14:00.000-07:00

ACI Journal
Title no. 82-4
by Peter Marti

Abstract
The application of consistent equilibrium and ultimate strength consideration to the design and detailing of reinforced concrete beams is described. Basic tools insclude struts and tie, nodes, fans, and arches. Comparisons with experiments on a shearwall coupling beam and on a deep beam and three design examples illustrate the practical application of these tools.

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STRUCTURAL DETAILS IN CONCRETE

2007-09-24T06:57:00.000-07:00

by M.Y.H. Bangash

Contents :
I. General Requirements for Structural Detailing in Concrete
II. Reinforced Concrete Beams and Slabs
III. Stairs and Staircases
IV. Columns, Frames and Wall
V. Prestress Concrete
VI. Composite Construction, Precast Concrete Elements, Joint, and Connection
VII. Concrete Foundation and Earth-Retaining Structures
VIII. Special Stuctures

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CORRELATION OF SITE CONDITION - BUILDINGS DAMAGES – AND GROUND RUPTURE OF THE 27 MAY 2006 YOGYAKARTA EARTHQUAKE – CENTER JAVA

2007-09-22T00:41:00.000-07:00

The 27 May 2006 earthquake produced a strike-slip ground rupture about ± 80 Km. long. It stretches along general N 220-245E direction from Desa Parangtritis – Distric Kretek- Kabupaten Bantul to Desa Prajinan, Distric Josonalan, Kabupaten Klaten. The sense of horizontal movement is left-lateral. Its epicenter lies within “the District Saden area” (?), Kabupaten Bantul and registered a magnitude of 6.3 (Ms) on the open ended Richter scale. The ground rupture was responsible for part of the damage inflicted by the earthquake. Hardest hit by rupturing are the Kampung Sengir, Piyungan, Srimartani, Derjo, Pathuk, Taji, Prambanan District. Many roads and one bridge were also cracked by the ground rupturing. Vibration triggered landslides and liquefaction and settling. Vibration was widely felt and its intensity varied with local ground conditions. Landslides affected Sengir. Liquefaction and settling damaged mostly the river deposits (flood plain) areas in and near Taji, Prajinan and Srimartani.

Post earthquake study of the ground ruptures provides additional insights into the possibilities that might be expected in case the Melange Cretaceous-Tertiary Fault (Kertapati, 1999) and Opak Fault or other faults move again. Future activities of similar magnitudes along the ground rupture will most probably follow the same trace. Structural controls that affected rupture propagation and arrest might provide us clues as to the size of the next earthquake and enable us to identify sites where high frequency energy inducing strong ground-motion might be expected along the trace.

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New Attenuation Relation for Earthquake Ground Motions in Indonesia Considering Deep Source Events

2007-09-22T00:29:00.000-07:00

by Rizkita Parithusta
(Department of Earth and Planetary Sciences Institute of Seismology and Volcanology — Kyushu University, and Indonesia Center for Earthquake Engineering)
Seminar dan Pameran HAKI 2007 - “KONSTRUKSI TAHAN GEMPA DI INDONESIA”

Abstract
Attenuation relation of the peak horizontal ground accelerations for Indonesia region is developed. The database is compiled for earthquakes with moment magnitudes Mw ≥ 5 that occurs during 1971 – 2007, which consists of horizontal peak ground accelerations and their 5 percent damped response spectra; the accelerograms are recorded on different site conditions classified as rock, hard and soft soils. Earthquake hypocenters with depths up to 150 km are used to attune the equation relevant to subduction, which are the most common earthquake events in Indonesia. The effects of the local site conditions and depth on the attenuation relation are considered simultaneously with the distance and magnitude using a two-stage regression procedure to separate the distance dependence from that of the magnitude.

An iterative partial regression algorithm is proposed to overcome the singularity of the resulting normal equations. It can be observed that the peak ground motions increase with depth for the same magnitude and distance. Considering the soil conditions, it is noticeable that the station coefficients correspond to the soil-type classification varies widely. For the peak ground accelerations, the station coefficients are closely related to the general soil-type classification; while the peak ground velocity have strong relationship with the soil-type classification.

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Seismic Chart In Performance-Based Earthquake Engineering

2007-09-22T00:19:00.000-07:00

by Sindur P. Mangkoesoebroto
(Indonesia Center for Earthquake Engineering and Institute of Technology Bandung, http://www.icfee.info, e-mail itbpauir@bdg.centrin.net.id.)
Seminar dan Pameran HAKI 2007 - “KONSTRUKSI TAHAN GEMPA DI INDONESIA”

Abtract
A seismic chart as design aid for simple structures is proposed. It is suitable to be used in the environment of the Performance-Based Earthquake Engineering together with the Non-linear Static Procedure (NSP) or pushover analysis. The chart utilizes the inelastic response spectra of 10% kinematic hardening SDOF system. The performance parameters to include strength, hysteretic energy and damage, as function of numbers of independent variables such as the intensity & duration of the input motions, site characteristic, ductility, with constraint on displacement, are discussed. The random variables involved and their uncertainties can be taken into account explicitly, enabling simple incorporation of the information on the Seismic Hazard Analysis, when available. Comparison with the experimental data confirms the prediction.

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West Sumatra Earthquake, 6 March 2007, Structural Damage Report

2007-09-22T00:07:00.000-07:00

by Teddy Boen
(Senior Advisor WSSI (World Seismic Safety Initiative)
Seminar dan Pameran HAKI 2007 - “KONSTRUKSI TAHAN GEMPA DI INDONESIA”

INTRODUCTION
On Thursday, March 6, 2007 at 10:49 AM, Singkarak Lake and its surrounding areas were shaken by a moderate earthquake while most people were working and children were studying at schools. According to USGS (United States Geological Survey), the epicenter of this earthquake is at 0.536°S, 100.498°E with 30 km depth and the magnitude was 6.3 Mw. The epicenter is 49 km from Padang, and 159 km from Pekanbaru.

The damaged places visited are Solok District, Tanah Datar District, and Agam District. The damage at those districts was scattered. The most damaged area in Solok is at Sumani Village (Singkarak Sub-District); in Tanah Datar is at Batipuh Village (Rambatan Sub-District) and Padang Panjang; in Agam is at Sungai Tanang Village (Banuhampu Sub-District) and Bukit Tinggi. There were no places / villages which were heavily damaged. The earthquake impact was not as big as exposed by newspapers and electronic media. The number of wounded casualties were also not as many as was the case during the Yogyakarta May 27, 2006 earthquake. The health care facilities in Solok did not experience an influx of wounded casualties. There was no mass emergency situation at all. The hastily built tents outside the hospital were not utilized.

Buildings that were damaged or collapsed during the March 6, 2007 West Sumatra earthquake were mostly masonry non engineered constructions, consisting of one or two stories houses, shop houses, religious and school buildings. The damaged buildings are scattered. The main cause of the damage buildings are poor quality of construction materials and poor workmanship.

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Bridge Engineering Construction and Maintenance

2007-09-21T03:19:00.000-07:00

The Bridge Engineering Handbook is a unique, comprehensive, and the state-of-the-art reference work and resource book covering the major areas of bridge engineering with the theme “ ridge to the Twenty-First Century.” It has been written with practicing bridge and structural engineers in mind. The ideal reader will be an M.S.-level structural and bridge engineer with a need for a single reference source to keep abreast of new development and the state-of-the-practice, as well as review standard practices.

The areas of bridge engineering include planning, analysis and design, construction, maintenance and rehabilitation. To provide engineers a well organized and user-friendly, easy to follow resource, the handbook is divided and printed into four Volumes: I Superstructure Design, II Substructure Design, III Seismic Design, and IV Construction and Maintenance.

Volume IV Construction and Maintenance contains constructions of steel and concrete bridges, substructures of major overwater bridges, construction inspections, construction control for cable-stayed bridges, maintenance inspection and rating, strengthening and rehabilitation.

The handbook stresses professional applications and practical solutions. Emphasis has been placed on ready-to-use materials. It contains many formulas and tables that give immediate answers to questions arising from practical works. It describes the basic concepts and assumptions omitting the derivations of formulas and theories. It covers traditional and new, innovative practices. An overview of the structure, organization, and content of the book can be seen by examining the table of contents presented at the beginning of the volume while an in-depth view of a particular subject can be seen by examining the individual table of contents preceding each chapter. References at the end of each chapter can be consulted for more detailed studies.

The chapters have been written by many internationally known authors in different countries covering bridge engineering practices, and research and development in North America, Europe, and Pacific Rim countries. This handbook may provide a glimpse of rapid global economy trend in recent years toward international outsourcing of practice and competition of all dimensions of engineering. In general, the handbook is aimed at the needs of practicing engineers, but materials may be re-organized to accommodate several bridge courses at the undergraduate and graduate levels. The book may also be used as a survey of the practice of bridge engineering around the world.

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AASHTO Standard Specifications For Highway Bridge 16th

2007-09-19T01:00:00.000-07:00

The structural design standards used by state bridge engineers, engineering colleges and universities, and practicing engineers worldwide. Customary U.S. Units. Loose-leaf with three ring binder. Replaces the 15th Edition and Interim Specifications-Bridges-1993, 9400 and 1995.

Major changes and revisions to this edition are as follows :

The Interim Specification of 1993, 1994, 1995, and 1996 have been adopted and are included.
Entire Division I-A, Seismic Design was revised.
Section 17, Soil-Reinforced Concrete Structure Interaction System, of Division I was revised.
Section 26, Metal Culverts, of Division II was revised
Section 27, Concrete Culvert, of Division II was revised
Section 29, Embedment Anchors, was added to Division II.

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Bridge Engineering Construction and Maintenance

2007-09-18T01:52:00.000-07:00

This chapter addresses some of the principles and practices applicable to the construction of mediumand long-span steel bridges — structures of such size and complexity that construction engineering becomes an important or even the governing factor in the successful fabrication and erection of the superstructure steelwork.

We begin with an explanation of the fundamental nature of construction engineering, then go on to explain some of the challenges and obstacles involved. The basic considerations of cambering are explained. Two general approaches to the fabrication and erection of bridge steelwork are described, with examples from experience with arch bridges, suspension bridges, and cable-stayed bridges.

The problem of erection-strength adequacy of trusswork under erection is considered, and a method of appraisal offered that is believed to be superior to the standard working-stress procedure. Typical problems with respect to construction procedure drawings, specifications, and practices are reviewed, and methods for improvement suggested. The need for comprehensive bridge erection-engineering specifications, and for standard conditions for contracting, is set forth, and the design-andconstruct contracting procedure is described.

Finally, we take a view ahead, to the future prospects for effective construction engineering in the U.S. The chapter also contains a large number of illustrations showing a variety of erection methods for several types of major steel bridges.

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DESIGN OF CONCRETE STRUCTURES

2007-09-15T20:46:00.000-07:00

The thirteenth edition of Design of Concrete Structures has the same dual objectives as the previous work : first to establish a firm understanding of the behavior of structural concrete, then to develop proficiency in the methods used in current design practice. The text has been updated in accordance with the provision of the 2002 American Concrete Institute (ACI) Building Code.

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part 1
part 2
part 3
part 4

SEISMIC DESIGN ASPECTS FOR PRECAST CONCRETE FRAMES

2007-09-15T00:53:00.000-07:00

Strong – Connection Systems

Ideal location for critical section of a plastic hinges:

1. Beam – to – column connection: not less than a distance hb (beam depth) from the connection.

2. Column – to – beam connection: at anywhere within the beam length, between column faces.

3. Beam – to – beam connection: not less than a distance hb (beam depth) from the connection.

4. Column – to – column connection: at anywhere within the beam length, between column faces

5. Column – to – footing connection: not less than a distance hc (column width in the direction considered) from the connection.

Location for ductile connection:

1. In beams – at any location. But it is better to locate it as close as possible to the columns

2. At column bases – to complete mechanism

Requirements for Special Moment Frames with Strong Connections

Shall satisfy all requirements for SRPMK

Segments between locations where flexural yielding is intended to occur follow bernoulli princpl (min 4 times h)

Design strength of the strong connection fSn shall be not less than Se

Primary long rebars shall be made continuous across connections and shall be developed outside both the strong connection and the plastic hinge region.

Column-to-column connections shall have design strength fSn not less than 1.4Se, the design flexural strength fMn not less than 0.4 times the maximum probable flexural strength Mpr for the column within the story height, and the design shear strength fVn of the connection shall be not less than that determined by Mpr .

SRPM with ductile connection constructed using precast concrete shall satisfy the following requirements and other requirement for SRPMK:

The nominal shear strength for connections, Vn , shall be greater than or equal to 2Ve, and

Mechanical splices of beam reinforcement shall be located not closer than h/2 from the joint face

Emulation Design

Based on SNI Concrete code chapter 23.2.1.5:

1. The system will have strength and toughness equal to or exceeding those provided by a comparable monolithic reinforced concrete structure

Procedures

1. Design the structure as if it is to be constructed by monolithic cast in place reinforced concrete methods.

2. Disassemble the structure “on paper” into appropriate sizes and shapes to meet the following criteria, i.e. suitable for plant fabrication, capable of being transported and can be erected by the available cranes.

3. Design the connection:

· connect rebars between the precast elements by mechanical splices, welding the rebars, or by grouting the conduit or sleeves with high-strength, non shrink grout

· connect the precast concrete elements using a high-strength, non shrink grout in the interfaces or by placing conventional concrete in the spaces between the precast elements.

