United States Department of Transportation
i
Use of Titanium Alloy Reinforcement to Strengthened Bridges in Alabama: Laboratory Testing and Analytical Investigations
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2024-09-01
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[PDF-7.86 MB]
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Abstract:This report presents findings from a comprehensive study evaluating the feasibility of using Near-Surface-Mounted (NSM) Titanium Alloy Bars (TiAB) to strengthen structurally deficient reinforced concrete (RC) bridges in Alabama. The research aimed to provide a cost-effective, efficient solution to extend the service life of aging and strength deficient highway infrastructure, focusing on a flexurally deficient bridge in Cullman. Three TiAB NSM anchorage methods were investigated: i) hooked-bonded, ii) straight-bonded, and iii) hooked-unbonded. The study was conducted in two phases. Phase 1 involved laboratory testing of 15 small-scale specimens to evaluate TiAB anchorage behavior and bond strength, essential for calculating the development length. The results confirmed the AASHTO NSM Guide bond strength recommendations for hooked-bonded anchorage, provided bond strength guidelines for straight-bonded anchorage, and evaluated the feasibility of hooked-unbonded anchorage. Phase 2 included full-scale testing of 16 girders representative of the Cullman bridge, assessing both positive- and negative-moment strengthening using the three anchorage methods. The results indicated the need for additional requirements for the hooked-bonded method for adequate strengthening, leading to proposed updates for the AASHTO TiAB NSM Guide. Design guidelines were also developed for the effective use of straight-bonded anchorage. Full-scale tests of the hooked-unbonded method indicated that this method might be suitable for temporary use but inadequate for permanent strengthening. The study developed detailed construction and field implementation guidelines for strengthening the Cullman bridge. While fatigue evaluations are necessary for final recommendations, these findings offer critical insights for ALDOT in implementing NSM TiAB as a reliable method to strengthen RC bridges.
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