Reconstruction of Canadian National Railway Br. 173.20 over the Fox River Planning, Design and Construction Considerations Oshkosh, Wisconsin

摘要

The existing three-span single track Fox River Bridge at CN Railway M.P. 173.20, Neenah Subdivision, was in need of rehabilitation or reconstruction in order to support reliable service on CN's core line between Winnipeg to Chicago. Located in downtown Oshkosh, Wisconsin, the bridge supports train traffic carrying primarily grain, pot ash, sulfur and forest products. During peak grain season, 22 trains per day at an operating speed of 25 mph pass over the structure. The Fox River Bridge is located in close proximity to the popular Lake Winnebago, requiring the existing swing span to open over 1,600 times per year during the recreational boating season that lasts from May to late October each year. Due to the age of the existing bridge, limitations of load capacity and periodic operational problems throughout the years, CN decided to evaluate alternatives to rehabilitate or reconstruct the existing structure. In 2009, CN embarked on a Three Phase project to implement improvements at the Fox River Crossing, which culminated with the on-line replacement of the historic bridge that will be fully completed in Fall 2013. The Three Phase project consisted of: 1. Phase 1: Project Planning and Conceptual Design of recommended alternative, including a detailed inspection, rating and investigation of various alternatives for the reconstruction or replacement of the bridge, providing guidance for the recommended alternative and the basis for the National Environmental Policy Act (NEPA) documentation. 2. Phase 2: Preliminary Design, Final Design and NEPA documentation, including preliminary design and refinement of the Phase 1 recommended alternative, development of final design and construction documents, and the completion of the Environmental Assessment and procurement of all necessary permits in the environmentally sensitive area. 3. Phase 3: Complete reconstruction of the historic bridge on the existing alignment, including environmental constraints for drilled shaft construction, waterline capbeams, two separate 10-hour change-out windows for the new approach span installations and a 36-hour change-out window for the new movable span. To replace the existing 180' movable span and 2-150' fixed truss spans, a new span configuration on the existing alignment was designed consisting of a 147' rolling bascule span, 5-57' deck plate girder spans and one 40' deck plate girder span. To accommodate these new spans, 6 new piers supported on drilled shafts were required with modifications to the two existing abutments. This paper will detail the planning and design of the new structure, the agency coordination and permitting necessary to replace the historic swing span and adjacent fixed truss spans, and the construction challenges leading to the phased implementation of the new rolling lift bascule span which will be fully was installed during a 36-hour track window in August 2013.