| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 89 === In recent years, a number of researches have revealed that the buckling restrained braced frame (BRBF) is an effective system for server seismic application. Buckling restrained bracing (BRB) members can be conveniently made from various kinds of structural steel shapes encased in steel tube and confined by infill concrete. When the brace is subjected to compressions, an unbonding material placed between the core bracing and the concrete infill is required in order to reduce the friction while restrain the bracing from buckling.
In this research, a combined experimental and analytical research program has been conducted in order to investigate the effectiveness of various kinds of unbonding material, the brace-to-gusset connection details, and the design procedures for the BRBFs. A total of sixteen BRB specimens were fabricated and tested in National Taiwan University. Test results of ten single cross-shaped BRB specimens indicate that the 2mm thick silicon rubber sheets are most effective in minimizing the difference between the peak compressive and tensile strengths of the BRB members. Test results of six additional specimens suggest that the proposed BRB member employing steel double-T and twin steel tubes can stably sustain severe cyclic axial load reversals. Moreover, the proposed BRB members can be conveniently connected to the gusset plate in the same manner as that in the traditional double-T brace to gusset plate connections.
These cyclic load test results have also made the implementation of a nonlinear brace element a success in a separate study on the development of a general purpose nonlinear structural analysis computer program. In this research, design examples are given for a six-story concentrically braced frame considering various stiffness ratios between the BRB member and the frame. Analytical results demonstrate that the BRB members can effectively dissipate seismic energy and reduce the nonlinear demands imposed on the beams and columns. This research concludes with the procedures and recommendation for the seismic resistant design of BRBFs.
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