Abstract Manager

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 transfer bridge was required as the MV Madeleine ferry was replaced in 2020 with the interim MV Madeleine II. Required modifications to accommodate MV Madeline II and other potential vessels and to achieve maximum allowable gradient changes necessitated 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 preliminary design phase included suitable configurations capable of achieving required vertical movement, setting elevation of the level deck in comparison to the terminal elevation, and the protection of the bridge elements against climatic hazard. As the new MTB will be in service for at least 40 years, the prediction of the future sea level rise due to climate change played a considerable role on selecting total vertical movement that needed to be accommodated and the abutment elevation. The increased lift together with requirements for low clearance and long overhang vehicles to be able to board the ship in most tidal conditions were main inputs on selecting the length of the MTB. An innovative structural concept was first proposed and then 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 presentation will detail the structural 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 CSA S826 and S6 standards 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.