Structural engineer Jane Wernick chooses her favourite steel structure: Stansted Airport

I could equally have chosen the beautiful and amazing engineering achievement of the Golden Gate Bridge in San Francisco, or Peter Rice’s station roof at Lille TGV with its ingenious arches and cable truss-supported roof. But in fact Stansted Airport is for me one of the most inspirational steel structures. 

The clear organisational structure of the airport itself is both enabled and enhanced by the expressed, prestressed, steel towers which support the uncluttered roof, 12m above the concourse. They are on a 36m grid, with branches that splay out to support the roof on an 18m grid. 

Foster + Parters collaborated with Arup to create Stansted’s distinctive steel towers, designed with a built-in 100mm sway tolerance.
Foster + Parters collaborated with Arup to create Stansted’s distinctive steel towers, designed with a built-in 100mm sway tolerance. · Credit: Ken Kirkwood
· Credit: Drawing:Foster+Partners

We [at Arup] had the – now rare – luxury to spend 18 months refining the design of the towers. Normally, we design a building to tight deflection limits so as to make sure the finishes don’t crack, but at Stansted, the towers are actually allowed to sway quite a bit – up to 100mm. Rather than put in more steel to stiffen them, we agreed that so long as the structure was strong enough, and wouldn’t buckle, we would work with Foster’s team to develop details for the perimeter glass walls that could accommodate the movement.

As a result, the towers are light and elegant and the high, undulating roof gives a great feeling of light and space.