The Golden Gate Bridge is located at the mouth of the Greater Bay Area (Golden Gate Strait) in California, California, USA. It is one of the world-famous bridges. The Central Valley, the world's largest granary, enters the Pacific Ocean from here and leads to the world. Before the Guangdong-Hong Kong-Macao Greater Bay Area was proposed in 2015, one of the three largest bay areas in the world was located here. The San Francisco Bay Area is the well-deserved hegemon in the field of science and education in the world today. In addition, there are also other places such as Silicon Valley , Apple, Stanford University and other world-class scientific research, brand and education bases.
Relying on the Central Valley's ultra-high crop production and efficient scientific research and education, San Francisco and its California state have been unparalleled for many years, ranking first in the total GDP of the United States and known as the world's largest economy. The fifth largest economy. And the Kinmen Strait has contributed a lot to all of this.
The Golden Gate Strait acted as a shipping channel inside and outside the Central Valley in the early days. Eastern California is surrounded by two to three thousand meter high mountains and vast large basin deserts, which are difficult to cross, so the Golden Gate Strait became the only external channel in the area during certain periods. And California rose because of the gold rush, so people like to call this strait the Golden Gate.
As California's population increases, the Pacific coast is almost entirely rugged and mountainous, so San Francisco Bay has naturally become the cradle of urban development, and the San Francisco Bay Area came from this.
As the San Francisco Bay Area continues to grow and develop, the Golden Gate Strait, which is only 1.6 kilometers wide, is in urgent need of a bridge to connect the north and south land. Otherwise, land transportation on both sides of the Strait will have to be detoured for more than 200 kilometers, which is very uneconomical. So in 1872, someone proposed to build a cross-sea bridge across the Kinmen Strait.
It stands to reason that a 1.6-kilometer cross-sea bridge would not be difficult even more than a hundred years ago. However, the plan for the Golden Gate Bridge was delayed again and again, and it was not until 1933 that construction began. Construction of the Golden Gate Bridge officially started on January 5, 1933, and was completed four years later. This project only uses two piers to build the bridge in a suspension manner. The main span is 1280 meters, the bridge body is 67 meters above the water, and the height of the tower above the water is 227 meters. At the same time, it has created many world records. Its height was the highest in the world in 1993. was surpassed.
A 1.6-kilometer bridge has a single main span of nearly 1.3 kilometers, and the tower is built extremely high. Why on earth do they have to make the construction so labor-intensive and time-consuming? Is it just to set a few Guinness World Records? You know, there is almost no comparability between the level of engineering more than 80 years ago and now.
Three-dimensional view of the Kinmen Strait
In fact, the bridge deck height of 67 meters from the sea is to ensure the long-term development of the Greater Bay Area’s shipping capacity, while the super-large span and high bridge tower are to more effectively use steel cables to pull the bridge body, because in Under this ultra-long span, if the tower bridge is too low, the steel cables will not be able to bear the weight of the bridge body. In fact, the reason why the span of the Golden Gate Bridge is so large is closely related to the hydrological conditions of the Golden Gate Strait.
Due to the perennial erosion of the rivers in the Central Valley and the continuous erosion of the Pacific Ocean tide , the Golden Gate Strait has formed a very deep trough in the narrow part of the Golden Gate Strait, with undercurrents surging. Not only that, the area of this trough with a depth greater than 80 meters is 0.7 kilometers wide, and the deepest reaches 115 meters. The average depth of the Pacific Ocean within 40 kilometers offshore of the Kinmen Strait is less than 50 meters. (As shown in the picture above)
Severe sea intrusion and excessive water depth are still a fatal technical problem even from today's perspective. Therefore, the construction team at that time could only use ultra-long spans to make up for this problem, which ultimately led to the glorious Kinmen. bridge.
