Analytical Calculation Method for Transverse Internal Force of Single-Box Double-Cell Box Girder with Inclined Webs Considering the Influence of Distortion Resistance Stiffness

The complex structural form of single-box twin-cell concrete box girders with inclined webs, featuring two internal cavities and angled webs, makes accurate calculation of transverse internal forces a pressing issue. This paper explores methods for calculating transverse internal forces in these structures by analyzing the mechanical behavior under eccentric loads using the single-box single-cell frame method, while fully considering structural characteristics. A method is proposed to decompose the analysis of released fictitious supports into three modes: torsion, distortion, and bending. This method clarifies shear force distribution patterns in the single-width frame for each mode of released support transverse internal forces, fully accounting for transverse flexural stiffness of each component. It establishes a general calculation method for transverse internal forces in single-box twin-cell box girders with inclined webs. The accuracy of this method is validated through comparison with results obtained from the finite element method (FEM). An in-depth analysis examines the relative magnitudes of transverse internal forces in each component and explores the effects of web inclination and middle web thickness on total transverse internal forces. Results show that the proposed calculation method aligns closely with FEM in terms of transverse internal force distribution patterns, demonstrating high accuracy. The total transverse internal force in the twin-cell box girder comprises fictitious support and released support transverse internal forces, with the latter primarily contributed by torsion and distortion modes. While tensile and compressive states of various slab elements differ in the two modes, the numerical values of transverse internal forces are very close under calculated conditions. When the eccentric load application point is near the middle web, the influence of the distortion mode increases significantly. In engineering practice, a rectangular section with the same top slab can be used as an approximate model to simplify transverse internal force calculations of the top slab in inclined web box girders. However, precise analysis is still required for the transverse internal force calculation of the middle web. To ensure the stability of transverse internal forces, it is recommended that the middle web thickness matches that of the side webs.