TRC was retained by the West Virginia Department of Transportation, Division of Highways (WVDOH) to provide engineering services associated with the rehabilitation or replacement of the Kanawha Falls Bridge. The project was initiated as a result of the bridge’s substructure and superstructure being rated as poor and in need of repair or replacement. The existing Kanawha Falls Bridge was constructed in 1927-28 and consists of three simple-span steel through trusses and one simple-span steel riveted deck girder. The bridge was renovated in 1979 and again in 1999. The bridge carries County Route 13 and spans a Norfolk Southern Railroad track from the west, the Kanawha River, a CSX Corporation track, and Fayette County Route 13/2 from the east. The total length of the structure is 1001’.
After evaluating eight (8) build alternatives and two (2) renovation alternatives which considered the affect each would have on the bridge’s historic eligibility with the National Register of Historic Bridges, the WVDOH selected a full rehabilitation option that will upgrade the existing truss to the full legal load limit.
A preliminary load rating analysis used STAAD and RISA software to identify members that would require additional attention during the design process. As part of the rehabilitation design effort, the work was initiated with a detailed hands-on inspection that served to identify deficient structural members, including measurements of deterioration and section loss. Based on load restriction to the existing bridges, unique access methods were utilized for the inspection of the below deck members. A LUSAS model was then developed to determine the member forces necessary to load rate the truss and determine which members required replacement or rehabilitation. After the model was completed, a final load rating analysis and design was performed using this 3-D LUSAS model.
Based on the results of TRC’s inspection and rating, it was determined that the rehabilitation work would consist of a complete replacement of the floor system, including floorbeams, stringers, deck and decorative railing, and significant repairs to the lower chord members and various verticals, diagonals and sway braces. In addition to the truss rehabilitation, repairs to the substructure units, including steel pier bents and concrete piers and abutments, were also developed. The existing Span 4 deck girder span was redesigned to incorporate a simple span rolled beam bridge on a new integral abutment.
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