Transverse Analysis of Strutted Box Girder Bridges

The computer program STRUTBOX is presented for the transverse analysis of strutted box girder bridges, and particularly for bridges designed and constructed using the strutted box widening method. The program allows the deck prestressing and other reinforcing to be proportioned for transverse flexure, and the web stirrups and slab reinforcing to be proportioned for longitudinal shear and torsion. The program also gives an indication as to the severity of shear lag effects. The program is based on the folded plate method and is no more difficult to use than a plane frame computer program. The paper also demonstrates how the results given by a folded plate analysis can be approximated by using some simple membrane force equations in conjunction with a plane frame analysis. What is particularly interesting is that there is danger in using a plane frame analysis alone to approximate the results of a folded plate analysis for strutted box girder bridges (as well as other box girder bridges) because there are significant differences in the axial force diagrams given by the two methods.