A century ago, a fire that lasted three days and nights reduced nearly all of Chicago to ashes. However, Americans took this opportunity to light a new torch for the art of architecture. Buildings made of glass and steel were built all over the country, and even chain stores were made of steel.

According to the relevant professional data statistics, until the middle of the 1980s, China's steel structure buildings have just had a "zero" breakthrough. Although it started late, China's steel structure building has developed rapidly from a very high starting point. Today, when talking about the masterpieces of architecture, people may immediately think of the "Bird's Nest", the new CCTV Building, the Guangzhou TV Tower, the Shanghai World Center... Throughout the urban construction, almost all tall and towering landmark buildings in the architectural form of steel structure.

According to Ouyang Chao, a steel structure expert of China Construction Third Bureau, the starting point of China's steel structure construction can be traced back to 1984, when China Construction Third Bureau won the bid for China ****** steel structure building - Shenzhen Development Center. In the concrete structure as the main form of domestic construction field, this is a virgin land. At that time, the bureau sent 10 top welders east to Japan to learn ****** advanced carbon dioxide gas protection welding technology. When Japanese experts learned that most of them had only a junior high school education, they shamefully asserted that "a third of them would be good", because even those with a solid education there had to study for three to six months, whereas the contract period for Chinese workers was only one month. The 10 Chinese WELDERS STUDIED FOR 7 HOURS EVERY DAY, AND DISCUSSED WITH EACH OTHER after SCHOOL and dinner. After 30 days, all the welders finished their courses successfully, and they had a solid grasp of the necessary welding skills to complete the Shenzhen Development Center Building project. In the construction of the project, from the welding thickness of 130 mm to the previous record of 110 mm, to 350 thousand meters of welds by ultrasonic and powder inspection, all qualified, and then 98% of the welding to the United States ******(grade D) standards...... The development of steel structure construction technology in China has entered a fast lane since then. With the support of technology, the steel structure skyscrapers on the land of China are also springing up like bamboo shoots after a spring rain and being built higher and higher.

Ouyang Chao said: "Steel structure is more popular now, and its shape and construction difficulty is getting higher and higher." For example, in China's representative public buildings, the CCTV new site project, both high and difficult, is a challenge to the construction of irregular building structure; The structure of Guangzhou TV Tower itself is very complex, and the construction with steel structure is more complex; And "Bird's nest" can be said to be a singular masterpiece. Taking "CCTV" as an example, it has a tilted (overall bidirectional tilt 6 degrees) and double lift (70 meters and 60 meters, respectively) structure, and in the oblique direction of the double lift structure will have a certain droop under the action of gravity; The steel grade used in the general steel structure engineering is Q345D or Q390D, and the "CCTV" project is used Q420D and Q460D, which is rare in the general public buildings. This brings a lot of technical difficulties and requirements to the production and welding of steel; The two towers are formed and connected by a large cantilever structure of 14 stories to form a huge "door" shape, which poses a daunting challenge to traditional construction techniques. The cantilever sags under the action of gravity, which requires the reverse deformation in the construction process, and the pre-adjustment value of the steel structure should be calculated in the welding process, which is hardly used in public buildings in the past. In addition, the engineering measurement is also a difficult problem, because the structure tilt, resulting in each column in the high air positioning, if coupled with the pre-adjusted value of its installation will be more difficult; As the grade of steel has increased, its thickness has also increased to 135mm, and the welding of ultra-long and ultra-thick steel structures has been widely used in engineering projects.

The characteristics of the "Bird's Nest" steel structure is the space curve structure, which brings higher requirements to the production of steel structure, because once there is an error, the welding between the steel structure is difficult to dock smoothly, in addition, the welding process is relatively more strict requirements; The Intime Center project's ****** difficulty is to assemble two 39-meter-long trusses on the ground and then hoist them with a tower crane. Ouyang Chao said, super high-rise steel structure buildings, are involved in the use of large span, long welding and other construction technology.

Ouyang Chao believes that the future development direction of steel structure buildings is in the super tall, long span and special shape three aspects. Special shapes are represented by the Guangzhou TV Tower, CCTV and Bird's Nest, which have in common the impossibility of concrete construction. At present, such as the capital city, Wuhan, Baiyun Airport and some modern railway stations have also begun to develop in the direction of space curve connection and large span. Such structures can only be completed by the form of steel structure. In addition, the grade of steel is higher and higher, and the amount of steel used in steel structure buildings will be larger and larger.