Compressive behaviour and design of compact to slender octagonal concrete-filled steel tubular stub columns

Abstract

This paper presents an experimental investigation into the compressive behaviour of compact to slender octagonal concrete-filled steel tubular (OctCFST) stub columns. In this study, a total of twenty OctCFST stub column specimens were tested. Five octagonal hollow sections with various cross-sectional slenderness were fabricated from 3 mm and 6 mm 460 steel plates. The measured yield strengths of the two batches of steel plates are 546.5 and 580.7 MPa, respectively. Three grades of concrete with measured cylinder strengths varying from 27.9 to 92.1 MPa were used to infill the hollow tubes. The test results, in terms of failure modes, axial load versus axial strain responses and cross-sectional capacities of the stub column tests are fully presented and discussed. The experimental results were then used to evaluate the applicability of current design methods in Eurocode EN 1994-1-1, American standard ANSI/AISC 360-16, Chinese code GB 50936-2014 and equivalent circle methods. It is shown that the circumcircle method and GB 50936-2014 approach produce excellent cross-sectional strength predictions for the OctCFSTs and the current cross-section slenderness limit of 135×235/fy for circular concrete-filled steel tubes specified in GB 50936-2014 can be safely extended to the design of OctCFSTs when the equivalent circumcircle method is used.