Types and characteristics of steel for common steel frame structure

1.Carbon plant alloy structural steel: Q195, Q215, Q235, etc

2.Alloy structural steel high toughness alloy structural steel

3.High quality carbon steel and alloy tool steel

4.Major purpose steel

Standard for raw materials of steel frame structure

The standard of raw materials used for steel frame structure is to ensure the bearing capacity of load-bearing structure and avoid ductile damage under certain standards. It is considered comprehensively according to the necessity of structure, load characteristics, structural form, in-situ stress situation, connection mode, thickness of stainless steel plate and office environment.

The four types of steel specified in code for design of steel structures (GB 50017-2003) are “suitable” for application. They are the first choice when the standard is approved. The application of other types and specifications is not strictly prohibited. If the applied stainless steel plate considers the provisions of the standard, it is OK.

Technical content of key steel frame structure

1.Technicality of steel frame structure in high rise residential buildings

According to the building density and design scheme, the structure, supporting point, tube section and super large frame shear wall are selected respectively, and the prefabricated components can be steel, reinforced concrete structure or concrete filled steel tube.Steel prefabricated members are light weight and have good ductility. They can be welded or cold-rolled channel steel, which is suitable for extremely high-rise building engineering buildings; the prefabricated members of reinforced concrete structure have large bending stiffness and good fire safety characteristics, which are suitable for medium and multi-storey buildings or bottom structure; the concrete-filled steel tube project is simple in construction and only used for column structure.

2.Technology of steel frame structure in interior space

The steel frame structure of indoor space is light in weight, large in bending rigidity, beautiful in shape design and faster in construction.The spherical grid of flat computer with seamless steel tube as the component, double-layer spherical grid with variable cross-section and reticulated shell are widely used in China.It has the advantages of large bending rigidity and low steel content in indoor space, and can show perfect CAD in design scheme, engineering construction and testing technical specifications.In addition to the steel structure grid, there are also long-span suspension structure, cable membrane structure and so on. 

3.Technology of light steel structure

With the light color coated steel plate made into the wall and flat roof bent structure of the new structural form.The light steel structure management system is composed of thick steel plate welding or cold rolling of large cross-section thick wall H-beam and steel purlin, round steel made of soft terminal software and high-strength bolt connection. The column spacing can be from 6 m to 8 m, the span can reach 30 m or more, and the height width ratio can reach more than 10 meters.The steel content is 20-30kg / m2.There are standardized design program flow and systematic manufacturing enterprises. The product quality is good, the installation speed is faster, the weight is lighter, and the project investment is less. The project construction will not be limited by the time, so it is suitable for all kinds of light-weight workshops.

4.Composition and structure of steel concrete

The load-bearing structure of beam and column composed of channel steel or steel management method and concrete engineering is composed of steel-concrete structure, and its application scope is expanding in recent years.The structure has the advantages of both steel and concrete, with high overall compressive strength, good stiffness and excellent seismic performance. When outsourcing concrete structure is selected, it has better fire resistance and corrosion resistance performance.Generally, the steel content can be reduced by 15-20%.It is composed of ribbed floor and precast concrete-filled steel tubular members. It also has the advantages of less support or no support, convenient and rapid engineering construction, and has great potential for marketing and promotion.It is suitable for frame column, column and multi ribbed floor of double or multi-storey building with large load, and column and ribbed floor of public building.

5.High strength bolt connection and welding technology

High strength bolt is based on friction to transmit in-situ stress, which is composed of anchor bolt, nut and sealing ring.The high strength bolt connection project has the advantages of simple construction, convenient disassembly, high bearing capacity, good fatigue relief and locking performance, and high safety factor. In the project, riveting and part of electric welding have been replaced and become the key connection mode in the fabrication and installation of steel frame structure.For the prefabricated steel components manufactured in the workshop, the thick steel plate should be fully automatic multi wire submerged arc welding, and the box column baffle plate should be welded by melting nozzle electroslag welding.The full-automatic welding technology, gas shielded welding flux cored wire and self maintenance flux cored wire should be selected for on-site installation and construction site.

6.Safety protection technology of steel frame structure

The safety protection of steel frame structure includes fire safety, anti-corrosion and anti rust treatment. Generally speaking, it is not necessary to do anti-corrosion treatment after the fire-proof material is solved, but it needs to be solved in the engineering construction with corrosive vapor.There are many types of fire-proof materials in China, such as TN series products, mc-10, etc. among them, mc-10 fire-retardant materials include alkyd enamel, chlorinated rubber paint, fluororubber building coating and chlorosulfonated building coating.In the construction site, the appropriate architectural coating and coating thickness shall be adopted according to the steel frame structure form, fire rating and natural environment regulations.

Overall goal and Countermeasure of steel frame structure

Steel structure engineering covers a wide range of construction, and the technical level is large. In the application and promotion, we must comply with the national and manufacturing industry technical standards.The competent authorities of capital construction administrative departments all over the country should attach great importance to the capital construction in the systematic link of steel structure engineering construction, conduct business training for quality inspection teams, and summarize the practical activities and new technologies in work immediately.Colleges and universities, technology departments and construction enterprises should speed up the molding of professional and technical personnel of steel structure engineering construction, and promote the technical and perfect CAD of steel frame structure.Members of people’s mass organizations should cooperate with each other in the development trend of steel frame structure technology, vigorously carry out academic forums and training courses in various countries, and actively improve the average level of design scheme, manufacturing and engineering construction and installation technology of steel frame structure in the near future.

Connection mode of steel frame structure

The connection modes of steel frame structure include welding connection, screw connection and rivet connection.

1.Welded joint

Welding connection is based on the heat generated by the arc, so that the welding wire and the welding part are partially melted, then cooled and solidified into welding, and then the welding parts are connected into a whole.

Advantages:

It can not weaken the cross-section of prefabricated components, save stainless steel plate, simple structure, convenient production and manufacturing, large joint bending stiffness, good sealing characteristics, and it is easy to select automation technology for work under certain standards, and the production and manufacturing efficiency is high.

Defects:

The thermal damage zone of stainless steel plate around welding may be that the materials in some positions become brittle due to the high temperature effect of electric welding; during the whole process of electric welding, the stainless steel plate suffers from uneven high temperature and cooling, which causes internal stress and residual deformation in electric welding, which is harmful to the bearing capacity, bending stiffness and performance index of the structure; the welding structure is due to bendingWith high rigidity, some cracks are easy to expand to the whole, especially brittle fracture under ultra-low temperature; the plastic deformation and ductility of welded joints are weak, which will cause defects during welding and reduce the fatigue limit.