Effect of spontaneous-combustion coal gangue aggregate on axial performance of square concrete-filled steel tube stub columns

Abstract

This work experimentally studied the effect of spontaneous-combustion coal gangue aggregate (SCGA) on the mechanical performances of the square concrete-filled steel tube (CFST) stub columns subjected to axial loading. The influences of the substitution level of SCGA and the steel tube thickness on the failure mode, axial load–displacement response, ultimate load, elastic stiffness, and ductile performance were investigated. Trial results showed that the reduction in the ultimate compressive load of the CFST stub columns at an SCGA substitution level of 50% and 100% is within 5.96% and 12.10% respectively, compared to the CFST specimens made of natural aggregate (NA). Moreover, the elastic stiffness of the columns made of SCGA declined by 4.58%–16.67% and 22.44%–24.20% and their ductility coefficient by 1.10%–14.76% and 8.04%–18.27% at an SCGA substitution level of 50% and 100% respectively. To extend the parametric range of the experiment, the finite element models were analyzed in detail for estimating the influences of the SCGA substitution level, the concrete strength, the yielding strength of the steel tube, and the diameter of the stub columns utilizing Abaqus software. The results demonstrated that influences of SCGA incorporation on ultimate compressive load of CFSTs with square section could be presented via concrete strength and confinement coefficient. The design equations described in standard GB50936 were comparable to predict the ultimate load of the square CFST stub columns according to the finite element modeling data and verified by experimental results, and could be used for the routine design of CFSTs with SCGA.