Experimental investigation on the residual axial capacity of close-in blast damaged CFDST columns

Abstract

Concrete-filled double-skin steel tubes (CFDSTs) are comprised of two concentrically placed steel tubes and concrete core filled in the annulus between the two tubes. A number of studies have demonstrated the excellent structural performance of CFDSTs as load-bearing columns under various loading conditions, which have attracted lots of interests of engineers and researchers. Despite the increasing popularity of using CFDSTs as load-bearing structural columns, there is limited knowledge on blast resistant performance of CFDST columns particular under close-in explosion. In this paper, an experimental study was conducted to investigate the residual axial load-carrying capacity of CFDST columns after being subjected to close-in explosion. Field blast tests were firstly carried out on CFDST columns. Then, the blast-damaged columns were subjected to axial compression till failure under quasi-static condition in the laboratory to examine their residual axial load-carrying capacities. Seven half-scale CFDST column specimens were constructed and tested, of which one column serves as a reference column that was directly tested under axial compression to check the ultimate axial load-carrying capacity of CFDST columns without blast damage. The influences of design factors including charge weight, stand-off distance, charge orientation, and section hollow ratio on blast resistant performance of CFDST columns were quantitatively assessed based on the residual axial capacity index. It was found that under close-in blast loading CFDST columns showed localized cross-section denting with slight global deformation. The damaged columns can maintain up to 60% of its ultimate axial load-carrying capacity and exhibited good strength and ductility.