Study on Shear Lag Effect of Single Box Double Chamber Corrugated Steel Web Composite Box Girder with Variable Thickness Roof

Abstract We focus on the study of a single‐box double‐cell corrugated steel web composite box girder (CSWCBG) with a variable thickness roof section, so the lower edge of the roof is considered according to the multi‐segment linear variation law, and its shear lag effect will be analyzed. Based on the energy variational method, the governing differential equation is established, and the analytical solutions of stress and shear lag coefficient of the simply supported beam under concentrated load are obtained. Taking the actual project as a sample, the finite element model is used to verify the analytical solution, and the roof thickness change rate's affection on the shear lag effect is studied. The research indicated that the error between the calculated value of the finite element model and the theoretical value considering the influence of variable thickness roof is less than 8%. Therefore, the derived calculation equation meets the accuracy requirements. The maximum error of the theoretical value after equivalent to the equal thickness roof is 11.35%, which indicates that the influence of the change rate of roof thickness cannot be ignored, and with the decrease of the change rate of roof thickness, the influence is more significant. When the thickness change rate of the box girder section top plate at the middle web is 0.28∼0.40 and both sides' thickness change rate of the side web is 0.16∼0.22 and 0.22∼0.34 respectively, the shear lag effect tends to be stable.