Emulation Details

Reinforcing steel splicing is accomplished in the same manner as in cast – in – place – concrete by:

1. Lapping

2. Welding

3. Joining with mechanical splices

SNI Specification

1. Connect the reinforcing bars by mechanical splices, welding, grouting or sleeves with high-strength and non-shrink grout.

2. Both welded and mechanical splices must achieve strengths of at least 125 percent of rebar yield strength, fy.

3. For lapped splices refers to chapter 14 of SNI Concrete Code

4. The bar size determines the size of connection device

5. Staging of the erection should be considered in design

CONNECTION MADE BY GROUTING OF PRECAST CONCRETE COMPONENTS

When cement-based grouts are used they should be high strength and non-shrink. The minimum grout compressive strength should be 10 MPa greater than that of the surrounding concrete.

For all grouting situations, extreme thoroughness with respect to cleanliness and the following of manufacturer’s instructions is required.

When bars are grouted in horizontal or inclined holes, bar locaters should be used to keep the bars in the center of the holes.

Designers should communicate to contractors at tender stage all the specialized requirements for the grouting operations, including the need for experienced operators and a satisfactory quality assurance programme.

The grout volume method should be used to determine whether or not the units have been fully grouted.

Before compressed air is used to blow out dust from holes, it should be tested for oil contamination.

Preferable Behaviour of Precast System

Behaviour of Precast System @ Behaviour of Monolithic System

Structural Element Yield Under Bending Type of Failure

Beam Yield First

Slip And Shear Mechanisms Do Not Dominate the Behaviour

Shows Stable Hysteretic Behaviour

Example of Strong Beam to Column Connection

Example of Strong Column to Column Connection

STRUCTURAL CONCRETE FORMWORK

2007-09-14T18:22:00.000-07:00

This guide specification covers the requirements for formwork for cast-in-place concrete and will be used with Section 03 31 00.00 10 CAST-IN-PLACE STRUCTURAL CONCRETE. Formwork for architectural cast-in-place concrete is specified in Section 03 33 00 CAST-IN-PLACE ARCHITECTURAL CONCRETE.

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Formwork Code of Practice 2006

2007-09-14T01:54:00.000-07:00

Formwork is the surface, supports and framing used to define the shape of concrete until the concrete is self-supporting: (see AS3610 Formwork for Concrete).

‘Formwork’ includes:
• the forms on which concrete is poured;
• the supports to withstand the loads imposed by the forms and concrete; and
• any bracing added to ensure stability.

Together these components make the formwork assembly.

Hazards associated with work involving the erection, alteration and/or dismantling of formwork include:
• formwork collapse (before, during and after placement of concrete);
• falls from heights;
• slips and trips;
• falling objects ;
• noise;
• dust; and
• manual tasks.

To properly manage risks, a person must
• identify hazards; and
• assess risks that may result because of the hazards; and
• decide on control measures to prevent, or minimise the level of, the risks; and
• implement control measures; and
• monitor and review the effectiveness of the measures.
Control measures must be implemented in an order of priority and implemented
before work commences. The following example illustrates the order of priority
where there is a risk a person could fall.

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GUIDELINES ON FALSEWORK/FORMWORK

2007-09-14T01:39:00.000-07:00

This guideline has been developed to provide information to engineers; contractors and others involved in the design, erection and use of false work and Formwork.

For specific regulatory requirements regarding false work and framework, please consult the Construction Safety Regulations, adopted under the Workplace Safety and Health Act.

Engineering Design Requirements
Contractors must determine if form work/false work that is to be used on a project requires design work by an engineer. The following types of concrete Formwork and false work require the provision at the job-site of design and erection drawings and necessary supplementary information signed and sealed by a professional engineer.
Some engineers may choose to design only the Support false work portion of a form work system or a specific portion of the whole project. This must be made clear to contractors and so specified in all relevant drawings and documents. Statements such as "THIS IS NOT A FORMWORK DRAWING REQUIRED BY W.S.H. MR 189/85 “ written in the large print of a drawing should prevent the possibility of any misunderstanding. False work and Formwork design drawings need not be submitted to the Branch for approval or retention, but must be available at the project site.
The design engineer must authorize any revisions or changes to a false work structure. The engineer should ensure that written authorization is immediately available at the job-site, to be followed by proper documentation as soon as practicable.

Codes and Standards
CSA Standard S269.1 "False work for Construction Purposes" deals only with the design and erection of false work and specifically excludes forms.
The practice of noting on the drawings: "FORMWORK IS THE RESPONSIBILITY OF CONTRACTORS," or "BLOCKING BY OTHERS," is not acceptable. Form work designers are expected to show details of forms and all associated connections, blocking, braces and ties that are necessary to ensure form work integrity during erection and concrete placement.
The CSA Standards 086, S16, S157 and A23 continue to provide the basis for Formwork compliance. ACI Sp4 and ACI Standard 347 are recommended as reference and guides for form work designers.
Where there are discrepancies between the regulations and the standards, the overriding or qualifying requirements of the regulations prevail.

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AISC Construction Management of Steel Construction

2007-09-11T02:46:00.000-07:00

PRECAST CONCRETE WALL PANELS MATERIAL

2007-09-07T01:01:00.000-07:00

Precast concrete panels are fabricated and erected using the same basic materials as for all concrete construction: Portland cement, fine and corse aggregates, admixtures, inserts, insulating materials, and specialty coatings to enhance esthetic appearance. Architectural precast panels are often made of two types of concrete because of the cost of decorative aggregates and white cement. A backup, or structural, concrete is used for most of the panel thickness, and the concrete for the exposed face of the panel thickness, and the concrete for the exposed face of the panel is selected for its architectural appearance.

FACADE FORMWORK

FACADE STOCK IN WAREHOUSE

FACADE STOCK AT STOCK YARD

FACADE ON TRUCK

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GUIDELINES FOR THE USE OF STRUCTURAL PRECAST CONCRETE IN BUILDING

2007-09-05T00:37:00.000-07:00

Generally, the emphasis is on building structures rather than civil engineering structures. Futher more, only structural elements are dealt with since architectural (non-structural) precast concrete is not normally designed to contribute to the overall structural integrity and requires a different set of design criteria.

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THE INTERNATIONAL EXISTING BUILDING CODE

2007-09-05T00:00:00.000-07:00

The provisions of the International Existing Building Code shall apply to the repair, alteration, change of occupancy, addition, and relocation of existing buildings. A building or portion of a building that has not been previously occupied or used for its intended purpose shall comply with the provisions of the International Building Code for new construction. Repairs, alterations, change of occupancy, existing buildings to which additions are made, historic buildings, and relocated buildings complying with the provisions of the International Building Code, International Mechanical Code, International Plumbing Code, and International Residential Code as applicable shall be considered in compliance with the provisions of this code.

The purpose of this code is to establish the minimum requirements to safeguard the public health, safety, and welfare insofar as they are affected by the repair, alteration, change of occupancy, addition, and relocation of existing buildings.

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COMPOSITE STRUCTURES OF STEEL AND CONCRETE

2007-09-04T23:04:00.000-07:00

This volume provides an introduction to the theory and design of composite structures of steel and concrete. Readers are assumed to be familiar with the elastic and plastic theories for the analysis for bending and shear of cross-sections of beams and column of a single material, such as structural steel, and to have some knowledge of reinforced concrete.

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DESIGN LOADS ON STRUCTURE DURING CONSTRUCTION

2007-09-04T21:58:00.000-07:00

The purpose of this standard is to provide minimum design load requirements during construction for building and other structures.
This standard address partially completed structures, as well as temporary structures used during construction. The loads specified herein are suitable for use either with strength design (such as USD and LRFD) or with allowable stress design (ASD) criteria. The loads are equally applicable to all conventional construction materials.
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BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE AND COMMENTARY (ACI 318M-05)

2007-09-04T19:54:00.000-07:00

This commentary discusses some of the considerations of Committee 318 in developing the provisions contained in “Building Code Requirements for Structural Concrete (ACI 318M-05),” hereinafter called the code or the 2005 code.

Emphasis is given to the explanation of new or revised provisions that may be unfamiliar to code users. In addition, comments are included for some items contained in previous editions of the code to make the present commentary independent of the previous editions. Comments on specific provisions are made under the corresponding chapter and section numbers of the code.

The commentary is not intended to provide a complete historical background concerning the development of the ACI Building Code,nor is it intended to provide a detailed résumé of the studies and research data reviewed by the committee in formulating the provisions of the code.

However, references to some of the research data are provided for those who wish to study the background material in depth. As the name implies, “Building Code Requirements for Structural Concrete” is meant to be used as part of a legally adopted building code and as such must differ in form and substance from documents that provide detailed specifications, recommended practice, complete design procedures, or design aids.

The code is intended to cover all buildings of the usual types, both large and small. Requirements more stringent than the code provisions may be desirable for unusual construction. The code and commentary cannot replace sound engineering knowledge, experience, and judgement. A building code states only the minimum requirements necessary to provide for public health and safety. The code is based on this principle. For any structure, the owner or the structural designer may require the quality of materials and construction to be higher than the minimum requirements necessary to protect the public as stated in the code.

However, lower standards are not permitted. The commentary directs attention to other documents that provide suggestions for carrying out the requirements and intent of the code. However, those documents and the commentary are not a part of the code. The code has no legal status unless it is adopted by the government bodies having the police power to regulate building design and construction. Where the code has not been adopted, it may serve as a reference to good practice even though it has no legal status.

The code provides a means of establishing minimum standards for acceptance of designs and construction by legally appointed building officials or their designated representatives. The code and commentary are not intended for use in settling disputes between the owner, engineer, architect, contractor, or their agents, subcontractors, material suppliers, or testing agencies.

Therefore, the code cannot define the contract responsibility of each of the parties in usual construction. General references requiring compliance with the code in the project specifications should be avoided since the contractor is rarely in a position to accept responsibility for design details or construction requirements that depend on a detailed knowledge of the design. Design-build construction contractors, however, typically combine the design and construction responsibility.

Generally, the drawings, specifications and contract documents should contain all of the necessary requirements to ensure compliance with the code. In part, this can be accomplished by reference to specific code sections in the project specifications. Other ACI publications, such as “Specifications for Structural Concrete (ACI 301)” are written specifically for use as contract documents for construction.

It is recommended to have testing and certification programs for the individual parties involved with the execution of work performed in accordance with this code. Available for this purpose are the plant certification programs of the Precast/Prestressed Concrete Institute, the Post-Tensioning Institute and the National Ready Mixed Concrete Association; the personnel certification programs of the American Concrete Institute and the Post-Tensioning Institute; and the Concrete Reinforcing Steel Institute’s Voluntary Certification Program for Fusion-Bonded Epoxy Coating Applicator Plants. In addition, “Standard Specification for Agencies Engaged in the Testing and/or Inspection of Materials Used in Construction” (ASTM E 329-03) specifies performance requirements for inspection and testing agencies.

Design reference materials illustrating applications of the code requirements may be found in the following documents. The design aids listed may be obtained from the sponsoring organization.

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Emulating Cast-in-Place Detailing in Precast Concrete Structures

2007-09-04T19:49:00.000-07:00

Emulative detailing is defined as designing connection systems in a precast concrete structure so that its structural performance is equivalent to that of a conventionally designed, cast-in-place, monolithic concrete structure (Ericson and Warnes 1990).

Emulative detailing is different than jointed design where precast elements are separated from each other but are connected with special jointing details like welded or bolted plates. As commonly applied, the term “emulation” refers to the design of the vertical or horizontal elements of the lateral-force-resisting system of a building. Emulative detailing of precast concrete structures is applicable to any structural system where monolithic reinforced concrete would also be appropriate, regardless of seismic region (Precast/Prestressed Concrete Institute 1999).

Design practice in some countries with a high seismic risk, such as New Zealand and Japan, follow design codes that address precast concrete designed by emulation of castinplace concrete design. Performance of joints and related details of emulative precast concrete structural concepts have been extensively tested in Japan. Because emulative precast concrete structures have been constructed there for over three decades, emulative methods for seismic design are widely accepted. Until recently, this practice has not been formally followed in the U.S.

Typical details showing proportional dimensions, as well as reinforcing steel, are schematic only and are provided solely to demonstrate the interactivity of the jointing essentials. All connection details will be subject to structural analysis and compliance with contemporary code requirements. At the time of this writing, splicing reinforcing bars by welding or lapping was not permitted by code whenever the bars were subjected to stresses beyond the actual yield points of the reinforcing steel being used. According to certain tests of mechanical splices reported by the California Department of Transportation (Noureddine, Richards, and Grottkau 1996), concern was expressed about staggering of mechanical splices of reinforcing bars. Staggering is not required by current and developing codes.

Only reinforcing bar details essential to make the illustration more understandable are shown to avoid congestion and provide clarity. Other reinforcing steel that would typically be incorporated into a conventional design is intentionally not shown. The specification and delineation of reinforcing bars or strand sizes and locations, layers, types, and numbers is the responsibility of the designer.

