Research On The Mechanical Performance Of Concrete-filled Thin-walled Square Steel Tube With Spiral Stiffener Under Axial Compression Load

Concretc-filled thin-walled steel tube has significant economic benefits.However,the excessive ratio of width to thickness makes its local stability poor.In order to improve the mechanical properties of concrcte-filled thin-walled steel tube the local buckling of thin-walled square steel tubes is delayed,local stability and the thin wall is enhanced The confining effects of steel pipes proposes a new form of restraint for the provision of spiral stiffeners.This paper designs a concrete-filled thin-walled steel tube and four concrete-filled thin-walled steel tube with spiral stiffener,spiral stiffener combined with vertical steel bars,spiral stiffeners and vertical steel plates combined with spiral stiffeners and vertical steel plates(vertical steel plates welded with steel pipes)are designed.The new laminated component is mainly intended to improve the bearing capacity and deformation capacity of concrete-filled thin-walled steel tube,and enhance its fire resistance and corrosion resistance.In this paper,the axial compression test is carried out the mechanical properties and failure modes of the spiral stiffened concrete-filled thin-walled steel tube arc revealed.The failure mechanism and strain law are analyzed.Based on the calculation model,the steel tube width-to-thickness ratio,spiral stiffener width ratio and steel bars arc used.The diameter analyzed by parameters.The main conclusions are as follows:The local buckling of the thin-walled square steel pipe with the spiral stiffener is significantly reduced.The integrity of the surrounding concrete after the addition of the vertical reinforcing bar on the spiral stiffener is significantly improved,and the concrete crack and spaling arc significantly reduced.Compared with ordinary thin-walled steel tube concrete,the bearing capacity of concrete-filled thin-walled steel tube with spiral stiffeners and vertical steel bars is increased by 18%and the ductility coefficient is increased by 7%.The restraining system consisting of spiral stiffener-vertical steel bar and stirrup can work together to coordinate deformation,improve the restraining ability of thin-walled square steel pipe,and enhance the ferrule strengthening effect of core concrete,so that the bearing capacity and ductility of the laminated column are significantly improved.The finite element analysis results of the concrete-filled thin-walled steel tube with spiral stiffeners and vertical steel bars are in good agreement with the test.The parameter analysis shows that increasing the thickness of the thin-walled square steel tube can increase the bearing capacity of the laminated column.The 3mm thick spiral stiffener can provide sufficient stiffening stiffness.Continue to increase the thickness of the spiral stiffener to improve the mechanical properties of the laminated column is not significant.Increasing the vertical steel bar diameter can effectively increase the bearing capacity of the superimposed column,but the diameter of the steel bar needs to match the thick soil of the surrounding concrete.