The islet has about 15,000 residents, while the nearest river crossing lies upstream 80 km away at the the Nanjing Second Yangtze River Bridge.
|Cable-stayed span was chosen for shorter link because of lower cost. |
(Photo by Wu Jun/Chinapix)
Contractor China Road & Bridge Group, Second Highway Engineering Bureau, began construction on the Runyang project in October 2000. The total project costs approximately $602 million. It includes the suspension span, the cable-stayed span and two interchanges, one of which is on the island. The project is scheduled to be completed in October of 2005, says Man-Chung Tang, chairman of San Francisco-based T.Y. Lin International, a special consultant on the project.
Hailed as the first major suspension crossing ever built in China, the span soars 50 m above the busy river, with precast concrete beams in place but no deck yet. When opened, it will rank third in the world for suspension bridge length, following only Japans 1,991-m-long Akashi Kyoko Bridge and Denmarks 1,624-m-long Great Belt East bridges.
The high elevation of the towers is to accommodate the eventual navigation of post-Panamax ships down the river toward what will be the worlds deepest port in Shanghai. Piles driven 57 m deep into rock support 215-m-tall towers. The anchorages, up to 30 m deep and sitting in the river on the north side and 50 m deep on the island side, had to be installed before flooding season, which occurs between May and August, says Wang. Underground work took two years, as planned, he says.
|Runyangs suspension bridge is a vital part of Jiangsu highway system that will link to major cities. (above). Wang Jun supervised the job with the aid of Wu Lianmin (right). (Photos by Aileen Cho for ENR)|
The suspension cables, held under 68,000 tons of pressure, consist of 5.3-mm-dia strands, 164 strands per cable, and 127 wires per strand, says Wang. Each main cable weighs about 21,000 tonnes.
The suspension bridge span will be a streamlined orthotropic steel box girder, 3 m deep. This is typical of long-span bridges being built in China, notes Tang. "Labor is cheaper here, so fabrication of orthotropic decks is cheaper [than in the U.S.]" he says. "In the last few years, Chinese engineers have been getting more into aesthetics." The Second Highway Bureau of China has the contract for the superstructure.
The width of the main span deck will be 34.3 m between hangers, with a 5-m-wide walkway on each edge to allow for maintenance access.
For deck placement, four deck erection gantries with hydraulic lifting capacity of 370 tonnes each will operate in pairs to erect 47 steel deck units, each weighing as much as 470 tonnes, says Wu Lianmin, assistant director of the synthesize division for the construction commanding department. The process is expected to take 52 days. The gantries strand jacks are designed to be reused on future bridges and to be self-erected and dismantled from the bridge cables at any point. Deck placement will begin later this year.
Due to the bridges length, expansion joints need to accommodate a movement of 2,160 mm, an unprecedented amount for joints, according to Gianni Moor, deputy general manager for Mageba, the Switzerland-based provider of the joints.
The cable-stayed bridge stretches 758 m long with a 406-m-long main span and 176-m-long side spans. It rises about 18 m above the river. A secondary crossing, it was cheaper to utilize a cable-stayed option, says Wang. The piles, up to 100 m deep, support diamond-shaped piers up to 150 m high. Steel rods were installed underground to support the anchors in case of a seismic event. The area lies in a moderate seismic zone, locals say.
The suspension bridge and cable-stayed bridge are connected by a new interchange on the island, about 1.3 km long. The road eventually connects to Yangzhou to the south. Overall, about 25 km of approach roads are being built.
|Southern approach is 23 km. (Photo by Aileen Cho for ENR)|
Anticipating future traffic levels, the six-lane highway is designed for 100 km per hour. The project is the highlight of a new road network for Jiangsu Province. The total 25.7 km of the Runyang road network will connect Yangzhou and Zhenjiang through 21 villages and four counties, and forms an important transportation link in the Beijing-Shanghai Expressway.
The pair of bridges are just some of many more to come in the future, says Wang. Tang agrees, noting that T.Y. Lin has expanded its China-based staff from five people only a few years ago to more than 100. The Runyang Bridge designer, the government-owned Highway Planning & Design Institute, now works with T.Y. Lin on a number of bridges, Tang says.
"There are 100 km of highway additions a year in China," says Tang. Other long-span structures in design or planning in China include the 1,418-m Tsing Lung Bridge, the 1,450-m Lingdingyang suspension bridges; plus cable-stayed structures such as the 1,018-m Stonecutters Bridge and 36-km-long Hangzhou Bay Bridge.
Yangtze River Bridge Builders Use Steel for Third Crossing
The Yangtze River Bridge No. 3, slated to be Nanjings third landmark crossing, is currently only two islands of steel and wood where the foundations are. But those foundations presented a deep-water challenge for its builders and a first for China.
The $362-million bridge will link two expressways that span Shanghai and Chengdu, says Man-Chung Tang, chairman of San Francisco-based T.Y. Lin International, special consultant to the Highway Planning and Design Institute, a Chinese government arm that acts as prime contractor for the project. The bridge will be 648 m long with 210-m-high towers "shaped like the Eiffel Tower," says Tang.
"This is the first time that a steel framework has been used in the bridge pylons," says Guo Zhiming, an engineer on the project. "The reason that we use steel pylons is that they will save time on the project." Much of the 3,000 tons of domestic steel can be fabricated and brought to the site as the foundation work proceeds.
The foundations of the southern and northern pylons are 120 m and 100 m deep respectively. Both pylons are 84 m long and 29 m wide.
The caissons are 62 m deep, with 3.3-m-dia piles and steel pipe castings. The north foundation work began five months ago with piles up to 82 m long, followed by the south tower foundation with piles up to 112 m long, says Guo. Twelve piles anchor each caisson against the strong current.
The foundations are due to be completed next spring, with superstructure work to be constructed with span-by-span cast-in-place concrete segments, each 50 m long. The contractor for the southern foundation is Hunan Road and Bridge Co. The northern foundation is being built by Second Co. of the Shipping Authority.
Typically, long-span cable-stayed or suspension bridges have concrete towers, says Tom Ho, T.Y. Lin vice president. "The fact that these have H-shapes add to the difficulties," he says. Because of the rapid currents, "it is difficult to position piledrivers accurately. They have plans to use a lot of anchors and bolts to hold the equipment barge in place."
When completed in 2007, the bridge will carry an estimated 60,000 motorists a day in six lanes of traffic, and span a total length of 1,088 m.
n Jiangsu Province about three hours west of Shanghai, the arch of what will be the worlds third-longest suspension bridge already stretches over the Yangtze River. The 1,490-m-long Runyang Bridge structure, along with its companion cable-stayed bridge on the other side of Zhenjiang Shiye Islet, is expected to spur growth in the still-rural area and eventually accommodate 10,000 vehicles, according to Wang Jun, chief of engineering for the Jiangsu Provincial Yangtze River Highway Bridge Construction Commanding Dept, which oversees the project.