## 2 Finite Element Numerical Simulation
### Analysis of Calculation Results
#### 2.3.3 Longitudinal Axial Bias Loads  
The effect of different longitudinal axial bias loads on the upper turntable and steel spherical hinge stresses was obtained by Ansys finite element analysis; the results were shown in Figure 17a. When the eccentricity value is 10 mm, the stress on each rotating device increases steeply, which was analyzed to be due to the large longitudinal span of the bridge girder box, so the eccentricity condition has a greater impact on the rotating device. By increasing the eccentricity on this basis, the rise in stress decreases, but the value of stress increases with increasing eccentricity. The local enlarged diagram at the eccentricity distance of 257.4 mm was shown in Figure 17b, from which it can be seen that  
Figure 16: Cloud diagram of lower steel spherical hinge (eccentricity is 257.4 mm): **(a)** equivalent stress cloud; **(b)** total deformation cloud.  
Figure 14: Cloud diagram of upper turntable (eccentricity is 257.4 mm): **(a)** equivalent stress cloud; **(b)** total deformation cloud.  
Figure 15: Cloud diagram of upper steel spherical hinge (eccentricity is 257.4 mm): **(a)** equivalent stress cloud; **(b)** total deformation cloud.  
when the ultimate eccentricity distance of 257.4 mm was reached, the normal compressive stress on the upper turntable was close to the permissible stress value of 37.5 MPa for the compressive strength of C50 concrete, which was in the ultimate working condition. At this time, the equivalent force on the upper turntable has reached 38.02 MPa, exceeding the allowable stress value. When the eccentricity is 200 mm, the equivalent force on the upper turntable is at the limit working condition. When the eccentricity is 257.4 mm, the stress on the steel spherical hinge is still much less than its yield strength. Therefore, under the influence of longitudinal axial bias loads, the limiting longitudinal axial bias loads distance of this bridge is 200 mm due to the properties of the material of the upper turntable, but longitudinal axial bias loads distance should be reduced as much as possible in order to ensure the safety and stability of the bridge construction.  
The simulation results with an eccentricity of 257.4 mm are shown in the following figures; the cloud diagrams of the equivalent stresses and deformations of the upper turntable are shown in Figure 18. The cloud diagrams of the upper steel spherical hinge equivalent stress and deformation are shown in Figure 19; the cloud diagrams of the lower steel spherical hinge equivalent stress and deformation are shown in Figure 20. From the figure, it can be seen that when reaching the limit of eccentricity, the rotating device of each part of the stress concentration is more obvious than not eccentric; the pattern of stress change is the same as that of transverse axial bias loads, and the stress value is slightly larger than that of transverse axial bias loads. The stress value is slightly larger than longitudinal axial bias loads; the maximum stress value point is located in the eccentricity position. In order to ensure the safety of the project, the need to pay attention to longitudinal axial bias loads of the conditions of the bridge to the impact of the process of the bridge turning.  
Figure 17: Effect of eccentricity on stress: (**a**) overall picture; (**b**) enlarged picture.  
Figure 18: Cloud diagram of upper turntable (eccentricity is 257.4 mm): (**a**) equivalent stress cloud; (**b**) total deformation cloud.