Impact of Railcar Weight Changes on Bridges of the State of Wisconsin-Owned Railroad System Final rept

摘要

Bridges on the state-owned Wisconsin railroad system are reaching their original design capacity due to increased railroad car weight limits. The condition of a majority of these railroad bridges has created additional concern. This report is the result of a railroad bridge assessment study commissioned by the Wisconsin Department of Transportation to determine the impact of 286,000-pound (286 kip) railcars (on state-owned railroad system bridges). The objective of the study was to evaluate a sample number of bridges by inspecting their current condition, determining their load carrying capacity, estimating their remaining useful life, and make repair and retrofit recommendations, to facilitate the heavier cars. Twenty-six sample bridges were evaluated. These are comprised of three steel bridges, one concrete bridge, twenty timber bridges and two bridges with combined timber and steel spans. These bridges were located on both the Milwaukee and the Monroe subdivisions of the Wisconsin & Southern Railroad Company. It was found that overall there is a need to perform a sizable amount of maintenance, repair and capital construction work to prepare the project bridges for sustained 286 kip operations. The rating analysis suggests that many of the timber trestle bridges will not be able to carry sustained 286 kip rail car traffic without accelerated deterioration of the structures. Deficiencies in the standard timber trestle bridges already present at the current load levels will be aggravated by 286 kip railcar loads. The steel and concrete bridges rated are adequate for carrying 286 kip railcar traffic. The study notes that the sample of steel and concrete bridges may not be representative of the remaining bridges in the Wisconsin & Southern inventory, and that further evaluation should be performed. Inspections of the project bridges found that, while conditions varied widely, overall the condition of the bridges was fair to poor. Several years of deferred maintenance were evident, particularly amongst those bridges on the Monroe Subdivision. The steel bridges included in the study were found to be in fair to good condition with a lesser number of defects per bridge. Over the next 5 years, $2.93 million will be required to bring the study bridges up to a condition that can sustain continuous 286 kip operations. Extrapolating that value to the entire state-owned rail system indicates as much as $24.2 million is needed to upgrade all bridges.