Gravity framing and composite action effects on residual drifts of steel SMFs

Abstract

In this study, the effects of gravity framing and composite action on the residual drift performance of steel special moment frames (SMFs) are investigated. Four steel structures including 4-, 8-, 12-, and 20-story SMFs are selected, and nonlinear models are created by considering the effects of gravity framing and composite action and neglecting these effects. Nonlinear dynamic analyses are performed on the structures subjected to the design basis earthquake (DBE) level ground motions. Under the DBE hazard level, accounting for the effects of gravity framing and composite action can reduce the maximum of median residual interstory drift ratios between 32% and 74%, when compared with that obtained by neglecting these effects. Incremental dynamic analyses are performed on the structures assuming the maximum residual interstory drift ratio (MRD) as the engineering demand parameter and four MRD limit states of 0.2%, 0.5%, 1.0%, and 2.0% to assess the residual drift performance of the structures in a probabilistic framework. The results show that considering the effects of gravity framing and composite action leads to significant decreases in the mean annual frequencies of exceeding different MRD limit states (i.e., λMRD values). These effects have the lowest impact on the λMRD values when the MRD is 0.2%. However, they have the highest impact on the λMRD values when the MRD is 1.0%.