Use of the Extended Consecutive Modal Pushover Analysis Method to Optimize the Design Process

Abstract

In the design of new structures subject to earthquake loading the use of nonlinear response history analysis (NRHA) can be an extremely effective tool for optimization of the lateral system, however it can be a time consuming endeavor. In the process of optimization the necessity of running multiple analysis iterations, each subject to a suite of ground motions, is computationally intensive and can slow down the design process. However, by utilizing a simplified simulation technique, the extended consecutive modal pushover (ECMP) analysis method, the analysis and data reduction effort in design optimization can be reduced. The consecutive modal pushover (CMP) analysis method (Poursh et al. 2009) is a multi-mode nonlinear analysis technique involving sequential application of different modal based load profiles. An extension of the CMP procedure, termed the extended consecutive modal pushover (ECPM) method has been developed by the authors to improve the predictive capabilities of the CMP method. In an ECMP analysis the sequence and sign (direction) of modal load patterns are varied, encouraging formation of different inelastic mechanisms with the goal of replicating the various mechanisms that are observed to develop in NRHA when using a suite of ground motion records. Since the results of an ECMP analysis are similar to that achieved in a more computationally intensive NRHA, the ECMP procedure is an ideal simplified method to use during design optimization, and when model size makes NRHA computationally unfeasible. This paper will present the ECMP analysis method and will describe a procedure for using ECMP analysis as a design optimization tool coupled with NRHA. The results of ECMP and NRHA will be compared for two actual buildings to demonstrate the new ECMP analysis procedure and its use as a design optimization tool.