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Joints in Concrete Construction

2007-09-04T19:23:00.000-07:00

Joints are necessary in concrete structures for a variety of reasons. Not all concrete in a given structure can be placed continuously, so there are construction joints that allow for work to be resumed after a period of time. Since concrete undergoes volume changes, principally related to shrinkage and temperature changes, it can be desirable to provide joints and thus relieve tensile or compressive stresses that would be induced in the structure. Alternately, the effect of volume
changes can be considered just as other load effects are considered in building design. Various concrete structural eleelements are supported differently and independently, yet meet and match for functional and architectural reasons. In this case, compatibility of deformation is important, and joints may be required to isolate various members.

Many engineers view joints as artificial cracks, or as means to either avoid or control cracking in concrete structures. It is possible to create weakened planes in a structure, so cracking occurs in a location where it may be of little importance, or have little visual impact. For these reasons, ACI Committee 224—Cracking, has developed this report as an overview of the design, construction, and maintenance of joints in various types of concrete structures, expanding on the currently limited treatment in ACI 224R. While other ACI Committees deal with specific types of structures, and joints in those structures, this is the first ACI report to synthesize information on joint practices into a single document. Committee 224 hopes that this synthesis will promote continued re-evaluation of recommendations for location and spacing of joints, and the development of further rational approaches.

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Chemical Admixtures for Concrete

2007-09-04T19:16:00.000-07:00

An admixture is defined in ACI 116R and in ASTM C 125 as “a material other than water, aggregates, hydraulic cement, and fiber reinforcement used as an ingredient of concrete or mortar, and added to the batch immediately before or during its mixing.” This report deals with commonly used admixtures other than those assigned to other ACI committees. Materials such as admixtures used to produce expansive-cement concrete (ACI Committee 223); fly ash and natural pozzolans (ACI Committee 232); silica fume (ACI Committee 234); admixtures for insulating and cellular concrete (ACI Committee 523); and polymers (ACI Committee 548), are not discussed in this report.

The chemical admixtures are classified generically or with respect to their characteristics. Information to characterizeeach class is presented along with brief statements of the general purposes and expected effects of using each group of materials. The wide scope of the admixture field, the continued entrance of new or modified materials into this field, and the variations of effects with different concreting materials and conditions preclude a complete listing of all admixtures and their effects on concrete. Summaries of the state-of-the-art of chemical admixtures include Ramachandran (1984), Ramachandran and Mailvaganam (1992), and Mather (1994).

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Design Recommendations for Precast Concrete Structures

2007-09-04T18:37:00.000-07:00

Recommendations of this report apply to design of precast concrete structures where all members or selected members are cast somewhere other than their final position in the structure.

This report should be used together with ACI 318, “Building Code Requirements for Reinforced Concrete,” the minimum requirements of which may be legally binding.
Because of the nature of precast concrete, certain recommendations contained in this report differ from the requirements of ACI 318. Some of these recommendations may not be applicable to special conditions. Engineering judgment should be used in implementing this report.

Tilt-up concrete construction is a specialized type ofprecast concrete construction. Because panel dimensions in tilt-up are generally much larger than those in plant-cast precast, and roof and floor diaphragms are generally not constructed with precast sections, certain recommendations in this report differ from common practice found in tilt-up concrete construction.

In design of precast members and connections, all loading and restraint conditions from casting to end use of the structure should be considered. The stresses developed in precast elements during the period from casting to final connection may be more critical than the service load stresses. Special attention should be given to the methods of stripping, storing, transporting, and erecting precast elements.

When precast members are incorporated into a structural system, the forces and deformations occurring in and adjacent to connections (in adjoining members and in the entire
structure) should be considered.

The structural behavior of precast elements may differ substantially from that of similar members that are monolithically cast in place. Design of connections to transmit forces due to shrinkage, creep, temperature change, elastic deformation, wind forces, and earthquake forces require special attention. Details of such connections are especially important to insure adequate performance of precast structures.

Precast members and connections should be designed to meet tolerance requirements. The behavior of precast members and connections is sensitive to tolerances. Design should provide for the effects of adverse combinations of fabrication and erection tolerances.
Tolerance requirements should be listed on contract documents, and may be specified by reference to accepted standards.

Tolerances that deviate from accepted standards should be so indicated. All details of reinforcement, connections, bearing elements, inserts, anchors, concrete cover, openings and lifting devices, and specified strength of concrete at critical stages of fabrication and construction, should be shown on either the contract documents prepared by the architect/engineer of record or on the shop drawings furnished by the contractor.

Whether this information is to be shown on the contract documents or shop drawings depends on the provisions of the contract documents. The shop drawings should show, as a minimum, all details of the precast concrete members and embedded items. The contract documents may specify that portions of connections exterior to the member are also to be shown on the shop drawings. The contract documents may also require the contractor to provide designs for the members and/or connections.

The contract documents should show the loads to be considered in design of the precast concrete elements of the structure, and they should indicate any special requirements or functions (for example: seismic loads, allowance for movements, etc.) that should be considered in design assigned to the contractor. In this case, the shop drawings should include complete details of the connections involved.

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MSC Nastran : Structure Analysis

2007-08-30T01:06:00.000-07:00

MSC.Patran is an analysis software system developed and maintained by MSC.Software Corporation. The core of the system is a finite element analysis pre and postprocessor. Several optional products are available including; advanced postprocessing programs, tightly coupled solvers, and interfaces to third party solvers. This document describes one of these interfaces.

The MSC.Patran MSC.Nastran interface provides a communication link between MSC.Patran and MSC.Nastran. It also provides for the customization of certain features in MSC.Patran. The interface is a fully integrated part of the MSC.Patran system. Selecting MSC.Nastran as the analysis code preference in MSC.Patran, activates the customization process. These customizations ensure that sufficient and appropriate data is generated for the MSC.Patran MSC.Nastran interface.

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HAND BOOK OF SOIL ANALYSIS

2007-08-30T00:50:00.000-07:00

This new book by Marc Pansu and Jacques Gautheyrou provides a synopsis of the analytical procedures for the physicochemical analysis of soils. It is written to conform to analytical standards and quality control.
It focuses on mineralogical, organic and inorganic analyses, but also describes physical methods when these are a precondition for analysis. It will help a range of different users to choose the most appropriate method for the type of material and the particular problems they have to face. The compiled work is the product of the experience gained by the authors in the laboratories of the Institute of Research for Development (IRD) in France and in tropical countries, and includes an extensive review of the literature. The reference section at the end of each chapter lists source data from pioneer studies right up to current works, such as, proposals for structural models of humic molecules, and itself represents a valuable source of information.
IRD soil scientists collected data on Mediterranean and tropical soils in the field from West and North Africa, Madagascar, Latin America, and South East Asia. Soil materials from these regions are often different from those found in temperate zones. As their analysis brought new problems to light, it was essential to develop powerful and specific physicochemical methods. Physicists, chemists and biologists joined forces with IRD soil scientists to contribute knowledge from their own disciplines thereby widening its scope considerably. This work is the fruit of these experiments as applied to complex systems, involving soils and the environment.

The methodological range is particularly wide and each chapter presents both simple analyses and analyses that may require sophisticated equipment, as well as specific skills. It is aimed both at teams involved in practical field work and at researchers involved in fundamental and applied research. It describes the principles, the physical and chemical basis of each method, the corresponding analytical procedures, and the constraints and limits of each. The descriptions are practical, easy to understand and implement.

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CIVIL ENGINEERING FORMULAS

2007-08-30T00:11:00.000-07:00

This handy book presents more than 2000 needed formulas for civil engineers to help them in the design office, in the field, and on a variety of construction jobs, anywhere in the world. These formulas are also useful to design drafters, structural engineers, bridge engineers, foundation builders, field engineers, professional-engineer license examination candidates, concrete specialists, timber-structure builders, and students in a variety of civil engineering pursuits.

The book presents formulas needed in 12 different specialized branches of civil engineering—beams and girders, columns, piles and piling, concrete structures, timber engineering, surveying, soils and earthwork, building structures, bridges, suspension cables, highways and roads, and hydraulics and open-channel flow. Key formulas are presented for each of these topics. Each formula is explained so the engineer, drafter, or designer knows how, where, and when to use the formula in professional work. Formula units are given in both the United States Customary System (USCS) and System International (SI). Hence, the text is usable throughout the world. To assist the civil engineer using this material in worldwide engineering practice, a comprehensive tabulation of conversion factors is presented in Chapter 1.
In assembling this collection of formulas, the author was guided by experts who recommended the areas ofgreatest need for a handy book of practical and applied civil engineering formulas.

Sources for the formulas presented here include the various regulatory and industry groups in the field of civil engineering, authors of recognized books on important topics in the field, drafters, researchers in the field of civil engineering, and a number of design engineers who work daily in the field of civil engineering. These sources are cited in the Acknowledgments.

When using any of the formulas in this book that may come from an industry or regulatory code, the user is cautioned to consult the latest version of the code. Formulas may be changed from one edition of a code to the next. In a work of this magnitude it is difficult to include the latest formulas from the numerous constantly changing codes. Hence, the formulas given here are those current at the time of publication of this book. In a work this large it is possible that errors may occur.

Hence, the author will be grateful to any user of the book who detects an error and calls it to the author’s attention. Just write the author in care of the publisher. The error will be corrected in the next printing.

In addition, if a user believes that one or more important formulas have been left out, the author will be happy to consider them for inclusion in the next edition of the book. Again, just write him in care of the publisher.

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Finite Element Analysis of Structural Steelwork Beam to Column Bolted Connections

2007-08-29T23:56:00.000-07:00

A combination of simple fabrication techniques and speedy site erection have made bolted endplates one of the most popular methods of connecting members in structural steelwork frames. Although simple in their use bolted endplates are extremely complex in their analysis and behaviour. In 1995 the Steel Construction Institute (SCI) and the British Constructional Steelwork Association (BCSA) jointly published a design guide for moment resisting connections [1].

The Green Book design method offers increased connection capacity using a combination of theoretical overstress in the beam compression zone and plastic bolt force distribution. This paper reports on a PhD research program at the University of Teesside which uses a combination of full scale testing and materially non-linear three dimensional finite element analyses (FEA) in order to investigate extended end plate beam-to-column connections. The FEA analyses, incorporating MYSTRO and LUSAS software [2], use enhanced strain solid and contact gap elements to model the connection behaviour.

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BRIDGE DESIGN MANUAL

2007-08-29T23:48:00.000-07:00

Unless otherwise noted, the design values, policies, practices, etc. that are established in this Manual are considered guidelines to promote uniform, safe and sound designs for bridges and structures in the State of Ohio. Deviation from these guidelines does not require formal approval from the Department; however, during the normal staged review process, the appointing authority may require the design agency to justify or otherwise seek recommendation from the Office of Structural Engineering when deviation is necessary.

The user of this Manual should be fully familiar with the AASHTO Standard Design Specifications For Highway Bridges including all issued Interim Specifications, the ODOT Construction and Material Specifications, and Office of Structural Engineering Standard Drawings and Design Data Sheets, along with the contents of this Manual.

The practicability of construction should be considered with reference to each detail of design. This applies particularly as new ideas are considered.
Where complete description or instruction is not provided in the Construction and Material Specifications, the description or instruction should be shown on the plans, but care should be taken to insure clarity both from a structural and contractual viewpoint.

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STRUCTURAL DETAIL IN CONCRETE

2007-08-29T23:34:00.000-07:00

A number of books on various aspects of concrete design and detailing have been published but this is believed to be the first comprehensive detailing manual. The aim of this book is to cover a wide range of topic, so simplifying and reducing the work required to prepare structural drawings and details in reinforced, prestressed, precast and composite concrete.

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STEEL STRUCTURE

2007-08-24T23:30:00.000-07:00

PART (PROPERTIES OF STRUKCTURAL STEEL) 1 :
This section presents and discusses the properties of structural steels that are of importance in design and construction. Designers should be familiar with these properties so that they can select the most economical combination of suitable steels for each application and use the materials efficiently and safely.

PART 2 (FABRICATION & ERECTION) :
Designers of steel-framed structures should be familiar not only with strength and serviceability requirements for the structures but also with fabrication and erection methods. These may determine whether a design is practical and cost-efficient. Furthermore, load capacity and stability of a structure may depend on design assumptions made as to type and magnitude of stresses and strains induced during fabrication and erection.

PART 3 (GENERAL STRUCTURAL THEORY) :
Safety and serviceability constitute the two primary requirements in structural design. For a structure to be safe, it must have adequate strength and ductility when resisting occasional extreme loads. To ensure that a structure will perform satisfactorily at working loads, functional or serviceability requirements also must be met. An accurate prediction of the behavior of a structure subjected to these loads is indispensable in designing new structures and evaluating existing ones.
The behavior of a structure is defined by the displacements and forces produced within the structure as a result of external influences. In general, structural theory consists of the essential concepts and methods for determining these effects. The process of determining them is known as structural analysis If the assumptions inherent in the applied structural theory are in close agreement with actual conditions, such an analysis can often produce results that are in reasonable agreement with performance in service.

PART 4 (ANALYSIS OF SPECIAL STRUCTURE) :
The general structural theory presented in Sec. 3 can be used to analyze practically all types of structural steel framing. For some frequently used complex framing, however, a specific adaptation of the general theory often expedites the analysis. In some cases, for example, formulas for reactions can be derived from the general theory. Then the general theory is no longer needed for an analysis. In some other cases, where use of the general theory is required, specific methods can be developed to simplify analysis.
This section presents some of the more important specific formulas and methods for complex framing. Usually, several alternative methods are available, but space does not permit their inclusion. The methods given in the following were chosen for their general utility when analysis will not be carried out with a computer.

