If Traffic Can't Wait, Prefabricate!

Most drivers have experienced delays and hazards when approaching the construction site of a new bridge. MTO recognizes the traffic dilemmas associated with bridge construction and is implementing initiatives that address these concerns while improving the durability and lowering the life cycle cost of new bridges. One of MTO's initiatives makes use of prefabricated design for new bridges built in high traffic areas. Such design allows bridge elements to be fabricated at a manufacturing plant, and then shipped to the construction site for rapid assembly. One of MTO's prefabricated bridge projects was recently completed, and is situated 680 km north of Toronto on Hwy 101. This prefabricated project is known as the Moose Creek Bridge.

Prefabrication, as a design technique, has been used by MTO in the past, but the Moose Creek project is a step above anything done before. Moose Creek is the first bridge in Ontario where prefabrication was used in constructing a bridge substructure (abutments and wing walls) as well as its superstructure (girders and deck). In past projects, prefabrication was only used for constructing superstructure elements and culverts.

During this fabrication, most of the concrete used was cast off site. The only concrete cast-in-place (cast on the construction site) was used for minor details such as the approach slabs, barrier walls, and the in-fill strips that were used to integrate prefabricated components. Future plans may call for even more precast components, less onsite work, and involve multi-span structures.

These future advancements would be made possible through MTO's co-operation with consultants, fabricators and contractors. This close co-ordination is needed because applying prefabrication to bridge construction is not common in Ontario. Given this market condition, the success of future initiatives depends on tightly coordinated planning, design, and construction. In the case of the Moose Creek project, MTO's partners were Stantec Consulting Ltd., Miller Paving Ltd., and Pre-Con Inc.

The bridge components were fabricated in two of Pre-Con's plants, one in Brampton and the other in Bellville. After fabrication, the bridge components were transported from the plants, by road, to Moose Creek. All components were transported and assembled in two installments taking a mere four days. If constructed on site using conventional methods it would have taken at least two months. Much of that time saving was achieved because work normally done on site was done in a manufacturing plant. On site time was also saved because special care was taken during the casting process to ensure that all bridge components would fit together when assembled. The entire project was completed without any major problem or concern.

The reduced on-site construction time resulted in benefits for all stakeholders. Road users did not face delays, workers did not have to deal with the safety hazards of a conventional construction site, and the risk of environmental damage was avoided due to reduced construction activity. Clearly, using prefabrication proved to be beneficial for all parties concerned.

Moose Creek Bridge is also expected to be more durable due to the prefabrication process. Since its components were fabricated in a controlled environment, this bridge will require less future maintenance and rehabilitation when compared to bridges built using normal construction practices. This means that the initial cost of Moose Creek, which was higher than average, will likely be offset by a less-than-average need for future maintenance.

This benefit of increased durability is just as impressive as those benefits offered to users, workers, and the environment. Considering these, it becomes clear why this prefabrication process is being pursued by MTO.

Future plans are directed at taking full advantage of this process. The Ministry hopes that increased use of this technology and its standardization will encourage even larger prefabrication projects which will ensure the future durability and cost effectiveness of Ontario's bridges.

The successful completion of the Moose Creek Bridge without any significant design, fabrication, transportation, or erection problems is encouraging and it is expected that techniques developed for this bridge will be used in future projects.