Performance of Reinforced Concrete Frame Structure Subjected to Progressive Collapse

Abstract

Contemporary reinforced concrete (RC) frame constructions are susceptible to progressive collapse, which is defined as a chain reaction event due to the local loss of a vital member. The paper explores the behavior of normal and abnormal 12-story RC buildings with extreme loading conditions. ETABS developed analytical models based on the Building Code of Pakistan, ASCE 7-16, and GSA provisions. Gravity, seismic, wind, dead and live loads were used, and progressive collapse was modeled by removing selective critical columns. The values of demand-capacity ratio (DCR) were assessed prior to and following column removal to measure the vulnerability of members and the reserve strength. Findings indicate that the DCR values were lower than unity before the removal, which represents good performance. DCR values of neighboring members exceeded 4.0 after column loss indicating extreme overstress and high collapse potential. The robustness index (R) was used to measure structural robustness, where R is the ratio of base shear damaged to intact configuration; R=1.0 indicated that alternate load paths were developed successfully. Comparative analysis showed that atypical frames are more prone to disproportional collapse because they have geometric anomalies and uneven distribution of loads. The paper has highlighted the significance of robustness-based design and the need to explain measures that can be used to reduce the risk of progressive collapse in high-rise RC frames. The practical implications are to have better design checks, plan redundancy, and do specific retrofitting to make urban reinforced concrete inventories of buildings more resilient and safer in the case of extreme hazards.