5. Fast Nonlinear Response History Analysis: An Application to Irregular Building Structures

The design or evaluation of high complexity structures requires non-traditional methods to estimate their seismic performance. Although structural engineering still relies on nonlinear static analysis for estimating seismic demands, the nonlinear response history analysis (RHA) is being now increasingly used for design-check and performance evaluation. In this approach, the engineering demand parameters are determined by performing a series of nonlinear RHAs using an ensemble of ground motion records that represent the site’s seismic hazard conditions. This type of analysis is computationally demanding and time consuming when applied to three-dimensional computer models subjected to multi-axial excitations. A procedure is presented to reduce the processing time of nonlinear RHA by minimizing the impact on the response of the structure while maximizing the time savings; it has three steps: (i) trimming a segment of the ground-motion record at the beginning; (ii) trimming a segment at the end; (iii) identifying an appropriate time-step to reduce the number of steps required to properly characterize the signal. This procedure has been tested through a parametric study by considering multiple structural periods and response modification factors for multi-story irregular buildings. Results show that the processing time can be reduced without compromising accuracy in estimates of peak EDPs.