Sutong Bridge Construction Management Group Steel cages for piles bored through platform help form the massive pile caps, said to be the world's largest of their kind.

Strong Superstructure

The Sutong Bridge was carefully designed and reviewed by a consortium of Chinese and international bridge experts, design firms and academic institutes. The China Highway Planning and Design Institute (HPDI) Consultants, Inc. is one of the three key Chinese design firms along with Jiangsu Provincial Communications Division and Tongji University. COWI Consulting Engineers and Planners, Copenhagen, is the consulting firm on the bridge portion. "Actually COWI has had two contracts concerning the Sutong Bridge," says Ole Rud Hansen, a COWI project manager. "One contract was related to consultancy during the design phase and one contract covered consultancy during construction."

The bridge is designed to withstand catastrophic earthquakes and typhoons. Key design issues were reviewed by joint efforts from the international bridge academic world. The main span is flanked by post-tensioned segmental box girders viaducts of 3,485 m and 1,640 m in length at the north and south ends, respectively.

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Sutong Bridge Construction Management Group Thousands of ships pass by every day.

The steel orthotropic deck was fabricated offsite and delivered by barge in 16-m-long segments. Each deck segment weighs 450 tonnes. Two pairs of gantries were used to lift and align the 107 deck segments. The hydraulic and electrical components of Dorman Long's gantries were manufactured in Europe and shipped to China, where they were assembled onto steel frames manufactured in China.

Each gantry has a 290-tonne strand jack for lifting and hydraulic rams that adjusted the position and slope of the segment to fit onto the installed deck segments with a 1-mm tolerance. "In order not to interrupt the busy navigation, the speed of lifting was critical," says DLT's Tao. "We were able to lift 45 m per hour, and finished one box girder lifting in two hours."

The longest 577-m cable weighs 59 tonnes, is 160 mm in diameter and has a 50-year design life. The cable is made up of 313 galvanized wires, each 7 mm in diameter. These wires recently were developed and manufactured by Bao Steel, one of the largest steel mills in China.

Sutong Bridge Construction Management Group Platform was used for piles in foundations.

Prior to this project, China did not have the capacity to make this type of wire, and the key supplier for Chinese bridges had been Nippon Steel of Japan. Cables for the Sutong were manufactured by a Sino-Japan joint venture located in Jiangyin City, west of the bridge. "It is exciting to many people that China now can make its own wires," says Jiangsu Province's chief engineer Jian Zhao. "This project provided opportunities for product development such as this."

The 577-m-long cable is part of a fan-like arrangement of 34 cables. Based on recommendations from COWI, engineers employed a construction control method using stay cable lengths–instead of the stay forces–as the primary construction control parameter. "To our knowledge, it is the first time that this method has been used for the construction of a cable-stayed bridge in China," says Hansen.

Sutong Bridge Construction Management Group Main span is 1,088 meters long, a world record.

Bridge Boom

In a country where construction superlatives are proliferating, even the Sutong Bridge's world records soon will be overshadowed. South of Shanghai, the Hangzhou Bay Bridge also is under construction with completion slated for 2008. The $1.4-billion Hangzhou Bay Bridge will be the longest trans-oceanic bridge in the world with a 36-km-long six-lane highway crossing, plus a service island halfway across the bridge supported by piers.

The cable-stayed bridge has two main spans of 448 m and 318 m, and a steel orthotropic deck. The crossing is meant to shorten the trip between Shanghai and Ningbo from 299 km to 179 km, which explains why 35% of the project funding is from private companies in the city of Ningbo. The bridge directly links Ningbo to Shanghai, where China's largest port is located, and will make Ningbo a "new suburb," skipping the city of Hangzhou on Hangzhou Bay.

The recent rapid growth of the Yangtze River Delta area, and the upcoming Shanghai 2010 World Fair, are the major inspirations for the two bridges. Traffic volume crossing the Yangtze is expected to increase 20% annually.

With the Sutong Bridge, China will boast eight out of the world's ten longest cable-stayed bridges.

With Aileen Cho