# Shear Lag Effect of Ultra-Wide Box Girder under Influence of Shear Deformation
## 7 Conclusions  
For the thin-walled box girder under the action of the shear deformation of each plate, the flexural displacement function of the wing and web plates of the box girder cannot satisfy the assumption of the plane section; the longitudinal flexural displacement function in the transverse direction of the wing plate is a quadratic function, and the height of the web plate is the sum of the primary and cubic functions.  
According to the theoretical analysis of the axial equilibrium conditions of the thin-walled box girder subjected to bending under the influence of the shear deformation of each plate, the actual neutral axis of the box girder under the influence of shear deformation no longer coincides with the horizontal axis of the box girder cross-section, having an offset distance of \(d\times g(z)\).  
The measured values of the model test, the simulated values of the finite-element model, and the calculated values of the theoretical method were compared, revealing sufficient agreement among the results. The majority of the shear lag coefficients had a relative error of \(<\)10.00%, confirming that the flexural displacement function of the flexural box girder under the influence of the shear deformation of the various plates derived in this study is reliable.  
Owing to the different constraint conditions at the edge of the cantilever plate and at the center of the top plate, the cantilever plate and top plate exhibit differences in their two-dimensional force characteristics and boundary constraints. The length of the cantilever plate should be appropriately reduced in engineering design to weaken its influence on the shear lag effect of the box girder.  
The article investigates the theoretical solution of shear hysteresis effects in bent box girders based on the energy method, along with the influencing factors of shear hysteresis effects. An empirical formula for shear hysteresis effects in single-box three-chamber box girders is fitted using Origin, addressing the issue of workload in calculating internal forces of box girders. In future developments, the following issues will continue to be addressed:  
During the derivation of the deflection function for thin-walled box girders, local constraints such as bulkheads and fillet welds were not considered. In future work, it is necessary to conduct a thorough analysis of the effects of these local constraints.  
As box girder structures continue to evolve towards wider cantilevered plates, larger flange-rib spacings, and lighter thin-walled materials, the nonlinear effects in geometric structure and material properties will become increasingly significant. This will become a major research area for thin-walled box girders in the future, requiring further study to refine the theoretical calculations for thin-walled box girders.  
Conceptualization, methodology, software, and validation, formal analysis, investigation, resources, data curation, Y.L. ([PERSON]) and J.X.; writing--original draft preparation, writing--review and editing, visualization, Y.L. ([PERSON]) and F.W.; supervision, project administration, funding acquisition, F.W. and Y.L. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This work was supported by National Key R&D Program of China (Nos. 2018 YFC0809600 and 2018 YFC0809606); Natural Science Foundation of Liaoning Province (No. 2019-MS-265); and Key Laboratory of the Ministry of Education on Safe Mining of Deep Metal Mines (No. 2019 SMDM-KF-A01); Shenyang Municipal Science and Technology Planning Project Fund (No. 23-407-3-19).  
Not applicable.  
Data Availability Statement: Data used to support the findings of this study are available from the corresponding author upon request.  
The authors declare no conflicts of interest.