Effect of Load Combinations on Distortional Behaviors of Simple-Span Steel Box Girder Bridges

Abstract

When eccentric live loads are applied on the deck overhang of steel-box girder bridges, torsional moments, comprising pure torsional and distortional moments are generated on the box sections. The torsional moment on the bridge girders distorts the box girder cross-sections, inducing additional normal stress components and causing instability of the box girder sections in severe cases. Hence, it is essential to install intermediate diaphragms in the box sections to minimize distortional behaviors. Although the applied live loads are critical parameters that influence intermediate diaphragm spacings, the effects of live load combinations have rarely been addressed in the design of intermediate diaphragm spacings. Thus, load combinations should be evaluated to design the intermediate diaphragm spacing of the box girder bridges more thoroughly. In this study, the load combination effects on the distortional behavior and adequate intermediate diaphragm spacing were evaluated through a finite element analysis (FEA). Composite rectangular box girder bridges with different cross-sectional aspect ratios (H/B) and spans (L) were analyzed in the parametric study. It was found that the truck load, which represents the concentrated load, significantly influences the distortional warping normal stress, normal stress ratio, and intermediate diaphragm spacing. In addition, the FEA results showed that the controlling load combinations could be varied with the span.

Research on Key Technology of Steel Box Girder Construction Based on Measured Temperature Mode

“…The influence of uniform temperature difference on the structural deformation of steel box girder is mainly reflected in the pre deflection setting of the longitudinal bridge direction of the support. The bearing pre deflection value includes not only the temperature effect, but also the pre deflection value caused by the load effect [13,14]. In order to study the influence of uniform temperature difference on bearing pre deflection, the longitudinal bridge displacement of bearing caused by non temperature load (such as structural dead weight, temporary load, etc.)…”