The composition of Zhaoyuan Rainbow Bridge is explained, and the information is acceptable.

The bridge is an overhead man-made passage. It consists of an upper structure and a lower structure. The superstructure includes bridge body and bridge deck; The substructure includes pier, abutment and foundation. They hang high and lie flat, with different shapes, and some are far away, simple and elegant; Some cross the rocks and streams, adding color to the mountains and rivers; Some are located in the main roads in the city center, with clever shapes; Some bridges are versatile and ingenious. No matter the wind and rain, no matter the heat and winter, they always cross the river to Tianjin in obscurity for the vast number of pedestrians, horses and chariots.

Significance and characteristics of bridges

The main purpose of building a bridge is to solve the traffic across water or valley, so that vehicles or pedestrians can walk on the bridge unimpeded. Judging from its earliest or most important function, a bridge should refer to a road across the water. Therefore, Duan Yucai's explanation of "Wen Jie Zi" is: "The word' Liang Zi' uses wood to cross the water, and today it is also a bridge." It shows that the original meaning of bridge refers to the passage with wood on the water, and later it is extended to the form of "plank road" on the cliff and "climbing over the wall" between pavilions and pavilions.

China, with many mountains and rivers, is a bridge country. In ancient times, both the bridge-building technology and the number of bridges were in the leading position in the world. For thousands of years, bridges have long been an indispensable part of people's social life. However, due to the vast territory of China, there are great differences in geography, climate, cultural customs and the development level of social productive forces from south to north and from east to west. Therefore, according to their own actual situation and needs, they have created a variety of bridge forms and gradually formed their own characteristics after a long time. Specifically, they have the following characteristics:

(1) regional. China, a vast country, is a bridge connecting the North and the South and the East and the West. Influenced by its natural geography and humanistic society, it has formed its own relatively independent style and characteristics according to local conditions. For example, the Central Plains and the Yellow River Basin in the north have relatively flat terrain and few rivers and waters, so people rely on mules, horses and carts to transport materials. Therefore, most of the bridges here are Guan Dan's majestic stone arch bridge and Liang Shi bridge, so that ships can pass under the bridge; In the northwest and southwest regions, it is difficult to build piers because of the high mountains and steep valleys. Therefore, rattan, bamboo cable, logs and other mountain materials are often used to build rope suspension bridges or outrigger wooden beam bridges. The coastal areas of Lingnan, Fujian and Guangdong are rich in hard granite, so stone bridges abound. In Yunnan minority areas, unique bamboo bridges can be seen everywhere because of the abundance of bamboo. Judging from the style of the bridge, the bridge in the north is as rough and simple as the northerners; Bridges in the south are as smart and light as southerners. Of course, this is also closely related to physical geography. For example, the rivers in the north have changed greatly due to the bullying of water flow and the impact of mountain torrents and ice, so the bridge must be thick and stable; However, the South River is gentle and easy to navigate, so the bridge is slender and beautiful.

(2) Diversity. China is an ancient civilization, with vast territory and abundant resources, beautiful mountains and rivers, and great differences in geology and geomorphology between the north and the south, so the technical requirements for bridge construction are also very high. Around the Han Dynasty, four basic types of bridges: beam bridge, pontoon bridge, cable bridge and arch bridge, all came into being. According to the different building materials and structural forms, these four kinds of bridges have evolved into: wooden bridge, stone bridge, brick bridge, bamboo bridge, salt bridge, ice bridge, rattan bridge, iron bridge, reed bridge, stone pillar bridge, stone pier bridge, flood bridge, cantilever bridge, covered bridge, wind and rain bridge, bamboo bridge, stone bridge, telescopic bridge, cable-stayed bridge and third bridge.

(3) Multifunctional. Ancient craftsmen in China paid great attention to the maximization of bridge benefits when building bridges. They should not only consider adjusting measures to local conditions, but also consider making the bridge play a multi-functional role as much as possible. For example, most arch bridges in the south of the Yangtze River are flat at both ends and high in the middle, which not only produces the beauty of arc in modeling, but also facilitates sailing. Covered bridges can be seen everywhere in the south of China, which fully embodies the multi-purpose characteristics of one bridge. There is a lot of rain and strong sunshine in the south, so the bridge builders built a gallery on the bridge, which not only provided a place for passers-by to avoid the wind and rain, but also increased the self-weight of the bridge, prevented the bridge from being washed away by the flood, and protected the wooden beams and iron cables from being corroded by the wind and rain. In particular, many of these covered bridges are also used for markets, accommodation and business activities, because people are used to being in a hurry. For example, Xiangzi Bridge in Chaoan County, Guangdong Province is more than 500 meters long. Quot "One Li Long Bridge and One Li City", there is a retractable pontoon bridge in the bridge, which is convenient for navigation; Build a gallery house on the bridge and make a market behind it. During this period, shops are lined up, from morning till night, bustling and lively, so that you can't smell the roaring tide and the wide river. Therefore, there is a joke among the people that "ask Xiangqiao when you arrive at Xiangqiao".

(4) public welfare. Since the bridge came into being, it has emerged as a kind of sociality belonging to the people. Traditional buildings in China are generally private, and only bridges (except those in private gardens) are owned by the society, whether government-owned or private. Therefore, for thousands of years, loving bridges and protecting roads has become a good fashion, while "repairing bridges and paving roads" is a charitable act that benefits the public and is highly respected by the public. Therefore, repairing or building a bridge has a broad mass character. According to historical records, there are probably four ways to build bridges in China: one is civil construction, that is, the bridge is built independently by one family and one surname; The second is to raise funds and report them to the government for support and joint construction. This is the most common, such as the famous Zhao Zhouqiao and Quanzhou Luoyang Bridge, which were all built in this way. Third, the official presided over the people's repair, which was pledged by local officials and gentry, and appointed officials or businessmen to preside over it. This is mostly a bridge; Fourth, it is all funded by the government. So there are ancient bridges all over China, and even more bridges are built in the hinterland. Its quantity and wide distribution rank first in the world.