Research On Behavious Of Short Square Thin-walled Concrete-filled Steel Tubes With Steel Bar Stiffeners Under Fixed High Temperature

Square Thin-Walled Concrete-Filled Steel Tubular Short Column structure with steel bar refers to that on the basic of the normal plain concrete with crossed reinforcement rib welded into the inner of steel tubular and decreased the thickness of the steel tubular step by step,which formed a new steel-concrete combined structure.The structure has a original form as well as improve the ability of mechanical and fire resistance of traditional steel tubular filled with plain concrete.Under normal atmospheric temperature :setting reinforced rib reduce the partly buckle due to the thinness of steel tubular.Although highly decrease the amount of the steel,it’s mechanical property can still fulfill the request of the structure.Under fixed atmospheric temperature :Because of the rising of the temperature,the steel intensity has a large damage,however,the crossed steel bar embedded in the core of the concrete has a damage positive restrain effect on the steel shell,which cuts down the mechanical property of the whole specimen.Setting reinforcement rib can prevent the structure from collapsing,what’s more,cut the cost and the degree of difficulty in the later step of structure repairmen and reinforcement.This article aimed to studied result of Square Thin-Walled Concrete-Filled Steel Tubular Short Column With Steel Bar Stiffness under axial compress as well as finite element analyze under the fixed atmospheric temperature.Main contents are as followers:(1)In this paper,6 with steel bar and 2 without steel bar stiffness are studied in the condition of 20℃,100℃,200℃,400℃,600℃,800℃.The results of the experiment in this paper said that: with the temperature rising,the whole model elements decreased obviously,which presented in the gradually reduce of Young’s modulus in elastic stage and the limit bearing capacity of the model.(2)The model of temperature field theoretical research and specimens under axial loading conditional as well as fixed atmospheric temperature had been done with the software ABAQUS.The calculated results are compared with the experimental results in this paper and some experimental results from other different reference,and they agreed well with each other.According to the results above,these numerical models have good precision,so that the models can be used in the follow-up works.(3)With the validated datum got from the specimens under axial loading condition with fixed high temperature,analyze the effect that conclude the size of steel bar stiffness,the directed separation distance between two steel bars stiffness,the steel content of the sections,the size of the sections and temperature on mechanical properties of the elements.It turned out to be that the size of the steel bar stiffness and distance of the two steel bars can improve the ductility of the specimen to some degree.With the rise of section steel contents and section size,the Young’s modulus in elastic stage becomes larger.Temperature has an enormous effect on weaken specimen’s mechanical property,which makes specimens’ Young’s modulus and limited bearing capacity in elastic stage decrease in different levels as a result of its risen.