A Temporary Stay Cable-Assisted Closure-Before-Rotation Method for Long-Span Cable-Stayed Bridges

Complex site conditions often impose constraints on the construction of cable-stayed bridges using the rotation construction method. To address this issue, a temporary stay cable-assisted closure-before-rotation method is proposed in this study. The proposed method completes the closure segment installation before bridge rotation and subsequently rotates the entire bridge structure, thereby reducing the impact on existing transportation lines beneath the bridge during construction. A (175 + 175) m single-pylon cable-stayed bridge with a central cable plane and a steel box girder crossing an expressway is selected as the engineering case study. A three-dimensional finite element model is established using Midas Civil to comparatively investigate the structural responses of the temporary stay cable-assisted closure-before-rotation method (Method I) and the temporary support closure construction (Method II). In addition, the sensitivity of key construction parameters to main girder alignment is evaluated. The results indicate that, for Method I, the secondary deck load has a significant influence on the alignment of the left-span main girder. The maximum vertical displacement of the main girder is −160.1 mm, the minimum safety factor of the temporary stay cables is 8.0, and the maximum stress of the steel box girder is −40.3 MPa, demonstrating satisfactory structural safety and deformation performance. For Method II, the maximum stress of the temporary supports is −112.4 MPa, and uneven load distribution occurs among the steel pipe piles. In the completed bridge state, the differences in main girder displacement, pylon-top displacement, and steel box girder stress between the two methods are relatively small, indicating that Method I can achieve comparable structural performance to Method II while reducing the dependence on temporary support systems and decreasing the required construction space during closure operations. Furthermore, the sensitivity analysis shows that main girder weight and stay cable force deviation significantly affect main girder deflection. A 5% variation in these parameters results in approximately 21.4 mm and 24.3 mm changes in girder deflection, respectively. Therefore, accurate estimation and control of the actual main girder weight and stay cable tension are essential to ensure that the final girder alignment and structural internal forces satisfy design requirements. The findings provide a reference for optimizing closure construction schemes of long-span cable-stayed bridges using the rotation construction method under complex construction conditions.