Abstract:
Pakistan is seismic active region and quality of construction is low. Terrorism is a major issue although it is being controlled now a days, but we must prepare for such unforeseen circumstances. The loss of one or more columns in a RC frame structure can lead to progressive collapse of building. Progressive collapse is being observed in building since last century but not considered while designing as there are no special regulations in the codes. The purpose of this research is to find vulnerability of existing buildings in Pakistan toward progressive collapse due to sudden loss of one or more columns in building. Sudden loss of column may be due to terrorist attack, car crash or any other event. Three-dimensional reinforced concrete frames are simulated to the column removal scenario to understand the progressive collapse behaviors by using ETABS. Case study buildings were of 4-,5- and 9-storey. The analysis procedures followed was Linear static analysis and linear dynamics analysis. The results for original building model and column removal cases were compared. Column removal was done on basis of probability of column loss in real scenarios. The properties of building which were dependent on mass of building did not changed as negligible change in mass occurred. Modal result showed that modeling was correct and there was no plan or vertical irregularities in buildings. Local result changed significantly. Beams above the removed column tend to exceed their capacity. Columns also exceed their capacity in many cases. The failure chain is developed in building which leads to progressive collapse. It is recommended to consider Progressive collapse as limit state and incorporate it at design phase. Incorporating it at design levels will reduce risk of local failures, due to columns loss, and causing more resistant structure against progressive collapse.
