space frame analysis

 Next is the analysis of the space frame structure

1. The application status of space frame structure in steel structure

In recent years, there have been more and more large-scale steel structure construction projects in China, and various forms of space structures have developed to super-span structures, among which space space frame structures are widely used. For example, Tianjin Sports Center, double-layer spherical reticulated shell, welded ball joints; the outer envelope of the National Grand Theater is steel structure reticulated shell, Shenzhen Airport Terminal Hall, Jinan Long-distance Bus Terminal Terminal Building, Tianjin Natural Museum... Some have been built or The steel structure project under construction has become a landmark building with its innovative ideas, novel shapes and unique structural forms.

2. Structural form of space space frame structure

(1) Rigid structural system

1. space frame

The space frame structure is the fastest growing and most widely used structural form in the current space structure. It is characterized by large space stiffness, good integrity, good seismic performance, simple structure, convenient construction, and uniform rod specifications (the upper and lower chords are of equal length, and the web rods are of equal length).

2. Reticulated shell

The reticulated shell structure is widely used, with various surface shapes, including cylindrical reticulated shells, spherical reticulated shells, and other complex surfaces and their combinations. The main advantage of the reticulated shell structure is that its flexibility can adapt to the creativity of architectural design, but because the reticulated shell structure mainly bears pressure, it has stability problems. When the span exceeds a certain value, the strength of the material cannot be fully utilized, which is not economical.

(2) Flexible structural system

1. Suspension cable structure

The suspension cable structure is a tension structure composed of high-strength cables. The Tianjin University Gymnasium was built earlier in China. According to its composition method and stress characteristics, it can be divided into single-layer suspension cable structure, double-layer suspension cable structure and cable net structure. The key issue in discussing the cable structure is the dynamic response of the structure under the action of wind and earthquake.

2. Membrane structure

Membrane structure can be divided into inflatable membrane structure and tension membrane structure. The membrane structure has the advantages of light weight, beautiful appearance, full of the atmosphere of the times, less energy consumption, fast construction speed, obvious economic benefits, safe and reliable use, and wide range of use. It is mainly used in large sports facilities, entertainment centers, supermarkets, etc. However, the membrane structure has not been widely used in my country at present. The main reasons are: the poor performance of domestic membrane materials and the high price of imported membrane materials; the development of computer-aided design systems for membrane structures is lagging behind; the lack of corresponding design and construction regulations.

3. Tensioned overall structure

The tension structure is a self-supporting and self-balancing space space frame structure composed of a set of discontinuous compression members and a set of continuous tension elements. The stiffness of this structural system is provided by the balanced prestress between the tension cable and the compression element. Before the prestress is applied, the structure has almost no stiffness, and the value of the initial prestress plays an important role in the shape and stiffness of the structure. decisive role.

3) Hybrid structural system

The hybrid structure can be a combination of rigid structural systems or a combination of flexible structural systems and rigid structural systems. Such as cable-stayed space frames, suspended space frames, arched space frames, string-supported structures, etc. The hybrid structure can play the advantages of different types of structures, such as: due to the effect of the arch, the overall reticulated shell is divided into several small sections, so that the overall stability of the reticulated shell is transformed into the stability of local sections, and some rods or Local failure of a section does not affect the entire structure. Therefore, hybrid structures can span large spaces more economically and rationally.

(4) Folding structure

The folding structure is a structure that is unfolded when used and folded when not in use, similar to umbrellas and sunshades. It can be divided into additional support folding structure and self-stabilizing folding structure. This structure has applications in various fields, such as: construction sheds, market sheds, temporary housing, etc. in life; military field command, field rescue, etc.; aviation: solar sails, deployable antennas, etc. Its main features are novel shape, light weight, easy to carry, easy to store and transport and can be reused, and it has a wide range of application prospects in various fields.

(5) Opening and closing structure

Move part or all of the roof in a short time, yes the building can be used with the roof open and closed. The opening and closing time is about 20~25min, and the opening and closing methods include horizontal movement, horizontal rotation, space movement and their combinations. The opening and closing structure is closely related to the development of sports: it protects spectators and athletes under relatively harsh environmental conditions, and achieves the purpose of being able to play scheduled games within a predetermined time. For example, the National Stadium "Bird's Nest" built for the 2008 Beijing Olympics, The plane form is oval, the long axis is 340m and the short axis is 292m. There is an opening of 146m×76m in the middle of the roof, and this part will be designed to open and close the roof. The structural form is that the space rigid frame rotates around the inner ring.

(6) Glass structure 

Materials of glass structure: float glass, tempered glass and tempered glass. The point glass curtain wall is a new type of glass structure, which eliminates the need for supporting frames and replaces cables, trusses and steel claws. The permeability of the glass is greatly enhanced, and the wind resistance and seismic performance of the structure are also better than ordinary glass curtain walls. .

3. Advantages and disadvantages of space space frame structure

The space space frame structure is widely used in sports buildings, airport buildings, station buildings, hotels, halls and exhibition halls, industrial plants and sketch buildings. Various structural forms have their own advantages and disadvantages. Their common main advantages are reasonable force, which can span a large span, flexible and regular structural composition, relatively mature computer-aided design, and high degree of mechanization in processing. The disadvantage is that the amount of steel used in the joint is large, the processing cost is high, and the single-layer reticulated shell is a defect-sensitive structure, and the calculation and analysis are relatively complicated.

4. Summary

With its obvious advantages, the space space frame structure has developed rapidly in various fields in our country. This requires us to be proficient in the design and application of these structures. In structural design, structural selection is a crucial step in conceptual design. Choosing the correct structural form can effectively reduce the cost of the building, improve the reliability of the structure, and improve the user experience of the building. The structural forms mentioned in this article basically include the general spatial space frame structure in the current steel structure. For more complex large-span buildings and construction areas with extremely harsh geological conditions, it is necessary to discuss the actual situation separately and choose unconventional structures. form to meet the functional needs and safety requirements of the building.