Rapid Replacement of Highway 417 Island Park Drive Overpass
When the Ontario Ministry of Transportation needed five bridges on a section of the TransCanada Highway, Highway 417 in Ottawa, to be replaced in conjunction with a road widening, it decided to use a ...
When the Ontario Ministry of Transportation needed five bridges on a section of the TransCanada Highway, Highway 417 in Ottawa, to be replaced in conjunction with a road widening, it decided to use a rapid replacement method.
As this was the first application of the technique for a major freeway bridge in Canada, the Ministry directed that the process be first implemented on a pilot contract for the twin Island Park Drive Overpass superstructures.
The Ministry retained McCormick Rankin Corporation to do the detailed design of the project. From a technical perspective, the project set a new standard across Canada for replacing bridges on provincial highways using rapid replacement technology.
An overnight sensation
An adjacent park owned by the National Capital Commission was the staging area for transporting the existing and new prefabricated superstructures to and from the bridge site on August 11-12, 2007.
The 650-tonne 27-metre long twin superstructures were replaced completely that night in a record-breaking time of under 17 hours. All Highway 417 lanes were then opened. The method resulted in a net savings of $2.4 million compared to a conventional construction approach.
As well, the elimination of peak traf- fic queues up to seven kilometres long for two years involving 150,000 daily users of the highway had a tremendous benefit for the city of Ottawa, resulting in millions of dollars in savings as well as significant social and environmental benefits. For example, carbon dioxide emissions are estimated to have been reduced from 400,000 kg. to 11,000 kg. compared with the emissions that would have occurred with a two-year replacement project.
The key to the rapid replacement method is the use of special transportation equipment known as Self Propelled Modular Transporters (SPMTs.) These are flatbed trailers that can be combined end-to-end and side-to-side and have engines attached. Each unit has maneouvrable rubber wheels on axles that can make sharp turns, sideways movements, or carousel on one spot with no turning radius.
McCormick Rankin’s role included: a risk management plan, traffic management plan, context-sensitive design, survey plan and movement plan, conversion to semi-integral configuration, control plan for prefabricated structures, prequalification of contractors and incentive/penalty contract provisions.
The project has been received as a monumental success, with film crews and over 1,000 people in attendance on the night of the rapid lift. The total project was completed in early November 2007 on schedule and on budget at $8.9 million.
In terms of technical innovations developed by McCormick Rankin, just two are detailed below.
Adjustable bearing system
Finishing 16 separate bearing seats at each abutment to a given theoretical elevation and then placing new superstructures that would bear 100% true was deemed to be practically impossible. To solve the problem, an adjustable bearing system was developed. This system ensured a precision fit at each bearing seat and minimized potential cracking in the deck associated with different support conditions.
The system used stainless steel shims, with thickness requirements at each bearing location predetermined by accurate surveying. Once the new structures were lowered into position, four anchor bolts with adjustable nuts allowed fine tuning of the final bearing seat elevation. The system meant the contractor spent little time fine tuning the bearing levels and the completed structures were set down in minimal time. The stainless steel shims were subsequently buried in a concrete overlay.
The clear dimensions between the ballast walls of the existing east and west abutments varied by 90 mm, so it was deemed necessary to completely remove the existing ballast walls to provide maximum flexibility for the fit-up on the night of the rapid lift. The 610-mm ballast walls were saw-cut in advance using a track-mounted saw. The operation involved the staged removal of the approach slabs, and excavating granular materials behind the walls. The ballast walls were shimmed and temporarily secured in place against each girder using bent steel plates and anchors, then were removed with the bridge superstructures. Special semi-integral details for the deck diaghragms had to be developed for the rapid replacement.
Name of project: Highway 417 Island Park Drive Overpass, Ottawa
Award-winning firm (prime consultant): McCormick Rankin Corporation, Ottawa (Paul Turner, P. Eng., Roy Skelton, P. Eng., Mario Tedesco, P. Eng., Michel Vachon, P. Eng., Manfred Goetz, P. Eng., Robert Lusk, P. Eng.
Owner: Min. of Transportation, Ontario
Other key players: Ecoplans (environmental), Golder (foundations, geotechnical)