# Study on the Fire Resistance of Axially Restrained H-Shaped Steel Beams Under Real Fire
## 3 Analysis of Fire Resistance of Steel Columns Based on Quasi-Real Fire Heating Curve
### Establishment of Finite Element Model of H-Section Steel Beam
#### 3.1.4 Model Verification  
In Reference [30], the calculation results of the finite element model of the high-temperature steel beam are compared with the measured results of the test specimens in the four dimensions of steel beam surface temperature, displacement-temperature curve, axial force-temperature curve, and failure deformation diagram. The results are in good agreement, which proves the reliability of the finite element model of the constrained Q460 steel beam for thermal-mechanical coupling analysis. Among them, the difference between the surface temperature of the steel beam calculated by the model and the measured value of the test is within 3%; the difference between the change law of the mid-span displacement of the steel beam with temperature and the measured value of the test is less than 4%.  
In order to verify the accuracy of the finite element model, the temperature-mid-span deflection curve and failure mode obtained from the finite element model results are compared with the experimental data in the reference paper.  
The application of the concentrated load on the Q460 steel beam is kept consistent with the experiment. The concentrated load is applied to the coupling point RP-7 in the mid-span area (Figure 10). After the steel beam fails, the temperature-mid-span deflection displacement curve is obtained, and the failure mode is observed (Figure 10b). The loss of stability of the specimen is regarded as the failure condition of the specimen. As specified in GB/T 9978-1999 _Test Methods for Fire Resistance of Building Components_[33], when the maximum deflection of the steel beam exceeds L/20, it is considered to have lost stability, and the temperature of the steel beam at this time is the critical temperature.  
In the process of thermal-mechanical coupling analysis, a static analysis step is first created to apply the predetermined load, which is kept stable in the subsequent analysis steps. Then, the time-temperature curves of the steel beams obtained from FDS simulations are set as air temperature rise curves and introduced into the model, being heated through the two mechanisms of surface thermal radiation and surface thermal convection. In this process, the thermal radiation coefficient of the model surface is specified as 0.5, and the heat transfer coefficient of surface thermal convection is set at 25 W/(m\({}^{2.\circ}\)C).  
In Figure 10a, the comparison between the temperature-displacement curve from the finite element simulation and that from the experimental results reveals that the critical temperature obtained by the simulation is slightly lower than the experimental value, with an error within 5% and a good agreement. In Figure 10b, the comparison of the failure modes shows that the failure locations and deformation magnitudes are largely consistent, indicating that the finite element model can effectively simulate the failure modes of steel beams. In summary, the finite element simulation method used in this paper can better simulate the fire resistance response of Q460 steel beams.