Lions Gate Bridge

​Lions Gate Bridge, Vancouver to North Vancouver, British Columbia, Canada

​The suspended structure of a suspension bridge hadnever been replaced while traffic continued to use the bridge - this was a world's first.

​Lions Gate Bridge is the longest suspension bridge in Western Canada. It has been a landmark of Vancouver since it was opened in 1938.

Since 1972, COWI Bridge has performed numerous studies, carried out many structural designs and has been the engineer for all significant work done on the bridge. The bridge is one of only two crossings between Vancouver and the communities to the north, and maintaining traffic is paramount to the economy of the area.

The work performed to date has included several world firsts, has won many awards and has led to changes in the structure that have resulted in significant structural and safety improvements to the crossing. Some of the work to date includes the following:

 

Designs

  • The world's first replacement of a concrete deck with a steel orthotropic deck during short night-time closures (typically 6.5 hours). In 1975, the heavily corroded north approach viaduct deck was progressively replaced with a wider, lighter deck, in full width strips from one end of the viaduct to the other; a total of 670 m (2200 ft.) was replaced in 56 nights. The traffic lanes were widened from 2.95 m (10 ft.) to 3.6 m (12 ft.) without interruption to normal daily traffic. This technique has subsequently been used to replace deteriorated decks on many bridges in the world, including the Golden Gate Bridge in San Francisco and the George Washington Bridge in New York.
  • The rotation of two foundations without interruption of traffic. In 1979, it was discovered that the foundations of the north cable bent had settled unevenly, which had introduced bending into the slender cable bent legs. The thin plates that made up the legs were dangerously close to buckling and urgent action was required. An ingenious solution was implemented that introduced a pin into the concrete footing of each cable bent leg by coring out the concrete and allowing the footing to rotate in a controlled fashion so that the high bending stresses were relieved. Due to the design of a controlled release mechanism, traffic was allowed to continue to use the bridge at all times during construction.
  • The addition of a ship protection collar around the foundation of the south main tower. In 1988, a collar was placed around the vulnerable south tower footing to increase the ship impact resistance of the bridge.
  • The world's first replacement of the complete suspended structure of a major suspension bridge during short night-time closures (typically 10 hours). In 2000 and 2001, the corroding suspended structure of the bridge was progressively replaced in 54 segments, typically 20 m (64 ft.) long (the segments at the towers and all of the south side span segments were 10 m (32 ft.) long). A typical replacement operation consisted of closing the bridge to traffic at 8 p.m., cutting free a 20 m section of the deck and stiffening trusses, lowering the section to a barge 60 m below, lifting a new section from the barge, connecting it into place, and opening the bridge to traffic by 6 a.m.

 

Studies

  • Development of analysis and survey techniques for evaluation of suspension bridges;
  • Derivation of modern traffic loading for long span bridges for the first time (this work was incorporated into the North American bridge codes;
  • Development of criteria for aerodynamic stability;
  • Derivation of wind buffeting forces;
  • The largest bridge model to be wind tunnel tested in turbulent flow (from 1976 to 1991);
  • Discovery of long term cable stretch; and 
  • Measured values of structural damping.

 

Total length including approach spans: 1517 m (4978 ft.)
Main span: 472 m (1550 ft.)
Tower height: 111 m (364 ft.) 

LAST UPDATED: 08.11.2016