Cowi has signed the contract to carry out detailed design of the Izmit Bay Bridge, which is part of an extended highway system to link Izmir and Istanbul. In the bidding phase, Cowi had prepared a bridge design in partnership with IHI that IHI was able to build faster and at lower cost than the competitors. The crossing will have the world’s fourth longest suspension span upon completion.
“The bridge over Izmit Bay is an extremely complex project with a free span of 1,550m between its pylons and a total length of about three kilometres," said Henrik Andersen, vice president of major bridges at 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.”
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 250m-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,” said project director Kent Fuglsang, who will head the nearly 80 Cowi engineers involved in the Izmit Bay Bridge design.
He explained 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,” he said.
The overall construction will require some 85,000t of steel and about 125,000
