Even Engineers Marvel Over the Curves of PDX’s New Roof

Published November 16, 2021

(Video credit: Alberta Poon)

Once the airport's nine-acre roof slides into place over the main terminal next year, what you see may depend on who you are.

You, we hope: a roofline you’ll recognize from a distance, with swooping wooden curves and giant round skylights.

Every architect, contractor, construction worker, and fabricator who built the roof: a brain-twisting feat of design and engineering.

After all, the roof's arched 80-foot-long ribs, made out of glue-laminated (glulam) wood, didn’t grow in that shape. The two-inch-thick plywood that covers those beams didn’t bend easily. It took hundreds of people and a full-scale test run just to figure out how to make the curves, well, curvy.

 

Zip-O Laminators, a 76-year-old family business based in Eugene, had to build a test beam merely to see if a one-piece, 80-foot arch would even fit in their plant, let alone their equipment. They used steel templates to make sure they shaped each beam correctly, pressed the glued boards together until they adhered, and carved the smooth curves by hand. Then they did it again — 272 times.

Covering the arcing beams

Next challenge: Connecting hundreds of thick, flat plywood panels together — without any gaps — to form domes and vaults that curve in three dimensions at the same time. Swinerton, which tackles construction logistics for this project, worked with CadMakers to use cutting-edge 3D-modeling software to calculate the shape of each panel and the angles at which it should be cut.

Another Swinerton partner, Freres, used a sophisticated computer-guided saw to cut the plywood, labeling each piece so the panels could be assembled on site like a jigsaw puzzle. (Sadly, they didn't scramble the pieces around just to make the puzzle more fun.)

Building the roof on site

Construction lead Hoffman Skanska Joint Venture are currently building the roof on the pre-fabrication site. Then they'll separate the roof into 18 cassettes to maneuver into place.

One other cool detail? Every major part of the roof was fabricated within 300 miles of here. The steel was milled locally. The metal girders and Y-shaped beams were fabricated in Oregon and Washington. We know the forests that supplied every one of the 35,000 boards in the ceiling lattice. (Let us introduce you to four of these sustainably managed forests and their caretakers.) The pandemic may have interrupted global supply chains and slowed construction jobs all over the world — but PDX Next has largely stayed on schedule because all our materials come from so close to here.

Jared Revay, senior project manager at Swinerton, says, "What I'd want people who see the roof to know is that all the people who made this happen — our craftspeople, our manufacturers, our vendors who stained it, even the trucking companies — everyone was so involved and so enthusiastic about this process. Without that cooperation, the success of a project like this would be very difficult."