Experimental investigation of axially loaded circular ultra-high performance concrete with coarse aggregate (CA-UHPC) filled steel tube slender columns

Abstract

This paper presents an experimental investigation on circular ultra-high performance concrete with coarse aggregate (CA-UHPC) filled steel tube (CA-UHPCFST) slender column subjected to axial compression. A total of 42 specimens were manufactured and tested to determine the effects of CA-UHPC strength, steel tube thickness, steel strength, and length-to-diameter ratio on axial compressive behavior of circular CA-UHPCFST slender columns. The test results show that elastoplastic instability failure with local buckling in the compression region is observed for intermediate columns, while overall buckling failure is occurred for slender columns. The inclusion of steel fibers significantly alleviates the tensile cracking and compressive crushing of CA-UHPC core, which in turn improves the ultimate strength and ductility of CA-UHPCFST slender columns. The ultimate bearing capacity and ductility index decrease remarkably with an increase in length-to-diameter ratio, while increase with steel yield strength and tube thickness. The interaction between steel tube and CA-UHPC core decreases as the length-to-diameter ratio increases, which mainly exists in compression zone but is weak or even nonexistent in tension zone. Finally, the feasibility of current design guidelines concerning the concrete-filled steel tubes for calculating the stability bearing capacity of circular CA-UHPCFST slender columns is evaluated, and a simplified model is proposed to estimate the stability carrying capacity. The simplified model demonstrates good accuracy in predicting the ultimate carrying capacity of axially loaded circular CA-UHPCFST slender columns.