In this paper the inelastic response of existing reinforced concrete (RC) buildings designed without seismic details is investigated, presenting the results from more than 80 nonlinear analysis. The seismic performance evaluation is conducted for two building types representing low-rise and a mid-rise residential buildings. The overall objective of the current study is to investigate the structural performance of RC buildings under different seismic loadings. For this purpose two performance earthquake engineering (PBEE) procedures are utilized: static and dynamic non-linear analysis. Zeus-NL, a finite element analysis program, is employed for the numerical analysis phase using a set of 20 natural ground motion records. In addition, a methodology is presented for the process and strategies followed up to conduct the mathematical model in Zeus-NL software. Afterwards, the structural performance under different loading conditions is investigated using nonlinear procedures. Results are interpreted based on the FEMA 356 guidelines. Moreover, a comparison between static and dynamic pushover curves is accomplished. The interstory drift results show that 50% of the ground motion records forced both structural models to exceed the life safety (LS) performance level. Due to the sudden changes in columns cross-section and reinforcement at the second and third stories, both structures possessed a higher amount of interstory drift at these story levels.