## 4 Three-Segment Cycle Construction Scheme  
The construction process of a composite beam cable-stayed bridge has significant impacts on the overall structural forces, construction duration, and material usage. In  
Figure 8: Cable force distribution at reasonable completion state. Figure 7: Stress in the main girder of the Xiangsizhou Bridge (unit: MPa). the engineering practice of the Xiangsizhou Bridge, factors, such as geographical location, hydrogeological conditions, time to open for traffic, and project economics, have imposed limitations on the construction. With a tight construction schedule, the installation period of the main beam determines the overall duration of the bridge project. Therefore, optimizing the construction process to shorten the duration while ensuring construction quality and structural safety is a critical issue that must be addressed for the Xiangsizhou Bridge. To expedite the construction progress of composite beam cable-stayed bridges, scholars have proposed three approaches. The first method aims to reduce the tensioning frequency of cable-stayed ropes. The second method aims to shorten the maintenance time of the bridge deck wet joint, and the third method is to use a double- or multi-segment cyclic construction mode. However, each method has its drawbacks. The first approach involves tensioning the cable-stayed ropes to the final position in one go, which can cause cracks in the bridge deck due to excessive tensile stress. This can negatively impact the structural stress and durability of the bridge. The second approach aims to shorten the maintenance time of the bridge deck wet joint. However, this may result in concrete cracking, which can affect the overall stress of the bridge deck and steel main beam. The third approach involves the adoption of a double- or multi-segment cyclic construction mode. Although the double-segment cyclic construction has been used in several large-span composite beam cable-stayed bridges in China, further three-segment cyclic construction may lead to excessive tensile and compressive stresses on the bridge deck and high stress on the steel main beam in the joint area. Therefore, necessary measures must be taken to reduce the stress on the bridge deck and steel main beam. According to the design requirements of the Xiangsizhou Bridge, the wet joint of the bridge deck panel adopts C55 concrete, and the strength of the wet joint concrete should reach 90% or more before proceeding to subsequent construction steps. Based on the analysis of the construction cycle of the main beam segment, the conventional single-segment construction cycle requires a duration of 10 days, of which 5-7 days are needed for curing the wet joint of the bridge deck panel, and during this curing period, no other operations are allowed on the bridge deck. Through comprehensive consideration and a large number of finite element simulation analyses and optimizations, a three-segment cycle construction of the bridge deck panel wet joint is adopted, as shown in Figure 9. For every three consecutive beam segments, the three-segment cycle scheme (simultaneous setting of three wet joints between four segments of the bridge deck panel, reinforcement binding, concrete pouring, and curing) is compared with the single-segment cycle scheme (one wet joint between two segments of the bridge deck panel, reinforcement binding, concrete pouring, and curing, usually requiring 10 days). The three-segment cycle scheme can save two segments of the wet joint construction time compared with the single-segment cycle scheme, which means at least 20 days of the construction period can be saved. Six rounds of three-segment cycle construction of the 20 beam segments can save 120 days of the construction period, which is of great significance for completing the main bridge closure plan on time.