CONCRETE-FILLED COLD-FORMED STAINLESS STEEL TUBE COLUMNS PARTIALLY CONFINED WITH CFRP

SUMMARY Concrete-filled steel tube (CFST) columns offer high ductility, strength, stiffness and full usage of construction materials. The steel tubes surrounding the concrete core are used as formwork, which decreases the construction cost. CFST columns have been used extensively for the construction of bridge piers, multi-story buildings and other supporting members due to theirs advantages compared with ordinary reinforced concrete columns. Concrete-filled carbon steel tube (CFCST) and concrete-filled stainless steel tube (CFSST) have been already investigated to explore their structural behaviour. The common mode of failure for CFCST and CFSST short columns is the outward local buckling, which prevent exploiting the full abilities of steel tubes strength and ductility. During the last decade, investigations were conducted to overcome the local buckling failure for CFCST columns by using full length jacketing with carbon fibre reinforced polymer (CFRP). The use of CFRP full length jacketing to strengthening CFCST columns against local buckling was demonstrated to be effective, it delayed or supressed the outward local buckling by increasing the confinement effect. The effect of CFRP confinement for CFSST columns was not addressed in literature so far. The objective of this research work is to evaluate the structural performance of CFSST short columns with partial confinement of CFRP sheets at potential local bucking regions. It is not economical to confine the whole length of CFSST columns with CFRP sheet since CFCST columns would be a better alternative in this case. It is intended in this work to minimize this confinement effect to both ends of CFSST columns. In this study, CFSST columns partially confined with CFRP will be experimentally tested under two cases of monotonic loading: pure axial and eccentric axial compression loadings. A three dimensional finite element model (FEM) will be developed using ABAQUS software and will be validated with experimental results. Thereafter, a parametric study will be conducted to evaluate in depth the effects of thickness and length of CFRP sheet partial confinement on CFSST columns performance with several variables. Finally, analytical model will be developed to estimate the capacity of CFSST columns partially confined with CFRP sheets.