Mersey Gateway bridge building machine gets to work

The machine, named Trinity, is a movable scaffolding system (MSS), specially designed and built to construct the curved viaducts leading to the Mersey Gateway Bridge.

Trinity began work in Widnes on Thursday 21^st January 2016 with a concrete pour for the first deck section of the northern approach viaduct, which will lead to the new bridge. The 24-hour pour consumed around 160 truckloads of concrete, poured into the 1,170 m³ formwork mould.

While most machines of this kind can only build bridge spans of up to 60 metres, the movable scaffolding system (MSS) for the Mersey Gateway Bridge was specially made so it is able to cast spans of up to 70 metres, making it the longest in Europe. Trinity is 157 metres long, 22 metres wide and weighs 1,700 tonnes. It took three months to assemble her on site from from 1,200 component parts held together by more than 60,000 bolts. She will now be on site for the next 14 months.

She will act as a giant  formwork for the central deck of the north and south elevated approach viaducts, which will be constructed in sections or ‘spans’ approximately 70 metres long. It will take a few weeks to build each of the 19 spans, with this element of work due for completion in March 2017.

The process involves locking Trinity onto the bridge piers and then pouring concrete into the mould to create a deck span. Once the first span is complete, the equipment will then move along via hydraulic jacks to create the next deck span, and the process begins again.

Hugh O’Connor, general manager of the Merseylink contracting joint venture (Kier, Samsung C&T and FCC), said: “This is a hugely exciting time for our construction teams. An enormous amount of effort has gone into preparing and testing Trinity ahead of today’s concrete pour. We are delighted to achieve this important milestone and get this next phase of the project underway.”

Once Trinity has constructed the central part of the deck, a wing traveller will then be used to build the outer part of the north approach viaduct. The wing traveller is currently being assembled on site.

See how Trinity works here:

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