Three aged, deteriorated concrete bridges located in West Virginia were selected as test candidates for in-depth investigations to be conducted by Drexel University personnel. The investigations included site visits and surveys, drawing and model development, instrumentation design and installation, field load testing, data reduction and model calibration. All of this was then utilized to develop load ratings which were used to aid in decisions regarding the future of the three bridges.The Barnett Bridge was slated for replacement due to extensive deterioration and movement of the spandrel walls. The route which crosses the bridge was to be taken out of service in the next 5 years by a new bypass, so it was desirable to keep Barnett in service until the completion of the bypass. Through structural identification, including a proof load test, the structure was deemed acceptable given minor cosmetic repair and a long term monitoring system. The Smithers Bridge was posted slightly lower than the state legal level for a Coal Resource Transportation System structure due to uncertainty associated with the design of the structure and some visible damage. The reroute for legal load level trucks was circuitous and it was desired that the posting be removed if possible. The testing of Smithers indicated adequate capacity allowing for removal of the posting. The Michigan Avenue Bridge was posted at a mere 9 tons, allowing little more than car traffic. The bridge exhibited substantial damage and deterioration and fire trucks were not permitted to pass over the bridge. After a partial load test, the bridge exhibited plastic deformation and the test was stopped. Based on this information, it was recommended that traffic be limited to the arch portion of the structure until it could be replaced. The bridge is currently slated for replacement in the near future.These three structures represent a subset of a large population of aged concrete bridges nationwide. In two cases, it was seen that the structure had substantial reserve capacity and could remain in service for many years to come. In one case, the condition of the structure was such that replacement was the only option. From these experiences the following key lessons can be taken and applied to future work in this population of structures:1. Understanding the history of the bridge, its place in the local transportation network, and the viewpoint of the bridge owner are crucial to any structural identification effort. This is especially true for aged, deteriorated bridges which are considered high priority structures.2. Comprehensive material testing, thorough surveying and accurate measurement of the structure are required to achieve maximum pre-test model accuracy and reliability, given a lack of documentation.3. A priori models should be as simple as possible while still being reliable for predictions. These predictions are crucial for instrumentation layout and test guidelines.4. Instrumentation should be robust enough to capture the entire global response of the structure as well as local responses at critical areas.5. Particularly in the case of aged bridges missing documentation, great care must be taken during testing to ensure the structure is remaining linear. The additional uncertainty associated with missing documentation makes this safety concern even more important.6. There can be substantial benefit to this type of investigation prior to major efforts like replacement in the case of many structures, not just aged, deteriorated concrete bridges.
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