Lion’s Gate Reborn

BUCKLAND & TAYLOR, N.D. LEA CONSULTANTSWork is under way to expand the capacity of the Lions’ Gate Bridge in Vancouver, one of the nation’s most famous landmarks.

Few bridges have provided such opportunities for innovative engineering as the Lions’ Gate Bridge in Vancouver. The original 1938 design by Monsarrat and Pratley of Montreal was exceptionally light. It had a roadway deck, made of inverted T’s filled with concrete, only 75 mm thick. It was the longest suspension bridge in the world to use pre-formed spiral “bridge” strand for the main cables, instead of parallel wires spun in place.

In the present renovation, another first is unfolding — the complete replacement of the suspended structure (everything that hangs from the cables) without interrupting daily traffic. Most of the work is done during 10-hour night closures of the bridge. The first segment of deck was replaced in September 2000, and by Christmas the north side-span had been completed.

The new suspended structure has wider lanes and sidewalks, with pedestrians protected by full-length barriers. The new structure is 47 per cent wider between the outside pedestrian (now cyclist) rails. In addition, there will be 35 mm of high quality epoxy asphalt paving. Drains duct rainwater and salt clear of the structural steel.

Despite the additional width, added paving and new barriers, the new suspended structure weighs the same as the old. This is accomplished by having an orthotropic steel deck (a stiffened 14 mm deck plate), truss members of tubular steel, and by placing the stiffening trusses under the deck, and using the orthotropic deck as the top chord of the trusses.

Even with the extra width, and the bent plate “trough” stiffeners under the steel deck, the amount of surface area to be painted is only half that of the old riveted structure, and the painted area is all under the deck, protected from salt spray. The bridge is also being upgraded to have good seismic performance.

The project includes widening of the “causeway” road through Stanley Park, new lights, signals, controls and electrical system, and seismic upgrading of the north approach viaduct. — By P.G. Buckland, P.Eng., Buckland & Taylor

Owner : Government of British Columbia, B.C. Transportation Authority

Bridge engineer: Buckland & Taylor, Vancouver

Engineer for overall administration and causeway design: N.D. Lea Consultants, Vancouver