Experimental study on seismic behavior of steel reinforced concrete column-reinforced concrete beam joint after fire

In order to study the seismic behavior of steel reinforced concrete (SRC) column-reinforced concrete (RC) beam joints after fire, four joints after fire and two comparative joints without exposure to fire were tested under low-cycle reversed loading. The hysteretic characteristics, ductility, energy dissipation performance, bearing capacity and stiffness degradation of this kind of joints after fire were studied, and the effects of fire duration and axial compression ratio on the seismic performance of this kind of joints after fire were analyzed. The test results show that after fire damage, the hysteretic curve of the SRC column-RC beam joint is still plump, but the bearing capacity decreases significantly. When subjected to fire for 75 min, the capacity decreases by 13.2%-15.8%, and when subjected to fire for 120 min, it decreases by 33.1%-34.9%. The ductility of joints after fire is affected by fire duration. When the fire duration is 75 min, the displacement ductility coefficient of the joint is 10.5%-10.7% lower than that of the joint without fire under the same conditions. When the fire duration is increased to 120 min, the ductility coefficient is 6.9%-7.4% higher than that of the joint at room temperature. Compared with the joints at room temperature, the stiffness of the joints at the initial stage of loading after fire decreases and the equivalent damping ratio increases. The longer the fire duration, the higher the degree of stiffness reduction and equivalent damping ratio increase. With the process of loading, the stiffness of the joints after fire is consistent with that of the original joints at room temperature, but the equivalent damping ratio decreases compared with the original joints at room temperature, the longer the fire duration, the higher the reduction degree. The axial compression ratio has a certain influence on the seismic performance of joints after fire. With the increase of axial compression ratio, the strength, initial stiffness and equivalent damping ratio of the specimen increase to a certain extent, but the ductility coefficient does not change significantly. equivalent damping ratio of the specimen are improved to a certain extent, but the ductility coefficient does not change significantly. © 2021, Editorial Office of Journal of Building Structures. All right reserved.