Investigation of the Shear Lag Effect of an Innovative Steel Box Girder in Cable-Stayed Bridges: Experimental and Bar Simulation Method Analysis

Abstract

As an innovative steel box girder, the normal stress patterns in the top and bottom plates of a cantilever steel box girder are complex. However, the influence of external and internal struts on the shear lag effect is poorly understood. To address this gap in knowledge, a 1:4.5 scale experimental segmental model was developed. The normal stress patterns in cross sections with and without external diagonal struts under different vehicular and train load cases were studied, and it was found that the vehicle load would result in a large normal stress at the junction of the outer web and top plate and the train load would cause a large normal stress at the junction of the inner web plate and top plate. In addition, compressive and tensile normal stresses appeared simultaneously in the bottom plate under vehicle or train loads, which led to negative and positive shear lag effects in the bottom plate. A bar simulation method was used to explain this phenomenon. In addition, to obtain the normal stress in the cantilever steel box girder, new assumptions about the shear flows that caused the vehicle and train loads in the web plates are presented. Based on the bar simulation method, the influence mechanism of the external and internal struts on the shear lag effect of the cantilever steel box girder was discovered. The external strut limited the shear deformation of the connection zone, which resulted in a small normal stress in the zone. The external and internal struts generated additional shear flow in the bottom plate, resulting in simultaneous compressive and tensile normal stresses in the bottom plate. The results of this study provide a reference for understanding the shear lag effect of cantilever steel box girders in cable-stayed bridges.