TWISTING IN THE WIND.

Wind tunnel tests of preliminary designs for Canada's Annacis Island bridge showed designers that they could achieve aerodynamic stability using 20% less structural steel than they had thought necessary. The bridge is the world's longest span cable-stay, and stability during construction was another concern. The tests were also used to check a tie-down system for the bridge during the vulnerable stage of cantilevering spans out from the towers. For the Annacis Island bridge, the design was changed as a result of the tests. Girders were moved to a more efficient structural position, and the sidewalk was arranged differently; the changes used significantly less steel.