## 5 Conclusions  
This paper proposes the three-dimensional contact constraint method, which facilitates the consideration of three-dimensional pavement roughness in vehicle-bridge coupling analysis. Three-dimensional vehicle-bridge coupling vibration analysis was conducted on a simply supported corrugated steel web box girder bridge. The effects of vehicle speed, pavement grade, pavement roughness dimension, and box girder configurations on the impact factor are analyzed. The calculated results are then compared with those of international standards. The conclusions are as follows:  
1. After verifying the correctness of the method, a vehicle-bridge coupling vibration study on corrugated steel web box girder bridges was conducted. The effect of vehicle speed on the impact factor is not entirely positively correlated and is often influenced by other factors. For example, under different pavement grades, the variation pattern of the impact factor with vehicle speed is inconsistent. Within the range of operating speeds, there is a peak value for the impact factor. It is recommended to avoid the speed corresponding to this peak during operation to reduce excessive impact vibrations on the bridge. 2. At all speed levels, the influence pattern of pavement grade on the impact factor is consistent, with the impact factor increasing as pavement conditions deteriorate. For each upgrade in pavement grade, the impact factor increases by an average of 19.1%. Therefore, regular maintenance of the bridge pavement significantly promotes the service performance of the bridge. 3. The comparison of impact factors between three-dimensional and two-dimensional pavement roughness reveals notable differences. In most cases, the impact factors on the three-dimensional pavement roughness are smaller than those for the two-dimensional pavement roughness. The average reduction is 2.4%, 7.3%, and 13.5% for grade A, B, and C surfaces, respectively. 4. In the grade A pavement condition, when passing through the box beam at speeds of 20 km/h, 60 km/h, and 120 km/h, the mid-span dynamic deflection of the flat steel web box beam is reduced by 4.2%, 4.7%, and 3.7% compared to the corrugated steel web box beam, respectively. However, the impact factors are quite similar; the difference between the two models is within 0.005. For the steel bottom plate  
Figure 17: Impact factor comparison chart. box girder, the mid-span dynamic deflection increases by 21.7%, 30.3%, and 33.4% compared to the concrete bottom plate box girder. Meanwhile, the impact factors increase by 274.2%, 196.8%, and 116.8%, respectively. Therefore, after replacing the concrete bottom plate in the corrugated steel web box beam with a steel bottom plate, the static load-bearing capacity remains unchanged. However, the vibration problem of the box beam is significantly exacerbated. * 5. A comparison of impact factors calculated based on various national standards reveals that most of the standard calculated impact factors exceed the average impact factors obtained in this study. They are also closer to the maximum impact factor calculated under grade A pavement conditions. Therefore, standard methods for calculating impact factors are more applicable to new bridges and well-maintained bridges. For older bridges with poorer maintenance conditions, simulation calculations based on vehicle-bridge coupling are recommended. * 6. This research has not yet conducted vehicle-bridge coupling analysis under multiple vehicles, vehicle-bridge coupling analysis of continuous multi-span bridges, and wheel-bridge separation assumption analysis. Additionally, the method used in this paper has been validated through numerical simulation experiments, and bridge testing validation is also part of our future plans to enhance the applicability of the method. Conceptualization, J.D. ; Methodology, L.C., H.X., J.D. and X.C. ; Validation, H.M., F.Q. and J.W. ; Formal analysis, H.X., F.Q. and J.W. ; Investigation, H.M., H.X., X.C. and J.W. ; Resources, L.C. ; Writing-original draft, L.C., H.M., H.X. and X.C.