Strengthening mechanism of steel tubed RC column joints with built-in section steel

This study investigates the behavior of steel-tube-reinforced concrete (STRC) column joints embedded with built-in section steel under low-cycle reversed loading. Finite element models (FEMs) of four groups of section-steel-reinforced concrete column joints were developed using ABAQUS. Based on this, FEMs were also developed for three groups of STRC column joints with built-in section steel and three groups without section steel. The mechanical behavior and working mechanisms of both joint types were analyzed in terms of failure modes, stress distributions of concrete, steel tubes, and section steel in the nodal zone under varying axial compression ratios. Additionally, their shear behavior was evaluated using the truss-arch model. Results indicate that STRC column joints with built-in section steel exhibit superior load-bearing capacity, ultimate displacement, and ductility compared to those without section steel. Their failure modes are characterized by plastic hinge formation at the beam ends. The shear capacity of joints with built-in section steel improved by 1.37 to 1.7 times.