Shear Lag Analysis in Prestressed Concrete Box Girders

Abstract

Most studies on shear lag effect in box girders are only concerned about concentrated loads and uniformly distributed loads. In this paper, a finite-element method based on the variational principle is presented to analyze the effect of prestressing on shear lag in box girders. The procedures and main steps are listed to demonstrate how to use the proposed FEM, which is verified by the analytical method and the numerical examples. The shear lag effect in box girders with different types of support conditions under prestressing is analyzed in detail. The shear lag effect in box girders under prestressing is more apparent than that under uniformly distributed loads or vertical concentrated loads. The values and distributions of shear lag coefficients are relate to the anchorage locations of prestressing and the distributions of internal forces along the girder under the combined uniformly distributed load and prestressing. Among the conclusions of the study is that negative shear lag under the uniformly distributed load and prestressing may occur both at the midspan of a simply supported box girder and at the fixed end of a cantilever box girder.