Blast Hardening of Reinforced Concrete Columns by External Post-tensioning

The design of blast-resistant civilian structures is not a common practice because blast is a rare event to occur. However, the rising concern from the increased number of terrorist attacks targeting civilian facilities triggered new challenges and accelerated the need for designing and building blast-resistant structures. Columns are critical structural elements, and loss of a column can trigger progressive collapse of the building. Protecting building columns through hardening can significantly improve the structure’s resistance to blast loads. The current research aims to address blast risk of reinforced concrete (RC) columns and potential improvements in their response by developing an innovative hardening technique. The experimental part of the study involves designing, building, and testing four half-scale RC columns that are hardened by externally anchored longitudinal prestressing seven-wire strands. The strands are anchored to the columns with three different longitudinal profiles: single harped, double harped, and triple harped or parabolic. A reference column and three hardened columns were tested under blast-induced shock waves generated by a blast simulator (shock tube). The test results included reflected pressure and impulse, maximum deflection, support reactions, and qualitative assessment of the level of damage. The results indicated that the behavior of hardened columns was significantly improved compared to the reference column. It was concluded that, on average the hardened columns could resist 20% higher reflected pressure and 40% higher impulse compared to the reference column before the onset of damage or failure. Moreover, in comparison with the reference column, the maximum deflection was noticeably lower in the hardened columns at each corresponding blast shot.