Influence of bracing systems on the behavior of curved and skewed steel I-girder bridges during construction
Sanchez, Telmo Andres
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The construction of horizontally curved bridges with skewed supports requires careful consideration. These types of bridges exhibit three-dimensional response characteristics that are not commonly seen in straight bridges with normal supports. As a result, engineers may face difficulties during the construction, when the components of the bridge do not fit together or the final geometry of the structure does not correspond to that intended by the designer. These complications can lead to problems that compromise the serviceability aspects of the bridge and in some cases, its structural integrity. The three dimensional response that curved and skewed bridges exhibit is directly influenced by the bracing system used to configure the structure. In I-girder bridges, cross-frames are provided to integrate the structure, transforming the individual girders into a structural system that can support larger loads than when the girders work separately. In general, they facilitate the construction of the structure. However, they can also induce undesired collateral effects that can be a detriment to the performance of the system. These effects must be considered in the design of a curved and skewed bridge because, in some cases, they can modify substantially its response. This research is focused on understanding how the bracing system affects the performance of curved and skewed I-girder bridges, as well as, the ability of the approximate analysis methods to capture the structural behavior. In this research, techniques that can be implemented in the creation of 2D-grid models are developed to overcome the limitations of this analysis method. In addition, efficient cross-frame arrangements that mitigate the collateral effects of skew are developed. These mitigation schemes reduce the undesired cross-frame forces and flange lateral bending stresses associated with the transverse stiffness of the structure, while ensuring that the bracing system still performs its intended functions.