| Beam-column joints as an important component of the steel frame plays a crucial role on the mechanical properties of the whole structure in case of fire, once the destruction of beam-column joints occurs may cause the whole building collapsed, causing immeasurable losses, therefore research on fire resistance behavior of beam-column joints under fire loads is the most critical part of fire resistance design of steel structures. Currently research on fire resistance of steel structure mainly focuses on the analysis of individual components of the steel frame in fire, but relatively few researches on beam-column joints, while domestic and foreign design specifications for fire resistance behavior of beam-column joints under high temperature is blank or coarser. This paper through the finite element simulation software ABAQUS mainly analysis of the following aspects:(1) First of all beam-column joints at room temperature static loading test examples are simulated and calculated, thus failure modes and the moment-rotation curves are obtained and compared with the experimental results, while it verifies that the finite element simulation software ABAQUS can effectively simulate and analyze the mechanical properties of beam-column joints.(2) At room temperature, the mechanical properties of the three beam-column joints are simulated and analyzed, such as:the extended end-plate connection, the flush end-plate connection and the flexible end-plate connection, then the initial flexural rigidity and ultimate flexural capacity are determined from the moment-rotation curves of three end-plate connections, which has provided reference for studying the fire resistance behavior of beam-column joints at high temperature. The dynamic analysis of the mechanical properties of connection at room temperature and high temperature have been done by ABAQUS/Explicit processor, by considering the geometric nonlinearity, the material nonlinearity and the contact nonlinearity in calculating process might cause the results non-convergence, while avoiding the adverse impact of inertial force to the results.(3) At elevated temperature, the fire resistance behaviors of the three beam-column joints are simulated, the critical temperature is obtained by contrasting and verifying the temperature-displacement curve and failure modes with the experimental results. Also found the trends of temperature-rotation curves are basically identical, but the curve has a slight decreasing trend in the early stages of heating, which shows that the thermal expansion leads to the phenomenon of reverse deflection.(4) Based on the end-plate connections simulation analysis, analyzing the impact of each parameter on the fire resistance of the beam-column joints, such as:the load ratio, the thickness of end plate, the friction coefficient, the column web plate stiffeners and the thickness of stiffeners. The results show that the load ratio and the column web plate stiffeners have a greater impact on the fire resistance behavior of the beam-column joints, but the thickness of end plate, the friction coefficient and the thickness of stiffeners have a little effect on improving fire resistance behavior of beam-column joints. |
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