Sabtu, September 29, 2007

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

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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