Mechanical performance of concrete-encased prismatic girders with corrugated steel webs

To enhance the shear buckling resistance of girder bridges with corrugated steel webs (CSWs), especially near the intermediate support where maximum shear force and negative bending moment are experienced, it is common practice to encase the CSWs with concrete. This paper analyses the mechanical performance of concrete-encased prismatic girders with CSWs based on finite element (FE) simulations, theoretical analysis and existing experiments. The concrete encasement restricts the axial free deformation of the concrete-encased CSWs (CCSWs), thereby diminishing the accordion effect of the CSWs. As a result, the normal strains in both the CCSWs and the concrete encasement become nearly identical, demonstrating a linear distribution that aligns with the plane section assumption. The study reveals that the concrete encasement assists the CCSWs in shouldering a portion of the shear force, and shear stress in the CCSWs is no longer uniformly distributed. In addition, a stiffness-based shear carrying calculation method for CCSWs and concrete encasement is theoretically derived. It is observed that due to the constraint of concrete encasement, the actual shear modulus of CCSWs surpasses that of CSWs without encased concrete, rendering it more similar to that of a flat steel plate. Lastly, this study firstly proposes a shear stress calculation formula for CCSWs, which theoretically explains the parabolic shear stress distribution in CCSWs. Error analysis reveals that traditional basic shear method, which assumes uniform shear stress distribution in CSWs, significantly underestimates the actual shear stress in CCSWs. Remarkably, the modified shear method proposed in this study accurately predicts shear stresses in CCSWs.