Dynamic-Based Pushover Analysis for Two-Way Plan-Asymmetric Buildings under Bidirectional Seismic Excitation

Abstract

A dynamic-based pushover procedure for two-way plan-asymmetric buildings (DPTPA) is proposed based on performing two nonlinear static analyses along the principal directions of the structural model to properly consider the torsional and higher modes effects. Along each direction, a lateral-torsional load pattern is developed for each of the stiff and flexible edges. For this purpose, in each direction, the peak story drift responses of the stiff and flexible edges and the center of stiffness (CS) are obtained from a response spectrum analysis (RSA). Then, the resulting peak story drifts for each of the stiff and flexible edges are decomposed into their translational and rotational components of the floor’s displacement. The displacement vectors determined for each of the flexible and stiff edges are used to construct two lateral load patterns consisting of equivalent lateral forces and torsional moments, corresponding to the flexible and stiff edges of the structural system. Then, two standard pushover analyses with the prescribed lateral load patterns are performed along each direction, and the envelope of the results for each direction are combined according to the square root of the sum of squares (SRSS) technique to determine the final structural response. The code suggested target displacements (for each direction) are also proposed to be modified using a modification factor with regard to the level of nonlinearity sustained by the structural model. To evaluate the efficiency of the proposed DPTPA procedure, the nonlinear time history analysis (NL-THA), the practical modal pushover analysis method (PMPA), and the extended-N2 method are employed using a couple of numerical examples. The required comparisons are made on global and local seismic demands. The obtained results clearly demonstrate the superiority of the proposed DPTPA procedure in efficiently estimating the induced seismic demands and in being much easier to use for professional application relative to other considered enhanced pushover procedures.