PART 5 (CONNECTIONS) :
In this section, the term connections is used in a general sense to include all types of joints in structural steel made with fasteners or welds. Emphasis, however, is placed on the more commonly used connections, such as beam-column connections, main-member splices, and truss connections.
Recommendations apply to buildings and to both highway and railway bridges unless otherwise noted. This material is based on the specifications of the American Institute of Steel Construction (AISC), ‘‘Load and Resistance Factor Design Specification for Structural Steel Buildings,’’ 1999, and ‘‘Specification for Structural Steel Buildings—Allowable Stress Design and Plastic Design,’’ 1989; the American Association of State Highway and Transportation Officials (AASHTO), ‘‘Standard Specifications for Highway Bridges,’’ 1996; and the American Railway Engineering and Maintenance-of-Way Association (AREMA), ‘‘Manual,’’ 1998.

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STANDART SPECIFICATION FOR READY-MIXED CONCRETE

2007-08-24T23:09:00.000-07:00

This specification covers ready-mixed concrete manufactured and delivered to a purchase r in a freshly mixed and unhardened state as hereinafter specified. Requirements for quality of concrete shall be either as hereinafter specified or as specified by the purchaser. In any case where the requirements of the purchaser differ from these in this specification, the purchaser's specification shall govern. This specification does not cover the placement, consolidation, curing, or protection of the concrete after delivery to the purchaser.

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CONSTRUCTION MANAGEMENT OF STEEL CONSTRUCTION

2007-08-24T21:43:00.000-07:00

This educational manual was developed for the American Institute of Steel Construction (AISC) to present the principal project management activities and issues for procuring and implementing steel construction. The manual was developed for use in undergraduate university level construction management programs. It should also be useful in project management courses in construction
engineering, civil engineering, architectural engineering, and architecture programs.

The manual is intended as a supplemental text which may be incorporated into junior and senior level project management, estimating, and scheduling courses. The manual was developed in two educational modules: Module One addresses project management activities and Module Two examines scheduling and estimating issues that pertain to steel construction.

Both educational modules have been designed to help students understand the unique roles and relationships of the general contractor, steel fabricator, erector, specialty contractors, suppliers, architect, structural engineer, and owner in the construction of a structural steel building frame. While the manual has been specifically developed to address steel construction, many of the issues presented are also applicable to the management of other construction subcontracts. Therefore, this manual may serve as a detailed case study of steel construction which will help students achieve a broader understanding of construction project management, estimating, and scheduling practices.

It is hoped that faculty teaching this material, will find this steel case study useful as they present the principles of project management, estimating, and scheduling in their courses.

Most construction management and construction related programs require students to take courses in construction science, technology, materials, and structural design. It is assumed that by the time students are enrolled in project management, estimating, and scheduling courses, they will have obtained sufficient understanding of the technical terminology and also have a general understanding of steel design and construction practices. This manual is not intended as a technical guide to steel, but focuses instead on the project management aspects of steel construction. Students may wish to consult other general texts on structural design and construction methods should they need additional technical information. AISC has developed numerous publications which address the technical and design aspects of steel. These publications may be obtained by contacting the AISC publication’s department. See Appendix D for a listing of AISC services.

To help students gain a better understanding of the text, a steel construction project case study has been included. This building is a steel framed seven-story midrise medical office building. This project is described below under the case study description. Project documents from the case study are included in Appendix A.

To assist faculty in using this manual as a supplemental text in their courses, several open-ended questions are provided at the end of the two modules. These questions are intended to be used for in-class discussion.

The development of this manual was sponsored by a grant from the AISC Education Committee and was prepared by Mr. Tim Mrozowski, A.I.A., Dr. Matt Syal, CPC, and Mr. Syed Aqeel Kakakhelof the Building Construction Management Program at Michigan State University. AISC appointed two advisory committees to provide input and oversee the development of the manual. The Industry Technical Committee included fabricators, erectors, contractors, and educators who provided input into industry practices. The Educational Advisory Committee consisted of construction management and engineering faculty who advised and reviewed the manual for both industry practice and educational use.

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BUILDING DESIGN AND CONSTRUCTION HANDBOOK

2007-08-24T20:07:00.000-07:00

Building design and construction handbook / Frederick S. Merritt, editor,
Jonathan T. Ricketts, editor.—6th ed.

ABOUT THE EDITORS
Frederick S. Merritt (deceased) was a consulting engineer for many years, with experience in building and bridge design, structural analysis, and construction management.
A Fellow of the American Society of Civil Engineers and a Senior Member of ASTM, he was a former senior editor of Engineering News-Record and an author / editor of many books, including McGraw-Hill’s Standard Handbook for Civil Engineers and Structural Steel Designer’s Handbook.

Jonathan T. Ricketts is a consulting engineer with broad experience in general civil engineering environmental design and construction management. A registered engineer in several states, he is an active member of the American Society of Civil Engineers, the National Society of Professional Engineers, the American Water Works Association, and is coeditor of McGraw-Hill’s Standard Handbook for Civil Engineers.

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METHODS OF CONCRETE PLACING

2007-08-07T00:37:00.000-07:00

Concrete may be conveyed from a mixer to point of placement by any of a variety of methods and equipment, if properly transported to avoid segregation. Selection of the most appropriate technique for economy depends on jobsite conditions, especially project size, equipment, and the contractor’s experience. In building construction, concrete usually is placed with hand- or power-operated buggies; dropbottom buckets with a crane; inclined chutes; flexible and rigid pipe by pumping; shotcrete, in which either dry materials and water are sprayed separately or mixed concrete is shot against the forms; and for underwater placing, tremie chutes (closed flexible tubes). For mass-concrete construction, side-dump cars on narrow-gage track or belt conveyers may be used. For pavement, concrete may be placed by bucket from the swinging boom of a paving mixer, directly by dump truck or mixer truck, or indirectly by trucks into a spreader.

A special method of placing concrete suitable for a number of unusual conditions consists of grout-filling preplaced coarse aggregate. This method is particularly useful for underwater concreting, because grout, introduced into the aggregate through a vertical pipe gradually lifted, displaces the water, which is lighter than the grout. Because of bearing contact of the aggregate, less than usual overall shrinkage is also achieved.

INSPECTION OF REINFORCEMENT

2007-07-31T03:37:00.001-07:00

This involves approval of rebar material for conformance to the physical properties required, such as ASTM specifications for the strength grade specified; approval of the bar details and placing drawings; approval of fabrication to meet the approved details within the prescribed tolerances; and approval of rebar placing.
Approvals of rebar material may be made on the basis of mill tests performed by the manufacturer for each heat from which the bars used originated. If samples are to be taken for independent strength tests, measurements of deformations, bending tests, and minimum weight, the routine samples may be best secured at the mill or the fabrication shop before fabrication. Occasionally, samples for check tests are taken in the field; but in this case, provision should be made for extra lengths of bars to be shipped and for schedules for the completion of such tests before the material is required for placing. Sampling at the point of fabrication, before fabrication, is recommended.
Inspection of fabrication and placement is usually most conveniently performed in the field, where gross errors would require correction in any event. Under the ACI 318 Building Code, the bars should be free of oil, paint, form coatings, and mud when placed. Rust or mill scale sufficiently loose to damage the bond is normally dislodged in handling.
If heavily rusted bars (which may result from improper storage for a long time exposed to rusting conditions) are discovered at the time of placing, a quick field test of suitability requires only scales, a wire brush, and calipers. In this test, a measured length of the bar is wire-brushed manually and weighed. If less than 94% of the nominal weight remains, or if the height of the deformations is deficient, the rust is deemed excessive. In either case, the material may then be rejected or penalized as structurally inadequate. Where space permits placing additional bars to make up the structural deficiency (in anchorage capacity or weight), as in walls and slabs, this solution is preferred, because construction delay then is avoided.
Where project specifications impose requirements on rust more severe than the structural requirements of the ACI 318 Building Code, for example, for decorative surfaces exposed to weather, the inspection should employ the special criteria required.

INSPECTION OF REINFORCEMENT

2007-07-31T03:37:00.000-07:00

BAR SUPPORTS

2007-07-31T03:34:00.000-07:00

Bar supports are commercially available in three general types of material: wire, precast concrete, and all-plastic. Descriptions of the various types of bar supports,as well as recommended maximum spacings and details for use, are given in the CRSI ‘‘Manual for Standard Practice.’’
Wire bar supports are generally available in the United States in three classes of rust prevention: plastic-protected, stainless-steel-protected, and no protection (plain). Precast-concrete bar supports are normally supplied in three styles; plain block, block with embedded wires, and block with a hole for the leg of a vertical bar for top- and bottom-bar support.
Various types and sizes of all-plastic bar supports and sideform spacers are available. Consideration should be given to the effects of thermal changes, inasmuch as the coefficient of thermal expansion of the plastic can differ significantly from that of concrete. Investigation of this property is advisable before use of all-plastic supports in concrete that will be exposed to high variations in temperature.
Bar supports for use with epoxy-coated rebars should be made of dielectric material. Alternatively, wire bar supports should be coated with dielectric material, such as plastic or epoxy.

PRESTRESSING STEEL

2007-07-20T17:51:00.000-07:00

Cold-drawn high-strength wires, singly or stranded, with ultimate tensile strengths up to 270 ksi, and high-strength, alloy-steel bars, with ultimate tensile strengths up to 160 ksi, are used in prestressing. The applicable specifications are:

ASTM A416/A416M, Uncoated Seven-Wire Stress-Relieved Strand

ASTM A421/A421M, Uncoated Stress-Relieved Wire

ASTM A722/A722M, Uncoated High-Strength Bar

Single strands are used for plant-made pretensioned, prestressed members. Posttensioned prestressing may be performed with the member in place, on a site fabricating area, or in a plant. Posttensioned tendons usually consist of strands or bars. Single wires, grouped into parallel-wire tendons, may also be used in posttensioned applications.

SPECIAL FORMS & INSPECTION OF FORMWORK

2007-07-20T17:48:00.000-07:00

Special formwork may be required for uncommon structures, such as folded plates, shells, arches, and posttensioned-in-place designs, or for special methods of construction, such as slip forming with the form rising on the finished concrete or with the finished concrete descending as excavation progresses, permanent forms of any type, preplaced-grouted-aggregate concreting, underwater concreting, and combinations of precast and cast-in-place concreting.

Inspection of formwork for a building is a service usually performed by the architect, engineer, or both, for the owner and, occasionally, directly by employees of the owner. Formwork should be inspected before the reinforcing steel is in place to ensure that the dimensions and location of the concrete conform to design drawings (Art. 9.16). This inspection would, however, be negligent if deficiencies in the areas of contractor responsibility were not noted also. (See ‘‘Guide to Formwork for Concrete,’’ ACI 347R, and ‘‘Formwork for Concrete,’’ ACI SP-4, for construction check lists, and ‘‘Manual of Concrete Inspection,’’ ACI SP-2.)

FORM REMOVAL AND RESHORING

2007-07-14T00:22:00.000-07:00

Much friction between contractors’ and owners’ representatives is created because of misunderstanding of the requirements for form removal and reshoring. The contractor is concerned with a fast turnover of form reuse for economy (with safety), whereas the owner wants quality, continued curing for maximum in-place strength, and an adequate strength and modulus of elasticity to minimize initial deflection and cracking. Both want a satisfactory surface.
Satisfactory solutions for all concerned consist of the use of high-early-strength concrete or accelerated curing, or substitution of a means of curing protection other than formwork. The use of field-cured cylinders (Arts. 9.7 and 9.14) in conjunction with appropriate nondestructive in-place strength tests (Art. 9.14) enables owner and contractor representatives to measure the rate of curing to determine the earliest time for safe form removal.

Reshoring or ingenious formwork design that keeps shores separate from surface forms, such as ‘‘flying forms’’ that are attached to the concrete columns, permits early stripping without premature stress on the concrete. Properly performed, reshoring is ideal from the contractors’ viewpoint. But the design of reshores several stories in depth becomes very complex. The loads delivered to supporting floors are very difficult to predict and often require a higher order of structural analysis than that of the original design of the finished structure. To evaluate these loads, knowledge is required of the modulus of elasticity Ec of each floor (different), properties of the shores (complicated in some systems by splices), and the initial stress in the shores, where is dependent on how hard the wedges are driven or the number of turns of screw jacks, etc. (‘‘Formwork for Concrete,’’ ACI SP-4). When stay-in-place shores are used, reshoring is simpler (because variations in initial stress, which depend on workmanship, are eliminated), and a vertically progressive failure can be averted.

One indirect measure is to read deflections of successive floors at each stage. With accurate measurements of Ec, load per floor can then be estimated by structural theory. A more direct measure (seldom used) is strain measurement on the shores, usable with metal shores only. On large projects, where formwork cost and cost of failure justify such expense, both types of measurement can be employed.

LOADS ON FORMWORK

2007-07-14T00:20:00.000-07:00

Formwork should be capable of supporting safely all vertical and lateral loads that might be applied to it until such loads can be supported by the ground, the concrete structure, or other construction with adequate strength and stability. Dead loads on formwork consist of the weight of the forms and the weight of and pressures from freshly placed concrete. Live loads include weights of workers, equipment, material storage, and runways, and accelerating and braking forces from buggies and other placement equipment. Impact from concrete placement also should be considered in formwork design.
Horizontal or slightly inclined forms often are supported on vertical or inclined support members, called shores, which must be left in place until the concrete placed in the forms has gained sufficient strength to be self-supporting. The shores may be removed temporarily to permit the forms to be stripped for reuse elsewhere, if the concrete has sufficient strength to support dead loads, but the concrete should then be reshored immediately. Loads assumed for design of shoring and reshoring of multistory construction should include all loads transmitted from the stories above as construction proceeds.

