Shear Lag Analysis in Tapered Box Girders with Steel Trapezoidal Corrugated Webs Using a Modified Analogy Bar Method

Quantifying shear lag effects (SLE) in tapered box girders with steel trapezoidal corrugated webs (BGSTCWs) is crucial for improving design accuracy and structural safety, especially as these girders are increasingly utilized in long-span bridges. However, existing analytical methods exhibit significant limitations in predicting SLE in tapered BGSTCWs. The energy variational method (EVM), although theoretically rigorous, faces practical challenges of incorporating warping displacement functions in girders with complex geometries and material variations. Similarly, the analogy bar method (ABM), though effective for prismatic BGSTCWs, fails to accurately capture shear flow in tapered counterparts due to significant differences in shear transfer mechanisms governed by the Resal effect. These limitations are addressed by proposing a modified analogy bar method (MABM) that explicitly incorporates Resal effect into SLE analysis for tapered BGSTCWs. The MABM derives the equivalent stiffening bar area and shear flow distribution considering cross-sectional variability, given the subsequent establishment and analytical solution of the governing differential equations under prescribed boundary conditions. The feasibility of the proposed MABM is verified through finite element (FE) simulations and experimental tests conducted on a tapered cantilever BGSTCWs given concentrated tip load. At the fixed end of tapered cantilever BGSTCWs, where the Resal effect is significantly intensified given maximum hogging moments, the MABM improves SLE prediction accuracy by 21.36% and 15.80% in the top and bottom slabs, respectively, compared to the conventional ABM. Additionally, this study systematically examines how geometric tapered configurations (regular versus reverse tapered) govern the development of either positive or negative Resal effects, which in turn directly determine the corresponding positive or negative SLE in the structural response. The degree of the SLE in tapered BGSTCWs is found to be directly influenced by the intensity of the Resal effect.