مقاله السیور- ANALYTICAL AND EXPERIMENTAL STUDIES ON BUCKLING RESTRAINE

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ANALYTICAL AND EXPERIMENTAL STUDIES ON BUCKLING RESTRAINED BRACED COMPOSITE FRAMES

SUMMARY

Analytical and experimental studies on the seismic behavior of buckling restrained braced frames(BRBFs) with concrete filled steel tubular (CFT) columns are being conducted at the ATLSSCenter, Lehigh University. The objectives of these studies are to investigate the seismicperformance of this type of frame, to evaluate existing design criteria, and to calibrate analytical models. The project is sponsored by the National Science Foundation in conjunction with the U.S.-Japan Cooperative Research Program on Composite and Hybrid Structures. A 4-story prototype building was designed with buckling restrained braced frames (BRBFs) as the lateral load resisting system. The columns in this frame are CFT members and the beams are structural steel sections. Design criteria were taken from the IBC 2000 and the AISC/SEAOC Recommended Design Provisions for BRBFs. A 1-bay prototype BRBF, representing one-quarter of the lateral load resisting system in one direction, was extracted from the prototype building for analysis. The analysis program DRAIN-2DX was used to model the prototype frame including material and geometric nonlinearities. The force-deformation relationship used in the buckling restrained brace model incorporates both isotropic and kinematic hardening. Nonlinear time history analyses were conducted using an ensemble of ground motions consisting of natural earthquake records and one artificial earthquake record. The earthquake records were scaled to two different seismic input levels: Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). A statistical summary of the analysis results was developed at both seismic input levels. Performance objectives were defined and used to evaluate the analysis results. The life safety (LS) performance level was the target level for the DBE and the collapse prevention (CP) performance level was the target level for the MCE. Acceptable BRBF behavior was observed at both seismic input levels. A large-scale BRBF experimental investigation is planned. This paper presents the results of the analytical study and briefly summarizes the upcoming experimental program.

Keywords: Ductile design; Seismic force reduction; Hysteretic behaviour