WEB EXCULSIVE: Canada's Golden Ears Bridge
By Richard High06 February 2009
Construction of the CA$ 956 million (US$ 770 million), 970 m-long Golden Ears Bridge, close to Vancouver, Canada started in July 2006 and is due for completion later this year, in time for the 2010 Winter Olympic Games in Vancouver in February. Richard High reports.
A 1 km-long, six-lane bridge that spans the Fraser River, the Golden Ears Bridge will connect the districts of Maple Ridge and Pitt Meadows on one side to Langley and Surrey on the other at 200 Street.
Besides the Golden Ears Bridge, the project includes the construction of 15 other bridges, ramps and viaducts. In total about 4.7 km of structures will be built once the bridge is complete.
More than 13 km of mainline roadway will be constructed, much of which will be landscaped, and the project includes a further 11.5 km of local road reconstruction.
The bridge, part of the Trans-Canada Trail, is the core element of a 14 km-long, six-lane highway project near Vancouver on Canada's west coast. It has been designed as an extra-dosed bridge, which is a cross between a girder and cable-stayed bridge.
This means the cables are positioned outside the main super structure thereby reducing the stress on the concrete pylons and allowing the designers to keep their height lower than on a "traditional" cable-stayed bridge.
Construction is in the hands of the Golden Crossing joint venture (Germany's Bilfinger Berger and the US's CH2M HILL). And for one of its most striking features - four, 86 m-high pylons - the joint venture approached Peri to design a crane independent formwork solution to enable their construction.
After careful study and discussion it was decided to use the company's ACS self-climbing system and Vario GT 24 girder wall formwork for the four H-shaped pylons. As a result, the continuously-changing pylon cross-sections were formed using a 4 m-high concreting cycle and, crucially, didn't require crane support.
Each pylon features a continuously changing cross-section from base to top. Below the bridge deck the pylon legs were constructed as double piers in a longitudinal direction, and above as individual piers in the form of a composite construction with prefabricated steel cores.
In both the longitudinal and transverse directions, the pylons turn between 1.0° and 1.2°. The cross-sections change from a hollow dispersed trapezoidal form, measuring 5.26 x 1.40 m at the base, to a single cross-section with external dimensions of 2.46 x 5.00 m at the top.
Designing the formwork for the piers had to take into consideration the fact that the 5 m opening would be reduced to around 4 m. Offset ACS brackets ensured the four level ACS platform could be securely interlocked. Anchoring the ACS units to the pylon´s slanted edges used a pivotable climbing shoe, which allowed the platforms to be fixed in any position up to 15° from the vertical axis.
This allowed the site staff to move safely between both climbing units at any height. Formwork elements for the 1.40 m wide, inclined front ends were mounted on climbing platforms, which were positioned on the longitudinal sides - the complete construction was suspended on rollers that ensured a simple and easy moving process.
Climbing brackets were not required on the front ends and only two climbing units were needed per individual pier. The benefit for the contractor was that less formwork material was needed, which saved time and money.
With the deadline for the 2010 Winter Olympic Games' opening ceremony set in stone, two sets of ACS and Vario formwork were supplied for each pier. One for the top, and one for the bottom.
Climbing took place every Monday. The 4 m-high cycle heights meant eight climbing stages up to the carriageway. After the cross-member had been concreted, eleven additional climbing cycles, using the second set of ACS climbing formwork, were needed for the top half of the pylon.
Safety during concreting both above and below the bridge deck was of paramount importance. As the Golden Ears Bridge crosses the Fraser River about 30 km before it flows into the Pacific the area is known for high windspeeds. So, for this particular job Peri's engineering team designed the ACS platform so that work could be carried out in even the most adverse conditions, including storms with winds of up to 80 km/hour.
Elaborate foundation work
Soft ground and the constant risk of earthquakes made elaborate and costly foundation work necessary. The bored piles for the four pylons are up to 95 m deep - longer than the visible part of the bridge piers.
In those areas where the ground´s load-bearing capabilities were limited the access roads and ramps rest on lightweight EPS rigid foam plastic. This so-called geo-foam construction method - better known through its use in dam construction - minimizes the additional loads arising from the required fill and absorbs any vibrations and shocks that may occur.
Golden Ears Crossing - in brief
The 13 km-long, CA$ 956 million (US$ 770 million) Golden Ears Crossing infrastructure project is one of the largest public-private partnership (PPP) projects in Canada. The six-lane route will be officially opened for traffic this summer and will relieve traffic congestion, improve traffic flows into the city centre and considerably shorten the travelling time for commuters.
The name has been taken from nearby Golden Ears Mountains. Golden Ears is derived from eyries, which refers to the eagles nests found in the mountains. For this reason, stylised steel eagles will be placed on the top of the pylons.
TransLink, the South Coast British Columbia Transportation Authority, retains overall responsibility and ownership of the project TransLink has negotiated a 35.5-year concession agreement with the Golden Crossing General Partnership to finance, design, build, maintain and rehabilitate the bridge and main roadway. The Partnership is owned by Ontario-based Bilfinger Berger BOT Inc.
For more information on this project see the Linked Articles on the right.