Investigation of progressive collapse in reinforced concrete frames, considering end rigid zones and various scenarios for column removal duration

In this study, some researches about end rigid zones parameters and column removal duration in progressive collapse reinforced concrete frames are taken place. Due to massive dimensions of beams and columns in reinforced concrete frames, the effect of end rigid zones cannot be ignored. Column removal duration is one of the variables that can have different values considering the cause of an accident in which this study it is assessed in conditions such as suddenly, standard and gradually removal. Therefore, two 4- and 8-storey reinforced concrete frames are designed via OpenSees Software. The impact of end rigid zones and column removal duration in either frames has been evaluated by removal of the middle and corner column. In order to evaluate end rigid zones for determining vertical stiffness of structure and beams rotation considering performance level, nonlinear dynamic analysis is used. In addition, to assess structural capacity, nonlinear static analysis of increasing load is applied. To evaluate column removal duration, nonlinear dynamic analysis is used to assess the vertical stiffness and performance level of beams. After analyzing the frames, it was shown that the end rigid zone can have a great impact on increasing vertical stiffness; while having much lower influence on beam rotation and structural capacity. Column removal duration can also have an impressive effect on maximum value of vertical displacement. This effect is highly demonstrated in gradually removal; however there is a slight difference in suddenly and standard removal.