The world's most impressive feats of structural engineering unveiled

In the world of structural engineering, form usually follows function. But finalists in one of the industry's most prestigious awards are showing that they can do both.

From a 250-foot-tall railway viaduct to a pencil-thin New York skyscraper, the year's most impressive feats of engineering have been revealed as part of the 2017 Structural Awards.

Now in its 50th year, the program recognizes not only engineering quality, but creativity, elegance and sustainability. The awards span 15 categories, including heritage preservation, tall buildings and "structural artistry."

"We used to have categories such as healthcare buildings, residential buildings, commercial buildings and so on," explained one of the judges, Professor Tim Ibell from the University of Bath. "But this year, the categories relate to structural challenges, and I think it's proved to be a huge success in terms of diversity."

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Extreme engineering

One of this year's new categories honors structures built in "extreme conditions." Nominees include an earthquake-resistant tower in New Zealand and a collection of tidal energy turbines installed in choppy seas off the coast of Scotland.

But good engineering can come in small packages.

Among the finalists is a one-story holiday home in southern England known as the Crow's Nest. The house has been built on an active landslip zone at the base of a cliff face, explained Robert Rock, an associate at Eckersley O'Callaghan, the firm behind the project.

"The steepness of the slope, along with rainfall and erosion, means that the location of the house is susceptible to shifts in the ground," he said on the phone. "These movements created a hole, which the previous building (on the site) had begun to sink into."

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To prevent damage -- which could include cracking walls, or even complete structural failure -- the new house sits on a foundation of beams that can adjust to how the land shifts.

"Even as the ground beneath slips or rotates, the structure is sufficiently stiff that it will move with it, rather than breaking apart," Rock said. "The ground beams ensure that the building moves as one, rather than rotating or folding.

"Instead of trying to prevent or limit the forces of nature, we're working with them."

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Structural innovation

As well as overcoming unique construction challenges, many projects offer innovative solutions to city living. This includes a mobile pedestrian bridge in Geneva that lifts to let boats through -- while still allowing people to cross.

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Using a scissor truss mechanism, the bridge rises like a wave, transforming the flat walkway into a set of steep steps, said J-r-me Pochat, one of the three structural designers behind the project.

"We didn't want to design an 'on-off' system in which either the pedestrians or the boats were blocked off (at any one time)," he said on the phone. "We imagined something that can change from a walkway into a staircase.

"We did a lot of on-screen testing, and before installation the structure was completely assembled and tested in the factory before being delivered -- in one piece. Hopefully we can create new (versions) of this bridge, not just in Geneva but in other cities too."

A total of 43 entries were shortlisted in the 2017 Structural Awards, which is organized by the UK's Institution of Structural Engineers. The winners will be announced on November 17 at a ceremony in London.