A modified analysis method of mechanical properties of trapezoidal composite box girders

In research on the vertical bending mechanical properties of trapezoidal box girders with corrugated steel webs, the maximum angular rotation attributable to the in-plane shear deformation of flanges is traditionally considered as the generalized displacement function. However, this analysis method is very complex and the mechanical concepts are not well-understood. To address this, the presented work adopts the additional deflection induced by the shear lag effect as the generalized displacement function. Furthermore, the accordion effect, shear lag, shear deformation, and the self-equilibrium conditions of the shear lag warping stress and bending moment are considered comprehensively. The differential equations and the corresponding natural boundary conditions of the composite box girders in the elastic range are established using the energy variational method. Further, the closed-form solutions of the generalized displacements are obtained. The results of the analysis method presented, a modification of the traditional shear lag theory algorithm, had high agreement with finite element simulation results. In comparison to the traditional analysis theories, the accuracy of this modified method was improved. Thus, the method presented provides a strong basis for understanding the mechanical properties of composite box girders.