Client: University of Oregon
Architects: Ellerbe Becket, Kansas City, Missouri, USA
Engineers: Ellerbe Becket
Glulam manufacturers: American Laminators, Drain, Oregon
Glulam suppliers: Wood Tech Services Inc. Oregon
Contractors: Hunt Construction Group, Indianapolis

This $89.5 million project for the ‘Oregon Ducks’ involved adding 12,500 new covered seats, concession areas, new suites, a state-of-the-art press box, a wider concourse and a new glulam roof canopy, all in just nine months, in time for the opening game of the season - a tight schedule for such a large construction project.

The spectacular 52m timber roof canopy, cantilevered nearly 30m over the new seating, provides the completely uninterrupted vision of the game nowadays considered essential.

It was designed as a pre-cambered cantilever with the additional feature of curvature over its width (as seen from the pitch). Modern design codes make all necessary deflection calculations available to engineers, whether working within North American or Eurocode design codes. However, to achieve this successful result, close co-operation between the specialist glulam suppliers and the main contractors, a high degree of accuracy in the prefabrication process, site assembly and lifting, and careful orchestration of the erection process were necessary. Erection of the glulam beams took less than two weeks, with the roof structure completely enclosed and sealed in two months.

The size and sheer quantity of beams required was a challenge. The glulam members were manufactured from Douglas fir, using special lay-ups in which higher strength grades of laminations were arranged in the outer layers. The main elements were built-up by sandwiching, using concealed steel plates and connectors. Two 311mm breadths were doubled up in this manner. The completed composite cantilevers had a maximum depth of 1,830mm. The total length of the main members was approximately 52m, with key nodes at a 29.6m position. The purlins were also Douglas fir glulam, with a 130mm x 380mm section.

Accuracy was critical for the final drilling and assembly at the area near the site, although considerable factory preparation had already been made. Because of the combination of camber and arch, detailed coordination was required to ensure that each beam took the correct shape before the next was assembled. A portion of the roof was left open over the top of the suites, and in this zone, the exposed beams had been pressure preservative treated at a specialist plant, prior to delivery. Connections for the glulam purlins were installed on the main members prior to lifting. The purlins were shaped and attached in segments, with plywood roof sheathing pre-installed on the ground. The glulam units were then lifted by crane onto their supporting steel columns, and connected by steel knee braces.

Douglas fir cladding was also included in the project, and glulams from an older structure were cleaned up and remachined for use as signage columns.