The Great Canadian Bridge Slide

An aging multispan swing bridge had to be replaced in Trenton, Ont., with minimal interference to both river and road traffic, and without changing its alignment. The solution was to build a three-span, high level bridge adjacent to the existing one, route traffic over the new, demolish the old, and then slide the new 3,200 ton structure to new piers on the old alignment. Such a slide, involving a major continuous bridge and a computer-controlled jacking system, had not been done before in North America. The jacks selected were double-acting, hollow-plunger designs developing 77 tons at safe working capacity. They pulled the bridge on high-strength strand which was in turn anchored to launching carriages. The entire slide was controlled from a central control room and monitored by closed circuit television. It moved the bridge 33 ft in just under 4 hours, 3/4 inch at a time. Jacking forces varied between 1% and 2% of the weight of the bridge. After the slide, the contractor encased the carriages and track beams in reinforced concrete and demolished the temporary piers. The bridge, therefore, appears to have been constructed conventionally.