Discussion of “Evolution of the Continuous Truss Bridge” by Francis E. Griggs Jr.

Abstract

As fans of truss bridges in general and of Gustav Lindenthal in particular, we commend the author for his comprehensive review of design, construction, and use of continuous truss bridges in the United States. We are pleased to have the opportunity to add his paper to our library of bridge history and engineering. To supplement the author’s effort, we respectfully offer information on what appears to be a generally overlooked milestone in continuous truss design and construction: the Sellwood Bridge in Portland, Oregon, a four-span continuous truss highway bridge designed by Lindenthal and still in use. Figs. 1 and 2 are recent photos of the bridge. To our knowledge, the four-span continuous figuration is exceedingly rare, if not unique. Also notable is the fact that the Sellwood Bridge opened for traffic in 1925, well before the 1929 Lake Champlain Bridge cited by the author as the first long-span continuous bridge built for highway traffic. Lindenthal himself acknowledged the four-span continuous configuration of the Sellwood truss spans in a 1929 letter to the editor of Engineering News Record as follows: “I believe also that I was the first engineer in this country to use continuous girders on a large scale, in the Sciotoville Bridge. Since then, the Steubenville bridge over the Ohio River, with three spans, was built for the Pennsylvania Railroad; I suggested the continuous system for this bridge and made the check calculations. Only recently I completed two city bridges of the continuous girder type over the Willamette River in Portland, Ore., one of three spans Ross Island Bridge , another of four spans Sellwood . G. Lindenthal, Consulting Engineer, New York City” Lindenthal 1929 The Sellwood Bridge is a two-lane structure over the Willamette River at the south edge of Portland. It now carries about 30,000 vehicles per day, the heaviest-traveled two-lane bridge in Oregon. The approach spans are reinforced concrete, and the main spans are four continuous subdivided Warren-type deck trusses with span lengths of 246, 300, 300, and 246 ft, respectively. Five concrete piers support the truss spans, with one pier founded on timber piles and four on spread footings. As-built drawings indicate that two other piers were designed with piles, but the piles apparently were deleted during construction. The truss spans are supported by a fixed bearing at the center pier and by expansion bearings at the other four piers. Gustav Lindenthal designed the Sellwood Bridge for Multnomah County which includes Portland as part of a multibridge program in the mid-1920s. The county commissioners brought