Assessment of Nonlinear Static Procedures for Determination of Target Displacement in Asymmetric Buildings

Abstract

The conventional procedure for pushover or non-linear static analysis (NSA) has some drawbacks in predicting the inelastic seismic demands of buildings which are asymmetric in plan. In this research, fifteen asymmetric buildings comprising of steel moment frames have been designed and their seismic responses have been studied by pushover analysis. Using methods proposed in FEMA-356, ATC-40, and FEMA-440, the target displacements for these structures have been obtained. Subsequently pushover analyses have been repeated using lateral forces corresponding to 100% of target displacement in principal direction and 30% of target displacement in perpendicular direction. Results of this study indicate that target displacements results from FEMA-440 methods for the roof center of mass (CM) are closest to the NTHA results but displacements obtained for the stiff side of structure in all NSA methods are underestimated. Therefore a correction factor has been derived using the Least Squares Method to modify the demand displacements obtained from pushover analysis for the stiff side of asymmetric buildings.

Keywords

pushover asymmetric building nonlinear static analysis target displacement

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