Complex Engineering Behind PDX’s Mass Timber Terminal Project

The Engineering News-Record has provided an in-depth update on the progress of construction at Portland International Airport’s (PDX) new terminal that is scheduled to open in 2025.

Original plans were to simply upgrade the existing terminal, but they gave way to the expansion when officials realized “we would need to move structural elements that couldn’t be moved,” said George Seaman, engineering project manager with the Port of Portland.

Christopher Pitt, associate with KPFF Portland Structural, told the Engineering News-Record that the short-term plan to add more security lanes would impact lateral elements of the existing building. With highly liquefiable earth beneath, “the existing foundations are expected to experience settlement. New elements would have to be designed not to. That creates worse differential conditions.” Having to upgrade existing foundations would severely impact airport operations.

So, the port decided to pursue long-term improvements, including wedging in the new terminal space between the arms of the old, and “this project as we know it was born,” Pitt said.

The design replaces 200 seismically outdated columns with 34—half of them new and half on existing footings—to hold the 18-million-lb, 380,000-sq-ft roof, while opening up 100-ft x 125-ft bays between the columns to create more operational flexibility.

The roof has nearly 400 glulam beams—more than 250 of them 80 ft long—paired with 40,000 lattice pieces atop 34 Y-shaped columns. The columns are about 96,000 lbs each, fabricated from 1-in plate steel and filled with thermal grout for fireproofing. The beams are continuous, with no splices.