The historic Thurmond Bridge is an important crossing over the New River Gorge for pedestrians, motorists and trains. The unique West Virginia Department of Transportation structure is cantilevered from an 827-foot-long truss and deep girder span bridge owned by CSX. It has a single lane that is used by both pedestrians and motorists. The bridge’s unusual design is further complicated by its location in an area on the National Register of Historic Places and within the protected New River Gorge National River.
B&N was selected to inspect and identify the best options for rehabilitating the aging bridge. The project goals included increasing the load posting to 12 tons, providing safe travel on a single lane for both vehicles and pedestrians, improving the structural stability, and maintaining the historical significance. Due to the environmental sensitivity, replacing the bridge wasn’t an option.
Services included:
- Hands-on inspection using rope access techniques
- Stability analysis
- Load rating
- Evaluation of alternatives for pedestrian crossing and access
- Repair recommendations and stakeholder coordination
- Design of the bridge rehabilitation, including a variety of steel strengthening repairs
- Submittal review and periodic observations during construction
The solution focused on structural repairs to maintain capacity and improve safety. While the evaluation indicated the main railroad bridge members had adequate capacity and could support the cantilevered roadway, repairs were needed to restore the bridge to its original condition. Renovation plans included cost-effective steel retrofits to the strengthen gusset plates, truss members, and girder flanges. A few of the pier caps were encased using post-tensioning rods to stabilize the concrete deterioration.
Model Helps Pinpoint Safety and Structural Concerns
The project team identified issues with bridge anchorage that were caused by corrosion in areas where steel connects to the bridge piers. Using Midas modeling software, team members modeled the stability of the bridge. This allowed them to zero in on the safety and structural issues that needed to be remedied with both immediate and long-term solutions. Based on the findings from the model, the team designed a system of large rods and bearing plates to improve anchorage of the spans. Detailed procedures were developed to jack up and temporarily support the truss and girders during the bearing replacements.
Observation Bays Enhance Pedestrian Safety
New observation bays were added about every 200 feet along the bridge as a refuge spot for pedestrians to use when a vehicle crosses the structure. The bays also offer a view of the river. They were made from lightweight fiberglass reinforced polymer to avoid adding weight to the span. A section of the open bridge deck was filled with concrete to block view of the rushing water below for those crossing on foot.
Honors & Awards
The West Virginia Department of Transportation, Division of Highways recognized the Thurmond Bridge project with a 2016 Engineering Excellence Award. The project also was recognized by the American Council of Engineering Companies of West Virginia with a 2019 Engineering Excellence Award in the Structural Systems Category.