Shanghai Daily news

A worker pulls reinforcing steel bars on the under-construction Donghai Bridge.
(Photo: Shanghai Daily)

The biggest problem facing engineers as they try to build the Donghai Bridge, a massive cable-stayed span across part of the East China Sea, is Mother Nature.
"I couldn't calculate or imagine how difficult this would be until the construction started," Cui Gejun, a senior engineer with Shanghai No. 2 Engineering Company, told Shanghai Daily yesterday.
Cui and several of his colleagues all said the difficulty in building the Donghai Bridge isn't its 31-kilometer length, but the fact they are working on an unenclosed part of the sea.
"The project itself opens a new major in bridge architecture that I was never taught by my teachers in university," Cui said.
Stretching from Nanhui District to an island in the East China Sea, the bridge is exposed to typhoons, strong winds and the threat of tidal, which engineers don't have to face when working along inland rivers.
"If the wind power reaches force 6 in the city, it will reach force 8 on the sea, making it tough for us to stand up, let alone work," Cui said.
One of the biggest challenges is to lay 670 bridge girders precisely on the pre-constructed piers in a situation that is tough for small ships to navigate.
"Our maximum error when laying each girder is less than 5 millimeters," Cui said, noting that the slow progress in building the bridge is largely due to bad weather.
Engineers said they have to use a state-of-the-art satellite positioning system to ensure all of the girders are laid properly. To fit the girders in place, builders use a special floating crane that can lift up to 2,500 tons and is fastened to the sea bottom by six huge anchors.
It takes about 10 hours to lay each of the girders, much longer than it would take along an inland river, according to Cui.
Transporting workers and construction material to the site is another tough challenge.
Zhou Chunwang, head of the company's logistic section, said construction had to be shut down for several weeks last year after a typhoon hit the site.