This is the fourth installment of a series about the 5 finalists for the ASCE’s Outstanding Civil Engineering Achievement (OCEA) awards. Established in 1960, the OCEA Award recognizes a project that makes a significant contribution to both the civil engineering profession and society as a whole. The winner of this year’s OCEA award will be announced at ASCE’s Outstanding Projects And Leaders (OPAL) Gala, March 20, at the Renaissance Arlington Capital View Hotel in Arlington, Virginia. Today, read about the Taizhou Bridge. The project also was featured in Civil Engineering magazine.
There is an old adage which states that bridges serve as both a physical and emotional link between people and places. If that is the case, then the Taizhou Bridge represents that sentiment in every way. With its three pylons, two 1,080-meter-long main spans, and two 3,110-meter-long suspension cables, the Taizhou Bridge is the first long-span suspension bridge of this integral configuration in the world.
Located over the Yangtze River in Taizhou, Jiangsu, China, the bridge is part of a new $1.5 billion, 62 kilometer (38 mi.) long freeway that connects the cities of Zhenjiang and Changzhou and will serve as a catalyst for further economic growth in the eastern part of China. The bridge opened for traffic on November 25, 2012.
Winner of the 2013 Institute of Structural Engineers Supreme Award for structural engineering excellence, the Taizhou Bridge set 5 new world records: the first long-span, three pylon, and two 1,080-meter-long main span suspension bridge; the tallest central pylon ever built, with a height of 200 meters (656 ft.); the deepest underwater bridge caisson foundation for a central pylon; the longest suspension cable with two 3,110 meter (10,200 ft.) long main cables; and the first concurrent erection of 2 long suspension deck girders.
ASCE News Associate Editor Doug Scott interviewed Robin Sham, Ph.D., designer of the Taizhou Bridge and AECOM’s global director of long-span and specialty bridges.
1. What is the most innovative or creative aspect of your project?
The most innovative aspect of the project is the creation of a new, and never previously attempted, ultralong-span bridge system. This is the world’s first attempt to design and construct such a long-span, 3-pylon suspension bridge. Very substantial research and development efforts were necessary to ensure safety and performance. The 3-pylon, 2 main span integral suspension bridge system enabled not only a breakthrough in spanning over large distances, but is also the beginning of a new generation of multiple-span, continuous ultralong-span bridges for conquering difficult terrains and obstacles.
2. What was the biggest challenge?
There were many recalcitrant challenges, but one of the most significant was in the central pylon design and construction, for the 3-pylon suspension bridge system and in the concurrent 2 main span erection. The structural behavior of a 3-pylon continuous suspension bridge system is different from that of a conventional 2-pylon suspension bridge system. The design must ensure that no cable slip occurs over the cable saddles under all loading conditions, in order to prevent collapse. Conflicting demands arise, therefore, on the central pylon stiffness: a flexible central pylon helps prevent cable slip but is ineffective in the control of girder deflection; a stiff central pylon renders it difficult to help prevent cable slip, although it improves on deflection control of the girder.
3. Did your project have any technical issues you had to overcome? If so, what were they and how did you overcome them?
There were numerous technical issues encountered, and they were overcome by meticulous planning and supreme engineering. This is the world’s first attempt to design and construct such a long-span, 3-pylon suspension bridge. The structural behavior of this innovative 3-pylon continuous suspension bridge system has its inherent challenges. The design reconciled the conflicting demands and fine-tuned the bridge behavior. The caisson foundation of the central pylon is located in the middle of the 2.1 km (1.3 mi.) wide river and founded some 70 m (230 ft.) deep in the riverbed. The conditions therefore led to the deepest underwater bridge caisson construction ever attempted. This warranted a sophisticated control system to mitigate oscillations induced by wind and current, together with a high-precision positioning system, for caisson construction. The central pylon is of steel construction and the control of stresses demanded a very substantial quantity of thick steel plates, some 60% of which were of thickness 50-60 mm (1.9-2.3 in). The distribution of weld seams, the torsional effects induced by welding, and the geometric complexity rendered the control of welding distortion and geometry control very difficult. The superstructure construction scheme for a 3-pylon suspension bridge system is much more complicated than that for a 2-pylon suspension bridge system, particularly in the main cable erection, main girder erection, and bridge geometry control.
4. What time and budget challenges did your project have and what did you do to overcome them?
Meticulous planning for material supply, bridge fabrication, erection and other construction logistics, followed by well-engineered project implementation, helped meet the budget demands. The freeway network will serve as a catalyst for further economic growth in the eastern part of China. Modular steelwork production for the bridge components and concurrent 2-main-span deck construction were among some of the endeavors to fast-track the construction.
5. Sustainability is one of the 3 strategic initiatives here at ASCE. Describe how your project adheres to being sustainable.
A very high priority was given to environmental protection during construction of the Taizhou Bridge. Bidders for the construction work were required to explicitly state the budgets set aside for environmental protection. For the first time, a project-specific Environmental Protection Center was established for the project and environmental monitoring was carried out both during construction and into the operation phase. The established practice for long-span bridges in China in the past has been to directly discharge the deck runoff into the waterways below. This project is the first in the country to use a patented centralized bridge-deck drainage system to mitigate the risk of polluting the waterway below. All rainwater on the deck is collected through a series of pipes and is routed to the side pylons for further processing at 2 Constructed Wetland Treatment Systems (CWTS), one on the north side of the bridge and one on the south. Each CWTS is 2.7 hectares (6 acres) in size and consists of a series of gravity-fed tanks, pipes, filter ditches, and submerged wetlands with ultimate disposal at a biological pond. The location, alignment, and navigational clearances of the structure were established as the best solution to minimize the impacts on nearby water intakes and water source areas, taking of farmland, existing roadway networks, existing irrigation, and drainage and flood control systems.
Next, read about the Tom Lantos Tunnels at Devil’s Slide