# Mechanical Performance Prediction Model of Steel Bridge Deck Pavement System Based on XGBoost
## 3 Dataset Creation
### The Most Unfavorable Load Position  
To investigate the changes in the force of the pavement system when the load acts on the bridge deck at different positions in the transverse and longitudinal directions, a simulation test was conducted by controlling the relative positions of the load concerning the U-shaped ribs and the transverse spacer. Three cases of transverse load position were set based on the relative position of the load position and the U-shaped stiffening ribs, as shown in Figure 5: (1) the centerline of the load acts directly above the center of the U-shaped stiffening rib; (2) the centerline of the load acts directly above the connection between the U-shaped stiffening ribs and the steel bridge panel; and (3) the centerline of the load acts directly above the centerline of two adjacent U-shaped stiffening ribs. Six cases of longitudinal load position were set based on the relative position of the load position and cross-sectional plate, as shown in Figure 6. The centerline of the load position is 0 mm, 300 mm, 600 mm, 900 mm, 1200 mm, and 1500 mm, respectively, from directly above the cross-partition. Figure 4: Finite element model. Figure 3: Load equivalent effect. In this study, the maximum transverse tensile stress _A1_(MPa) on the surface of the pavement, the maximum longitudinal tensile stress _A2_(MPa) on the surface of the pavement, the maximum transverse shear stress _B1_(MPa) between the pavement and the steel bridge deck, the maximum longitudinal shear stress _B2_(MPa) between the pavement and the steel bridge deck, and the maximum vertical displacement _C_(mm) of the pavement were used as the control indexes of the mechanical properties of the steel bridge deck pavement. The results of the calculation of the mechanical properties of the steel deck pavement system are shown in Table 2.  
Figure 5: Transverse load level. Figure 6: Longitudinal load level. The relationship between the maximum transverse tensile stress on the surface of the paving layer and the longitudinal load position under different transverse load positions is plotted, as shown in Figure 7. From the figure, it can be seen that the most unfavorable load position of the maximum transverse tensile stress on the surface of the paving layer is at transverse load position one (longitudinal 1500 mm). From the transverse partition to the span, the maximum transverse tensile stress on the surface of the paving layer shows a gradually increasing trend. In the distance from 0 mm to 600 mm in the longitudinal direction, transverse load level two is much larger than transverse load level one and load level three. The difference between the maximum transverse tensile stress on the pavement surface at transverse load level two (longitudinal 1500 mm) and transverse load level one (longitudinal 1500 mm) is 5%. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Transverse Load** & **Longitudinal Load Level** & \(A1\) **(MPa)** & \(A2\) **(MPa)** & \(B1\) **(MPa)** & \(B2\) **(MPa)** & \(C\) **(mm)** \\ \hline \multirow{4}{*}{Load position one} & 0 & 0.111 & 0.056 & 0.086 & 0.051 &  
The relationship between the maximum longitudinal tensile stress on the surface of the paving layer and the longitudinal load position under different transverse load positions was plotted as shown in Figure 8. From the figure, it can be seen that the most unfavorable load position of the maximum longitudinal tensile stress on the surface of the paving layer is at transverse load position two (300 mm longitudinal). From the transverse partition to the middle of the span, the maximum longitudinal tensile stress on the surface of the paving layer tends to increase first and then decrease.