Experimental Study on Seismic Performance of Fire-Damaged Concrete-Filled Steel Tubular Column-Steel Beam Joints Under Low-Cycle Reversed Loading

As a typical steel-concrete composite structure, Concrete-Filled Steel Tubular (CFST) structures utilize the synergistic mechanical advantages of steel and concrete, showing good performance in bearing capacity, ductility and fire resistance, and becoming important in modern buildings. However, CFST structures may suffer hazards like fire, which causes performance degradation affecting subsequent seismic behavior. To study seismic performance of fire-damaged CFST column-steel beam joints, low-cycle repeated loading experiments were carried out on 3 specimens: 2 exposed to different fire temperatures and 1 ambient temperature control. Tests examined hysteretic behavior, ductility, energy dissipation, bearing capacity and stiffness degradation under post-fire axial compression ratios. Results show fire-damaged specimens had similar ductile failure modes to the control. Despite high temperatures, they maintained relatively full hysteretic curves and strong energy dissipation, but with reduced bearing capacity, increased deformation, nonlinear ductility growth, and more significant degradation at higher temperatures.