Axial compressive property of square and rectangular UHPC-filled duplex stainless steel tube stub columns

This study presents experimental and numerical investigations of the axial compression performance of square and rectangular ultrahigh performance concrete (UHPC)-filled duplex stainless steel tube (UFSST) stub columns. A total of twelve UFSST stub columns, six ordinary concrete filled duplex stainless steel tube (CFSST) stub columns, and six hollow duplex stainless steel tube (HSST) stub columns were tested under axial compression. The test parameters include the section type, three kinds of concrete strength grades, and three kinds of duplex stainless steel tube thicknesses. The test results showed that UFSST stub columns behaved with high bearing capacity and favourable ductility. In the UFSST stub columns with & xi; & GE; 1.87, the square and rectangular duplex stainless steel tubes could well confine the shear failure of UHPC. The developed finite element model could effectively reflect the compressive behavior of the HSST, CFSST and UFSST stub columns. The available experimental database was employed to evaluate the feasibility of current design codes and existing calculation models in the literature to design UFSST stub columns. Finally, a modified computational model was proposed that takes into account the nonuniform confinement effect induced by square and rectangular section tubes on concrete and showed a higher prediction accuracy.