Cyclic Pushover Analysis procedure to estimate seismic demands for buildings

Abstract

Conventional Pushover Analysis relies on the use of monotonic lateral load distribution. The seismic displacement demands based on this procedure are considered an approximate solution that has not taken into account the cyclic loading effects. Under earthquake loading, structural components experience stiffness degradation and strength deterioration, which are the important characteristics of reinforced concrete members under cyclic loading, causing a reduction of deformation capacity. The Cyclic Pushover Procedure is proposed to estimate seismic demands of buildings that take into account the cumulative damage under cyclic loading. The cyclic lateral force distribution is developed based on the mode shapes and the prescribed displacement history. The cyclic pushover curve is converted to the equivalent SDOF pseudo-acceleration and displacement relationship based on the first mode response of the structure. The seismic demands of a 9-story reinforced concrete building are evaluated by Cyclic Pushover Procedure. Four types of loading protocol, i.e., Laboratory, ATC-24, International Organization for Standardization (ISO), and Sequential Phased Displacement (SPD) protocols are employed to investigate the effects of displacement histories on seismic demands. The seismic demands include the peak roof displacement, the peak floor displacement and the peak inter-story drift ratio. The results are compared with the exact demands resulting from nonlinear time history analyses of MDOF structure subjected to 20 ground motions, as well as the demands estimated from the Modal Pushover Analysis. The results demonstrate that the Cyclic Pushover Analysis provides a reasonable and accurate estimate of seismic displacement demands.