Progressive collapse in asymmetric RC moment frame buildings

The present paper deals with nonlinear assessment of progressive collapse in low-rise three-dimensional (3D) reinforced concrete (RC) frame buildings with mass irregularities in plan. To this end, 3 story 3D frame buildings, with 0%(symmetrical), 10% and 20% mass eccentricity in plan and designed based on the provisions of the Iranian seismic code of practice (Standard No.2800), were modeled using strength and stiffness degrading material models adopted in FEMA P-695. Then incremental dynamic analyses (IDA) were performed to quantify the frames performances from linear elastic through the overall collapse level of response along with assessing the IDA curve of each record. The results show that response of asymmetrical frames are quite different from the symmetrical ones. Also, it is observed that irregularities in plan may cause a very irregular pattern of progressive yielding in critical sections of all asymmetric structures, especially in frames located on the flexible side of the plan. Such a poor response is shown to be intensified with increasing eccentricity