State-of-the-art solution used in London bridge replacement

04/12/2012 Sarnia Road Bridge re-constructed with glass fibre reinforcement Schöck ComBAR®

The Sarnia Road Bridge, located in London, Ontario, underwent significant reconstruction in 2011. The bridge was replaced and re-fitted beginning in March, 2011 and completed in November, 2011.

The Sarnia Road Bridge stretches along Sarnia Road over the Canadian Pacific Railway, and is located between Alderbrook Road and Beaverbrook Avenue in London, Ontario.   The length of the bridge is approximately 33m, with total length of parapet walls 67.2m. Elevations varied along the bridge. For example, the north side of east parapet wall has a height of 1,950mm and the south side of east parapet wall has a height of 2,370mm.

The aim of the construction project was to replace the previously existing bridge and expand the road from two to four lanes.  As a result of this undertaking, the new bridge structure is now wider, with large sidewalks and multiple-vehicle lanes. A broader goal of the project, aside from making the bridge more efficient for transportation, was to make it more durable. The latter aim was especially significant given the severe and harsh weather conditions experienced during the Canadian winter months, with multiple frost-thaw cycles and frequent periods of extremely low temperatures.

Glass fibre reinforcement products were included in the project's construction to enhance its durability.  The Sarnia Road Bridge team included glass fibre reinforcement in the parapet walls of the bridge as part of the design.

Glass fibre reinforcement products, specifically the product ComBAR® from Schöck Canada Inc. which was used in this particular case, ensure structural strength and stability and significantly reduce future repair costs as they do not corrode.

High strength and economical

With Canada's winters wreaking sleet, snow, hail and rain on bridge structures for several months each year, there are pitfalls frequently encountered with transportation structures constructed using steel. These result out of the fact that steel is very susceptible to corrosion.

As a general trend, bridges often have to be replaced or heavily repaired long before having reached their design service life because the steel reinforcement within them has corroded, destroying the concrete microstructure. The most frequent cause of such rapid corrosion damages in reinforced concrete bridges is the exposure to de-icing salts in combination with the numerous frost–thaw cycles occurring every year.

To avoid premature damages due to corrosion in the Sarnia Road Bridge, the rebar supplier decided to be proactive and install the glass fibre reinforcement from Schöck ComBAR®.  ComBAR® does not rust, and therefore provides safe and strong structures for more than 75 years of service life. Shifting to ComBAR® allowed the Sarnia Road Bridge team to save significantly on future repair and maintenance costs.

Before the start of the project, the Sarnia Road Bridge team was aware of a few of ComBAR's benefits, namely its ability to significantly reduce repair and maintenance costs. Initially, however, low grade GFRP was specified in the contract drawings for the project.  After all the high grade ComBAR benefits came to light, the team decided to reconsider.

"Originally the engineers planned to use a low grade GFRP system for construction, but after hearing about the benefits of ComBAR® , including how light it is and  how much more durable it is, the steel rebar supplier decided to propose the switch," said Ekaterina Tropynina, Engineer at Schöck Canada Inc.  "The client wanted to look forward to better, more sustainable long-term solutions."

The ultimate long-term strength of ComBAR® is nearly three times that of reinforcing steel and over two times that of low grade GFRP systems. Furthermore, the reinforcement was successfully tested in a full-scale crash test on a PL-3 barrier wall in the fall of 2010. The product is the perfect reinforcing material for barrier and parapet walls on bridges, like those on the Sarnia Road Bridge. Furthermore, the product greatly extends the service life of the bridge by increasing its durability, contributing to sustainable construction and cost-savings in the long run.

In addition, the construction team found that ComBAR® was competitively priced with low grade GFRP systems and was easier and faster to install, as fewer bars were required on the project.

The construction industry in Canada, especially in Ontario, plans to use glass reinforcement more often in the future. ComBAR's benefits, including on-time delivery by Schöck Canada and assistance with installation and handling, make it easier for clients to obtain and install the product.  More importantly for the Sarnia Road Bridge project, it made the bridge replacement quicker and more effective in the long run, too.

Help at every step

Schöck Canada Inc. was deeply involved with the project, providing engineering services that included the redesign using ComBAR, intensive communication and coordination with Dillon Consulting, and production of new drawings based on MTO standards for high grade GFRP.  Schöck Canada Inc. also prepared cutting drawings for exact bar lengths and locations, and then submitted them together with the shop drawings.  An Ontario Professional Engineer finalized the shop drawings with a stamp.

Schöck also handled on-site services, namely providing handling and safety instructions for the rebar contractor, coordinating material delivery, supplying additional materials to the contractor during installation to deal with architectural finishes on the parapet wall and inspecting delivered materials.

Details

Project: Sarnia Road Bridge
Steel rebar supplier: AGF Dietrich Steel Ltd.
Structural Engineer: Dillon Consulting Ltd.
Contractor: McKay Cocker Construction
Products: Schöck ComBAR®
Start of construction: March, 2011
End of construction: November, 2011