With the development of the times and the steady progress of the national new urbanization plan, many places are faced with demolition and reconstruction, but the concrete construction waste produced by the collapse of old houses can not be treated and digested.For the new type of steel structure residence, if demolished, it will not produce construction waste, but recycled materials, which is called “hiding steel for people”.People’s energy-saving requirements for buildings are gradually improved.Steel structure is a kind of building structure which is widely used in all kinds of construction engineering structures. Steel structure can be considered for the structure with high height and large span, the structure with large load or crane lifting capacity, the workshop structure with vibration or high temperature, the structure that can be moved or frequently installed and dismantled, and the building structure in the earthquake prone area.

 Main structural forms and characteristics of steel structure

 　　1.1Long span steel structure

 From the function point of view, spatial structure refers to the structure system which can form a large continuous space, mainly including grid structure, reticulated shell, cable membrane structure, combination and hybrid structure.Its characteristics are: continuous large span, large space and large area; light, beautiful and modern linear appearance; good seismic performance and simple structural stress; fewer component types, short construction period, easy to realize industrialization; green environmental protection and recyclable use. 

Three dimensional large span steel structure case

Large span steel structure is mainly used in gymnasium, conference hall, exhibition hall, activity center and other large-scale public activity buildings, hangar, workshop and decorative hall.

 Spatial structure has been developing steadily since 1960s.The new trend of spatial structure is the increase of grid structures with rectangular steel tube members.In recent years, space truss is widely used in terminal buildings, and its members are mostly made of round steel tubes.Most chords are curved.The appearance of bow structure has aroused people’s interest, but its performance and application scale should be further explored.Some colleges and universities are researching and improving the cone head and other parts of the grid structure in order to further improve the quality of the products.With the renewal of modern new structure concept and new materials, space structures include space truss, lattice shell, cable membrane, cable tension, prestressed structure system, etc.

 　　1.2Steel structure residence

 Due to its light weight, low foundation cost, suitable for soft foundation, easy installation, fast construction, short cycle, fast investment recovery, less environmental pollution and good seismic performance, steel structure residence has been paid attention to by all parties.Compared with brick concrete structure and concrete structure, steel structure has advantages in function, design, construction and comprehensive economy.The advantages of steel structure in residential buildings are mainly reflected in the following aspects:

 　　(1) Taking advantage of the high strength of steel, large bay layout can be adopted in the design, so that the building plane can be reasonably separated, flexible and convenient, and the open residence can be created, and the functional area can be reasonably arranged.

 　　(2) The same building area of the building floor, steel structure weight is light.According to the comparison, the weight of 6-storey light steel structure residence is only equivalent to that of 4-storey brick concrete structure residence.Moreover, steel has ductility, which can better consume the energy brought by earthquake, so it has good seismic performance and high structural safety. 

Three dimensional steel structure housing case

　　(3) Steel structure components can be produced in factory and installed on site.Due to the small amount of work on site, less pollution to the surrounding environment, and at the same time,

 The high degree of construction mechanization accelerates the construction speed.According to the concrete structure, the construction period can be shortened by one third.

 　　(4) Due to its light weight, lower foundation cost, lower overall material consumption, lower direct cost, shorter construction period and less indirect cost, the comprehensive cost is low.

 　　(5) Steel structure is suitable for large-scale production in factories with high degree of industrialization, and it can integrate energy-saving, waterproof, heat insulation, doors and windows and other advanced products into one, which can integrate design, production and construction to improve the level of housing industrialization.

 From the above analysis, we can see that steel structure is suitable for innovative residential structure system.Steel structure can be designed with people’s different aesthetic standards and functional requirements to design new types of rooms with various shapes, scales and spaces.The manufacturer can finish the building with high precision, high quality and high speed, which makes the building beautiful and economical.

