## 6 Conclusions  
In the presented study, the stress and displacement of curved steel box girders, incremental launching piers, and guide girders during the construction process are monitored in combination with the incremental launching project of small-curvature-radius curved steel box girders at the intersection of Xuchang-Xuguang Expressway and Yongdeng Expressway. For the analysis, five of the most adverse working conditions were selected. At the same time, finite element analysis was performed by altering the location of the temporary support to realize the simulation of the incremental launching process. The states of internal forces and displacements under the five working conditions were evaluated, and the following conclusions were drawn:  
Figure 15: Steel box girder bridge of span expressway is pushed in place and opened to traffic after construction is completed. (**a**) is the scene of the curved steel box girder bridge across the highway after being incrementally launched into position, (**b**) is the scene after the construction is completed and the bridge is open to traffic. (1) The comparison of monitored and theoretical values for the steel box girder and guide girder under key working conditions shows that their internal forces and deflections are within the safe range, ensuring the safety of incremental launching construction. (2) During the incremental launching process in working condition 4, the foundation displacement of each incremental launching cycle first increased and then decreased, with the variation range of the minimum value within 4 mm. This indicates the relatively small impact of the incremental launching process on the foundation settlement. (3) Temporary pier L3 is in an ideal low-stress state in the first stage of incremental launching. The stress is generally large in the second stage of incremental launching, but it is within the safe range. In the third stage of the incremental launching process, when the incremental launching distance of \(Z_{3}\) is about 36-42 m, the stress exhibits significant fluctuations and demands heightened attention. Although it poses a relatively higher risk level compared to other scenarios, it remains within the acceptable safety boundaries. Therefore, temporary pier L3 is in a safe state during the whole pushing process. (4) The second stage of incremental launching is the most unfavorable working condition of the guide girder (working condition 2). As the incremental launching distance increases, the stress of the guide girder section first rises and then falls. When the guide girder is reaches its maximum cantilever position, the stress on it increases, but the peak stress does not occur at this position. Therefore, the construction process must be monitored throughout to effectively ensure construction safety and quality. Meanwhile, considering that the construction monitoring is carried out in the summer season, where temperatures are over 35 \({}^{\circ}\)C and the surface temperature of the steel box girder is 50-60 \({}^{\circ}\)C, the strain value will be affected, which will make the strain larger, but the stress is still in the safe range. In subsequent research, the influence of increased temperatures on the strain of steel box girders should be addressed. Conceptualization, H.H. ; methodology, H.H. and H.M.; software, X.X. ; validation, H.H., X.X. and J.D. ; formal analysis, H.M., J.D. and Z.Z. ; investigation, Z.Z., H.Y., E.G. and J.M. ; resources, H.M.; data curation, Z.Z. and E.G. ; writing--original draft preparation, H.H. and H.M.; writing--review and editing, H.H., H.M. and J.D. ; funding acquisition, H.M. and J.M. All authors have read and agreed to the published version of the manuscript. This work was supported by the Key R&D and Promotion Special Project in Henan Province-Science and Technology Research (joint fund) Project (Grant No. 232103810082) and the Key R&D and Promotion Special Project in Henan Province-Science and Technology Research Project (Grant No. 22210320462).