Progressive Incremental Dynamic Analysis for First-Mode Dominated Structures

Incremental dynamic analysis (IDA) is a widely used method for assessing structural performance under earthquake excitations. It enables direct evaluation of the record-to-record variability in structural response through a set of ground-motion records. If the number of ground-motion records is large then, the method becomes computationally demanding. To facilitate its practical application, a precedence list of ground-motion records has been introduced, aiming at selecting the most representative ground-motion records for IDA analysis. In progressive IDA analysis, the IDA curves are computed progressively, starting from the first ground-motion record in the precedence list. After an acceptable tolerance has been achieved, the analysis is terminated. This approach may significantly reduce the computational effort for first-mode-dominated structures, since the seismic response can be computed only for a certain number of ground-motion records from the precedence list to achieve an acceptable level of confidence in the prediction of the summarized (16th, 50th, and 84th fractiles) IDA curves. The proposed implementation of incremental dynamic analysis, which is demonstrated using an example of a 4-story reinforced concrete frame, can also be used for the selection of ground-motion records from a very large set of records, provided that all the records properly represent the seismic scenario for a given site.