The Roosevelt Island Tramway, constructed in the early 1970s, was the first Tramway built for routine commuter use in the United States. As it approached 35 years of continuous service, the Tramway's owner commissioned various engineering studies to define and evaluate the potential options for upgrading and modernizing the system. Thornton Tomasetti performed one of the studies, which focused on a multi-disciplinary condition evaluation of the Tramway's two stations and three steel support towers. That study concluded that, overall, the primary structural members of the Tramway system were in adequate condition and could remain in service with appropriate maintenance for the foreseeable future. The subsequent Tramway modernization project, however, included replacement of the Tramway's mechanical and electrical systems and Tram cars, with a new system that has significantly different structural loadings than the original. Because the project's budget and schedule did not allow for wholesale replacement of the existing support towers and stations, a detailed structural analysis was needed to evaluate how the new structural requirements could be accommodated, while minimizing structural alterations and reinforcement to the existing towers and stations. This paper focuses on the engineering team's solutions to the various engineering challenges faced in analyzing and designing the upgrade for the 35 plus year old structures to meet the new system's requirements.
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