United States Department of Transportation
i
Protecting Critical Civil Infrastructure Against Impact from Commercial Vehicles - Phase I
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2019-07-01
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[PDF-8.53 MB]
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Edition:January 1, 2018-June 30, 2019
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Abstract:Bridge pier columns are critical load carrying elements and are often positioned in a fashion where it is neither possible nor economically feasible to place protective devices around them. Pier columns could be under-designed for commercial vehicle impacts and additional events that could occur, such as blast. The project is focusing on improving pier column resiliency and robustness in the event of an accidental or purposeful vehicle impact coupled with an additional event, e.g., an air blast, and a fire. To achieve this goal, a literature search was performed that focused on the studies that investigate the behavior of reinforced concrete (RC) structures under vehicle impact and blast, current design specifications related to the bridge piers subjected to these demands, and general reinforced concrete bridge element design and detailing criteria. Based on the literature review, a multi-column, highway, bridge pier and its supporting foundation was used as the prototypical supporting unit for the analytically focused project. Initial studies used a 3D, LS-DYNA numerical model of a single, circular, reinforced concrete column from the piers along with that column’s supporting spread footing and piles. Surrounding soil and air volumes were also modeled using LS-DYNA. Impact was supplied from a Ford F800 Single-Unit truck. Air blasts of varying magnitude were represented using an Arbitrary Lagrangian-Eulerian approach. The model was validated against published RC structural element impact and blast tests and predicted response well. As a result, the validated modeling approach was recommended for future studies in association with the project. After a literature review, experimental efforts were undertaken to characterize adhesion of the retrofitting polymer to concrete also with impact and blast properties for resistance of the retrofitted specimens. Adhesion testing as accomplished by a modified single edge notched beam (SEND) with a cement-polyurea (PU)-glue-cement sandwiched layers in the middle. Adhesion test results indicated a strong interface bonding between cement and PU which further improved by treatment of the cement surface to increase the roughness. Impact testing was performed using a drop-tower, where the results showed that PU coating increased damping behavior of the concrete specimen by permitting the impact load to be distributed on a larger area and for a longer time. Blast testing will be carried out using TNT explosives on reinforced concrete slabs which will require assistance from the Nebraska State Patrol for the testing.
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