On August 11, 2007 Ministry of Transportation (MTO) used rapid replacement technology for the first time to lift, remove and replace 2 existing bridges at Island Park on Highway 417 in Ottawa. The successful operation took only 15 hours to complete. The Highway was closed at 8:00pm and all lanes were officially open by 1:00pm on August 12th 2007.
Rapid replacement technology is a construction technique whereby a new structure is erected in an enclosed staging area (figure 1), while the existing sub-structure is rehabilitated. Once built, the new structure is then carried over to the site and put in place using Self Propelled Modular Transporters (SPMT) (figure 2), while the old structure is moved to the staging area and dismantled. By replacing the Island Park bridges using rapid replacement technology, impacts on traffic are greatly reduced. A conventional approach would have required extensive lane closures over a period of at least two construction seasons. The savings realized by the rapid replacement approach, in the order of $2.4 Million, can be attributed mainly to the reduced traffic control requirements.
The design of the Island Park Bridges proved to be a challenging task, as it had to account for the bridges being moved by SPMTs along with the associated stresses and loadings. Other challenges associated with the design and rapid replacement included:
* The elimination of expansion joints through the use of semi-integral abutments.
* Several weekends of preparatory work involving lane closures on the Queensway, due to the excavation of the approach slab in order to cut the ballast wall.
* The top of the ballast wall had to be fastened to the bridge deck so that they could be lifted out and transported together.
* Base plates were installed on the existing bearing seats after the old bridges were moved out. It was a challenge to place the base plates at the correct elevation with shim plates.
* Temperature proved to be a time-prolonging factor. Due to the increasing temperature throughout the day, the hot asphalt cooled at a much slower rate then anticipated
Although the use of rapid replacement technology was very successful, designers learned a number of lessons on how to further improve and facilitate a rapid bridge replacement project. Some key lessons include:
* Allowing the Contractor to use 4 temporary platforms to facilitate removal of existing bridges
* Stressing the importance of the surveying requirements by the Contractor
* The use of adjustable bearing plates cannot be minimized
* Consider specifying temporary lateral restraint plate angles to further facilitate installation of structures
* Replacing longitudinal joint type from "Jeenie" to "Evacon T-300"
* Emphasizing closure times for ramps including limit of closure in modified SP 100F08 Not sure if the bolded means anything to the average reader
* Increased planning and coordination of local road closures by the City in which the construction is taking place
* Increased coordination and communication between MTO, the city, and the C.A.
Currently MTO is scheduling more rapid replacement projects. The Clyde Avenue structures are scheduled to be replaced in summer 2008 using the same rapid lift technology. Starting in 2010 the structures at Carling Avenue Eastbound, Kirkwood Avenue and Carling Avenue Westbound will be replaced using rapid technology.
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