Investigation of Behavior of Skewed and Un-Skewed Reinforced Concrete T-Beam Bridges and Load Rating Improvement through Proxy Finite Element Analysis

US Transportation Collection2019PDFTech ReportSchanck, AndrewDavids, BillUniversity of Maine. Advanced Structures and Composites CenterMaine. Dept. of Transportation. Transportation Research DivisionMaine. Department of TransportationUnited StatesLive loadsLoad factorLoad testsReinforced concrete bridgesSkewed structuresReinforced concrete T-beam bridgesME 20-01Technical Report 20-0120-20-1613Project 23833.00Note: While the third page of the report is stamped "Confidential," this item is publicly available via the Maine DOT website at https://www.maine.gov/mdot/research/publications/ and was submitted directly to NTL for inclusion in our repository in 2020.2019-12-20-Rev00Maine\u2019s bridge inventory includes a significant number of reinforced concrete T-beam bridges, both with and without skew. Many of these bridges were built in the first half of the 20th century for design loadings much lower than those considered today, causing a significant number of them to have low flexural rating factors. Despite this, these bridges continue to carry modern levels of loading with little to no apparent distress. This observation has resulted in new efforts to better understand the behavior of these bridges and to develop new methods of analysis which more accurately reflect their true capacities. In the summers of 2017 and 2018, ten reinforced concrete T-beam bridges were non-destructively live-load tested to update their rating factors and to observe their load-strain responses. Five bridges were un-skewed and five were skewed between 15\ub0 and 35\ub0 relative to a perpendicular alignment. This selection of tested bridges allowed their responses to loading to be compared with the aim of identifying differences in behavior arising from the presence of skew. The understanding of these differences was also enhanced through the construction, calibration, and analysis of detailed, linear finite element models of the tested bridges. The ten bridges that had been live-load tested were also load-rated through Proxy finite element analysis (FEA) to give a more accurate picture of their behavior at capacity. Each of these bridges\u2019 flexural rating factors were able to be significantly improved relative to their American Association of State Highway and Transportation Officials (AASHTO) calculated ratings, and nine of the ten were improved relative to their ratings updated through live-load testing. It is demonstrated that these ratings are optimistic, yet also realistic considering the technique\u2019s reliance on well-established mechanics and conservative assumptions. The possible future development of this technique as a general load rating tool for older structures is discussed.137