约束Q460GJ钢梁耐火性能OA

In order to investigate the fire resistance of Q460GJ steel beams,fire tests on six restrained steel beams were carried out by considering different cross-sectional dimensions,load ratios,and restrained stiffness.The temperature,axial deformation,lateral deformation,and internal forces of the specimens were measured.The test results show that the restrained Q460GJ steel beam specimen exhibits a failure mode of overall bending instability at high temperature,accompanied by lateral instability.The load ratio is an important factor affecting the fire resistance of the restrained Q460GJ steel beam.The increase of the load ratio from 0.3 to 0.4 leads to a decrease in the critical temperature by about 22 ℃.A finite element model of constrained Q460GJ steel beam was established,and was used for parameter analysis,and the effects of load ratio,rotational constraint stiffness ratio,axial constraint stiffness ratio,section aspect ratio,and span height ratio on the fire resistance of Q460GJ steel beams were examined.The analysis result has shown that increasing the load ratio from 0.4 to 0.9 results in a 28％decrease in critical temperature.The axial constraint stiffness has a significant impact on the yield temperature,but has little effect on the critical temperature and catenary temperature.The rotational constraint stiffness has a significant impact on the critical temperature,with the maximum increase of about 26％.The aspect ratio has a relatively small impact on the critical temperature,with the maximum impact within 10％.As the aspect ratio increases,the yield temperature,critical temperature,and catenary temperature of the steel beam do not change significantly.A method for calculating the critical temperature of restrained Q460GJ steel beams was proposed.The relative error of the calculated results is within 10％.The fire resistances of restrained Q460GJ steel beams and Q460 steel beams were compared and discussed.The difference in mechanical properties of materials at high temperatures leads to a lower critical temperature of the restrained Q460 GJ steel beam than that of the restrained Q460 steel beam,and the average critical temperature difference is 16.7％.