| Rigid joints of concrete filled steel tubular column-steel beam have various forms, in which the joint with reinforcing ring has been researched more and applied widely. But the related research on the fire resistance behavior of joint with reinforcing ring is very little, so in this paper, numerical simulation theoretical researches are carried out according to international standard ISO834 for composite Joint with external reinforcing ring of concrete filled steel tubular column-steel beam, which provide evidence for fire resistance design of joint.Fire makes great effect to the properties of steel and concrete, especially to mechanical properties. Mastering the properties of steel and concrete in high temperature is the premise and foundation for structural analysis and design of fire resistance, therefore, in this paper, based on previous studies, the appropriate material properties are selected first. Secondly, the finite element model to calculate the temperature distribution of joint with external reinforcing ring is established by using ANSYS software, the temperature filed of the joint is obtained under the standard temperature curve, the results agree well with the experimental results of related literatures, and many influencing factors are analyzed by parameters. The main conclusions are the following:1) in the ISO834 standard temperature curve, the member section temperature distribution is not uniform and the change is non-linear.2) Fire protection has significant effect to temperature distribution of the joint, and the thicker the protective layer, the lower temperature. The filled concrete can decreased the temperature of steel tube, but this effect gradually disappeared in 1 hour. Concrete slab has great influence on the steel beam and the reinforcing ring, but again this effect is not obvious in the late heating.The finite element model is established for solving the bearing capacity at room temperature, the bearing capacity at room temperature for various different parameters is obtained, and the impact of parameters on the bearing capacity is analyzed, which provides a basis for the static load level in fireThe finite element model is established for solving the fire endurance of the joint in the standard temperature curve, the fire endurance for the joints of different parameters is obtained, and the impact of parameters on the fire endurance is analyzed. The main conclusions are the following:1) generally, the fire endurance of the joint with no protection is 10-20min when the static load level h=0.6. So to improve the fire resistance of the joint, in most cases, the joint needs fire protection.2) The load level makes great influence on the fire resistance of the joint with external reinforcing ring; With a certain load level, thickness of fire protection has a significant influence on fire resistance of the joint; With a certain load level, the beam height and width has a certain influence on the fire resistance of the joint, but other parameters such as steel yield strength, thickness, concrete strength, column section size, etc. have little effect on fire resistance of the joint.Finally, based on above analysis, some guidance suggestion has been put forward for the fire resistance design of the joint with external reinforcing ring. |
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