Role of Ground Motion Characteristics on Inelastic Seismic Response of Irregular Structures

Abstract

There is no general consensus among researchers for selecting appropriate set of ground motions for the evaluation of inelastic seismic response of plan-asymmetric structures. In this backdrop, the role of important ground motion characteristics on the demand of a plan-asymmetric system is studied by using a number of records with widely varying characteristics but adjusted (using wavelets) to a common spectral shape. An equivalent single-story rigid-diaphragm model with simple elastoplastic hysteresis behavior is employed. Efficient strength design, viz, center of strength–center of mass (CV-CM)–coinciding strategy, is adopted in recognition of the strength-dependent stiffness characteristics of the load-resisting elements. It has been shown that the torsion-induced response of such systems is statistically insensitive to important ground motion parameters such as duration, frequency content, the interrelationship between two horizontal components, and the energetic length scale. Conversely, this study shows that a remarkable correlation exists between the carefully selected ground motion parameters and overall seismic demand as a result of coupled lateral-torsional vibration. The results motivated the authors to conceptualize a master curve that offers an a priori estimate of inelastic seismic demand of asymmetric systems when two widely used ground motion parameters, viz, peak ground acceleration (PGA) and mean period (Tm), are known. Thus, this study provides a background for dispelling the long-held controversy regarding the selection of an appropriate ground motion suite for assessing torsional response.