Details:

Creators:
Wang, Jiaji ; Oz, Yagiz ; Joshi, Bhagirath ; Roy, Satya Sapath ; Mo, Y L ; ... More +
Wang, Jiaji ; Oz, Yagiz ; Joshi, Bhagirath ; Roy, Satya Sapath ; Mo, Y L ; Hsu, Thomas T C Less -
Corporate Creators:
University of Houston
Corporate Contributors:
Texas. Dept. of Transportation. Research and Technology Implementation Office ; United States. Department of Transportation. Federal Highway Administration
Texas. Dept. of Transportation. Research and Technology Implementation Office ; United States. Department of Transportation. Federal Highway Administration Less -
Subject/TRT Terms:
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Bents Bridge Design Cracking Finite Element Method Inverted-T Bridge Cap ITBC Reinforcement Design Skew Bridges Transverse Reinforcement
Publication/ Report Number:
FHWA/TX-21/0-6905-R1
Resource Type:
Tech Report
Geographical Coverage:
United States
Edition:
January 2016–August 2020
Corporate Publisher:
Texas. Department of Transportation
Abstract:
Reinforced concrete inverted-T bridge caps (ITBCs) have been widely used in the bridges in the United States as they are aesthetically pleasing and offer a practical means to increase vertical clearance. Many of the ITBCs are skewed when two roads are not aligned perpendicularly and exceed the 45-degree angle of the construction requirements. The Texas ITBCs are designed using the traditional empirical procedures outlined in the Texas Department of Transportation (TxDOT) Bridge Design Manual (TxDOT BDM) Load and Resistance Factor Design (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 ITBCs. However, any kind of improper detailing can cause poor placement of concrete and cracks within the concrete structure, which would reduce the load-carrying capacity and increase future maintenance costs. Faster and easier construction can be obtained if the skew transverse reinforcing throughout ITBCs is utilized. According to the results of lab tests, skewed transverse reinforcement will yield the same load capacity as the traditional design. In addition, using skewed transverse reinforcement throughout ITBCs will result in fewer cracks and smaller crack widths when compared to the traditional design. The Research Team selected three bent caps from an existing bridge to perform the preliminary finite element (FE) analysis using ABAQUS. The analysis indicated that the critical locations to paste the strain gauges and attach LVDTs are the cantilever end faces of the bent caps. All the bent caps with skewed transverse reinforcing were observed to be safe under service and ultimate state loading. Three cases of reinforcement design for ITBCs are investigated. The parametric FE simulation of 96 specimens and the cost-benefit analysis results yielded these conclusions: (1) The skew transverse reinforcement (Case 1) achieves better structural performance compared to traditional transverse reinforcement (Case 2 and Case 3) with notably reduced construction cost. Therefore, the skewed transverse reinforcement can well be used for the design of skewed ITBCs. (2) The increase of the S Bar area notably enhances the stiffness and ultimate strength. In addition, the increase of the S Bar area also reduces the crack width. The increase of the S Bar area will contribute notably to the construction cost. Based on the parametric simulation results, the current design of the S bar area is adequate for structural safety and crack resistance. (3) The increase of the G Bar area notably reduces the maximum crack width with a negligible influence on the stiffness, ultimate strength, and construction cost. The current design of the G Bar (No. 7 Bars) is adequate for crack control. (4) When the concrete strength increases from 5 ksi to 7 ksi, the ultimate strength and the stiffness of ITBCs increase with reduced crack width. In addition, the influence of concrete strength on the construction cost is negligible. Updates from AASHTO (2010) to AASHTO (2017) are summarized in Appendix 1.
Format:
PDF
Funding:
0-6905
Collection(s):
US Transportation Collection
Main Document Checksum:
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urn:sha256:f33418fca6d4790b4cd71f734baa5ea70b61c3be673a9295e2f2e2cf4eb8237e
Download URL:
https://rosap.ntl.bts.gov/view/dot/59033/dot_59033_DS1.pdf
File Type:

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