A 22-mi. (35 km) long bridge that its builders claim is the world’s longest sea-crossing structure was formally linked-up June 26 just south of the business hub of Shanghai.

The bridge links Shanghai to the industrial city of Ningbo across Hangzhou Bay, cutting the distance between them from about 250 mi. (402 km) to just 50 mi. (80.5 km).

Officials welded together a final section to complete the link at a ceremony attended by several hundred workers from the various companies building the bridge.

Costing $1.54 billion, the structure will open to traffic next year following completion of the six-lane roadway.

The bridge, a mix of viaducts and cable-stayed spans to allow shipping to pass beneath, lies just south of the Yangtze River Delta, one of China’s most economically vital regions, which is undergoing a massive construction boom aimed at boosting transport links.

Just north of Shanghai, builders in June connected the final link in the 20-mi. long bridge across the Yangtze, said to be the longest cable-stayed structure of its kind.

Construction on the Hangzhou Bay Bridge began in 2003 with a percentage of its financing coming from private sources, a first for such a large Chinese infrastructure project.

Hangzhou Bay has been a particularly challenging site for construction. The area is subject to typhoons and seismic disturbances, so the bridge was designed to maintain structural integrity even if experiencing earthquakes up to the seventh level of the Richter scale. Natural gas also is present in the bay and its location and effect on the seabed had to be investigated and arrangements made for its safe release before pile driving could begin.

The bay also features one of the tallest tides in the world. They can be as high as 25 ft. (7.5 m), moving between 15 and 18 mph (24 to 29 kmh) per hour. These tides are considered a natural wonder and are a major tourist attraction. Over the years several million visitors have viewed them and special provisions were made for tourists in the project’s design.

The bridge features off-ramps leading to a sea platform with an area approximately 111,111 sq. ft. (10,000 sq m). This artificial island is to be built on piers to ensure its presence does not interfere with the famous tidal movements, and will feature gas stations, restaurants, and hotels as well as a tower offering travelers excellent views of the phenomena. Emergency service personnel also will be based there.

So complicated was the planning process, construction could only begin after several hundred experts from various countries had conducted more than 100 studies over the course of a decade.

The “S”-shaped toll bridge is a cable-stayed structure with an overall length of 22 mi. of which its trans-oceanic section stretches 20 mi. (32 km). It is 203 ft. (62 m) high, allowing container ships free passage. Designed to last for a century, the span will be completed in 2008 and opened to traffic the following year. Vehicles will travel its six lanes at up to 62 mph (100 kmh), with 52,000 crossing daily in 2009, rising to an estimated 80,000 by 2015 and 96,500 in 2026.

The bridge will form part of a highway approximately 3,250 mi. (5,200 km) long between Tongjiang to the northeast and Sanya in the south, part of an extensive $242-billion highway program, which will have constructed 52,817 mi. (85,000 km) by 2030.

(Associated Press contributed to this article.) CEG Staff

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