Compressive behavior of steel-reinforced concrete-filled square steel tubular stub columns after exposure to elevated temperature

摘要

This paper presents the results of axial compression tests of steel-reinforced concrete-filled square steel tubular (SRCFSST) stub columns after exposure to elevated temperature. A total of 135 SRCFSST specimens are designed and tested, including 27 specimens that are unheated and 108 that are heated for different times. Each test examines the effects of concrete strength, width-to-thickness ratio of the square steel tube, section steel ratio and heating times on the strength, deformation and ductility characteristics of the specimen. Test results indicate that the section steel ratio has the greatest effect on the post-yield behavior of the SRCFSST stub columns. On the other hand, temperature has the greatest effect on the residual bearing capacity of the SRCFSST stub columns. The section steel ratio has the second greatest effect on the residual bearing capacity, followed by the concrete strength grade and the width-thickness ratio of the steel tube. Equations are proposed to predict the ultimate strength of the composite columns at room temperature and after exposure to elevated temperature. The computed values from the formulae are consistent with the experimental results.