Experimental investigation on hollow-steel-tube columns with external confinements

Tubular steel members with slender cross-sections in compression arc prone to local buckling. Different approaches, such as mulling concrete, installation of internal stiffeners and externally bonding fiber-reinforced polymer reinforcement, have been developed to retard the local buckling of steel tubular sections, and hence to improve the performance of tubular structures. In this study, a total of 35 circular hollow-steel-tube (HST) stub columns with both non-slender and slender cross-sections confined by different types of external confinements, namely steel ring, spiral and jacket confinements were tested in the experimental program. The uni-axial behavior of externally confined HST columns, including the failure mode, ultimate load-carrying capacity, stiffness and ductility, were studied and discussed. The enhancements in strength, stiffness and ductility of HST columns with different external confinements were assessed. The results indicated that the improvements on strength and stiffness of the confined HST columns were insignificant for columns with non-slender cross-sections and were considerable for columns with slender cross-sections, whilst the ductility of the HST columns was substantially enhanced by external confinements. Based on the results, equations for column ductility evaluation considering the effects of cross-section slenderness ratio, steel strength and external confinement, are proposed in this study, which are able to predict the column ductility for unconfined and externally confined HST columns. (C) 2020 Elsevier Ltd. All rights reserved.