Compressive behaviour of UHPC-filled square high-strength steel tube stub columns under eccentric loading

Abstract

This paper presents experimental and numerical studies on the compressive behaviour of ultra-high performance concrete (UHPC) filled rectangular high-strength steel tube (UFHST) stub columns under eccentric loading. A total of 16 compressive specimens with a maximum concrete strength of 150 MPa and a maximum steel strength of 846 MPa were designed and tested. The test results showed that the use of high-strength steel tube and UHPC without steel fibres largely enhanced the load-carrying capacity of concrete-filled steel tube columns. The use of fibre-free UHPC adversely influenced the ductility of the columns. The incorporation of steel fibres into UHPC when casting the columns, however, improved the ductility of the composite columns and at the same time gained additional load-carrying capacity. A finite element (FE) model was then developed using ABAQUS and verified with test results. The numerical parametric study using the verified FE model showed that the confinement effect from the high-strength steel tube onto the UHPC was obscure before peak stress of the column was achieved, but was gradually activated/increased in the post-peak stress stage. Therefore, subsequent to the peak value, the axial stress of the confined UHPC experienced a short decrease first and then a continued growth. The findings from the present study set an experimental and numerical basis for future investigations to expose optimistic design of the UFHST stub columns.