Seismic Collapse Safety and Behavior of Modern Reinforced Concrete Moment Frame Buildings

Abstract

A primary goal of seismic design requirements of building codes is to protect the life safety of building inhabitants during extreme earthquakes. Fundamentally, this requires that the likelihood of structural collapse be at an acceptably low level. However, building codes and standards are largely empirical in nature, such that the implied collapse safety is not known. The primary objective of this study is to quantitatively predict the collapse safety of twelve modern reinforced concrete (RC) special moment frame (SMF) buildings designed according to the governing provisions of the 2003 IBC [ICC 2003], ASCE7-02 [ASCE 2002], and the ACI 318-02 [ACI 2002]. In particular, this study examines the effects of building height on collapse performance and the related effects of building height on static overstrength, building deformation capacity (as measured by roof and interstory drifts at collapse), and the collapse mechanism. The secondary objective is to examine how changes to the required minimum base shear introduced in the 2005 edition of ASCE7 [ASCE 2005] affect collapse safety. These predictions of collapse safety are made using tools and methods that have been developed by the authors and other researchers in the Pacific Earthquake Engineering Research (PEER) Center, including careful consideration of the important uncertainties associated with ground motion variability and uncertainty in nonlinear structural response. The twelve buildings examined in this paper are part of a more extensive study, which provides further details on the assessment methods and finding for a broader set of buildings [Haselton, 2006].