Retained by the Acciona and Pacer Joint Venture, Pedelta provided engineering services for the demolition of the 100-year old structure over the Saskatchewan River. Built in 1913, the Old Walterdale Bridge was a truss bridge consisting of three 70 m long spans and a width of 8.23 m. Its service life was terminated in the fall of 2017 when it was replaced by a new arch bridge built beside the original.
Pedelta closely collaborated with the contractor and crane supplier to produce a safe and cost-effective demolition plan. During October-November 2017 the three spans were lifted using a crawler crane, shipped away, and dismantled. After the removal of the north truss, the south span was lifted and dismantled, followed by the center truss. Steel structures will be recycled, and small parts will be salvaged for a future project.
A refined weight estimate was produced for the spans based on an incomplete drawings package over 100 years old and information collected during site visits. Three-dimensional structural models along with other specific tools were created to check the strength and stability of the structural components during the lifting operations. It was concluded that spans did not need extra reinforcement on members during the lifting operation if some non-structural components were removed. The members were also checked during the dismantling process using a step-by-step approach.
In addition, Pedelta designed the temporary towers to support the spans during intermediate steps. Specific lifting devices were developed for the demolition procedure, protecting the slings and providing an easy connection between slings and the spans. For each lift, the weight of a span after removing all identified non-structural elements was up to 220 tons.