Sponsor: Texas Department of Transportation
PI: Todd Helwig
Co-PI's: Michael Engelhardt, Eric Williamson, Oguzhan Bayrak
Horizontally curved girders are commonly required in highway bridge construction where the roadway necessitates a curved geometry. The overwhelming majority of steel girder systems that have historically been constructed consist of either I-shaped girders or trapezoidal box girders (often referred to as tub girders) built up from steel plates with a horizontally curved geometry. Although steel girder systems are often efficient from an erection and performance perspective, the material and fabrication costs of the girder systems are often relatively high compared to concrete girders. Due to the greater costs, spliced precast post-tensioned curved U-girders have been previously used in other states and are currently being considered for use in some Texas bridges. Regardless of whether steel or concrete girders are used for the bridge system, one of the most critical loading stages, from both a strength and stiffness perspective, occurs during placement of the fresh concrete for the bridge deck. The girders are generally designed to act compositely with the concrete slab in the finished bridge; however during placement of the concrete deck, the non-composite girders alone must resist the full construction load. Although the cured concrete deck can substantially improve the stiffness of the superstructure in the finished bridge, steel girder systems require a significant amount of bracing to resist the applied loads and to control deformations during construction. The curved precast concrete girders that have been previously constructed also require a lid slab consisting of a precast panel and topping slab to close the box section prior to placement of the full concrete deck slab so as to improve the resistance to the torsional loads. The use of the bracing in steel girders and the lid slab in concrete girders complicates the fabrication and construction process and reduces the economy of these structural systems. To improve the economy and speed of construction for horizontally curved bridges, alternative forms of bracing are of interest. One source of potential bracing is the formwork that is necessary for the concrete bridge deck. Partial depth precast concrete deck panels (PCPs) have been commonly used in straight concrete bridge girders. The PCPs are an efficient means of forming a work surface and also serving as formwork for the concrete bridge deck. The panels are not currently permitted to be utilized on horizontally curved girders. With adequate connection, the PCPs can potentially eliminate some of the bracing systems required in steel girder systems and also eliminate the required topping slab in curved concrete U-beams.
The primary objective of this research is to extend the use of PCPs to curved girder systems. The focus of the study includes steel I-girder systems, steel tub girder systems, and spliced prestressed concrete U-beams, which are currently being considered for use in some Texas bridges. The research methods that are to be employed in this study consist of full-scale laboratory testing and parametric finite element modeling of the PCPs and the corresponding curved girder systems.