Numerical Studies On The Progressive Collapse Resistance Of Multi-story RC Buildings With And Without Infill Walls

Progressive collapse of a structure is triggered by the localized damage of a major supporting element by an event that sets the chain reaction of failures of the adjacent elements resulting in a partial or total collapse of the structure.It is extremely challenging to predict the occurrence of the abnormal event due to the unforeseen nature of it.However,it is possible to mitigate the potential of progressive collapse in the design stage by investigating the robustness of structures subjected to the damage of a major supporting element by the alternate load path method.In the alternate load path method,a structure is designed to be able to transfer additional loads when subjected to local damage.This approach is very popular and is accepted by most of the progressive collapse design guidelines.Therefore,progressive collapse analyses are performed by using alternate load path method in this study.It is noticed that most of the progressive collapse events in history were high-rise structures,therefore,this research will mainly focus on the study of progressive collapse resistance of multi-story reinforced concrete(RC)structures.When a structure is subjected to column failure condition,infill walls are helpful in transferring irregular loads and mitigating local damages.However,research of infill wall effects on progressive collapse resistance is still limited.Therefore,the influence of perforated and full-height masonry walls on the progressive collapse of multi-story reinforced concrete(RC)structures is examined in this study.Additionally,it is noticed that the beam-slab floor system can considerably increase the structural resistance under the damage of a critical supporting member.Therefore,the influence of slabs on the failure resistance of RC structures,with and without infill walls are investigated to assess the structural resistance under column damage.Bare,perforated and full-height infill-wall frames are studied by considering column damage at different locations of the ground story.Infill-wall panels are simulated by using equivalent compression struts and their provision of alternate load paths under the damage of a critical load-bearing column is investigated.Linear static,linear dynamic,nonlinear static and nonlinear dynamic analyses are conducted by following the guidelines of the General Service Administration(GSA).The analysis results show that the perforated and full-height infill walls are beneficial in distributing loads after the damage of the column and increase the collapse resistance of the RC building.Empirical dynamic amplification factors(DAF)are also calculated in the sequel and the factor instructed in the GSA guidelines is judged by comparing with these computed dynamic factors.The results show that the DAF of 2 is conservative and the presence of infill walls does not significantly affect the value of DAF.It is also investigated in this research that slabs help in transferring the load and enhance the structural resistance in the bare frame whereas the effects of slabs are not significant in the perforated and full-height infill wall frames.