Shear performance of tapered composite beams with concrete-encased corrugated steel webs and steel bottom plate

Tapered composite girders integrating steel bottom flanges and corrugated steel webs (CSWs) offer promising solutions for large-span bridges through weight reduction and improved structural performance. However, the incorporation of concrete encasement in the negative moment region—specifically within the CSWs and bottom flanges—significantly alters the shear behavior of these members. This study evaluates the shear performance of such girders with concrete-encased CSWs (CCSWs) through theoretical derivation, experimental testing, and finite element (FE) analysis. Analytical expressions for shear stress distribution in the webs were derived and validated using a 1:6 scaled specimen designed based on the negative moment region of a 200 m main span continuous rigid frame bridge. Results showed good agreement between measured shear stresses and both analytical predictions and FE results. The inclined configuration of bottom flanges caused shear force variations with bending moment changes, leading to significant discrepancies when using conventional beam theory. Concrete encasement effectively reduced shear stress in CSWs by approximately 70 %, mitigating shear buckling risk. However, stress concentration was observed near the encasement termination, with a concentration factor of approximately 2.0. A parametric FE analysis was performed to compare various design configurations of the transition region between the CCSWs and CSWs, and design recommendations were proposed to alleviate the stress concentration. The shear force ratio between CSWs and concrete encasement (0.47–0.55) closely approximated their shear modulus ratio (0.54), providing valuable insights for design optimization of such innovative bridge structures.