An adaptive modal pushover procedure for asymmetric-plan buildings

An innovative single-run adaptive modal pushover procedure based on the modal story shear and torque has been developed for seismic assessment of asymmetric-plan buildings. In which the load pattern consists of the lateral forces and torques which are derived from the instantaneous combined modal story shear and torque profiles in each step. The contribution of the higher and torsional modes and the effects of the changes in the structural properties during the inelastic domain are considered. Although the quadratic combination rule is used in defining the load pattern, the effects of reversal signs in the higher modes are simulated in the load pattern. The interaction between modes in the inelastic phase is reflected in the single load pattern and the structural responses during the analysis are easily traced through the single-run procedure. Furthermore the capacity spectrum curve is obtained from a formulation based on the modal energy concept and the ambiguity of choosing controlling point to obtain the target displacement in asymmetric-plan buildings has been eliminated. Accuracy of the proposed method has been verified on three asymmetric-plan buildings under different earthquake records. The results indicate that this method could predict the results of the nonlinear time history analysis appropriately.

► An adaptive modal pushover procedure is proposed for asymmetric-plan Buildings. ► The load pattern is derived from the instantaneous modal story shear and torque. ► The effects of the higher and torsional modes are considered. ► The interaction between modes in nonlinear phase is reflected in the load pattern. ► This procedure estimates the seismic demand of asymmetric structures accurately.