Compressive Mechanical Properties Of Concrete Filled Double Skin Steel Tubular Members After Exposed To Fire

Concrete-filled double skin steel tubular(CFDST),not only inherits a series of advantages of concrete-filled steel tube,but also has the advantages of cross section,bending rigidity,light weight,good seismic performance and so on.The mechanical properties of steel and concrete will decreased when the concrete filled double skin steel tubular after exposed to fire.The study on the mechanical properties of concrete filled double skin steel tubular has little published in home or abroad,so further study on mechanical properties of concrete filled double skin steel tubular after exposed to fire has important theoretical significance and practical value.In this paper,compressive mechanical properties of CFDST columns after fire were investigated.The main achievements can be summarized as follows:(1)Experimental study on axial compression and bias voltage of CFDST after fire.These specimens were heated following as closely as possible the ISO-834 standard fire curve or the standard fire curve prescribed by the Regulation of GB/T 9978-1999(Structural Member Fire-Resistant Experimental Method).The parameters in the study included the fire duration time,void ratio,the concrete strength and the eccentricity of CFDST.The bearing capacity,ductility and rigidity of the columns were compared and analyzed.(2)Based on the stress-strain relations for steel and concrete after high temperature.In the model,force-temperature-time path was considered.The theoretical analysis model of the axial compression and the bias voltage of concrete filled double skin steel tubular after exposed to fire was established by using the finite element(FE)software ABAQUS.The whole process curve of compression members after fire was calculation.The results from the FE analysis of the composite specimens compared favorably with the experimental results.(3)The finite element model was established,and the compressive mechanical properties of the members after fire was analyzed,it also further study on the working mechanism of axial and bias members after fire.The load-displacement and load-span deflection curves of members after fire were analyzed,the compressive mechanical properties of members after fire were analyzed in depth.the parameters such as time of fire、viod ratio、the concrete strength、slenderness ratio and eccentricity which influence on the remaining bearing capacity coefficient of CFDST after exposed to fire were analyzed,on the basis of this,the caculate methods of residual bearing capacity of CFDST after exposed to fire were established.