Ottawa Construction News staff writer
The National Capital Commission (NCC) board of directors has selected Motion as the preferred concept for replacing the Alexandra Bridge.
The winning concept was selected by an integrated project team consisting of representatives from Public Services and Procurement Canada, the NCC, and technical advisor Arup Canada Inc., following a comprehensive and rigorous evaluation process, which incorporated public input, stakeholder feedback, and consultations with Indigenous communities.
“After a thorough review, Motion has been identified as the preferred design for the Alexandra Bridge replacement,” said the NCC in a statement. “This selection reflects a balanced approach, taking into account public input, technical evaluations, and the desire to preserve and enhance the site’s historical and cultural significance.”
The vision for the Motion design concept is inspired by nature and particularly the eel, which is native to the river and honouring efforts of indigenous communities for the restoration of traditional habitat of the eel and their respected wisdom and dedication to reconciliation and reconnection to the Land.
Three arches rise and fall, flowing over the river offering interest both above and below. Gathering points are marked by the sections of the bridge where the structure curves below the deck. These are supported below by a structural form that reaches out in a sculpted support.
This option uses a different cross-section arrangement than the other two concepts. This is an efficient ladder deck system with both the bike lane and vehicle lanes separated within the bridge structure and the pedestrian lane on the outer side.
The design concept will undergo further refinement, with efforts to incorporate elements from other proposed designs that received support through consultations. This phase will address identified challenges and opportunities, ensuring the final design meets both practical and aesthetic goals.
The NCC said it will continue engaging with the public, Indigenous communities, and other stakeholders as the project progresses through the design-build procurement process.
The Alexandra Bridge, which spans the Ottawa River, is over 120 years old and has reached the end of its service life. It has faced significant deterioration due to age, natural elements, and salt exposure, which has led to frequent closures for repairs.
Despite “best efforts” to maintain the bridge, it has continued to deteriorate resulting in more frequent closures for necessary repairs,” the NCC explained.
The decision to replace the bridge was made in 2019, following a government mandate to address concerns related to the structure. Detailed reports and studies highlighted issues with areas including the boardwalk, structural articulation, buckling, eye bars, and pins of the truss members. The bridge’s condition continues to decline, further emphasizing the need for a replacement.
The Alexandra Bridge is the only example of a true-pin cantilevered truss bridge in the region. Its design, which is rare in modern construction due to high costs and maintenance challenges, has made the bridge more susceptible to corrosion and difficult to repair. The bridge’s extensive exposure to steel has contributed to its deteriorating state, leading to the decision for a full replacement.
While the bridge will be replaced, efforts will be made to respect its historical legacy during the design and construction of its replacement.
