Damage assessment of prototype RC frame structure with masonry-infilled walls under external explosion: Tests and numerical simulations

External explosive terrorist attacks have a higher occurrence probability and wider impact scope. To investigate the damage of buildings under external explosions, a two-story prototype reinforced concrete (RC) frame structure with masonry-infilled walls is constructed. Two external explosion tests (11.6 kg TNT) are carried out to analyze the blast loadings propagated into the structural interior and the dynamic behavior of the RC structure. The validity of the numerical simulation method is verified by comparing the overpressure-time histories and failure modes obtained from two tests. Furthermore, based on the explosion threat scenarios specified by the Federal Emergency Management Agency (FEMA), a numerical simulation study on the structural damage for seven explosion threats is conducted. The results show that the slab B1 shows a through hole with a diameter of 300 mm in test 1, and the wall QW12 shows a trapezoidal punching hole with a minimum horizontal length of 1100 mm, a maximum horizontal length of 2700 mm, and a vertical height of 1300 mm. However, the damage to RC columns and beams is negligible. Masonry-infilled walls can block the propagation of shock waves and significantly reduce the shock wave pressure propagated into the structural interior. It is recommended that the attenuation coefficient be taken as 0.9 for contact explosions and 0.95 for near-field explosions. For the seven typical explosion threats, the main RC frame remains relatively intact due to the significant reduction of shock wave pressure. The ejection of wall debris driven by the explosion becomes a secondary damage factor that expands the damage scope. The impact effect of wall debris is one of the primary reasons for damage to internal structural components.