Parsons, as prime consultant and lead structural designer with subconsultants Wiss, Janney, Elstner Associates (WJE), Baird, and GEMTEC, was selected to provide engineering services to Public Services and Procurement Canada to design a new Movable Transfer Bridge (MTB) at the Souris Ferry Terminal in Prince Edward Island. The replacement of the existing MTB was required as the MV Madeleine ferry was replaced in 2020 with the interim MV Madeleine II. Required modifications to accommodate MVMadeleine II and other potential vessels and to achieve maximum allowable gradient changes necessitated the complete replacement of the MTB. The project included the design of the new bridge, a control building, all the mechanical and electrical equipment related, and civil works.
Design challenges faced by the team during the preliminary design phase included suitable configurations capable of achieving the required vertical movement, setting the elevation of the level deck in comparison to the terminal elevation, and protecting the bridge elements against climatic hazards. As the new MTB will be in service for at least 40 years, predicting the future sea level rise due to climate change played a considerable role in selecting total vertical movement that needed to be accommodated and the abutment elevation. The increased range of movement, together with requirements for low clearance and long overhang vehicles to be able to board the ship in most tidal conditions were the main inputs on selecting the length of the MTB. An effective structural concept was proposed and selected by the client to improve the bridge serviceability and durability: it consisted of the minimization of the number of pivot bearings, their raising on pedestals to improve their protection, and the consideration of a non-redundant structural system consisting of only two (2) main girders and one (1) lifting beam.
This paper will detail the challenges encountered during the design process, including the development of a live load model and load combinations adapted to project specifics, a reliability analysis to improve structural safety of the non-redundant structure and limitations of Canadian codes and standards (CSA S826:011 and S6:192) for this specialized bridge type. Other challenges, such as the detailed design of a small box section lifting beam, the request from the client to galvanize all the structural steel, and the design of a simplified orthotropic steel deck will also be investigated.