The highly nonlinear behavior associated with buckling and nonductile fracture of braces reduces the ability of the special concen trically steel braced frame (SCBF) system to dissipate energy, resulting in undesirable modes of behavior. We analyzed archetype buildings of SCBFs and buckling restrained braced frames (BRBFs). The seismic demands of the system and structural elements were computed and interpreted for 3-, 6-, and 16-story SCBFs and BRBFs under various hazard levels. The analysis results show large seismic demands for the 3-story SCBF, which may result in unexpected damage of structural and nonstructural elements.
We performed evaluations of seismic design pa rameters for 2-, 3-, 6-, 12-, and 16-story SCBFs and BRBFs, which demonstrated that short-period braced frame systems, especially SCBFs, had higher probabilities of collapse than longer-period braced frame systems. The response was substantially improved by lowering the response reduction factor of the 2-story SCBF building; this reduced the collapse risk at the hazard level of 2% probability of exceedance in 50 years.
The investigation of system performance and member behavior provides seismic demands to more accurately assess the socioeconomic losses of SCBFs and BRBFs for performance-based earthquake engineering.
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