Engineering major Mammoet has started working on a key construction contract related to building a new, seismically isolated roof structure over the central area of Portland International Airport, which is anticipating a substantial growth over the next two decades.
Portland International Airport is scaling up in preparation to better serve 35 million passengers annually by undergoing a main terminal expansion project–nearly doubling its size.
“Mammoet was contracted to jack up, transport, and install twenty roof panels of five distinct types at the airport in Portland, Oregon, USA – all while avoiding passenger disruption,” Mammoet wrote in a statement posted on its website.
The roof, crafted mainly from regionally and sustainably sourced wood, was fully prefabricated between the active runways of the airport over the course of a year, Mammoet said while adding, prior to being moved, the roof panels were disconnected into approximately football field sized pieces to be transported to the new terminal expansion.
This allowed the airport to carry-on as usual while minimising disruption to airport operations. Depending on the type of panel, each was launched, rolled into place, set directly with self-propelled modular transporters (SPMTs), or lifted with a crane into its final position.
The complex project
A major complexity of the project was the wood material used in the roof panels’ construction. Deflection of the roof panels was a major concern of the client and the roof designers, so at each point in the jacking, transport, and installation process deflection of the roof was monitored and kept within stringent criteria.
Only the super cassette pieces had steel girders in the longitudinal direction to support the 25m wooden arches and to allow the panels to be “launched” using stationary skidding equipment. Also, the supports for the launching jacks were temporary towers supported by wooden piles which were installed in the 1950s.
To mitigate any issues, Mammoet performed extensive friction testing in its Rosharon, Texas yard prior to execution to ensure no structural damage occurred to a mockup roof panel, and that the design values presented to the client for strand jack anchoring were realistic.
When executing the job on site, Mammoet closely monitored the loads and deflections to ensure that they were in line with the tested values.