Blast resistance of grouting sleeve connected precast concrete columns under close-in explosions

Abstract

Attributed to the promotion of environmental protection and efficient construction, the precast concrete (PC) columns are gradually replacing the traditional reinforced concrete (RC) columns as the main load-bearing members of building structures. However, with the aggravation of deliberate or accidental explosions, there is a lack of study on the damage modes as well as dynamic responses of grouting sleeve connected PC columns. To systematically assess and compare the blast resistance of PC and RC columns, four PC columns and two control RC columns were firstly fabricated and tested under close-in explosions, in which the influences of the scaled distance (0.50 m/kg1/3 and 0.61 m/kg1/3), burst height (1/4- and 1/2-heights of column, i.e., 0.75 m and 1.5 m) and axial compression ratio (0.18 and 0.36) were experimentally examined. Secondly, the present test on PC/RC columns and the existing contact explosion test on PC specimens were numerically simulated. The reliability of the adopted numerical simulation approach was comprehensively verified by comparing the test and predicted incident and reflected overpressure-time histories, as well as the damage modes and displacement-time histories of specimens. Finally, the blast resistances of the prototype PC and RC columns under four design basis threats specified by U.S. Federal Emergency Management Agency were assessed, and the corresponding site mitigation measures were proposed. It indicates that, compared with RC columns, PC columns exhibited greater blast resistance, i.e., slighter maximum and residual lateral displacements, as well as concrete spalling sizes. However, both of PC and RC columns cannot survive under the contact explosion of suicide vests (9 kg of TNT equivalence) or the explosion induced by sedan bombs (454 kg of TNT equivalence) near the sidewalks at the standoff distance of 4 m.