Belfast firm creates largest 'flat-pack' bridge

Engineers create the world's largest flat-pack, precast concrete bridge spanning 16 metres

Photo: Emma Martin at Story Contracting Ltd, from Macrete's website.
Photo: Emma Martin at Story Contracting Ltd, from Macrete's website.

Engineers at Queen's University in Belfast have developed a 'flat-pack' bridge that can be quickly hoisted into place and remain in place for hundreds of years.

The bridge is made from 17 slabs of precast concrete which are delivered on the back of a tuck and hoisted into position. The bridge relies on gravity to hold it in place, and arches. It's a modern take on the traditional stone arch bridge, but is faster to erect.

Professor Adrian Long of Queen's University Belfast invented the FlexiArch system over a 10 year period working with Macrete Ireland. It uses techniques used by the Romans int heir stone arch bridges but greatly simplifies construction. Rather than cementing tapered blocks on a form, the FlexiArch uses precast one-metre blocks set in lengths and backed with a flexible polymeric membrane. The arch rings are hoisted into position and lock together with their neighbouring segment. The arch is set, secured before they are infilled and roads built on top.

According toe Queens University, the bridge can be installed in eight hours, not months.

It doesn't rely on rebar reinforcing either, so won't weaken over time. Engineers say that means the bridge will last at least 300 years, outlasting conventional bridge designs considerably.

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