The application and development of steel structures not only depend on their own characteristics, but also are constrained by the development of the national economy. For a long time after the founding of the People’s Republic of China, due to the restriction of steel output, steel structures were restricted to be used in Megaproject projects that could not be replaced by other structures, which, to a certain extent, affected the development of steel structures. In 1996, China’s steel production reached 100 million tons, and in 2003, it reached a record high of 220 million tons. Gradually changing the situation of steel supply exceeding demand. China’s steel structure technology policy has also been changed from “restricting use” to “actively and reasonably promoting application”. With the wide application of steel structure, the science and technology of steel Structural engineering will be further improved.
- Development of high-performance steel
The prominent feature of steel structures is their high strength, making them particularly suitable for large spans and loads. The use of high-strength steel can better leverage the advantages of steel structures. To ensure the necessary plasticity, toughness, and weldability, high-strength steel used in steel structures is generally low alloy steel. In terms of steel bridges, China currently adopts a yield point of
16Mnq is already very common, and Nanjing Yangtze River Bridge uses this kind of steel to save 15% of steel compared with 16q. Yield point reaches 420
15MnVNqC (Q420qD) was used for Baihe Bridge of Beijing–Chengde railway as early as 1977, saving more than 10% of steel compared with 16Mnq. The above two low alloy steels have been officially listed in the Code for Design of Railway Bridge Structures. The highest yield point of steel recommended in the “Code for Design of Steel Structures” has also reached 420
High strength steel is developing rapidly abroad, and Japan, the United States, Russia, and others have already set their yield point at 700
The above steel is listed in the specifications.
The development of corrosion resistant steel has also received extensive attention. Weathering steel has been used in coastal engineering construction and bridge structures in the United States, Japan and other countries. Some companies are developing fire-resistant steel, which can maintain a strength of over 2/3 of room temperature even when heated to 600 ℃. In addition, wide flange I-shaped steel (also known as H-shaped steel), square steel pipes, profiled steel plates, and cold-formed thin-walled steel sections can all effectively utilize the efficiency of steel, achieve good economic results, and have broad development prospects.
- Research and improvement of Theory of computation
The current Code for Design of Steel Structures in China adopts the Limit state design based on Probability theory, which is the result of a lot of theoretical research and experimental analysis, but there are still many problems to be further studied and improved, and a lot of work needs to be completed. For example, statistical analysis of geometric defects in actual components and structures, distribution of residual stresses, and the impact of defects and residual stresses on the ultimate bearing capacity state; The ultimate bearing capacity of compression components and its influencing factors; The ultimate state of structures and components under repeated and dynamic loads; The plastic utilization of steel and the strength of plate components after buckling, considering second-order inelastic analysis of the overall height of steel frames, and so on. The deeper the understanding of the actual performance of components and structures, the more accurate the calculation results can reflect the actual situation, thereby fully utilizing the role of steel and ensuring the safety of the structure.
- Structural Innovation
The progress of Theory of computation and calculation means, as well as the emergence of new materials and new processes, provide conditions for the innovation of steel structure forms.
Computers are able to quickly calculate results for very complex structures, which has led to the rapid promotion and application of spatial structures such as grid structures with multiple members and high degrees of indeterminacy; The research of Theory of computation and the application of high-strength steel wire have made long-span suspension structures and cable-stayed structures applied to bridges and construction projects; Prestressed steel structure is also a new type of structure, its main form is to add some high-strength steel components to the general steel structure and apply pre-stress to the structure. Its essence is to replace some ordinary steel with high-strength steel to save materials; Steel and concrete composite structures can fully utilize the advantages of materials. Steel tube concrete structures filled with plain concrete in steel tubes have been applied in bridges and factory columns, and are a promising new type of structure.
Another form of structural form innovation is the integration of beams, arches, suspension cables and other structures with different stress types into the same structure, such as Jiujiang Yangtze River Bridge, Wuhan Tianxingzhou Yangtze River Bridge, Beijing Beijiao Comprehensive Stadium, Asian Games Village Natatorium, Beijing Beijing National Indoor Stadium, etc.
With the development of high-strength bolts and welding technology, riveted structures have been replaced by bolted or fully welded structures. High strength bolt connection has been widely used in plant steel structure, tower mast structure and grid structure. The box stiffening beam of Xiling Yangtze River Bridge adopts full welded structure, and the beam of Sunkou Yellow River Bridge adopts a new form of integral welded joint and joint external splicing.
The study of steel structures in high-rise buildings is also an important aspect. In recent years, China has built a number of high-rise buildings, such as the main building of Shimao International Plaza (333 m), Nanning Emperor International Building (276 m), Jing Guang Centre Building (208 m), Jinjiang Hotel Branch (153 m), Shenzhen Development Center Building (165 m), etc.
- Application of optimized design
The purpose of optimizing design is to minimize the amount of steel used or the cost of steel structures. To achieve this, it is necessary to choose an optimized structural form and determine the optimized cross-sectional size. Due to the widespread application of computers, optimization design has become possible and has been able to develop. At present, optimized design has been applied to the design of bridges, crane beams, and other steel structures, achieving significant economic benefits.
- Research on manufacturing and construction technology
In order to ensure the quality of steel structures, improve production efficiency, further shorten construction cycles, and reduce costs, further research and improvement should be conducted on manufacturing processes and installation and erection techniques; For products with larger batches, standardization and serialization can be gradually achieved.
Source：https://zhuanlan.zhihu.com/p/436405293
