Study on Shear Lag Effect and Effective Width of PSC Box Girder

Nowadays most efficient and economical structural system for bridge decks has been the Box Girder Bridges. However, the box section suffers from shear lag effect which causes a non-uniform axial stress along its cross-sectional direction which violates the main assumption of Simple Beam theory i.e. Plane sections remain plane. In this project, three dimensional finite element analysis of a simply supported PSC box girder section for dead load and pretressing using four nodded shell elements is done to evaluate the effect of shear lag. The structure is modeled and analyzed in SOFiSTiK software. The results obtained show, the effects of loading, support and geometry of cross-section on the behavior in terms of development of normal stresses in different box girders. The effective flange width is also calculated considering shear lag effects in the design of box girders bridges as per AASHTO LRFD Bridge design specifications (2017). It can be concluded from the present study that the Simple Beam theory is a rough assumption for analysis of box sections.