Accuracy Investigation of CSM-DAP Method in Comparison with FEMA356 Method for Estimating Seismic Demands of Steel Moment Resisting Frames with Geometric Irregularity in Elevation

Estimating seismic demands of structures has acquired renewed importance as a result of recent interests in performance-based seismic design. Consequently, in recent years, different equivalent nonlinear static analysis procedures have been developed to estimate structural seismic demands. However, just a few studies have been conducted to examine the accuracy and adequacy of these developed methods. Thus, it is necessary to conduct thorough investigations of these methods’ limitations, possible shortcomings, and their performance. In this paper, the accuracy of CSM-DAP method in comparison with FEMA356 method has been evaluated for estimating seismic demands of low-rise steel moment resisting frames with geometric irregularity in elevation. The CSM-DAP method is an equivalent displacement-based adaptive nonlinear static analysis method combined with the FEMA440 capacity spectrum method. The CSM-DAP and FEMA356 methods are used to analyze 44 five-story moment resisting frames subjected to 14 far-field earthquake ground motions and their results are compared with the results of nonlinear dynamic analyses. The selected sample includes wide range of geometric irregularities in elevation for low-rise structures. The estimated demand responses are namely roof displacement, inter-story drift ratio, and base shear. This study shows that considering the CSM-DAP computational effort, this method does not present significant advantages with respect to FEMA356 method at least for low-rise structures with geometric irregularity in elevation.