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Floor accelerations in buildings having different structural systems

Abstract:

The default procedure indicated by the current seismic design code in the United States (ASCE 7-10) to determine seismic demands on acceleration-sensitive nonstructural components (NSCs) is a practical but perhaps somewhat overly simplified procedure that is intended to be applicable to NSCs located in any type of structure, regardless of whether the structure behaves elastically or inelastically, regardless of the fundamental period of the structure, and, perhaps more importantly, regardless of the kind of structural system. This paper investigates the differences between floor accelerations in Special Steel Moment Frames (SMFs) and in Buckling Restrained Braced Frames (BRBFs). The building structures analyzed in this study were taken from the ATC 76-1 project, and their mathematical models are very detailed since they were also used to evaluate collapse performance using the FEMA P-695 methodology. Floor accelerations were obtained through linear and nonlinear time history analysis, and results are expressed in terms of Peak Floor Accelerations (PFAs, which is the acceleration demand on "rigid" NSCs) and Floor Response Spectra (FRA, which is the acceleration demand on "flexible" NSCs). It is found that floor accelerations generally exhibit similar trends in both structural systems (SMFs and BRBFs), but the differences are large enough to justify further research on the development of practical procedures where the type of structural system is taken into account.