Envelope-based pushover analysis procedure for the approximate seismic response analysis of buildings

An envelope-based pushover analysis procedure is presented that assumes that the seismic demand for each response parameter is controlled by a predominant system failure mode that may vary according to the ground motion. To be able to simulate the most important system failure modes, several pushover analyses need to be performed, as in a modal pushover analysis procedure, whereas the total seismic demand is determined by enveloping the results associated with each pushover analysis. The demand for the most common system failure mode resulting from the first-mode' pushover analysis is obtained by response history analysis for the equivalent modal-based' SDOF model, whereas demand for other failure modes is based on the failure-based' SDOF models. This makes the envelope-based pushover analysis procedure equivalent to the N2 method provided that it involves only first-mode' pushover analysis and response history analysis of the corresponding modal-based' SDOF model. It is shown that the accuracy of the approximate 16th, 50th and 84th percentile response expressed in terms of IDA curves does not decrease with the height of the building or with the intensity of ground motion. This is because the estimates of the roof displacement and the maximum storey drift due to individual ground motions were predicted with a sufficient degree of accuracy for almost all the ground motions from the analysed sets. Copyright (c) 2013 John Wiley & Sons, Ltd.