Numerical studies on the effects of infill walls for progressive collapse resistance of RC building

Numerical investigations were carried out on the progressive collapse resistance of reinforced concrete (RC) building with and without perimeter masonry walls when subjected to multiple column removal scenario and beam-column removal scenario. SAP2000 software was used. Linear static analysis and time history analysis was performed to assess the effect of masonry infill walls on the 8-storey RC frame building. The dynamic amplification factor (DAF) was assessed for both RC bare frame and infill wall frame for multiple column removal combination scenarios. Progressive collapse demand (PCD) was evaluated for both multiple column and beam-column removal scenarios. Assessment of demand capacity ratio (DCR) revealed that the presence of infill walls increases the structural stiffness and resistance of the RC frame building when more than one column fails at the ground floor. Infill wall frames exhibited 44–85% reduction in number of DCR points exceeding the limiting the value of 2 to that of RC bare frame for column removal combination scenarios. The presence of an infill wall in the RC frame leads to the redistribution of loads to the adjacent columns and due to this the vertical displacement of the beam-column joint was reduced when compared to the RC bare frame. The General Service administration (GSA) guidelines recommended DAF value of 2.0 is very conservative and may be reconsidered since the results of DAF values are within 1.5 to 1.6. The values of PCD were less than 1 which is considered safe for all column removal and beam-column removal combination scenarios. Time history vertical displacement response of RC infill wall frame is superior to that of RC bare frame. 1.49 to 1.99 times increased vertical displacement responses are observed at the location of elements removal for beam-column removal combinations within RC bare frame due to non-existence of infill walls. Hence infill walls are recommended on the perimeter beams for RC building frames.