A rapid damage assessment framework for regular RC frame structures under external explosions

Abstract

Local damage of the structural members and even progressive collapse of structures occurred in terrorist or accidental explosions, but there are few unified frameworks of integrating the member damage into the structural damage for rapid assessment against blast loads. To fill this gap, a framework is proposed for engineering practice to rapidly assess damage levels of regular reinforced concrete (RC) frame structures under external explosions, in which the structural damage level is eventually determined with only two inputs: scaled distance and structural redundancy. A regular 5-story RC frame structure subjected to external explosions is adopted as an example to illustrate the proposed framework. Firstly, damage indexes of structural members are formulated under far-field explosions or close-in explosions, and the structural damage index is further derived through the weighted integration of the damage indexes of structural members. Subsequently, the damage modes and collapse processes of the designed RC frame structure are simulated under different explosion scenarios, and the energy-based damage indexes for assessing structures against blast loads are developed and validated. Through numerical results of 23 case studies, the structural damage assessment formula as a function of scaled distance and structural redundancy is derived through regress analysis, and on the other hand, two key threshold values of the energy-based damage indexes are introduced to classify the structural damage levels (minor, moderate and severe levels). Finally, the structural damage index is correlated to the energy-based damage index through curve-fitting to determine the corresponding threshold values of structural damage index as well, and the effectiveness of the damage assessment framework is further validated. The results show that the proposed damage assessment framework can rapidly and accurately assess the damage levels of the regular RC frame structures under external explosions, and the deviation between the predicted damage indexes and the numerical results are 4.11 %–9.52 %.