Composite Box Girder Bridge Behavior During Construction

Steel‐concrete composite box girder bridges may have a flexible open box section‐prior to the placement of the slab. Excessive twist or distortion can arise under construction loading. Bracing systems are usually installed within the girder during construction to increase the torsional and distortional stiffness of the open section. The influence of these bracing systems on open box behavior is discussed usingsfinite strip analysis results and a one‐quarter scale girder model test data. Tie and distortional bracing were found effective in preventing distortion, with web stiffening found to be more effective than interior cross bracing. Horizontal bracing at the flange level was considered to reduce twisting of the section. This bracing can take the form of either torsion boxes or top chord bracing, both being effective. A torsion‐bending analysis based on a rigid section behavior is reviewed.