Residual axial capacity of square recycled aggregate concrete-filled steel tube columns after blast loads

Abstract

To study the residual axial capacity of square recycled aggregate concrete-filled steel tube (RACFST) columns after close-range explosion loads, the explosion tests and the axial compression tests were performed. Firstly, 18 square RACFST columns were fabricated, and 15 of them were subjected to explosion tests. Secondly, the axial loads were applied to 3 intact columns and 9 blast-damaged columns. The curves of the load-displacement, the load-strain, and the load-mid-span deflection of all columns are analyzed. After the tests, the failure modes of the columns and core concrete were analyzed. Furthermore, the theoretical axial capacity of the RACFST columns was calculated according to the Chinese standard GB50936-2014. Based on the residual load-bearing capacity, the damage index is adopted to assess the damage degree of 9 blast-damaged columns. It indicates that both the blast-damaged and intact columns show diagonal shear failure under axial compression; the range of bearing capacity loss of the blast-damaged columns is approximately 1.9–32.1%, of which 5 columns are slightly damaged and 4 columns are moderately damaged, indicating that the columns still maintain a strong axial capacity reserve after explosion loads.