|Caiyuanba Bridge will carry both cars and monorails.|
|Shibanpe Bridge will be longest box-girder crossing.|
|Dagu Bridge features sun" and moon" arches tied to deck. (Renderings courtesy of T.Y. Lin)|
A U.S. engineer is busy building bridges in China. T.Y. Lin International designed two record-breakers just getting under way, and is in a construction joint venture for one of them. The San Francisco-based firm also performed conceptual design for an unusual structure, currently half-built.
The city of Chongqing celebrated groundbreaking on Dec. 28 for both a bridge set to have the worlds longest double-deck, tied-arch main span and one with the worlds longest box-girder span. Man-Chung Tang, T.Y. Lins chairman, led design for both.
Chongqing, a gateway city to western China, is divided into three sections by two rivers, the Jialing and the Yangtze. The new bridges are needed to handle growing traffic. The Caiyuanba Yangzte River Bridge will carry six lanes on its upper deck. Steel girders on the lower deck will carry monorail tracks.
The 420-meter-long, half-through, tied-arch span will surpass Oregons Fremont Bridge at 283 m, but this was done out of necessity rather than as a goal, says Tom Ho, T.Y. Lin vice president. The city wanted a tied-arch bridge, and the need to accommo-date rail and vehicles turned it into a double decker crossing, longer than the current record-holder for that type.
T.Y. Lin and its design partner, Chongqing Communications Research & Design Institute, designed the steel box arch for a slender, aesthetic look, while the prestressed concrete frames of the lower level will provide rigidity against barge impact. China Chungtie Major Bridge Engineering Group Co. Ltd. holds the main contract for the bridge, to be completed in late 2005.
Downstream, a joint venture of Chongqing City Construction Group and T.Y. Lin has the main contract for the Shibanpe Yangtze River Bridge, which T.Y. Lin designed in partnership with subsidiary Chongqing DRC Engineering Co. Cost estimates were not available for either project.
Also slated for completion by the end of 2005, the Shibanpe Bridge will help relieve traffic on the original bridge adjacent to it. To satisfy a navigational requirement of 300-m horizontal clearance, updated to reflect slowly rising water levels due to the Three Gorges Dam, the new bridge will have seven box girder spans. A suspension or cable bridge would have been incompatible with the old bridge, says Ho. To eliminate the center pier yet maintain length while minimizing shear and bending, a 100-m-long steel box section will be placed midspan between the prestressed concrete box girders. The main span of 330 m will pass the current record of 301 m on Norways Stolmastsunde Bridge.
T.Y. Lin and its Chongqing subsidiary conceptualized another bridge in Tianjin, near Beijing. The Tianjin Urban Construction Group did final design and is building the signature Dagu bridge, set to open late this year. The 106-m tied-arch span will carry six lanes between two asymmetrical, inclined arches held to the deck by two planes of suspender cables. The larger "sun" arch inclines at a 1:3 ratio, the smaller "moon" at a 1:2.2 ratio. Work began last June on the crossing over the Haihe River, which runs through the city center.