MATERIALS AND ACCESSORIES FOR FORMS

2007-07-09T21:14:00.000-07:00

When a particular design or desired finish imposes special requirements, and only then, the engineer’s project specifications should incorporate these requirements and preferably require sample panels for approval of finish and texture. Under competitive bidding, best bids are secured when the bidders are free to use ingenuity and their available materials (‘‘Formwork for Concrete,’’ ACI SP-4).

RESPONSIBILITY FOR FORMWORK

2007-07-04T01:35:00.000-07:00

The exact legal determination of responsibilities for formwork failures among owner, architect, engineer, general contractor, subcontractors, or suppliers can be determined only by a court decision based on the complete contractual arrangements undertaken for a specific project.
Generally accepted practice makes the following rough division of responsibilities:
Safety. The general contractor is responsible for the design, construction, and safety of formwork. Subcontractors or material suppliers may subsequently be held responsible to the general contractor. The term ‘‘safety’’ here includes prevention of any type of formwork failure. The damage caused by a failure always includes the expense of the formwork itself, and may also include personal injury or damage to the completed portions of a structure. Safety also includes protection of all personnel on the site from personal injury during construction. Only the supervisor of the work can control the workmanship in assembly and the rate of casting on which formwork safety ultimately depends.
Structural Adequacy of the Finished Concrete. The structural engineer is responsible for the design of the reinforced concrete structure. The reason for project specifications requiring that the architect or engineer approve the order and time of form removal, shoring, and reshoring is to ensure proper structural behavior during such removal and to prevent overloading of recently constructed concrete below or damage to the concrete from which forms are removed prematurely. The architect or engineer should require approval for locations of construction joints not shown on project drawings or project specifications to ensure proper transfer of shear and other forces through these joints. Project specifications should also require that debris be cleaned from form material and the bottom of vertical element forms, and that form-release agents used be compatible with appearance requirements and future finishes to be applied. None of these considerations, however, involves the safety of the formwork per se.

AT THE PLACING POINT-SLUMP ADJUSTMENTS

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With good quality control, no water is permitted on the mixing truck. If the slump is too low (or too high) on arrival at the site, additional cement must be added. If the slump is too low (the usual complaint), additional water and cement in the prescribed water-cementitious materials ratio can also be added. After such additions, the contents must be thoroughly mixed, 2 to 3 min at high speed. Because placing-point adjustments are inconvenient and costly, telephone or radio communication with the supply plant is desirable so that most such adjustments may be made conveniently at the plant.
Commonly, a lesser degree of control is accepted in which the truck carries water, the driver is on the honor system not to add water without written authorization from a responsible agent at the site, and the authorization as well as the amounts added are recorded on the record (trip ticket) of batch weights.
Note: If site adjustments are made, test samples for strength-test specimens should be taken only after all site adjustments. For concrete in critical areas, such as lower-floor columns in high-rise buildings, strictest quality control is recommended.

AT THE PLACING POINT-SLUMP ADJUSTMENTS

2007-07-01T17:53:00.000-07:00

With good quality control, no water is permitted on the mixing truck. If the slump is too low (or too high) on arrival at the site, additional cement must be added. If the slump is too low (the usual complaint), additional water and cement in the prescribed water-cementitious materials ratio can also be added. After such additions, the contents must be thoroughly mixed, 2 to 3 min at high speed. Because placing-point adjustments are inconvenient and costly, telephone or radio communication with the supply plant is desirable so that most such adjustments may be made conveniently at the plant.

Commonly, a lesser degree of control is accepted in which the truck carries water, the driver is on the honor system not to add water without written authorization from a responsible agent at the site, and the authorization as well as the amounts added are recorded on the record (trip ticket) of batch weights.

Note: If site adjustments are made, test samples for strength-test specimens should be taken only after all site adjustments. For concrete in critical areas, such as lower-floor columns in high-rise buildings, strictest quality control is recommended.

CHECK TESTS OF MATERIALS

2007-06-28T23:22:00.000-07:00

Without follow-up field control, all the statistical theory involved in mixed proportioning becomes an academic exercise.
The complete description of initial proportions should include: cement analysis and source; specific gravity, absorption, proportions of each standard sieve size; fineness modulus; and organic tests for fine and coarse aggregates used, as well as their weights and maximum nominal sizes.
If the source of any aggregate is changed, new trial batches should be made. A cement analysis should be obtained for each new shipment of cement. The aggregate gradings and organic content should be checked at least daily, or for each 150 yd3. The moisture content (or slump) should be checked continuously for all aggregates, and suitable adjustments should be made in batch weights. When the limits of ASTM C33 or C330 for grading or organic content are exceeded, proper materials should be secured and new mix proportions developed, or until these measurements can be effected, concrete production may continue on an emergency basis but with a penalty of additional cement.

ADMIXTURES

2007-06-28T23:12:00.000-07:00

The ACI 318 Building Code requires prior approval by the engineer of admixtures to be used in concrete.
Air Entrainment. Air-entraining admixtures (ASTM C260) may be interground as additives with the cement at the mill or added separately at the concrete mixing plant, or both. Where quality control is provided, it is preferable to add such admixtures at the concrete plant so that the resulting air content can be controlled for changes in temperature, sand, or project requirements.
Use of entrained air is recommended for all concrete exposed to weathering or deterioration from aggressive chemicals. The ACI 318 Building Code requires air entrainment for all concrete subject to freezing temperatures while wet. Detailed recommendations for air content are available in ‘‘Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete,’’ ACI 211.1, and ‘‘Standard Practice for Selecting Proportions for Structural Lightweight Concrete,’’ ACI 211.2.
One common misconception relative to air entrainment is the fear that it has a deleterious effect on concrete strength. Air entrainment, however, improves workability. This will usually permit some reduction in water content. For lean, lowstrength mixes, the improved workability permits a relatively large reduction in water content, sand content, and water-cementitious materials ratio, which tends to increase concrete strength. The resulting strength gain offsets the strength-reducing effect of the air itself, and a net increase in concrete strength is achieved. For rich, high-strength mixes, the relative reduction in the ratio of water to cementitious materials, water-cementitious materials ratio, is lower and a small net decrease in strength results, about on the same order of the air content (4 to 7%). The improved durability and reduction of segregation in handling, because of the entrained air, usually make air entrainment desirable, however, in all concrete except extremely high-strength mixtures, such as for lower-story interior columns or heavy-duty interior floor toppings for industrial wear.
Accelerators. Calcium chloride for accelerating the rate of strength gain in concrete (ASTM D98) is perhaps the oldest application of admixtures. Old specifications for winter concreting or masonry work commonly required use of a maximum of 1 to 3% CaCl2 by weight of cement for all concrete. Proprietary admixtures now available may include accelerators, but not necessarily CaCl2. The usual objective for use of an accelerator is to reduce curing time by developing 28-day strengths in about 7 days (ASTM C494).
In spite of users’ familiarity with CaCl2, a number of misconceptions about its effect persist. It has been sold (sometimes under proprietary names) as an accelerator, a cement replacement, an ‘‘antifreeze,’’ a ‘‘waterproofer,’’ and a ‘‘hardener.’’ It is simply an accelerator; any improvement in other respects is pure serendipity.
Experience, however, indicates corrosion damage from indiscriminate use of chloride-containing material in concrete exposed to stray currents, containing dissimilar metals, containing prestressing steel subject to stress corrosion, or exposed to severe wet freezing or salt water. The ACI 318 Building Code prohibits the use of calcium chloride or admixtures containing chloride from other than impurities from admixture ingredients in prestressed concrete, in concrete containing embedded aluminum, or in concrete cast against stay-in-place galvanized forms. The Code also prohibits the use of calcium chloride as an admixture in concrete that will be exposed to severe or very severe sulfate-containing solutions. For further information, see ‘‘Chemical Admixtures for Concrete,’’ ACI 212.3R.
Retarders. Unless proper precautions are taken, hot-weather concreting may cause ‘‘flash set,’’ plastic shrinkage, ‘‘cold joints,’’ or strength loss. Admixtures that provide controlled delay in the set of a concrete mix without reducing the rate of strength gain during subsequent curing offer inexpensive prevention of many hotweather concreting problems. These (proprietary) admixtures are usually combined with water-reducing admixtures that more than offset the loss in curing time due to delayed set (ASTM C494). See ‘‘Hot Weathering Concreting,’’ ACI 305R, for further details on retarders, methods of cooling concrete materials, and limiting temperatures for hot-weathering concreting.
Superplasticizers. These admixtures, which are technically known as ‘‘high-range water reducers,’’ produce a high-slump concrete without an increase in mixing water. Slumps of up to 10 in. for a period of up to 90 min can be obtained. This greatly facilitates placing concrete around heavy, closely spaced reinforcing steel, or in complicated forms, or both, and reduces the need for vibrating the concrete. It is important that the slump of the concrete be verified at the jobsite prior to the addition of the superplasticizer. This ensures that the specified water-cementitious materials ratio required for watertight impermeable concrete is in fact being
achieved. The superplasticizer is then added to increase the slump to the approved level.
Waterproofing. A number of substances, such as stearates and oils, have been used as masonry-mortar and concrete admixtures for ‘‘waterproofing.’’ Indiscriminate use of such materials in concrete without extremely good quality control usually results in disappointment. The various water-repellent admixtures are intended to prevent capillarity, but most severe leakage in concrete occurs at honeycombs, cold joints, cracks, and other noncapillary defects. Concrete containing waterrepellent admixtures also requires extremely careful continuous curing, since it will be difficult to rewet after initial drying.
Waterproof concrete can be achieved by use of high-strength concrete with a low water-cementitious materials ratio to reduce segregation and an air-entraining agent to minimize crack width. Also, good quality control and inspection is essential during the mixing, placing, and curing operations. Surface coatings can be used to improve resistance to water penetration of vertical or horizontal surfaces. For detailed information on surface treatments, see ‘‘Guide to Durable Concrete,’’ ACI 201.2R.
Cement Replacement. The term ‘‘cement replacement’’ is frequently misused in reference to chemical admixtures intended as accelerators or water reducers. Strictly, a cement replacement is a finely ground material, usually weakly cementitious (Art. 9.1), which combines into a cementlike paste replacing some of the cement paste to fill voids between the aggregates. The most common applications of these admixtures are for low-heat, low-strength mass concrete or for concrete masonry. In the former, they fill voids and reduce the heat of hydration; in the latter, they fill voids and help to develop the proper consistency to be self-standing as the machine head is lifted in the forming process. Materials commonly used are fly ash, silica fume, ground granulated blast-furnace slag, hydraulic lime, natural cement, and pozzolans.
Special-Purpose Admixtures. The list of materials used from earliest times as admixtures for various purposes includes almost everything from human blood to synthetic coloring agents. Admixtures for coloring concrete are available in all colors. The oldest and cheapest is perhaps carbon black. Admixtures causing expansion for use in sealing cracks or under machine bases, etc., include powdered aluminum and finely ground iron.
Special admixtures are available for use where the natural aggregate is alkali reactive, to neutralize this reaction. Proprietary admixtures are available that increase the tensile strength or bond strength of concrete. They are useful for making repairs to concrete surfaces. For special problems requiring concrete with unusual properties, detailed recommendations of ‘‘Chemical Admixtures for Concrete,’’ ACI 212.3R, and references it contains, may be helpful.
For all these special purposes, a thorough investigation of admixtures proposed is recommended. Tests should be made on samples containing various proportions for colored concrete. Strength and durability tests should be made on concrete to be exposed to sunlight, freezing, salt, or any other job condition expected, and special tests should be made for any special properties required, as a minimum precaution.

MEASURING AND MIXING CONCRETE INGREDIENTS

2007-06-27T05:07:00.000-07:00

Methods of measuring the quantities and mixing the ingredients for concrete, and the equipment available, vary greatly. For very small projects where mixing is performed on the site, the materials are usually batched by volume. Under these conditions, accurate proportioning is very difficult. To achieve a reasonable minimum quality of concrete, it is usually less expensive to prescribe an excess of cement than to employ quality control. The same conditions make use of airentraining cement preferable to separate admixtures. This practical approach is preferable also for very small projects to be supplied with ready-mixed concrete. Economy with excess cement will be achieved whenever volume is so small that the cost of an additional sack of cement per cubic yard is less than the cost of a single compression test.
For engineered construction, some measure of quality control is always employed. In general, all measurements of materials including the cement and water should be by weight. The ACI 318 Building Code provides a sliding scale of
overdesign for concrete mixes that is inversely proportional to the degree of quality control provided. In the sense used here, such overdesign is the difference between the specified and the actual average strength as measured by tests. Mixing and delivery of structural concrete may be performed by a wide variety of equipment and procedures:
Site mixed, for delivery by chute, pump, truck, conveyor, or rail dump cars. (Mixing procedure for normal-aggregate concretes and lightweight-aggregate concretes to be pumped are usually different, because the greater absorption of some lightweight aggregates must be satisfied before pumping.)
Central-plant mixed, for delivery in either open dump trucks or mixer trucks. Central-plant batching (weighing and measuring), for mixing and delivery by truck (‘‘dry-batched’’ ready mix).
Complete portable mixing plants are available and are commonly used for large building or paving projects distant from established sources of supply.
Generally, drum mixers are used. For special purposes, various other types of mixers are required. These special types include countercurrent mixers, in which the blades revolve opposite to the turning of the drum, usually about a vertical axis, for mixing very dry, harsh, nonplastic mixes. Such mixes are required for concrete masonry or heavy-duty floor toppings. Dry-batch mixers are used for dry shotcrete (sprayed concrete), where water and the dry-mixed cement and aggregate are blended between the nozzle of the gun and impact at the point of placing.
(‘‘Guide for Measuring, Mixing, Transporting, and Placing Concrete,’’ ACI
304R.)

