Modeling viscous damping in nonlinear response history analysis of steel moment‐frame buildings: Design‐plus ground motions

Abstract

AbstractInvestigated in this paper is the question: Can seismic demands on steel moment‐frame buildings due to maximum considered earthquake (MCER) design‐level ground motions (GMs) be estimated satisfactorily using linear viscous damping models or is a nonlinear model, such as capped damping, necessary? This investigation employs an enhanced model with several complex features of a 20‐story steel moment‐frame building. Considered are two linear viscous damping models: Rayleigh damping and constant modal damping; and one nonlinear model where damping forces are not allowed to exceed a predefined bound. Presented are seismic demands on the building due to two sets of GMs: MCER design‐level GMs (2% probability of exceedance [PE] in 50 years) and rarer excitations (1% PE in 50 years). Based on these results, we conclude that linear damping models are adequate for estimating seismic demands on steel moment‐frame buildings—designed to satisfy current story drift and plastic rotation limits due to MCER design‐level GMs. Between the two linear damping models, constant modal damping is preferred; it is available in commercial computer codes for earthquake structural analysis.