Aerial view of bridge.
Perley Bridge, originally built in 1931, stretches over the Ottawa River linking Hawkesbury, Ontario and Grenville, Quebec. In early 1996, Public Works and Government Services Canada (PWGSC) made a tender call to construct a new four-lane 700-meter bridge to replace the existing steel structure. The project was a joint effort by the Provinces of Ontario and Quebec, and PWGSC. The tender requested that contractors price either a precast concrete I-girder or a steel girder option for the new construction.
The completed bridge from the Quebec shore.
In May 1996, the contract was awarded to the lowest bidder, Dufferin Construction Co., for their precast concrete girder solution. Construction began that summer with the demolition of the existing bridge and continued over three years. The bridge superstructure was constructed using post-tensioned spliced concrete I-girders. The length of each girder extended to a record 70 meters, a first for Canada. The finished bridge consisted of ten girders extending over the deep, fast flowing Ottawa River, for a total length of 700 meters.
The Ottawa River is subject to abrupt changes in water level when water is diverted for power generation. Consideration also had to be given to ice jams and flows, which vary from 1,000 m3 /sec to 7,500 m3 /sec. This made typical construction methods, such as the use of barge-mounted erection cranes, more difficult.
The launching gantry on pier cap.
To meet project challenges, the superstructure and custom precast girders were redesigned to suit gantry-based erection. The heavy (150 tonnes) concrete girders were moved to the central gantry using self-powered, rail-mounted carriages, and side-shifted using a carriage at the front of the girder and girder-mounted traversing beam at the back. This unique girder erection gantry system won an innovation award for Canadian construction engineering.
A redesign of the precast girders eliminated pre-tensioning, simplified the custom forms and post-tensioning requirements, and allowed the girders to reach a span of 68.5 meters. The underwater pier footings were built using a gantry barge and incorporated large reinforced tremie concrete pours within a specialty modular formwork system.
Pier footing modular forms mounted at gantry bridge.
|Owner||Public Works Government Services Canada/MTO/MTQ|
|Engineer||LEA Consulting Ltd.|
|Contractor||Dufferin Construction Co.|
|Material Supplier||Pre-Con Company|
|Project Design||Groupe HBA, Pasquin St-Jean Associates|
|Contract Admin||Desjardins Engineering|
For additional technical details on this project visit the Ontario Concrete Awards site at: http://www.ontarioconcreteawards.ca/01cs.htm