Experimental investigation on cold-formed high strength steel circular hollow sections under combined compression and bending

Abstract

Cold-formed high strength steel tubular members are gaining increasing attention from engineers due to their high strength-to-weight ratio, strong resistance against torsional buckling and aesthetic appearance. This paper presents a test program on cold-formed high strength carbon steel tubular sections under combined compression and bending. The nominal 0.2% proof stresses of the test specimens were 900 MPa and 1100 MPa. The specimens were loaded through knife edges at both ends to provide pinned boundary conditions. Different loading eccentricities were applied to the test specimens by shifting the position of knife edges from the centroid of the specimens. As a result, a wide range of bending moment-to-axial load ratio was achieved. The beam-column test set-up and experimental procedures are detailed in the paper. Furthermore, the ultimate strengths, load-end rotation histories and the failure modes of the test specimens are also reported. The test results were compared with the design strengths predicted from the American, European and Australian codes. The comparison showed that the existing design rules underestimate the ultimate strengths of the cold-formed high strength steel tubular beam-columns.