Blast performance prediction of circular column with improvised equivalent helical mesh transverse reinforcement substituted for single helix, UHPFRC plaster and CFRP wrapping under close-in blast

The explosion from bombshells develops an excessively high impulsive load on structures. Columns being important key load-bearing members of a structure are vital to providing strength and stability to the building. A circular column performs better than a square/rectangular column under blast loading. Following the validation of experimentally tested square RC column with seismic lateral reinforcement carrying 950kN axial load subjected to an explosive charge of 100kg ANFO (82kg-TNT equivalent) at a scaled distance of 1.00m/kg1/3 with 10mm mesh size using ABAQUS/EXPLICIT software equipped with concrete damage plasticity (CDP) model, an equivalent circular reinforced concrete (RC) column is considered. It is well known that the performance of the circular RC column with single helical transverse reinforcement is superior compared to circular lateral ties. To improve the blast-impact resistance of circular column provision for helical reinforcement mesh using six bars turning successive bars in opposite direction is attempted in this work. The performance of a column with equivalent helical mesh is compared with the column with single helical transverse reinforcement. Further, UHPFRC plaster, as well as CFRP wrapping, are considered on the two columns under the close-in blast loading. The thickness of UHPFRC plaster and CFRP wrapping considered in this study are 15mm and 2mm respectively. The effect of plaster and wrapping on the two columns in terms of confinement of concrete and stresses in longitudinal steel are investigated and compared. Maximum deflection and damage of the columns are predicted.