Behaviour of Concrete Filled Steel Tube Reinforced Concrete Columns Subjected to Long-term Sustained Loading

An analytic model of concrete filled steel tube(CFST) reinforced concrete(CFSTRC) columns subjected to long-term sustained loading was established based on the reasonable material models,and load-deformation relationship curves of CFSTRC columns under sustained loading were analyzed.By the finite element method,the mechanical behavior analysis and parameter analysis of CFSTRC column subjected to long-term sustained loading were carried out.The results show that longterm sustained loading decreases the ultimate strength of the CFSTRC column while increases the corresponding deformation;the proportion of the load carried by the CFST increases with the increasing steel tube ratio during the long-term sustained loading stage;under sustained loading,when the slenderness ratio is greater than 10,the ultimate bearing capacity of the CFSTRC columns decreases with the increase of slenderness ratio and outer concrete strength,or the decrease of steel tube ratio and reinforcement ratio.