Contract for key expansion works of Portland airport awarded to Mammoet

The firm’s airport-related expertise includes Seattle-Tacoma International Airport’s elevated pedestrian walkway, the world’s longest airside bridge in Hong Kong, and the transport of airport structures in Texas

Twenty roof panels of five distinct types of a new, seismically isolated roof structure are being installed over the central area of Portland International Airport, Portland, Oregon in the United States. The contract to jack up, transport and install the panels was awarded to Mammoet.

The panels are said to vary in weight between 40t and 632t and measure up to 72m x 50m x 6m. Mammoet noted that it used four towers of Mega Jack 800 to jack up the roof panels to approximately 17m to allow self-propelled modular transporters (SPMTs) with falsework to be driven underneath each roof section. At midnight on the day of each move, the runways were closed for the one-mile transport of the panel from laydown yard to terminal. The roof sections were moved with care at a speed of about 1.6 kilometres, or one mile, per hour, the company noted.

The firm said that most panels had to be installed over the top of populated areas of the existing terminal building. Making safety a priority, works were done during strict overnight closures when the public could be kept clear of the work area. Once the area was verified to be clear of all pedestrians, the installation of the roof panels could begin, the firm said.

Each panel, referred to as a super cassette, was installed using stationary skidding propelled by strand jacks and lowered with the skidding jacks onto column isolators. The next set of panels were then rolled into position down the bottom flanges of the previously set panels. The panels were safely secured with consideration for potential elevated wind and project specific seismic requirements before the public were allowed to reoccupy the area below, Mammoet added.

The roof was crafted mainly from regionally and sustainably sourced wood and was completely prefabricated between the active runways of the airport over the course of a year. Prior to being moved, the roof panels were disassembled 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 SPMTs, or lifted with a crane into its final position.

Mammoet said that a major challenge on the project had to do with 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, the firm explained.

The firm also pointed out that the supports for the launching jacks were temporary towers supported by wooden piles, which were installed in the 1950s. To mitigate issues, Mammoet said that it 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 explained that it closely monitored the loads and deflections to ensure that they were in line with the tested values.

Mammoet stated that it has successfully placed sixteen panels, thus wrapping up phase one of the project. Four additional panels will be installed in 2024 during phase two (once the interior of the new terminal expansion has been built by the client for general occupancy), the statement concluded.

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