A bascule bridge is a drawbridge that operates like a teeter-totter. As the bridge span rises, its counterweight lowers, and as the span lowers the counterweight rises.
During 1932 and 1933, the University Bridge was reconstructed. The timber trestles were replaced with approaches of concrete and steel; the wooden block paving on the deck was replaced with an Irving Open Mesh steel deck, two additional lanes were constructed on the lift span, and the control towers were rebuilt. The reconstructed bridge was re-opened to traffic on April 7, 1933.
New Technology Saves Lives
The use of open steel-mesh grating on the University Bridge was the first use of this technology in the United States. Steel-mesh grating (invented by Walter F. Irving, of the Subway Grating Co. of Long Island, New York), represented a tremendous improvement over timbered bridges. It made the bridge spans lighter and easier to raise and lower. It was safe for horses and cattle (a concern in 1933). Its open-mesh design lets wind through during gales and reduces the chances of the bridge blowing down. It does not have to be replaced every 10 years, as did the surfaces of timber bridges. The steel mesh on University Bridge was replaced once, in 1990.
The steel-mesh is not as slippery as wood in wet weather. In his history of Northwest technology, Adam Woog notes that before the steel-mesh surface was installed, the University Bridge averaged 182 accidents and 6 deaths annually. No deaths or accidents due to a slippery surface have been recorded since the installation of steel-mesh grating.