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COWI to design one of the world’s longest suspension bridges in record time


COWI will serve as consultant for the Japanese contractor IHI, which will build a bridge spanning Izmit Bay in Turkey over the next four years. Upon completion, the bridge will be the world’s fourth longest suspension bridge.

COWI has just signed the contract for detailed design of the Izmit Bay Bridge in Turkey in cooperation with the Japanese contractor IHI. The bridge, which is part of a new, extended highway system which links the two Turkish metropoles Izmir and Istanbul, will be the world’s fourth longest suspension bridge upon completion.

The project cements COWI’s role as the world’s leading consultancy firm on suspension bridges.

“The bridge over Izmit Bay is an extremely complex project with a free span of 1550 metres between its pylons and a total length of about three kilometres," says Henrik Andersen, Vice President of Major Bridges in COWI.

"We have experience from a number of similar international projects, however. We’re currently consultants on the bridge over the Messina Strait in Italy which with a free span of over three kilometres will be the world’s longest upon completion,” he adds.

Earthquake-resistant suspension bridge
Izmit Bay Bridge will be built in one of most seismically active areas in the world, which places additional demands on the bridge’s design. In contrast to the Great Belt Bridge in Denmark, which COWI was also involved in, the design team decided to use steel instead of concrete for the Izmit Bridge’s 250-metre-high pylons.

“The risk of an earthquake places unique demands on our services. Fortunately, we can draw on our earthquake specialists from our daughter company in California,” says Project Director Kent Fuglsang, who will head the nearly 80 COWI engineers involved in the Izmit Bay Bridge design.

He explains that the bridge will be made earthquake resistant by building its pylons on a concrete foundation that rests on a large gravel bed the pylons can slide on in the event of a major earthquake.

“In this way, the bridge will be partly isolated from the enormous energy which a major earthquake releases.”

The overall construction will require some 85,000 tonnes of steel and about 125,000 m3 concrete.

 Background on the Izmit Bay Bridge
IHI won the contract to design and build the Izmit Bay Bridge, beating out competition from Chinese and Korean contractors. In the bidding phase, COWI prepared a bridge design in partnership with IHI which IHI was able to build faster and at lower cost than the competitors. The bridge will be constructed in record time – only three years.

Detail design will be performed over the course of the next year and will take place in COWI’s head office in Lyngby with assistance from specialists at COWI’s offices in San Francisco and London. 

The overall price for the bridge will be about EUR 800 million (USD 1.1 billion). Construction is expected to commence in the beginning of 2012 and will be completed in 2015. COWI will provide consultancy services during the entire period. The Danish firm Dissing+Weitling is the architect of the bridge.

The world’s longest suspension bridges

 Akashi Kaikyo-broen, Japan, free span of 1991 meters (1998)

 Xihoumen broen, Kina, free span of 1650 meters (2009)

Great Belt Bridge, Denmark, free span of 1624 meters (1998)

Golden Gate Bridge, San Francisco, USA, free span of 1280 meters (1937)

LAST UPDATED: 17.09.2016