The signature span cable stayed bridge over the North Arm of the Fraser River in Vancouver, British Columbia, Canada is slated to become part of the Canada Line Light Rail System. The bridge is of precast segmental box girder construction with back spans of 456 feet and a main span of 590 feet to allow for marine traffic to pass under it without obstruction. Most notable is that this project incorporates design and construction firsts for bridge construction in North America. 

The North Arm Bridge is the first extradosed bridge in North America.  An extradosed bridge can have the stays tensioned up to 60% of the strand's capacity compared to only 45% on a traditional cable stayed bridge.  By using a greater percentage of the strand's capacity and anchoring the stays to a shorter, stiffer pylon, the design is more efficient resulting in both material and labor savings.  Additionally, the lower pylon in proportion to the span length allowed the designers to keep the bridge out of the glidepath clearance envelope of the adjacent Vancouver International Airport.

Early in the project and prior to erection of the bridge, a comprehensive testing program was conducted to qualify the materials and to confirm the performance of the anchorage system at the higher stress levels of an extradosed bridge.  This testing included fatigue, static strength and leak tightness tests.   As an added measure, for each test an angular deviation was introduced at the end anchorages resulting in much more rigorous tests than customary.

The system chosen also allows for strand by strand installation where each strand is stressed using an automatic stressing system consisting of a specialized ram, pump, and computerized control box.  The automatic stressing equipment is light-weight, hand-held, reliable and user friendly.  Each successive strand in a stay cable is stressed to a specifically calculated force that is slightly less than the previous strand so that when the last strand is stressed all strands have the same force.  The stressing results have been very accurate and the general contractor is pleased with the performance of the stressing equipment. In total, the bridge contains 24 pairs of stay cable anchorages and over 260,000 feet of stay cable strand.

Another first for North America is the use of the Gensui Dampers.  These specialized dampers are made from a highly engineered rubber designed to absorb transverse vibration in the stay cables to protect them from damage.

History will show this bridge to be one of the great milestones in construction. The extradosed design has now been proven as a successful approach in North America as in other parts of the world. Additionally, the advanced stressing system utilized provided a great advantage in installation and quality control documentation.  With procurement and engineering started in early 2006 and final completion expected in 2008, the Fraser River Bridge is set to serve the many visitors coming to the 2010 Winter Olympics and to stand as a testament to innovative bridge design and construction.