Static and Dynamic Analyses of Asymmetric Reinforced Concrete Frames T. Mahdi Building and Housing Research Centre, Tehran, Iran V. Soltangharaie Faculty of Building and Housing, Tehran, Iran SUMMARY: In this paper, the seismic behavior of three concrete intermediate moment-resisting space frames with unsymmetrical plan in five, seven and ten stories are evaluated. In each of these three cases, plan configurations of the structure contain reentrant corners. Nonlinear static and linear dynamic procedures have been used to analyze these structures. To measure the accuracy of these two methods, the non-linear dynamic analysis has been used. Although the differences between the results of these two methods with the nonlinear dynamic procedure are quite wide, the linear dynamic analysis has shown slightly better results than nonlinear static analysis. Keywords: RC frame, irregular building, pushover, nonlinear time history, linear time history 1. INTRODUCTION The selection of a suitable procedure to evaluate performance of structures under seismic loads is one of the most sensitive issues that structural engineers face. This would be especially important when dealing with irregular structures since the wrong choice of a procedure would lead to results that are far away from the correct solution. One of the most common types of irregularities that found in most buildings is the plan irregularities. The existence of an asymmetry in the plan is usually leading to an increase in stresses of certain elements that consequently results in a significant destruction. Several methodologies involving nonlinear pushover analysis using an invariant height-wise lateral force distribution, such as the FEMA356 (ASCE 2000), FEMA440 (ATC 2005), and ASCE 41 (ASCE 2007), have routinely been used in structural engineering practice for estimation of global and local structural deformations. As shown by many authors (Kunnath & Kalkan, 2004; Themelis, 2008), these methods have proven their superiority over existing elastic force-based procedures. For structures responding primarily in the first mode, they represent reliable options to estimate inelastic demands. However, many studies have shown that conventional pushover methods are ineffective in dealing with some types of plan irregularities. Based on this and by using three-dimensional models, new pushover methods are proposed (Moghadam & Tso, 2000; Chopra & Goel, 2004; Fajfar et. al, 2005; Kalkan & Kunnath, 2006). To evaluate the seismic behavior of complex tall asymmetric buildings with significant higher mode effects, the nonlinear dynamic analysis methods generally provide more realistic models of structural response and, thereby, provide more reliable assessment of earthquake performance than other methods. However, this method is not feasible for complex and large buildings. Thus, it is the purpose of this paper to strike a balance between practicality on one hand and accuracy on the other. The most logical alternatives in this respect are the nonlinear static analysis (pushover) and the linear dynamic analysis. The pushover analysis can be an effective design tool to investigate aspects of the analysis