Evaluation of modal incremental dynamic analysis, using input energy intensity and modified bilinear curve

Abstract

AbstractIn this paper, a technique for the study of nonlinear performance of structures in different levels of earthquakes is developed. In this method, the Incremental Dynamic Analysis (IDA) curves are not achieved from nonlinear dynamic analysis of multi‐degree‐of‐freedom (MDF) structure. However, the procedure of constructing these curves is based on modelling of the entire structure with several single‐degrees‐of‐freedom (SDF) structures and evaluating them through the modal pushover analysis method. An innovative idea for approximating pushover curves that is based on error distribution is introduced in this investigation. Furthermore, the total input energy applied towards the SDF oscillator, which gets converted into MDF structure, is used as intensity measure to impose the different levels of scaled earthquakes.This technique possesses all the advantages of the IDA method in studying the performance of structures in different levels of earthquake. In addition, it benefits from easy usage, high solving speed and less computational CPU time and in attendance with the modified bilinear curves. In this paper, six earthquake records have been applied over four different 4, 8, 12 and 16‐storey structures. The structural responses derived by this method, in the format of multi‐modal incremental curves, containing maximum displacement, drift, hinge rotation and hysteretic energy at the end of the earthquake, have been compared with the IDA method. Comparison of the results is found to have acceptable precision and reveals good agreement between two methods. Copyright © 2008 John Wiley & Sons, Ltd.