PROPERTIES AND TESTS OF FRESH (PLASTIC) CONCRETE

2007-06-26T06:12:00.000-07:00

About 21⁄2 gal of water can be chemically combined with each 94-lb sack of cement for full hydration and maximum strength. Water in excess of this amount will be required, however, to provide necessary workability.
Workability
Although concrete technologists define and measure workability and consistency separately and in various ways, the practical user specifies only one—slump (technically a measure of consistency). The practical user regards workability requirements simply as provision of sufficient water to permit concrete to be placed and consolidated without honeycomb or excessive water rise; to make concrete ‘‘pumpable’’ if it is to be placed by pumps; and for slabs, to provide a surface that can be finished properly. These workability requirements vary with the project and the placing, vibration, and finishing equipment used.
Slump is tested in the field very quickly. An open-ended, 12-in-high, truncated metal cone is filled in three equal-volume increments and each increment is consolidated separately, all according to a strict standard procedure (ASTM C143, ‘‘Slump of Hydraulic-Cement Concrete’’). Slump is the sag of the concrete, in, after the cone is removed. The slump should be measured to the nearest 1⁄4 in which is about the limit of accuracy reproducible by expert inspectors. Unless the test is performed exactly in accordance with the standard procedure, the results are not comparable and therefore are useless.
The slump test is invalidated if: the operator fails to anchor the cone down by standing on the base wings; the test is performed on a wobbly base, such as formwork carrying traffic or a piece of metal on loose pebbles; the cone is not filled by inserting material in small amounts all around the perimeter, or filled and tamped in three equal increments; the top two layers are tamped deeper than their depth plus about 1 in; the top is pressed down to level it; the sample has been transported and permitted to segregate without remixing; unspecified operations, such as tapping the cone, occur; the cone is not lifted up smoothly in one movement; the cone tips over because of filling from one side or pulling the cone to one side; or if the measurement of slump is not made to the center vertical axis of the cone. Various penetration tests are quicker and more suitable for untrained personnel than the standard slump test. In each case, the penetration of an object into a flat surface of fresh concrete is measured and related to slump. These tests include use of the patented ‘‘Kelley ball’’ (ASTM C360, ‘‘Ball Penetration in Freshly Mixed
Hydraulic Cement Concrete’’) and a simple, standard tamping rod with a bullet nose marked with equivalent inches of slump.
Air Content
A field test frequently required measures the air entrapped and entrained in fresh concrete. Various devices (air meters) that are available give quick, convenient results. In the basic methods, the volume of a sample is measured, then the air content is removed or reduced under pressure, and finally the remaining volume is measured. The difference between initial and final volume is the air content. (See ASTM C138, C173, and C231.)
Cement Content. Tests on fresh concrete sometimes are employed to determine the amount of cement present in a batch. Although performed more easily than tests on hardened concrete, tests on fresh concrete nevertheless are too difficult for routine use and usually require mobile laboratory equipment.

YIELD CALCULATION

2007-06-26T06:08:00.000-07:00

Questions often arise between concrete suppliers and buyers regarding ‘‘yield,’’ or volume of concrete supplied. A major reason for this is that often the actual yield may be less than the yield calculated from the volumes of ingredients. For example, if the mix temperature varies, less air may be entrained; or if the sand becomes drier and no corrections in batch weights are made, the yield will be under that calculated.
If the specific gravity (sp. gr.) and absorption (abs.) of the aggregates have been determined in advance, accurate, yield calculations can be performed as often as necessary to adjust the yield for control of the concrete.

PROPORTIONING CONCRETE MIXES

2007-06-26T05:35:00.000-07:00

Principles for proportioning concrete to achieve a prescribed compressive strength after a given age under standard curing are simple.
1. The strength of a hardened concrete mix depends on the water-cementitious materials ratio (ratio of water to cementitious materials, by weight). The water and cementitious materials form a paste. If the paste is made with more water, it becomes weaker.
2. The ideal minimum amount of paste is that which will coat all aggregate particles and fill all voids.
3. For practical purposes, fresh concrete must possess workability sufficient for the placement conditions. For a given strength and with given materials, the cost of the mix increases as the workability increases. Additional workability is provided by more fine aggregate and more water, but more cementitious materials must also be added to keep the same water-cementitious materials ratio.

AGGREGATES

2007-06-26T05:08:00.000-07:00

Only material conforming to specifications for normal-weight aggregate (ASTM C33) or lightweight aggregate for structural concrete (ASTM C330) is accepted under the ACI 318 Building Code without special tests. When an aggregate for which no experience record is available is considered for use, the modulus of elasticity and shrinkage as well as the compressive strength should be determined from trial batches of concrete made with the aggregate. In some localities, aggregates acceptable under C33 or C330 may impart abnormally low ratios of modulus of elasticity of strength (Ec /ƒc) or high shrinkage to concrete. Such aggregates should not be used.

CEMENTS

2007-06-26T05:06:00.000-07:00

The ACI 318 Building Code requires cement to conform to ASTM C150, ‘‘Standard Specification for Portland Cement;’’ or ASTM C595, ‘‘Standard Specification for Blended Hydraulic Cements;’’ or ASTM C845, ‘‘Standard Specification for Expansive Hydraulic Cement.’’ Portland cements meeting the requirements of ASTM C150 are available in Types I to V and air-entraining Types IA to IIIA for use under different service conditions. The ACI 318 Building Code prohibits the use of slag cement, Types A and SA (ASTM C595), because these types are not intended as principal cementing constituents of structural concrete.
Although all the preceding cements can be used for concrete, they are not interchangeable. Note that both tensile and compressive strengths vary considerably, at early ages in particular, even for the five types of basic portland cement. Consequently, although project specifications for concrete strength are usually based ƒc on a standard 28-day age for the concrete, the proportions of ingredients required differ for each type. For concrete strengths up to 19,000 psi for columns in highrise buildings, specified compressive strengths are usually required at 56 days after initial set of the concrete. For the usual building project, where the load-strength
relationship is likely to be critical at a point in strength gain equivalent to 7-day standard curing (Fig. 9.1), substitution of a different type (sometimes brand) of cement without reproportioning the mix may be dangerous.
The accepted specifications (ASTM) for cements do not regulate cement temperature nor color. Nevertheless, in hot-weather concreting, the temperature of the fresh concrete and therefore of its constituents must be controlled. Cement temperatures above 170F are not recommended (‘‘Hot Weathering Concreting,’’ ACI 305R).
For exposed architectural concrete, not intended to be painted, control of color is desirable. For uniform color, the water-cement ratio and cement content must be kept constant, because they have significant effects on concrete color. Bear in mind that because of variations in the proportions of natural materials used, cements from different sources differ markedly in color. A change in brand of cement therefore can cause a change in color. Color differences also provoke a convenient check for substitution of types (or brands) of cement different from those used in trial batches made to establish proportions to be employed for a building.

PROFESSIONAL AND BUSINESS REQUIREMENTS OF ARCHITECTS AND ENGINEERS

2007-06-22T04:59:00.000-07:00

Management of the building process is best performed by the individuals educated and trained in the profession, that is, architects and engineers. While the laws of various states and foreign countries differ, they are consistent relative to the registration requirements for practicing architecture. No individual may legally indicate to the public that he or she is entitled to practice as an architect without a professional certificate of registration as an architect registered in the locale in which the project is to be constructed. This individual is the registered architect. In addition to the requirements for individual practice of architecture, most states and countries require a certificate of registration for a single practitioner and a certificate of authorization for an entity such as a corporation or partnership to conduct business in that locale.

An architect is a person who is qualified by education, training, experience, and examination and who is registered under the laws of the locale to practice architecture there. The practice of architecture within the meaning and intent of the law includes:

Offering or furnishing of professional services such as environmental analysis, feasibility studies, programming, planning, and aesthetic and structural design Preparation of construction documents, consisting of drawings and specifications, and other documents required in the construction process Administration of construction contracts and project representation in connection with the construction of building projects or addition to, alteration of, or restoration of buildings or parts of building.

All documents intended for use in construction are required to be prepared and administered in accordance with the standards of reasonable skill and diligence of the profession. Care must be taken to reflect the requirements of country and state statutes and county and municipal building ordinances. Inasmuch as architects are licensed for the protection of the public health, safety, and welfare, documents prepared by architects must be of such quality and scope and be so administered as to conform to professional standards.

Nothing contained in the law is intended to prevent drafters, students, project representatives, and other employees of those lawfully practicing as registered architects from acting under the instruction, control, or supervision of their employers, or to prevent employment of project representatives from acting under the immediate personal supervision of the registered architect who prepared the construction documents.

Formwork

2007-06-22T04:56:00.000-07:00

Formwork is the surface, supports and framing used to define the shape of concrete until the concrete is self-supporting: (see AS3610 Formwork for Concrete).

‘Formwork’ includes:
• the forms on which concrete is poured;
• the supports to withstand the loads imposed by the forms and concrete; and
• any bracing added to ensure stability.
Together these components make the formwork assembly. Hazards associated with work involving the erection, alteration and/or dismantling of formwork include:
• formwork collapse (before, during and after placement of concrete);
• falls from heights;
• slips and trips;
• falling objects ;
• noise;
• dust; and
• manual tasks.
To properly manage risks, a person must
• identify hazards; and
• assess risks that may result because of the hazards; and
• decide on control measures to prevent, or minimise the level of, the risks; and
• implement control measures; and
• monitor and review the effectiveness of the measures.
Control measures must be implemented in an order of priority and implemented before work commences. The following example illustrates the order of priority where there is a risk a person could fall.

GUIDELINES ON FALSEWORK/FORMWORK

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This guideline has been developed to provide information to engineers; contractors and others involved in the design, erection and use of false work and Formwork. For specific regulatory requirements regarding false work and framework, please consult the Construction Safety Regulations, adopted under the Workplace Safety and Health Act.

Engineering Design Requirements
Contractors must determine if form work/false work that is to be used on a project requires design work by an engineer. The following types of concrete Formwork and false work require the provision at the job-site of design and erection drawings and necessary supplementary information signed and sealed by a professional engineer.

Some engineers may choose to design only the Support false work portion of a form work system or a specific portion of the whole project. This must be made clear to contractors and so specified in all relevant drawings and documents. Statements such as "THIS IS NOT A FORMWORK DRAWING REQUIRED BY W.S.H. MR 189/85 “ written in the large print of a drawing should prevent the possibility of any misunderstanding. False work and Formwork design drawings need not be submitted to the Branch for approval or retention, but must be available at the project site.
The design engineer must authorize any revisions or changes to a false work structure. The engineer should ensure that written authorization is immediately available at the job-site, to be followed by proper documentation as soon as practicable.

Codes and Standards
CSA Standard S269.1 "False work for Construction Purposes" deals only with the design and erection of false work and specifically excludes forms.
The practice of noting on the drawings: "FORMWORK IS THE RESPONSIBILITY OF CONTRACTORS," or "BLOCKING BY OTHERS," is not acceptable. Form work designers are
expected to show details of forms and all associated connections, blocking, braces and ties that
are necessary to ensure form work integrity during erection and concrete placement.
The CSA Standards 086, S16, S157 and A23 continue to provide the basis for Formwork
compliance. ACI Sp4 and ACI Standard 347 are recommended as reference and guides for form
work designers.
Where there are discrepancies between the regulations and the standards, the overriding or
qualifying requirements of the regulations prevail.

Design Recommendations for Precast Concrete Structures

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In design of precast members and connections, ail loading and restraint conditions from casting to end use of the structure should be considered. The stresses developed in precast elements during the period from casting to final connection may be more critical than the service load stresses. Special attention should be given to the methods of stripping, storing, transporting, and erecting precast elements.

When precast members are incorporated into a structural system, the forces and deformations occurring in and adjacent to connections (in adjoining members and in the entire structure) should be considered. The structural behavior of precast elements may differ substantially from that of similar members that are monolithically cast in place. Design of connections to transmit forces due to shrinkage, creep, temperature change, elastic deformation, wind forces, and earthquake forces require special attention. Details of such connections are especially important to insure adequate performance of precast structures.

Precast members and connections should be designed to meet tolerance requirements. The behavior of precast members and connections is sensitive to tolerances. Design should provide for the effects of adverse combinations of fabrication and erection tolerances. Tolerance requirements should be listed on contract documents, and may be specified by reference to accepted standards. Tolerances that deviate from accepted standards should be so indicated.

