Structural Performance and Economic Impact of Skewed Reinforcing in Inverted-T Bridge Caps

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Inverted-T bridge caps (ITBCs) are commonly used in highway designs in the United States, as well as in Texas. In some cases, the bent caps are needed to be designed as skew because the bridge may not be aligned perpendicularly with the crossing roads. There is no design method for the skew ITBCs either in the American Association of State Highway and Transportation Officials (AASHTO) and Texas Department of Transportation (TxDOT). In the TxDOT practice, the traditional method of flaring the transverse reinforcement out is applied where the transverse reinforcement is placed as matching the skew angle of the bent cap at the end faces and placed perpendicular to the centerline throughout the rest of the bent cap. The transition from the skew bars to the straight bars is carried out at the location of column supports. The traditional transverse reinforcement has some complexities in the design and the construction processes because flaring the reinforcement out causes changes in spacing and length of bars. Another method of detailing named skew transverse reinforcement was proposed to TxDOT where all transverse reinforcements are placed as matching the skew angle of the bent caps. Skew transverse reinforcement resolves all complexities that traditional transverse reinforcement has. However, studies on skew transverse reinforcement in ITBCs is very limited. In this research, full-scale ninety-six skew ITBCs are modeled in ABAQUS to investigate the structural performance. In the parametric analysis, the design parameters are selected as the skew angle, the detailing method of the transverse reinforcement, the size of the hanger reinforcement, the amount of the end reinforcement, and the compressive strength of concrete. From the analytical results, the stiffness at the service load, the maximum crack width at the service load, and the ultimate strength of the specimens are investigated and compared. Following some basic assumptions on materials and construction time, design and construction costs of the investigated specimens are estimated. Combining the finite element analysis results and the estimated costs, a cost-benefit analysis is conducted to compare the specimens with the skew transverse reinforcement to the specimens with the traditional transverse reinforcement. As a result of the extensive finite element analyses, the structural performance of skewed reinforcing in ITBCs is presented and a set of design recommendations is proposed.

Inverted-T Bridge Caps, Reinforced Concrete, Skew Reinforcing, Cost-Benefit Analysis, Parametric Analysis