Structural Performance of Skew Reinforcing in Inverted-T Bridge Caps

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For the past decades, the inverted-T bridge caps (ITBC) are widely used in most of the bridges in the United States as they are aesthetically pleasing and offer a practical means to increase vertical clearance. In some typical cases, the bridge caps are skew when two roads are not aligned perpendicularly and exceed the angle of 45 degrees based on the construction requirements. Most of these ITBC in Texas are designed using the traditional empirical procedures outlined in the TxDOT Bridge Design Manual (TxDOT BDM) LRFD that conform to the AASHTO (American Association of State Highway and Transportation Officials) LRFD (2014) Bridge Design Specifications. There are no precise calculation methods or guidelines given in the AASHTO LRFD (2014) or TxDOT BDM-LRFD (2015) to design skew ITBC. For a skew ITBC, the TxDOT Manual states only that hanger and ledge reinforcement should be placed perpendicular to the centerline of the skew bent. The detailing of the skew ends of the bent should be done with a section of skew stirrups and ledge reinforcements. The traditional method of flaring the transverse reinforcement out in skew ITBC brings in significant complexity in design and during construction. An alternative way is to provide skew reinforcing, which will substantially reduce the design complexities and construction period. In this research, thirteen full-scale ITBC specimens of skew angle 00, 300, 450 and 600 were subjected to shear action. The performance of these skew ITBC were evaluated and compared to these traditional reinforcement. Then the test results are calibrated with 3D FE simulation. A parametric analysis was also performed in order to understand the overall structural behavior of skew reinforcement in ITBC taking into account unexplored parameters in the test matrix. The physical test results and FE simulation show that the skew reinforcement arrangement does not weaken the bridge cap’s capacity, and the structural performance remains almost the same as that of the traditional arrangement. Also, the serviceability performance of skew reinforcements is better as compared to traditional reinforcements. As a result of the extensive experimental and FE program on inverted-T bridge caps, general design guidelines and typical drawings for the design and construction of the skew reinforcing in inverted-T bridge caps are provided.

Inverted-T Bridge Caps, Skew Transverse Reinforcing
Portions of this document appear in: Roy, Satya Sapath, Jamshaid Sawab, Tianmin Zhou, Y. L. Mo, and Thomas TC Hsu. "Performance of Skew Reinforcing in Inverted-T Bridge Caps." Transportation Research Record 2672, no. 41 (2018): 65-74.