Demands on acceleration-sensitive nonstructural components in special concentrically braced frame and special moment frame buildings

Abstract

This study investigates demands on acceleration-sensitive nonstructural components (NSCs) in code-compliant Special Concentrically Braced Frame (SCBF) and Special Moment Frame (SMF) structures. Previous studies have highlighted that the assumption of ASCE 7-16 for the ratio of Peak Floor Acceleration (PFA) to Peak Ground Acceleration (PGA) is overly conservative. In most previous studies, the results were based on generic analytical models with non-deteriorating structural behavior or recorded data from instrumented buildings subjected to ground motions that were significantly weaker than the design-level earthquakes. This study evaluates the acceleration demands on NSCs in 11 archetype buildings modeled using advanced techniques. The ground motions used elicit inelastic response in the frames at the level expected by ASCE 7-16 compliant designs. The study examines the effect of the ratio of NSC period to structural period, NSC damping ratio, and NSC vertical location on these demands. Results of this investigation are compared with the provisions of ASCE 7-16 and the recommendations of the recently completed effort by the Applied Technology Council 120 project (ATC-120), which are the basis for the seismic design requirements for nonstructural components in the forthcoming ASCE 7-22 standard. Equations for the PFA/PGA ratio and NSC amplification factor, which account for the dynamic characteristics of the buildings, are developed based on regression analysis of the generated data. Results of the analyses indicate that the formula recommended by ATC-120 for estimating PFA/PGA along the height of the structure, which includes building nonlinearity effects through a constant building ductility reduction factor, overestimates floor accelerations at the top floors but underestimates them in the lower floors of the archetypes considered. At the same time, results show that the NSC seismic design force equation recommended by ATC-120 is conservative for the SCBF archetypes, while it underestimates the NSC force demands in the SMFs.