(Looking at China along the highway) How does the “Sichuan-Tibet First Bridge” stand in the area of high seismic intensity and “magnitude 12”?
Chinanews.com, Ganzi, Sichuan, June 14 (Reporter Wang Peng) The Dadu River, which runs between the Hengduan Mountains, cuts a cliff between Tianquan County, Ya'an City, Sichuan Province and Luding County, Ganzi Prefecture, which has always been Sichuan-Tibetan. The traffic sky moat on the highway.
Now in Luding County, the Yakang Expressway Luding Dadu River Bridge spans the Dadu River Gorge, shortening the space-time distance between the Ganzi-Tibet area and Chengdu.
The picture shows the Luding Dadu River Bridge on Yakang Expressway.
Photo by Liu Zhongjun
This kilometer-class suspension bridge, known as the “First Sichuan-Tibet Bridge”, was completed and opened to traffic at the end of 2018. It has a total length of 1,411 meters and a main bridge of 1,100 meters. It is currently the largest bridge in Tibet-related areas in China.
In order to make the bridge stand in the high seismic intensity area and the complex wind field of the Dadu River Canyon, what world-class problems did the Chinese builders overcome?
"During the bridge planning, we selected more than a dozen bridge locations along the upper and lower reaches of the Dadu River. In order to avoid the active fault zone, but also to take into account the cost, we finally decided to build a thousand-meter-level suspension bridge here." Sichuan Provincial Highway Planning Survey Tao Qiyu, a senior engineer of the Design and Research Institute, is the person in charge of the design of the Dadu River Bridge in Luding. He told reporters that the bridge is located at the intersection of the "Y-shaped fracture zone" formed by the Longmenshan fault zone and the Xianshuihe fault zone. The seismic requirements are extremely high. Rare in the world.
The picture shows the Luding Dadu River Bridge on Yakang Expressway.
Photo by Liu Zhongjun
"How to resist the earthquake of the concrete bridge tower is one of the biggest problems in our design." Tao Qiyu said that compared with the steel bridge tower, the concrete bridge tower used in Luding Dadu River Bridge has weak seismic resistance. After many scientific researches, the design The team finally cleverly designed the corrugated steel web composite beams on the bridge towers, which not only reduced the weight, but also enhanced the seismic performance, thus overcoming the world-class technical problems in the design of concrete bridge towers in the high-intensity earthquake area, and also making the bridge a thousand Chinese people. The bridge with the strongest earthquake resistance among the meter-class suspension bridges.
Another major difficulty in the design and construction of the Luding Dadu River Bridge comes from the local complex wind farm environment.
Tao Qiyu said that the Dadu River Canyon has a typical canyon wind field, which is different from the flat wind in coastal areas. The wind field is disordered, and the instantaneous wind speed can reach 32.6 meters per second, which is equivalent to a level 12 gale.
The wind blows diagonally upwards from under the bridge. The angle of attack of the wind is very large. Unlike the monsoon on the seashore, there are strong winds here all year round.
"In order to solve this problem, we made a 1:2000 scale terrain model based on the surrounding area of 18 square kilometers, and moved into the wind tunnel laboratory to find an accurate design of wind speed and accurately grasp the wind environment." Tao Qiyu said, the bridge finally The upper and lower stabilizers are used to ensure the wind resistance. Under the action of the conventional wind angle of attack, the wind speed greater than 90 m/s may cause the flutter of the Luding Dadu River Bridge.
In terms of structural measures, unlike general suspension bridges, the Luding Dadu River Bridge uses an articulated energy-dissipating central buckle for the first time to limit the longitudinal dislocation of the main girder and the main cable, increase the torsional stiffness of the structure, and improve the anti-flutter performance of the bridge. To achieve the purpose of anti-wind.
"The central buckle of the anti-buckling support can first'yield' in a strong earthquake, and the rods will withdraw from work to reduce the reaction force, thereby protecting the main beam from damage." Tao Qiyu said proudly.
The ingenuity of Chinese builders has also been recognized by the world.
At the 36th International Bridge Conference in 2019, Luding Dadu River Bridge won the "Gustav Linden Shao" Gold Award, which is known as the "Nobel Prize" in the bridge industry.
"It's natural to be proud of receiving world-class awards. In fact, we were under a lot of pressure when designing this bridge because'Zhu Yu is in front'." Tao Qiyu said.
5 kilometers downstream of the Dadu River Bridge in Luding, is the Luding Bridge built during the Kangxi period of the Qing Dynasty and famous for the Red Army flying across the world. It was the first bridge across the Dadu River.
In the west of Luding County, there is also a steel cable suspension bridge that can pass cars. It was built in the early days of the founding of New China to connect the Kang-Tibet Highway (later renamed the Sichuan-Tibet Highway).
"These two old bridges represent the highest level of bridge construction in China at that time, and our latecomers must work harder." Tao Qiyu said that now the Luding Dadu River Bridge is the largest bridge on the Qinghai-Tibet Plateau, which is important for future large-span bridges in the region. The construction of long-diameter suspension bridges has great significance for reference.
(Finish)