All details of reinforcement, connections, bearing elements, inserts, anchors, concrete cover, openings and lifting devices, and specified strength of concrete at critical stages of fabrication and construction, should be shown on either the contract documents prepared by the architecilengineer of record or on the shop drawings furnished by the contractor. Whether this information is to be shown on the contract documents or shop drawings depends on the provisions of the contract documents. The shop drawings should show, as a minimum, all details of the precast concrete members and embedded items. The contract documents may specify that portions of connections exterior to the member are also to be shown on the shop drawings. The contract documents may also require the contractor to provide designs for the members
and/or connections.

BUILDING SYSTEM : ZONING CODES

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Like building codes, zoning codes are established under the police powers of the state, to protect the health, welfare, and safety of the public. Zoning, however, primarily regulates land use by controlling types of occupancy of buildings, building height, and density and activity of population in specific parts of a jurisdiction.

Zoning codes are usually developed by a planning commission and administered by the commission or a building department. Land-use controls adopted by the local planning commission for current application are indicated on a zoning map. It divides the jurisdiction into districts, shows the type of occupancy, such as commercial, industrial, or residential, permitted in each district, and notes limitations on building height and bulk and on population density in each district.

The planning commission usually also prepares a master plan as a guide to the growth of the jurisdiction. A future land-use plan is an important part of the master plan. The commission’s objective is to steer changes in the zoning map in the direction of the future land-use plan. The commission, however, is not required to adhere rigidly to the plans for the future. As conditions warrant, the commission may grant variances from any of the regulations.

In addition, the planning commission may establish land subdivision regulations, to control development of large parcels of land. While the local zoning map specifies minimum lot area for a building and minimum frontage a lot may have along a street, subdivision regulations, in contrast, specify the level of improvements to be installed in new land-development projects. These regulations contain criteria for location, grade, width, and type of pavement of streets, length of blocks, open spaces to be provided, and right of way for utilities.

A jurisdiction may also be divided into fire zones in accordance with population density and probable degree of danger from fire. The fire-zone map indicates the limitations on types of construction that the zoning map would otherwise permit.

In the vicinity of airports, zoning may be applied to maintain obstruction-free approach zones for aircraft and to provide noise-attenuating distances around the airports. Airport zoning limits building heights in accordance with distance from the airport.

Control of Building Height. Zoning places limitations on building dimensions to limit population density and to protect the rights of occupants of existing buildings to light, air, and esthetic surroundings. Various zoning ordinances achieve these objectives in a variety of ways, including establishment of a specific maximum height or number of stories, limitation of height in accordance with street width, setting minimums for distances of buildings from lot lines, or relating total floor area in a building to the lot area or to the area of the lot occupied by a building.

Some zoning ordinances, however, permit an alternative that many designers prefer. If the building is set back from the lot lines at the base to provide a streetlevel plaza, which is a convenience to the public and reduces building bulk, zoning permits the building to be erected as a sheer tower The code may set a maximum floor-area ratio of 15 or 18, depending on whether the floor area at any level of the tower does not exceed 50 or 40%, respectively, of the lot area.

BUILDING SYSTEM : TRADITIONAL DESIGN PROCEDURES

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Systems design of buildings requires a different approach to design and construction than that used in traditional design. Because traditional design and construction procedures are still widely used, however, it is desirable to incorporate as much of those procedures in systems design as is feasible without destroying its effectiveness. This will make the transition from traditional design to systems design easier. Also, those trained in systems design of buildings will then be capable of practicing in traditional ways, if necessary. There are several variations of traditional design and construction. These are described throughout this book. For the purpose of illustrating how they may be modified for systems design, however, one widely used variation, which will be called basic traditional design and construction, is described in the following.

In the basic traditional design procedure, design usually starts when a client recognizes the need for and economic feasibility of a building and engages an architect, a professional with a broad background in building design. The architect, in turn, engages consulting engineers and other consultants. For most buildings, structural, mechanical, and electrical consulting engineers are required. A structural engineer is a specialist trained in the application of scientific principles to the design of load-bearing walls, floors, roofs, foundations, and skeleton framing needed for the support of buildings and building components. A mechanical engineer is a specialist trained in the application of scientific principles to the design of plumbing, elevators, escalators, horizontal walkways, dumbwaiters, conveyors, installed machinery, and heating, ventilation, and air conditioning. An electrical engineer is a specialist trained in the application of scientific principles to the design of electric circuits, electric controls and safety devices, electric motors and generators, electric lighting, and other electric equipment.

For buildings on a large site, the architect may engage a landscape architect as a consultant. For a concert hall, an acoustics consultant may be engaged; for a hospital, a hospital specialist; for a school, a school specialist. The architect does the overall planning of the building and incorporates the output of the consultants into the contract documents. The architect determines what internal and external spaces the client needs, the sizes of these spaces, their relative locations, and their interconnections. The results of this planning are shown in floor plans, which also diagram the internal flow, or circulation, of people and supplies.

Major responsibilities of the architect are enhancement of the appearance inside and outside of the building and keeping adverse environmental impact of the structure to a minimum. The exterior of the building is shown in drawings, called elevations.

The location and orientation of the building is shown in a site plan. The architect also prepares the specifications for the building. These describe in detail the materials and equipment to be installed in the structure. In addition, the architect, usually with the aid of an attorney engaged by the client, prepares the construction contract.

The basic traditional design procedure is executed in several stages. In the first stage, the architect develops a program, or list of the client’s requirements. In the next stage, the schematic or conceptual phase, the architect translates requirements into spaces, relates the spaces and makes sketches, called schematics, to illustrate the concepts. When sufficient information is obtained on the size and general construction of the building, a rough estimate is made of construction cost. If this cost does not exceed the cost budgeted by the client for construction, the next stage, design development, proceeds. In this stage, the architect and consultants work out more details and show the results in preliminary construction drawings and outline specifications. A preliminary cost estimate utilizing the greater amount of information on the building now available is then prepared. If this cost does not exceed the client’s budget, the final stage, the contract documents phase, starts. It culminates in production of working, or construction, drawings and specifications, which are incorporated in the contract between the client and a builder and therefore

become legal documents. Before the documents are completed, however, a final cost estimate is prepared. If the cost exceeds the client’s budget, the design is revised to achieve the necessary cost reduction.

In the traditional design procedure, after the estimated cost is brought within the budget and the client has approved the contract documents, the architect helps the owner in obtaining bids from contractors or in negotiating a construction price with a qualified contractor. For private work, construction not performed for a governmental agency, the owner generally awards the construction contract to a contractor, called a general contractor. Assigned the responsibility for construction of the building, this contractor may perform some, all, or none of the work. Usually, much of the work is let out to specialists, called subcontractors. For public work, there may be a legal requirement that bids be taken and the contract awarded to the lowest responsible bidder. Sometimes also, separate contracts have to be awarded for the major specialists, such as mechanical and electrical trades, and to a general contractor, who is assigned responsibility for coordinating the work of the trades and performance of the work.

Building design should provide for both normal and emergency conditions. The latter includes fire, explosion, power cutoffs, hurricanes, and earthquakes. The design should include access and facilities for disabled persons.

BUILDING SYSTEM : TRADITIONAL CONSTRUCTION PROCEDURES

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Construction under the traditional construction procedure is performed by contractors. While they would like to satisfy the owner and the building designers, contractors have the main objective of making a profit. Hence, their initial task is to prepare a bid price based on an accurate estimate of construction costs. This requires development of a concept for performance of the work and a construction time schedule. After a contract has been awarded, contractors must furnish and pay for all materials, equipment, power, labor, and supervision required for construction. The owner compensates the contractors for construction costs and services.

A general contractor assumes overall responsibility for construction of a building. The contractor engages subcontractors who take responsibility for the work of the various trades required for construction. For example, a plumbing contractor installs the plumbing, an electrical contractor installs the electrical system, a steel erector structural steel, and an elevator contractor installs elevators. Their contracts are with the general contractor, and they are paid by the general contractor.

Sometimes, in addition to a general contractor, the owners contracts separately with specialty contractors, such as electrical and mechanical contractors, who perform a substantial amount of the work required for a building. Such contractors are called prime contractors. Their work is scheduled and coordinated by the general contractor, but they are paid directly by the owner.

Sometimes also, the owner may use the design-build method and award a contract to an organization for both the design and construction of a building. Such organizations are called design-build contractors. One variation of this type of contract is employed by developers of groups of one-family homes or low-rise apartment buildings. The homebuilder designs and constructs the dwellings, but the design is substantially completed before owners purchase the homes.

Administration of the construction procedure often is difficult. Consequently, some owners seek assistance from an expert, called a professional construction manager, with extensive construction experience, who receives a fee. The construction manager negotiates with general contractors and helps select one to construct the building. Managers usually also supervise selection of subcontractors. During construction, they help control costs, expedite equipment and material deliveries, and keep the work on schedule. In some cases, instead, the owner may prefer to engage a construction program manager, to assist in administrating both design and construction.

Construction contractors employ labor that may or may not be unionized. Unionized craftspeople are members of unions that are organized by construction trades, such as carpenter, plumber, and electrician unions. Union members will perform only the work assigned to their trade. On the job, groups of workers are supervised by crew supervisors, all of whom report to a superintendent.

During construction, all work should be inspected. For this purpose, the owner, often through the architect and consultants, engages inspectors. The field inspectors may be placed under the control of an owner’s representative, who may be titled clerk of the works, architect’s superintendent, engineer’s superintendent, or resident engineer. The inspectors have the responsibility of ensuring that construction meets the requirements of the contract documents and is performed under safe conditions. Such inspections may be made at frequent intervals.

In addition, inspections also are made by representatives of one or more governmental agencies. They have the responsibility of ensuring that construction meets legal requirements and have little or no concern with detailed conformance with the contract documents. Such legal inspections are made periodically or at the end of certain stages of construction. One agency that will make frequent inspections

is the local or state building department, whichever has jurisdiction. The purpose of these inspections is to ensure conformance with the local or state building code. During construction, standards, regulations, and procedures of the Occupational Safety and Health Administration should be observed. These are given in detail in ‘‘Construction Industry. OSHA Safety and Health Standards (29CFR1926/1910),’’ Government Printing Office, Washington, DC 20402.

Following is a description of the basic traditional construction procedure for a multistory building:

After the award of a construction contract to a general contractor, the owner may ask the contractor to start a portion of the work before signing of the contract by giving the contractor a letter of intent or after signing of the contract by issuing a written notice to proceed. The contractor then obtains construction permits, as required, from governmental agencies, such as the local building, water, sewer, and highway departments. The general contractor plans and schedules construction operations in detail and mobilizes equipment and personnel for the project. Subcontractors are notified of the contract award and issued letters of intent or awarded subcontracts, then are given, at appropriate times, notices to proceed.

Before construction starts, the general contractor orders a survey to be made of adjacent structures and terrain, both for the record and to become knowledgeable of local conditions. A survey is then made to lay out construction.

Field offices for the contractor are erected on or near the site. If desirable for safety reasons to protect passersby, the contractor erects a fence around the site and an overhead protective cover, called a bridge. Structures required to be removed from the site are demolished and the debris is carted away.

Next, the site is prepared to receive the building. This work may involve grading the top surface to bring it to the proper elevations, excavating to required depths for basement and foundations, and shifting of utility piping. For deep excavations, earth sides are braced and the bottom is drained.

Major construction starts with the placement of foundations, on which the building rests. This is followed by the erection of load-bearing walls and structural framing. Depending on the height of the building, ladders, stairs, or elevators may be installed to enable construction personnel to travel from floor to floor and eventually to the roof. Also, hoists may be installed to lift materials to upper levels. If needed, temporary flooring may be placed for use of personnel.

As the building rises, pipes, ducts, and electric conduit and wiring are installed.

Then, permanent floors, exterior walls, and windows are constructed. At the appropriate time, permanent elevators are installed. If required, fireproofing is placed for steel framing. Next, fixed partitions are built and the roof and its covering, or roofing, are put in place.

Finishing operations follow. These include installation of the following: ceilings; tile; wallboard; wall paneling; plumbing fixtures; heating furnaces; air-conditioning equipment; heating and cooling devices for rooms; escalators; floor coverings; window glass; movable partitions; doors; finishing hardware; electrical equipment and apparatus, including lighting fixtures, switches, outlets, transformers, and controls; and other items called for in the drawings and specifications. Field offices, fences, bridges, and other temporary construction must be removed from the site. Utilities, such as gas, electricity, and water, are hooked up to the building. The site is landscaped and paved. Finally, the building interior is painted and cleaned.

The owner’s representatives then give the building a final inspection. If they find that the structure conforms with the contract documents, the owner accepts the project and gives the general contractor final payment on issuance by the building department of a certificate of occupancy, which indicates that the completed building meets building-code requirements.

BUILDING SYSTEM : SYSTEMS DESIGN AND ANALYSIS

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Systems design comprises a logical series of steps that leads to the best decision for a given set of conditions. The procedure requires:

Analysis of a building as a system.

Synthesis, or selection of components, to form a system that meets specific objectives while subject to constraints, or variables controllable by designers.

Appraisal of system performance, including comparisons with alternative systems.

Feedback to analysis and synthesis of information obtained in system evaluation, to improve the design.

The prime advantage of the procedure is that, through comparisons of alternatives and data feedback to the design process, systems design converges on an optimum, or best, system for the given conditions. Another advantage is that the procedure enables designers to clarify the requirements for the building being designed.

Still another advantage is that the procedure provides a common basis of understanding and promotes cooperation between the specialists in various aspects of building design.