 　　1.3Light steel structure

 Light steel structure is only composed of round steel, small angle steel and thin-walled steel [1] (this is relative to ordinary steel structure).The roof load of light steel structure is light, so the cross-section of members is small and thin.In addition to the characteristics of light weight, uniform material, accurate and reliable stress calculation, simple manufacturing, high degree of industrialization and convenient transportation of ordinary steel structure, it also has the advantages of convenient material acquisition, less material consumption and lighter self weight.The steel consumption of light steel roof structure is generally 8 ~ 15kg / m2, which is close to the steel consumption of reinforced concrete structure under the same conditions, and can save a lot of wood, cement and other building materials, reduce the self weight of the structure to 70 ~ 80% of the ordinary steel structure, and the total cost is low. 

Three dimensional light steel structure workshop case 

Light steel structure is a field of rapid development in recent 10 years. In the United States, the use of light steel structure accounts for more than 50% of the investment in non residential buildings.This structure has been widely used in warehouses, offices, industrial plants and sports facilities because of its high degree of industrialization and commercialization, rapid construction, high comprehensive benefits and large market demand.The research and development of light steel housing has been carried out in various places, which is another important direction of light steel development. At present, there are many design schemes and examples of low-rise, multi-storey and high-rise buildings.Because of its large span, large space, flexible separation, fast construction speed and favorable seismic resistance, it will have a great impact on the traditional residential structure mode in China.

 　　1.4Concrete filled steel tube structure

 Concrete filled steel tube (CFST) is a kind of building component which is filled with plain concrete.It is widely used in high-rise and super high-rise buildings because of its high bearing capacity, good seismic performance, steel saving and simple construction.Its promotion and development speed is very rapid, and will become the 21st century high-rise and super high-rise building group is very practical and the main structural form.

 The characteristics of this structure are as follows:

 　　(1) The compressive and shear bearing capacity of concrete-filled steel tubular columns is high, which is more than two times of the sum of steel tube and concrete;

 　　(2) The cross-section of CFST column can be reduced by more than 60% than that of RC column, and its outline size is also smaller than that of steel column, which expands the use space and area of buildings;

 　　(3) The reduction of column cross-section and self weight is beneficial to the seismic resistance of the structure, which is equivalent to the reduction of fortification intensity by one grade;

 　　(4) The self weight of CFST column is reduced, which reduces the load on the foundation and reduces the cost of foundation;

 　　(5) The thin wall of steel pipe is convenient for material selection, manufacturing and field welding, which is a very fast construction structure;

 　　(6) The concrete in concrete-filled steel tubular columns can absorb a lot of heat energy, and its fire resistance is better than that of steel columns, so the fire-resistant coating can be saved by more than 50% compared with steel columns;

 　　(7) Concrete filled steel tube (CFST) has three-dimensional compression characteristics of core concrete, which is conducive to the safe and reliable application of C60 ~ 80 high-strength concrete.At the same time, in the design of high-rise buildings, the slenderness ratio of CFST columns can only be controlled without limiting the axial compression ratio.In addition, because of its good overall performance, it also overcomes the shortcomings of local instability of ordinary steel structure steel columns.Therefore, compared with reinforced concrete columns, the section design can be reduced by more than 60%.

 　　1.5  Steel structure construction

 With the increasing number of long-span structures and super high-rise structures, the research of construction technology, the innovation of construction technology and the resulting construction mechanics problems are increasingly prominent.The traditional construction technology is gradually fading out in the complex structure such as tall and high-precision, followed by some innovative construction technology, such as the overall lifting construction technology, the overall lifting construction technology, the overall sliding construction technology and other special structure construction technology.Their great characteristics are as follows: first, the innovation of construction scheme is closely combined with the new structure form, and the construction scheme is innovated according to the composition and stress characteristics of the new structure; second, the solution of construction mechanics problems closely depends on the development of calculation technology. Through the simulation of the construction process, we can really understand and master the deformation and internal force change process of the structure in the construction process.

 The innovation of construction technology also includes the injection of new technology on the basis of some existing construction technologies, such as the combination of hydraulic through core Jack and computer control technology for integral lifting, and the application of integral lifting technology in the overall installation of Panzhihua dome grid structure and reticulated shell structure.Some special construction technology, such as Ferris sightseeing wheel, can be treated according to its structure, but the common problems can be studied first.The implementation of the new construction technology needs to be guided by the data of simulation analysis, and the analysis results are also an important basis for evaluating the advantages and disadvantages of the scheme.