A major milestone has been reached on the £1.3 billion Queensferry Crossing project over the Firth of Forth.

Work to develop the bridge's central deck has now been completed and the overall structure is on schedule to open in May 2017.

Since last September, each 16-metre 750-tonne section of deck has been added piece by piece by construction consortium FCBC, made up of Hochtief from Germany, American Bridge from Pittsburgh, USA, Dragados from Spain and Morrison Construction.

However, the deck is still free standing and the 644-metre cantilever has been examined by Guinness World Records experts, who have ratified the deck as the largest freestanding balanced cantilever in the world.

Soon the deck will be connected to the flanking towers and viaducts to form the final superstructure.

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Each deck section is added to ensure the cantilever remains balanced, which avoids placing too much stress on the concrete tower by adding deck segments sequentially at alternate ends.

Until now, the balanced cantilever method has never been used to develop a bridge this big.

Iain Cookson, FCBC Manager Centre Tower said: "It's not every day you get to achieve a Guinness World Records title. The construction of this record-breaking cantilevered structure has involved the installation of 36 separate steel and concrete composite deck sections. 

"These massive sections measure approximately 40 metres wide, 16 metres long are five metres deep and weigh an average of 750 tonnes. Each one had to be lifted up 60 metres above sea-level before being welded and bolted into position. Simultaneously, we had to create and install the steel stay- cables which will bear the weight of each deck section for decades to come.

"It has been a tremendous team effort ever since we lifted the first deck section in October 2015."

Economy Secretary Keith Brown added: "We can all agree the Queensferry Crossing is a modern marvel and a world-class feat of engineering. It's only fitting then that the bridge has been awarded a Guinness World Records title.

"It won't be long before the balanced cantilever disappears, when the small gaps between the towers are closed. But the record is still there to be beaten and the Queensferry Crossing will still be the tallest bridge in the UK and longest bridge of its type anywhere in the world."

(LM)