Transportation Technology Center, Inc. (TTCI) tested three open-deck steel bridges to measure longitudinal forces induced by high-adhesion alternating-current (AC) locomotives. The project was funded jointly by Association of American Railroads (AAR) and Federal Railroad Administration, under the auspices of the AAR Bridge Research Program. Bridges tested include a 50-foot single-span riveted deck plate-girder bridge, a 122-foot two-span welded deck plate-girder (DPG) bridge, and a 400-foot four-span bridge made up of a 210-foot truss, a 107-foot truss, and 39-foot and 42-foot beam spans. Analysis shows that the bridges generally resist a significant portion of the applied longitudinal forces. Findings include: 1. Longitudinal forces calculated from measurements were much greater than those recommended for design from 1968 to 1996 in the AREA Manual. 2. Longitudinal forces calculated from measurements are closer to those recommended for design in the 1997 AREA Manual. 3. The greater the applied longitudinal force, the greater the force into the bridge. 4. Generally, the longer the span, the greater the longitudinal force resisted by the span. 5. In order to generate sustained high longitudinal forces, a significant amount of train resistance is necessary, such as a unit train on a long steep grade. The results from these tests are being used to refine the American Railway Engineering and Maintenance of Way Association bridge-design guidelines.
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