Designer: Parsons, Brinckerhoff, Quade & Douglas (New York), 1973
Owned by the State of Oregon,
average daily traffic 113,000
Welcome to Oregon's largest bridge! After the aesthetic debacle that was the Marquam Bridge (1966), it was generally agreed that Portland's next bridge could not be similarly repulsive. Although the Fremont cost five times more than the Marquam, the investment in its appearance seems to have been worth it.
The Fremont is designed to carry its own weight (which, aside from the road surface, is all steel) by acting as a spring. Technically, it is known as a tied-arch, orthotropic upper-deck bridge. Basically, the girders beneath the road tie the arches together, the arches take the brunt of the vertical load, and the overall weight is transferred to the piers. Steel tied-arch bridges of this type currently have a federal building moratorium on their construction, as they have been deemed overly volatile. (Ulp.)
The top of the Fremont's arch is nearly four hundred feet above the Willamette River. The main span is bigger than any other bridge in Oregon, including the Astoria-Megler Bridge. And the 902-foot, 6,000-ton span was constructed at Swan Island, then dead-lifted 175 vertical feet into place with thirty-two hydraulic jacks.
During construction in 1971, a girder running the length of the bridge cracked and nearly broke in two, something that would have been nothing less than catastrophic once the bridge was in operation. Four new sections of girder had to be installed, delaying the opening of the bridge over a year.
* The Fremont has no piers in the Willamette River.Less Text