To study the mechanical performance of a new type of composite joint in a gymnasium

we designed three concrete-filled steel tube (CFST)-wrapped reinforced concrete (RC) composite joints using hot-bent steel tubes by taking the arch foot from the gymnasium project as the prototype

in which the long-span truss structural chord steel tube was bent and inserted vertically into the RC frame column. Load test and finite element simulation of the joints were carried out under complex loading with chord compression and web tension. The effects of residual stress

different bending angles

and whether the steel tube at the root of the chord is filled with concrete on the failure forms and bearing capacity of the hot-bent steel tube of composite joints were studied. Results show that the failure form of the hot-bent steel tube CFST-wrapped RC composite joints was mainly the buckling failure of the steel tube at the root of the chord. The bearing capacity of the joint depended on the compressive bearing capacity of the chord root. The residual stress generated by hot bending of the steel tube reduced the stiffness of the joint

and the greater the bending angle of the steel tube was

the less the stiffness of the joints was

but it basically had no effect on the bearing capacity. The stiffness and bearing capacity of the joints were significantly improved by filling concrete in steel tube

and were increased with the increase in the diameter of the steel tube.