In Portland, on the US West Coast, the city is preparing for the big earthquake that everyone knows is coming in the not-too-distant future. All new public buildings are required to be earthquake-proof – but few have gone as far as Portland Airport, with the recently completed remodelling expected to withstand earthquakes of up to magnitude 9 on the Richter scale.
»In the earthquake we’re expecting, bridges and other infrastructure will be knocked out. For society to continue to function, it’s essential that we can bring in resources from outside, and the airport is the first link in the chain. So it was important to our client that we really aimed as high as possible, « says Nat Slayton, lead architect at ZGF, which designed the remodelled and expanded airport.
More greenery, sustainability and flexibility combined with less energy use
With more than 19 million passengers annually, Portland Airport is one of the 20 busiest in the United States. It has also long been one of the most popular, due in part to the human scale of the airport, its interior design with lots of greenery and abundant natural light, and its generous shopping and dining areas.
When the airport decided it needed to double its capacity, it was keen to maintain that feel. Other important aspects to consider – besides earthquake-proofing the building – were sustainability, reduced energy use and future flexibility. In addition, the refurbishment and expansion had to be done without disrupting ongoing operations.
Using local wood resources
»Our region is a real wood economy, with sawmills, wood product manufacturers and significant timber exports. So we were clear early on that we wanted to use local wood resources to build our new airport,« says Nat Slayton.
Both the design and construction are inspired by the surrounding landscape – almost half of Oregon, Portland’s home state, is covered by forest. The vision was therefore to make you feel like you are in the forest as soon as you enter the building. The airport has more than 5,000 plants and 72 trees, many of them up to eight metres tall. Growing them in pots helps to keep their root systems in check, thus preventing them from growing too tall.
»This only works for certain species, such as fig and black olive trees. The idea of the trees and all the natural materials in general is also to establish a more human scale that reduces stress levels,« says Nat.
Each part of the building has been given its own identity, and the trees therefore appear with varying frequency. The same applies to the rest of the building – no two parts are alike.
Glulam arches, laminated plywood and wooden lattice
The load-bearing roof structure is created from a combination of glulam arches with a span of up to 30 metres, laminated plywood (a cross between LVL and CLT) and an airy wooden lattice, all made from durable Douglas fir felled within a 300 km radius. The bearing Y-shaped columns, on the other hand, are made of steel filled with concrete so they can be left untreated and still be fire-resistant.
»On top of them rests a half-metre-thick layer of rubber that allows the wooden roof to move in relation to the ground in the event of an earthquake,« explains Samuel Dicke, Client Development Manager for the project at timber construction company Timberlab.
In all, the undulating wooden roof covers an area of 37,000 square metres, equivalent to more than five full-size football pitches. Despite this, no more than 34 pillars have been used – compared with the 600 pillars previously in place in the smaller original airport. This has allowed great flexibility in how the space can be used and changed over time. The design also made it easier to assemble the prefabricated parts, which was quite a challenge in itself.
»Airports often have quite large areas of land at their disposal, so we were able to create a production facility on site and build to scale less than a kilometre away. Everything was then divided into 18 modules, which we put in place one by one,« says Nat Slayton.
This had multiple advantages. Since all the work on the airport site had to be done alongside regular operations, they had to make use of the 3–4 hours a night when no planes were landing or taking off. The proximity made it possible to move one module at a time and get it in place within that window. Working so much just outside the airport perimeter also saved a lot of time, as everyone working on the construction would otherwise have spent much of their time going through security checkpoints.
»We placed a huge emphasis on safety, and this process turned out to be a safer way of working. In fact, we didn’t have a single incident the whole time,« states Nat.
Halved energy use with the help of material selection, efficient insulation and new heating system
The new airport also has many sustainability benefits. Despite having twice the capacity of its predecessor, its energy use has been halved. This is due to both the choice of materials, including more efficient insulation, and a new groundsource heating system based on water pumped around in a loop. In addition, with such large skylights, daylight provides around 60 percent of the light needed.
»We’ve also tried to use wood in as many of the interior details under the roof as possible. The shop and restaurant counters, for example, are made of wood from local companies. For the flooring, we contacted a family business that produces oak parquet on a small scale. The oak trees around here are more like bushes and were generally considered useless, until someone realised that they could be sawn into small pieces and turned into parquet. We asked this company if they would be willing to make a lot more for us, so they built a plant and hired new people. Since then, they’ve continued to sell their products on the general market, and it’s been quite a success,« adds Nat.
Despite the many challenges along the way, Nat feels that the project has gone very well.
»The biggest challenge lay in drawing up the plan that made all this happen, because there is a lot of work behind it. But we’ve been fortunate to work with extremely talented people across North America. And the owners have really given us time to test things out and think things through – it’s not often we get the opportunity to spend so much time on the preparation,« he says.
Open areas to the public
When the new airport opened at the end of August this year, it was welcomed with open arms by staff, passengers and the wider public.
»I went there the day after the opening and I asked the taxi driver what he thought of it. He told me he had already driven three people there who just wanted to see what it looked like,« says Samuel Dicke.
What is unusual about Portland Airport is that so many areas are open to the public – you can even watch the planes take off and land through the large glass panels in the entrance hall. There are also many areas where you can sit down if you want to stop for a while or wait for someone to land – not least the large stand-like staircase in the centre.
»We’ve already noticed many people arriving earlier and have even seen videos of people dancing on the stairs,« says Nat Slayton.