Adaptive Load Patterns Versus Non-adaptive Load Patterns for Pushover Analysis of Building

Nowadays, concepts of the performance-based design engineering constitute the main basis for compilation of most of the seismic analysis and design codes. During the past 2 decades, broad attempts have been made by the researchers to narrow the gap between the nonlinear static procedures (NSP), and the nonlinear time-history analysis (NTHA) as the most exact method for structural analysis. It is well known, ignoring the higher-mode effects and dynamic characteristics alterations, are the main shortcomings of the NSPs. In this regard, procedures with adaptive load pattern have been addressed by many researchers and consider the effects of changes in modal characteristics of structures during monotonically increasing load process. In this paper, two advanced adaptive modal pushovers, namely SSAP and FAP, have been investigated versus their non-adaptive load pattern counterparts. In order to evaluate the efficiency of the procedures, three moment-resistant steel frames of SAC group, SAC-3, SAC-9 and SAC-20, are chosen. The NTHA is performed for the typical far-fault ground motion records, LA01–LA40, consisting of both 10 and 2% probability of exceedance in 50 years. Although adaptive load pattern seems plausible, the results show it cannot improve the accuracy of the responses significantly, especially in low-rise structures. Moreover, its efficiency depends on basic source of the lateral load pattern.