Hangzhou Bay Bridge, China

The 36km long Hangzhou Bay Bridge will be the longest ocean-crossing bridge in the world, spanning across the Hangzhou Bay on the East China Sea and crossing the Qiantang River at the Yangtze River Delta.

The S-shaped Hangzhou Bay Bridge will be an important connection in China’s East Coast Superhighway. Starting in Jiaxing to the north, the bridge will end at Ningbo to the south. It will shorten the ground transportation distance from Ningbo to Shanghai by 120km and travel time from four hours to two hours. It will be a six-lane, two-direction highway with a 100km/h speed limit, and a 100-year, service guaranteed, cable-stayed design.

Wang Yong, chief director of the Hangzhou Bay Trans-Oceanic Bridge Construction Command Post, said the bridge will be one of the most important, not only in China but in the world “for it is not only the longest one (over a sea) but also will be built in the world’s most complicated sea environment, with one of the three biggest tides on Earth, the effect of typhoons and the difficult content of the sea soil”.

Preparatory work started on the bridge as far back as 1994. Construction work began in June 2003 and completion is scheduled for 2008. When opened to the public in 2009, it is estimated that the bridge will carry 45,000 to 50,000 vehicles per day in its first year of operation.

INVESTMENT PARTNERS

Of the total project cost of CNY11.8bn ($1.42bn), approximately CNY149m ($18m) has been contributed by 17 non-governmental enterprises in the province. Around 35% of this amount was raised from private companies in Ningbo; 59% was provided as loans from China’s central and regional banks. The Songcheng Group is the biggest non-governmental shareholder in the project with its investment accounting for 17.3% of the basic capital. Construction of the new sea-crossing bridge is an indication of China’s increasing economic power, and it is expected to boost economic development in the Yangtze River Delta.

Lv Zushan, Governor of Zhejiang, China’s fourth-largest provincial economy said: “The bridge will help form a more convenient and efficient traffic network in the Yangtze River Delta, enabling each part to develop much closer relations with one another… We believe the bridge will open many more opportunities for the region’s overall development and greatly enhance its economic strength and competitive power.”

CONTRACTORS

China Railway Bridge Bureau Group Co. Ltd. is the main contractor for the project. The contract for consulting and engineering services was awarded to Hardesty & Hanover, LLP. ICE is participating in the project by the use of three ICE V360 tandem vibratory pile drivers to produce the foundations for the bridge in the middle of Hangzhou Bay. Ty Lin International is the designer of the bridge. Ben C Gerwick is providing ship impact protection systems for the bridge.

ARCHITECTURE, DESIGN AND STRUCTURE

The Hangzhou Bay is a gulf in the East China Sea where one of China's natural wonders, the Qiantang River Tide, creates fast water and large waves. The area is also a typhoon prone zone. These factors made construction feasibility a major concern for the project and the plan was only finalised after nine years of consultation and over 120 technical studies with the help of more than 700 experts from throughout the world.

The cable-stayed bridge design was selected for the project as it can withstand the adverse conditions, multi-directional currents, high waves, and geologic conditions at the site. The bridge structure has also been designed to seismic criteria and will retain integrity in earthquake conditions up to seven on the Richter scale.

The 36km length will be of highway-class road with six, 3.75m lanes, three in each direction. The overall width of the bridge will be 33m. The roadway grade at cross-slope will be 2% and a maximum 4% at longitudinal slope.

Designed for 100 years of service life, the bridge has speed limits of 100km/h for the main spans and 120km/h for land approaches. The bridge has a height of 62m, enabling fourth and fifth generation container ships to pass through in all conditions. The total length of cable used in the project will be 32.2km.

CONSTRUCTION CHALLENGES

One major challenge faced by the project was the eruption of natural gas in a shallow layer along the bridge line. A special study was conducted and exploration was performed to investigate the distribution of the gas and the property of the soil during and after releasing the gas. The gas was released before pile driving to avoid any disturbance to the soil, collapsing of ground or eruption and flaming of gas.

Mostly, construction activity will be performed on land and then the prefabricated components will be transported to the site for erection and final installation. For shipping and erecting the girders in sea, giant floating cranes with accurate anchoring devices and launching gantries are being used.

Construction on mudflats near the south shore, in an alternating wet and dry tidal area, presented serious technical problems. A temporary 10km trestle has been erected for pile driving and pier construction. Girders weighing 1,430t will be erected from the top, starting from the land end and launching towards the sea. Each previously erected span will serve as the deck for transportation and erection of the next girders as the launching gantry moves forward.

Also, severe marine conditions caused difficulties in anchoring barges and construction vessels. Under turbulent tidal flow and typhoon influences, water flow currents are in the range of 2m/s to 3.32m/s at the Hangzhou Bay Bridge sites. The floating cranes can safely transport the 2,000t girder from the shore to the site and then anchor stably to erect and install the precast concrete box girder.

BRIDGE LAYOUT AND STRUCTURE

The Hangzhou Bay Bridge consists of nine sections. The first is the bank lead road to the north approach.

The north approach rests on low piers with post-tension concrete box-girder spans spanning pre-stressed continuous concrete box-girders and drill-shaft pile

The north approach leads to the north navigable bridge; a cable-stayed bridge with twin diamond-shaped towers, double cable and steel box-girders. The main span of the north approach is 448m. Including side spans, the total length is 908m.

The north high piers have continuous, 70m, post-tensioned, concrete box-girder spans with a total length of 1,470m.

The middle bridge approach is laid on low piers with 70m, post-tension, concrete box-girder spans with a total length of 9,380m.

The south navigable bridge is a cable-stayed bridge with an A-shaped single tower, double-cable and steel box-girders. The main span is 318m, and the total length including side spans is 578m.

The south high piers have continuous 70m, post-tension, concrete box-girder spans with a total length of 1,400m.

The eighth section measures to a total of 19,373m, and is composed of three sections:

• 6,020m in-water section with 70m girders and steel piles
• 10,100m mud-flat section with 50m girders and drill-shafts
• 3,253m land section with 30m to 80m girders and drill shaft foundations

The ninth section is Bank Lead Road at the south approach.

GLOBAL POSITIONING SYSTEM

Trimble is providing Global Positioning Systems for the monitoring of the construction. The project requires precise positioning for the bridge span off the coast. By using the Trimble 5700 RTK GPS systems with a reference station for differential corrections, accuracy is improved at longer distances enhancing the productivity.

50 5700 RTK GPS systems have been set up where the bridge crosses the Bay of Hangzhou and additional systems are located on barges in order to provide millimetre accuracy for the real-time positioning of piles and pre-fabricated sections of the bridge.

AUXILIARY FACILITIES AND STRUCTURES

At the middle of the bridge, there will be a 10,000m² service island for drivers to rest and enjoy a full range of services, including hotels, restaurants, petrol stations and a viewing tower. It is also expected the service island will become a tourist destination for watching the Qiantang River Tide. The service island will be built entirely on piers to avoid disrupting the tide.

The bridge requires the installation of traffic safety devices, monitoring systems, communications equipment, toll plazas, power supply, lighting and maintenance and office buildings. Two public parks are planned on each side of the bridge.