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Friday, Jan 15, 2021

[AE75] High-quality, low-cost - a winning combination

As we celebrate our 75th anniversary in 2021, we take a look back at our legacy of achievements and milestones over the years, as chronicled in our company newsletter that began publishing in 1967...

Originally appeared in AE Today, April 1986 issue

A logging truck crosses a resource bridge

More and more Associated-designed forest industry bridges are showing up in the Prince George area of BC's central interior. The past year saw timber licensee Lakeland Mills commissioning three bridge designs as part of their program to upgrade and extend their Teardrop Forest Service Road. Sharing in the activity was Prince George contractor Crossroads Construction who built all three structures. 

Associated's first contract with Lakeland Mills resulted in a gravel surfaced, steel concrete composite design supported by steel pipe piles with replaceable timber abutments. The economical, low ­maintenance structure across the Muskeg River was described in the October 1985 issue of AE Today. 

During the construction phase of the Muskeg River Bridge, Associated was asked to design a similar replacement for a crossing of Doc's Creek that had been condemned by the Forest Service. "We used a similar superstructure but cantilevered the ends of the girders beyond the supporting piles to achieve a 30-metre long structure with non­loadbearing concrete abutments at each end," reports senior bridge engineer David Harvey. "We saved a lot of steel and avoided expensive abutments."

The low-maintenance gravel running surface and the reduced driving time resulting from the realignment of the road and bridge are adding up to benefits for Lakeland Mills. "We expect even bigger benefits from the Crocker Creek Bridge," says David. 

In this case, Associated encouraged Lakeland to relocate a road and bridge straight through a swamp area to shorten the route and avoid an alignment problem. This called for an innovative design to cope with the swamp itself. "The main problems we had to tackle were the stability of the 3.5-metre high embankment over the swamp and the short time frame we had available for construction," reports David. 

To avoid the problems caused by severe winter temperatures during the construction of the Doc's Creek Bridge, the Crocker Creek structure was specially designed for winter construction. The 18-metre long bridge features four precast concrete box beams supported by concrete caps and timber piles. Extra stub piles were driven through the bridge end fills to prevent them from sliding into the creek. 

"The bridge proved to be even more economical than we had anticipated," says David. "At $3,300 per metre, the 100-year life bridge was only 50 per cent more expensive to build than a 12-metre, eight ­year life log stringer bridge." High-quality, low-cost designs with maintenance saving features and speedy construction are adding up to a winning combination for bridges in the forest industry.