Corrosion on bridges is a common issue since it can be caused by multiple agents such as marine environments or deicing chemicals. The damages caused by these agents, if left unmitigated, may lead to failure of the superstructures. If corrosion is present in the end regions of the beams, failure of the girders will likely be in shear, which is a sudden failure mode and not the preferred limit state. Therefore, it is beneficial to study repair practices and their advantages, as repairs are often more cost-effective than building entirely new structures. Repairing prestressed girders for shear is not common practice, but with the number of superstructures considered structurally deficient in the United States, additional consideration should be given to repair methods.
In this study, two beams were extracted from two decommissioned bridges and were repaired using Carbon Fiber Reinforced Polymer (CFRP) to investigate how well proposed repairs functioned. One of the beams is an American Association of State Highway and Transportation Officials (AASHTO) Type II beam, while the second one is an adjacent box beam. Before repairs were done, the beams had their ends further damaged with accelerated corrosion induced via electrolysis to ensure that the beams would have enough deterioration in their shear span to simulate the worst-case scenario found in the field. Afterwards, the girders had their damage and residual strength estimated, and repairs were designed using guidelines from the American Concrete Institute (ACI) and AASHTO for CFRP repairs.
Since the adjacent box beam could only be repaired in flexure, it failed in shear with a load similar to previous studies done in beams from the same bridge, which indicates that repairs for box beams need further investigation. The repairs on the AASHTO Type II beam worked well for shear, and both ends failed in flexure, which is an improved failure mode since failing in flexure is more ductile and predictable than shear failures. One end of the AASHTO Type II beam failed by concrete crushing and CFRP rupturing, and the other end failed by strand rupturing, which shows that the accelerated corrosion worked as was predicted. / Master of Science / Corrosion on bridges is a major problem across the United States, especially in marine environments and in cold areas where deicing chemicals are needed to ensure the safety of the drivers. These external agents typically accelerate the deterioration of bridges and lead to expensive repairs and sometimes total replacement of structures. In order to study repair methods for bridges that have been exposed to corrosive agents, bridge girders were extracted from two decommissioned bridges in Virginia. The level of damage in these girders was assessed and it was determined that more corrosion had to be induced into the girder to ensure repairs were needed. After that process, the strength of the girders was estimated using guidelines from the American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO), and the girders were repaired for shear using sheets of Carbon Fiber Reinforced Polymers (CFRP). These repairs were done by using two different wrapping schemes, one that enveloped the sides of the girder, and one that was only at the bottom of the girder. The girders then had their ends tested under three-point bending to evaluate the effectiveness of the repairs. The girder that had the sides repaired as well performed better since the failure mode of it changed from shear to flexure. The girder that only had its bottom repaired did not do as well since its failure mode was still shear.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/108133 |
| Date | 03 February 2022 |
| Creators | Alves de Moraes, Alana |
| Contributors | Civil and Environmental Engineering, Roberts-Wollmann, Carin L., Hebdon, Matthew Hardy, Koutromanos, Ioannis |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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