Looking back on the developments of cable stayed bridges in China, we have to mention the Shanghai Nanpu Bridge at the estuary of Yangtze River, which is an important milestone in the development of China’s long-span cable-stayed bridges. The Nanpu Bridge is the first cable stayed bridge with a span of over 400m in China and holds a critical position in the developmental history of cable stayed bridges in China.
Being viewed across the entire spans, the Nanpu Bridge, with a total length of 8,346m, looks like a dragon lying across the Huangpu River, with its head and tail in a spiral shape linking the old city area of Puxi with Pudong Developing Zone. The main bridge is 846m long with a main span length of 423m. Two “H”-shape RCC main towers, each of 150m high, are set up on both banks, with 22 pairs of steel cables being arranged in fan pattern and to support main girders. The construction of the Nanpu Bridge was commenced on December 15, 1988 and completed and open to traffic on December 1, 1991.
Before the Nanpu Bridge was constructed, China had not built any long-span cable stayed bridge. Obviously, building such a bridge across Yangtze River has been a dream of Chinese bridge builders for generations. Then experts have paid great efforts and thrown huge passion into building this great Bridge.
In early 1980s, China planned to build the Nanpu Bridge across Huangpu River. At that time, Chinese bridge experts had made adequate preparation for the bridge’s design, while relevant foreign organizations and experts had also gazed at this opportunity. Companies from Japan even proposed to prepare a feasibility study report on the Nanpu Bridge without any charge. Facing the strong competitors, Chinese experts treasured this rare opportunity. Bridge Master, Professor Li Guohao represented Chinese bridge experts to appeal to Comrade Jiang Zemin, then acting as the Mayor of Shanghai City, for independent design of Nanpu Bridge. In August 1987, Mayor Jiang personally visited Tongji University and inquired about the feasibility study conducted by experts from this university. Afterwards, on behalf of Bridge Engineering Department of Tongji University, the bridge expert, Academician Xiang Haifan wrote to Mayor Jiang, stating the objective conditions and determination for an independent design. In a short time, Mayor Jiang made comments on letter of Mr. Xiang approving the suggestions proposed by Mr. Xiang for an independent design and construction of the Nanpu Bridge. After two rounds of expert evaluation, a cable stayed bridge scheme designed by Chinese experts was eventually selected.
Academician Lin Yuanpei, Chief Design Engineer of the Nanpu Bridge, told us that the Chinese bridge engineers have been well prepared for the design of Nanpu Bridge thanks to the experience accumulated through the prosesses of building the Songjiang River Maogang Bridge, the Hengfeng Road Cable Stayed Bridge and the Chongqing Shimen Jialing River Bridge.
In 1975, during the course of building the Songjiang River Maogang Bridge, experts studied the deep bridge foundation and increased bridge span, thus strengthening the length design of stayed cables. Additionally, this bridge also helped the designers to practice in using computers for structural analysis and so on. For the subsequent the Hengfeng Road Cable Stayed Bridge, engineering personnel made further improvement on steel cables and anchor heads for sharp increase of their quality. In view of the features of the bridge and its special geographic location, experts had also worked out the 80m-deep steel pipe pile technology, and resolved a series of theoretical problems such as bridge anti-torsion. In 1989, during the course of designing the Chongqing Shimen Jialing River Bridge, experts tried to increase the bridge span up to 200+300m, which was the biggest one for the same kind of bridges in China to that time. With Shimen Bridge built, China succeed in building cable stayed bridges capable of surpassing the span of 400m for the first time, which laid a good foundation for building the Nanpu Bridge on Huangpu River.
With various trials and effors, experts mastered the mature techniques for building large-span cable stayed bridges and made outstanding contributions to the design and construction of the Nanpu Bridge. In the process of designing the Nanpu Bridge, experts not only applied their experience and techniques mastered over the years, but also encountered a hard nut: how to avoid the cracks observed in bridges of the same kind in the world. With extensive studies and investigations, Academician Lin proposed four solutions for the crack problem in the Nanpu Bridge: the mid-span intermediate deck slabs were designed with internal pre-stress to resolve the transverse through cracks of the deck; in construction, temporary longitudinal tripods were used to resolve the inclined cracks at the juncture of stayed cables and bridge deck; in design, new cable stayed girder connection structure was adopted to successfully resolve the radiation cracks at the anchoring points of stayed cables; in construction, crossbeam counter-process was used to successfully resolve the longitudinal cracks of bridge deck. With these four methods, China has successfully resolved the world-wide problem of cracking concrete decks and removed the huge risk of overlapped-beam cable stayed bridge in the Nanpu Bridge. As the practice has proven, over the last 17 years since the Nanpu Bridge was completed and opened to traffic, no cracks have been found at all, and thus the experts had made worthwhile efforts.
The building of the Nanpu Bridge was just on the right time period for the development of Pudong region in Shanghai. This opportunity provided an excellent environment for the construction of the Bridge, and in turn the the completed Bridge also serves as a convenient bridge for the development of Pudong and even for Shanghai. Due to its successful construction, the Nanpu Bridge was honored with the first prize of National Award for Science and Technology Advancement and 2000 Shanghai Municipal Golden Prize.
The Nanpu Bridge, as a milestone, has not only promoted the rapid development of economy in Shanghai, but also enhanced the confidence of the whole bridge industry of China and promoted the nationwide independent construction of long-span bridges.