Stress Analysis of Ultra-Wide Orthotropic Steel Box Girder with Large Width-Span Ratio and Single Inclined Pylon

Geometrical asymmetry in cable-stayed bridges with single pylon leads to differences in stresses and deformation in comparison to conventional ones. Thin-walled orthotropic steel girder with big width/span ratio has more complicated loading and deformation performance, which cannot be calculated accurately using conventional approaches. Jialuhe bridge is such an example with even more complicated properties. The 120 m long main span consists of three segments:The first 100 m from the pylon is orthotropic steel girder, followed by 8 m transition segment, and the last 12 m reinforced concrete plate is a cantilever from the abutment on the opposite bank. The width of the steel girder is 54.8 m, not supported on the abutment directly, but connected to the cantilever through a transitional segment with 8×54.8 m side length instead. So there are three materials of different stiffness connected in a small space, leading to two seaming sections, which not only reduces the monolith of the structure, but also increases difficulties in construction controlling.
The investigate shows:The transverse deformation of the steel girder is identical, with a maximal relative difference of-2.8 mm, so that no transverse camber is needed in construction phase. The maximal Mises stress due to gravity is 93.7 MPa, and that due to secondary deadload is about 1/4 of this value. This reveals a big safety reserve of the steel girder. When the height of the U-stiffeners varies between 260~320 mm, the variation of displacements of the bridge deck lies within 5%, variation of maximal stresses of the bridge deck within 8%. In this range the variation of the height of the U-stiffeners has less impact on displacement and stress of the deck. The internal cause is that the height of U-stiffener and the stiffness delivered by the transverse girder are supplementary each other, just demonstrating the salient plate property of this orthotropic girder. Height of U-stiffeners in this range should be chosen when designing.