Evaluation of modified nonlinear dynamic and static analyses for seismic behavior of steel moment-resisting frames

With the progresses made in the field of structural and earthquake engineering and with more exact knowledge gained on seismic behavior of structures, earthquake engineering and various structures have advanced a great deal and various types of analytical methods have been developed for the assessment of structures. Dynamic analysis methods are aimed at determining the accurate behavior of structures and static analysis approaches are employed to predict structural behavior for engineering purposes. Most of nonlinear dynamic techniques are time-consuming and require a large volume of computations; moreover, performing these analyses and interpreting the obtained results need special skill and expertise. Conversely, although numerous approximations and simplifications in the nonlinear static approaches have extended and promoted their applications, they have reduced the accuracy of the results obtained by these methods. For evaluation of the seismic performance of structures, the precision and speed of the process of different analytical methods are the most important factors. This has led to the development of many novel methods based on the modern nonlinear static and dynamic analyses concepts. In this research, the results of two new different methods (modal incremental dynamic and incremental modified pushover analysis) for two 3-story and 9-story steel moment-resisting frames, as typical low and mid-rise steel lateral load-carrying systems, have been evaluated and compared with the results of the exact nonlinear incremental dynamic analysis. Based on the findings of this research, for the studied frames, the application of both analytical methods for low-rise frames gives appropriate results for all seismic records at different intensity levels; while for the mid-rise frames, the accuracy of the static analysis method has decreased; although a proper safety margin exists for this approach and also the sensitivity of the static method is less than that of the dynamic method.