This study investigates the effect of prestress tensioning in the negative moment region on the mechanical behavior of flange plate wet joints, using an under-construction simply-supported-to-continuous T-beam bridge as a case study. Through construction process monitoring and parametric numerical simulations, the stress distribution patterns in the wet joints were analyzed. For construction convenience, the referenced project adopted the sequence of tensioning prestressing tendons first, followed by casting longitudinal wet joints. The parametric analysis considered two additional scenarios beyond the original construction sequence (Method 1): casting wet joints before tensioning prestress (Method 2), and partially casting wet joints in the negative moment region before tensioning prestress, followed by casting the remaining wet joints (Method 3). Monitoring results showed that while the actual prestress tensioning levels varied by over 10% during construction, the wet joints remained largely unaffected due to post-tension casting. After completion of wet joint casting, transverse stresses were predominantly compressive, with longitudinal tensile stresses only observed near transverse beams at low levels (maximum value: 15 × 10^-6).Monitoring data indicated that prestress tensioning did not directly increase the cracking risk of wet joints. Parametric analysis demonstrated that all three construction methods provided certain stress margins for wet joints, with maximum principal tensile stresses under permanent loads measuring 0.3, 1.5 and 0.9 MPa respectively. The first two methods showed continuous significant tensile stress development after superimposed dead load application, while the third method (staged casting of wet joints) maintained low tensile stresses even after superimposed dead load, though it involved more complex construction procedures. These findings provide valuable references for mechanical analysis and process optimization in similar structural construction projects.

In order to investigate the optimization design method of medium and large span continuous steel girder steel fiber reinforced concrete (SFRC) composite bridge deck, the study used SFRC to replace C50 concrete pavement in the original design, and established SFRC composite bridge deck steel box girder segment model by Abaqus for parameter analysis. And the influence characteristics of SFRC plate thickness, steel roof thickness and reinforcement ratio on the bending stiffness and steel structure stress of the main beam were investigated. The study is based on the cracking characteristics of SFRC obtained by the combination of SFRC composite plate partial tension test and numerical simulation and the existing continuous steel girder structural characteristics. On this basis, the main girder elastic bending stiffness and key cross-section stress were taken as the constraints, and the upper structural self-weight and material cost were taken as the optimization objectives to optimize the mid-span 50 m and 80 m continuous steel girders. Finally, based on the variable optimization results, Midas was used to establish a bar model considering SFRC cracking in the negative moment region to verify the reasonableness of the optimization results. The results show that the finite element analysis method of plastic damage introduced in the paper is reliable, and the relationship between the SFRC crack width and the tensile damage factor can characterize the SFRC cracking state. The 80~120 mm thick SFRC layer on the continuous steel girder increases the elastic bending stiffness of the main girder by 17%~24% after participating in the force; the bending stiffness of the main girder decreases by 13%~20% when the width of the SFRC crack reaches 0.20 mm; the stress of the steel roof plate decreases by 7%~12%, and the negative bending capacity of the main girder does not change significantly. Increasing the thickness of top plate and reinforcement ratio can effectively improve the stress of steel roof. Through the optimization analysis of SFRC layer thickness, reinforcement ratio, steel roof and roof stiffener size, compared with the original design, the optimized steel consumption of 50 m and 80 m continuous steel girders with SFRC deck panels is reduced by 13% and 6% respectively, the weight of the superstructure is reduced by 12% and 6% respectively, and the cost of the material is reduced by 14% and 9% respectively. The optimized design process and optimization results can be used for the design of the continuous steel girder in SFRC deck panels. The optimized design process and optimization results can provide reference for the popularization and application of SFRC composite bridge deck in continuous steel girder.