For a building to be treated as a system, as required in systems design, it is necessary to know what a system is and what its basic characteristic are.

A system is an assemblage formed to satisfy specific objectives and subject to constraints and restrictions and consisting of two or more components that are interrelated and compatible, each component being essential to the required performance of the system.

Because the components are required to be interrelated, operation, or even the mere existence, of one component affects in some way the performance of other components. Also, the required performance of the system as a whole, as well as the constraints on the system, imposes restrictions on each component.

A building meets the preceding requirements. By definition, it is an assemblage. It is constructed to serve specific purposes. It is subject to constraints while doing so, inasmuch as designers can control properties of the system by selection of components. Building components, such as walls, floors, roofs, windows, and doors, are interrelated and compatible with each other. The existence of any of thee components affects to some extent the performance of the others. And the required performance of the building as a whole imposes restrictions on the components. Consequently, a building has the basic characteristics of a system, and systems-design procedures should be applicable to it.

Systems Analysis. A group of components of a system may also be a system. Such a group is called a subsystem. It, too, may be designed as a system, but its goal must be to assist the system of which it is a component to meet its objectives. Similarly, a group of components of a subsystem may also be a system. That group is called a subsubsystem.

For brevity, the major subsystems of a building are referred to as systems in this

book. In a complex system, such as a building, subsystems and other components may be combined in a variety of ways to form different systems. For the purposes of

building design, the major systems are usually defined in accordance with the construction trades that will assemble them, for example, structural framing, plumbing, electrical systems, and heating, ventilation, and air conditioning. In systems analysis, a system is resolved into its basic components. Subsystems are determined. Then, the system is investigated to determine the nature, interaction, and performance of the system as a whole. The investigation should answer such questions as:

What does each component (or subsystem) do?

What does the component do it to?

How does the component serve its function?

What else does the component do?

Why does the component do the things it does?

What must the component really do?

Can it be eliminated because it is not essential or because another component

can assume its tasks?

BUILDING SYSTEM : ROLE OF THE CLIENT IN DESIGN AND CONSTRUCTION

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Administration of building construction is difficult, as a result of which some clients, or owners, engage a construction manager or construction program manager to act as the owner’s authorizing agent and project overseer. The reasons for the complexity of construction administration can be seen from an examination of the owner’s role before and during construction.

After the owner recognizes the need for a new building, the owner establishes project goals and determines the economic feasibility of the project. If it appears to be feasible, the owner develops a building program (list of requirements), budget, and time schedule for construction. Next, preliminary arrangements are made to finance construction. Then, the owner selects a construction program manager or an architect for design of the building. Later, a construction manager may be chosen, if desired.

The architect may seek from the owner approval of the various consultants that will be needed for design. If a site for the building has not been obtained at this stage, the architect can assist in site selection. When a suitable site has been found, the owner purchases it and arranges for surveys and subsurface explorations to provide information for locating the building, access, foundation design and construction, and landscaping. It is advisable at this stage for the owner to start developing harmonious relations with the community in which the building will be erected.

During design, the owner assists with critical design decisions; approves schematic drawings, rough cost estimates, preliminary drawings, outline specifications, preliminary cost estimates, contract documents, and final cost estimate; pays designers’ fees in installments as design progresses; and obtains a construction loan.

Then, the owner awards the general contract for construction and orders construction to start. Also, the owner takes out liability, property, and other desirable insurance.

At the start of construction, the owner arranges for construction permits. As construction proceeds, the owner’s representatives inspect the work to ensure compliance with the contract documents. Also, the owner pays contractors in accordance with the terms of the contract. Finally, the owner approves and accepts the completed project.

One variation of the preceding procedure is useful when time available for construction is short. It is called phase, or fast-track, construction. In this variation, the owner engages a construction manager and a general contractor before design has been completed, to get an early start on construction. Work then proceeds on some parts of the building while other parts are still being designed. For example, excavation and foundation construction are carried out while design of the structural framing is being finished. The structural framing is erected, while heating, ventilation, and air-conditioning, electrical, plumbing, wall, and finishing details are being developed. For tall buildings, the lower portion can be constructed while the upper part is still being designed. For large, low-rise buildings, one section can be built while another is under design.

BUILDING SYSTEM : PRINCIPLES OF ARCHITECTURE

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A building is an assemblage that is firmly attached to the ground and that provides total or nearly total shelter for machines, processing equipment, performance of human activities, storage of human possessions, or any combination of these.

Building design is the process of providing all information necessary for construction of a building that will meet its owner’s requirements and also satisfy public health, welfare, and safety requirements. Architecture is the art and science of building design. Building construction is the process of assembling materials to form a building.

Building design may be legally executed only by persons deemed competent to do so by the state in which the building is to be constructed. Competency is determined on the basis of education, experience, and ability to pass a written test of design skills.

Architects are persons legally permitted to practice architecture. Engineers are experts in specific scientific disciplines and are legally permitted to design parts of buildings; in some cases, complete buildings. In some states, persons licensed as building designers are permitted to design certain types of buildings.

Building construction is generally performed by laborers and craftspeople engaged for the purpose by an individual or organization, called a contractor. The contractor signs an agreement, or contract, with the building owner under which the contractor agrees to construct a specific building on a specified site and the owner agrees to pay for the materials and services provided.

In the design of a building, architects should be guided by the following principles:

1. The building should be constructed to serve purposes specified by the client.

2. The design should be constructable by known techniques and with available labor and equipment, within an acceptable time.

3. The building should be capable of withstanding the elements and normal usage for a period of time specified by the client.

4. Both inside and outside, the building should be visually pleasing.

5. No part of the building should pose a hazard to the safety or health of its occupants under normal usage, and the building should provide for safe evacuation or refuge in emergencies.

6. The building should provide the degree of shelter from the elements and of control of the interior environment—air, temperature, humidity, light, and acoustics-specified by the client and not less than the minimums required for safety and health of the occupants.

7. The building should be constructed to minimize adverse impact on the environment.

8. Operation of the building should consume a minimum of energy while permitting the structure to serve its purposes.

9. The sum of costs of construction, operation, maintenance, repair, and anticipated future alterations should be kept within the limit specified by the client.

The ultimate objective of design is to provide all the information necessary for the construction of a building. This objective is achieved by the production of drawings, or plans, showing what is to be constructed, specifications stating what materials and equipment are to be incorporated in the building, and a construction contract between the client and a contractor. Designers also should observe construction of the building while it is in process. This should be done not only to assist the client in ensuring that the building is being constructed in accordance with plans and specifications but also to obtain information that will be useful in design of future buildings.

BUILDING SYSTEM : BUILDING COSTS

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Construction cost of a building usually is a dominant design concern. One reason is that if construction cost exceeds the owner’s budget, the owner may cancel the project. Another reason is that costs, such as property taxes and insurance, that occur after completion of the building often are proportional to the initial cost.

Hence, owners usually try to keep that cost low. Designing a building to minimize construction cost, however, may not be in the owner’s best interests. There are many other costs that the owner incurs during the anticipated life of the building that should be taken into account.

Before construction of a building starts, the owner generally has to make a sizable investment in the project. The major portion of this expenditure usually goes for purchase of the site and building design. Remaining preconstruction costs include those for feasibility studies, site selection and evaluation, surveys, and program definition.

The major portion of the construction cost is the sum of the payments to the general contractor and prime contractors. Remaining construction costs usually consist of interest on the construction loan, permit fees, and costs of materials, equipment, and labor not covered by the construction contracts.

The initial cost to the owner is the sum of preconstruction, construction, and occupancy costs. The latter covers costs of moving possessions into the building and start-up of utility services, such as water, gas, electricity, and telephone.

After the building is occupied, the owner incurs costs for operation and maintenance of the buildings. Such costs are a consequence of decisions made during building design.

Often, preconstruction costs are permitted to be high so that initial costs can be kept low. For example, operating the building may be expensive because the design makes artificial lighting necessary when daylight could have been made available or because extra heating and air conditioning are necessary because of inadequate insulation of walls and roof. As another example, maintenance may be expensive because of the difficulty of changing electric lamps or because cleaning the building is time-consuming and laborious. In addition, frequent repairs may be needed because of poor choice of materials during design. Hence, operation and maintenance costs over a specific period of time, say 10 or 20 years, should be taken into account in optimizing the design of a building.

Life-cycle cost is the sum of initial, operating, and maintenance costs. Generally, it is life-cycle cost that should be minimized in building design rather than construction cost. This would enable the owner to receive the greatest return on the investment in the building. ASTM has promulgated a standard method for calculating life-cycle costs of buildings, E917, Practice for Measuring Life-Cycle Costs of Buildings and Building Systems, as well as a computer program and user’s guide to improve accuracy and speed of calculation.

Nevertheless, a client usually establishes a construction budget independent of life-cycle cost. This often is necessary because the client does not have adequate capital for an optimum building and places too low a limit on construction cost. The client hopes to have sufficient capital later to pay for the higher operating and maintenance costs or for replacement of undesirable building materials and installed equipment. Sometimes, the client establishes a low construction budget because the client’s goal is a quick profit on early sale of the building, in which case the client has little or no concern with future high operating and maintenance costs for the building. For these reasons, construction cost frequently is a dominant concern in design.

BUILDING SYSTEM : BUILDING CODES

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Many of the restrictions encountered in building design are imposed by legal regulations. While all must be met, those in building codes are the most significant because they affect almost every part of a building.

Building codes are established under the police powers of a state to protect the health, welfare, and safety of communities. A code is administered by a building official of the municipality or state that adopts it by legislation. Development of a local code may be guided by a model code, such as those promulgated by the International Conference of Building Officials, Inc., Building Officials and Code Administrators International, Inc., and Southern Building Code Congress International, Inc.

In general, building-code requirements are the minimum needed for public protection. Design of a building must satisfy these requirements. Often, however, architects and engineers must design more conservatively, to meet the client’s needs, produce a more efficient building system, or take into account conditions not covered fully by code provisions.

Construction drawings for a building should be submitted to the building-code administrator before construction starts. If the building will meet code requirements, the administrator issues a building permit, on receipt of which the contractor may commence building. During construction, the administrator sends inspectors periodically to inspect the work. If they discover a violation, they may issue an order to remove it or they may halt construction, depending on the seriousness of the violation. On completion of construction, if the work conforms to code requirements, the administrator issues to the owner a certificate of occupancy.

Forms of Codes. Codes often are classified as specifications type or performance type. A specification-type code names specific materials for specific uses and specifies minimum or maximum dimensions, for example, ‘‘a brick wall may not be less than 6 in thick.’’ A performance-type code, in contrast, specifies required performance of a construction but leaves materials, methods, and dimensions for the designers to choose. Performance-type codes are generally preferred, because they give designers greater design freedom in meeting clients’ needs, while satisfying the intent of the code. Most codes, however, are neither strictly specifications non performance type but rather a mixture of the two. The reason for this is that insufficient information is currently available for preparation of an entire enforceable performance code.

The organization of building codes varies with locality. Generally, however, they consist of two parts, one dealing with administration and enforcement and the other specifying requirements for design and construction in detail.

Part 1 usually covers licenses, permits, fees, certificates of occupancy, safety, projections beyond street lines, alterations, maintenance, applications, approval of drawings, stop-work orders, and posting of buildings to indicate permissible live loads and occupant loads.

Part 2 gives requirements for structural components, lighting, HVAC, plumbing, gas piping and fixtures, elevators and escalators, electrical distribution, stairs, corridors, walls, doors, and windows. This part also defines and sets limits on occupancy and construction-type classifications. In addition, the second part contains provisions for safety of public and property during construction operations and for fire protection and means of egress after the building is occupied.

Many of the preceding requirements are adopted by reference in the code from nationally recognized standards or codes of practice. These may be promulgated by agencies of the federal government or by such organizations as the American National Standards Institute, ASTM, American Institute of Steel Construction, American Concrete Institute, and American Institute of Timber Construction.

Code Classifications of Buildings. Building codes usually classify a building in accordance with the fire zone in which it is located, the type of occupancy, and the type of construction, which is an indication of the fire protection offered.

The fire zone in which a building is located may be determined from the community’s fire-district zoning map. The building code specifies the types of construction and occupancy groups permitted or prohibited in each fire zone.

The occupancy group to which a building official assigns a building depends on the use to which the building is put. Typical classifications include one- and two-story dwellings; apartment buildings, hotels, dormitories; industrial buildings with noncombustible, combustible, or hazardous contents; schools; hospitals and nursing homes; and places of assembly, such as theaters, concert halls, auditoriums, and stadiums.

Type of construction of a building is determined, in general, by the fire ratings assigned to its components. A code usually establishes two major categories: combustible and noncombustible construction. The combustible type may be subdivided in accordance with the fire protection afforded major structural components and the rate at which they will burn; for example, heavy timber construction is considered slow-burning. The noncombustible type may be subdivided in accordance with the fire-resistive characteristics of components.

Building codes may set allowable floor areas for fire-protection purposes. The limitations depend on occupancy group and type of construction. The purpose is to delay or prevent spread of fire over large portions of the building. For the same reason, building codes also may restrict building height and number of stories. In addition, to permit rapid and orderly egress in emergencies, such as fire, codes limit the occupant load, or number of persons allowed in a building or room. In accordance with permitted occupant loads, codes indicate the number of exits of adequate capacity and fire protection that must be provided.