A robust pushover analysis for multi-component seismic excitation: a new frame work

Abstract

Seismic performance evaluation of a structure against seismic excitation is a crucial part of the

safety examination. Incremental Dynamic Analysis (IDA) is the best option for the performance

evaluation which is not popular among the practicing engineers. Nonlinear Static Pushover (NSP)

methods are approximate and reliable alternate for the time consuming and complex IDA. The

conventional NSP methods are based on pushing a structure with constant load profile, however it

is restricted to single mode response. In order to overcome these issues, NSP based on multiple

modal pushovers were introduced. Among the various NSP methods, Modal Pushover Analysis

(MPA) is one of the popular method. But the multiple modal methods are not able to predict the

plastic hinge formation due to individual modal pushovers and the hinge formation is not directly

related to the mode wise distribution.

This thesis presents a new robust pushover (Alternate pushover analysis, APA) method which

keeps the simplicity of conventional methods and gives a reliable solution. It is based on a single

pushover and multiple modal target displacement calculations. The proposed pushover method is

extended to buildings subjected to bidirectional and the multi-directional excitations including the

torsional component.

The APA is applied to two reinforced concrete buildings designed as per Indian standards, one is

symmetric and other is asymmetric in nature. Seismic demands of these buildings under

unidirectional, bidirectional and multidirectional including torsional components are calculated

using the proposed Alternate pushover analysis (APA). The estimated demands by APA is

compared with the benchmark solution obtained from nonlinear time history analysis (NLTH) as

well as the predictions from MPA. It is demonstrated that the proposed APA is effectively

calculating the seismic demands in all the cases.