Types and structure of domestic solar photovoltaic steel structure bracket
With the rapid development of China's green economy, monocrystalline silicon / polycrystalline photovoltaic power generation and thin-film BIPV technologies are becoming more mature. Compared with other structures, the steel structure has huge advantages in terms of use function, design, construction and comprehensive cost. Therefore, it is of great significance to actively develop and produce a new type of steel structure photovoltaic mounting system to replace the existing angle steel mounting system.
Steel type for solar steel bracket
At present, in view of the simple structure and small size of solar photovoltaic stents, most of the steel materials used are light structural steel and small-section ordinary steel structural steel.
Lightweight structural steel: Lightweight structural steel mainly refers to round steel, small angle steel and thin-walled steel. Among them, when the angle steel is used as a supporting member, the strength of the steel can be better utilized, and the installation of the overall bracket is facilitated, but when used as a bending and compression member, the deformation generated is relatively large. At present, compared with solar brackets, there are not many models available for the national standard angle steel, so more small angle steel models are needed to adapt to the current rapid development of the solar market. The purlin members of thin-walled steel are generally made of thin steel plates with a wall thickness of 1.5-5 mm. After cold bending or cold rolling, thin-walled steel products of various cross-sectional forms and sizes are made. Compared with hot-rolled steel, under the same cross-sectional area, the radius of gyration of thin-walled steel can be increased by 50-60%, and the moment of inertia and resistance of the cross-section can be increased by 0.5-3 times, so the material can be used more reasonably Strength, but because the processing of thin-walled steel is mostly in the factory, high-precision drilling is required to match the screw hole behind the photovoltaic panel. The hot-dip galvanizing can be prevented after the drill buckle is processed by the factory; when it is transported to the site for installation, the tool is difficult to operate due to the small steel cross-section and the construction is more difficult. At present, most domestic solar panels cannot be directly connected and installed with thin-walled steel, and other auxiliary fixing structures (such as pressing blocks, etc.) are required.
Ordinary steel structural steel:
Ordinary structural steel often uses carbon structural steel or low alloy steel that is easy to smelt and low in cost. There are many types of cross sections. Commonly used in photovoltaics mainly include I-shaped, H-shaped, L-shaped and various shaped cross-sections required by various designs. There are also various processing methods. Welded steel is made of steel plates with different thicknesses. Welded and processed shaped steel at the factory according to the design requirements. This forming method can be calculated according to the stress of different structural parts of the photovoltaic engineering project. The thickness of the steel plate is more reasonable than that of the hot-rolled one-time forming product, which is more suitable for on-site installation and can also save steel.
The requirements of solar support on steel performance The steel of solar steel structure should have the following properties:
1) Tensile strength and yield point. The high yield point can reduce the cross-section of the steel member, reduce the structural weight, save steel, and reduce the overall project cost. High tensile strength can increase the overall safety reserve of the structure and improve the reliability of the structure.
2) Plasticity, toughness and fatigue resistance. Good plasticity can cause large deformation of the structure before failure, so that people can find and take remedial measures in time. Good plasticity can also adjust the local peak stress. Solar panel installation itself often uses forced installation to adjust the angle, and the plastic property causes the internal force redistribution of the structure, so that the stress of some original stress concentration parts of the structure or component tend to Uniform, improve the overall bearing capacity of the structure. Better toughness can make the structure absorb more energy when it is destroyed under the impact of external impact loads, especially in desert power stations and rooftop power stations with high winds. The wind vibration effect is obvious, and the toughness of steel can effectively reduce the degree of danger. Better fatigue resistance can also make the structure more resistant to alternating wind loads.
3) Processing performance. Good processing performance includes cold processing performance, hot processing performance and weldability. The steel used in photovoltaic steel structures not only needs to be easily processed into various forms of structures and components, but also needs these structures and components not to be adversely affected by the excessive strength, plasticity, toughness and fatigue resistance caused by the processing.
4) Service life. Since the designed service life of solar photovoltaic systems is more than 20 years, good anti-corrosion performance is also an important indicator to measure the quality of the support system. If the service life of the bracket is short, it will inevitably affect the stability of the entire structure, leading to an extension of the investment recovery period and reducing the economic benefits of the entire project.
5) Under the above conditions, the steel for photovoltaic steel structure should also be easy to buy, produce, and cheap.
Technical analysis of a new type of solar steel support
At present, the use of angle steel solar brackets is increasingly restricted by conditions. The main reason is that the current steel quality is uneven, and installation requires a lot of on-site drilling, but the steel is easily corroded after drilling, so new brackets are needed to Replace these angle steel brackets to achieve the purpose of slowing down corrosion and prolonging service life.
The main structural form of the new solar support: 1) Special-shaped cold-bent thin-walled steel support structure system. Special-shaped cold-formed thin-walled steel is a mass-produced, assembled light steel structure system that can be quickly assembled and completely dry. It has the characteristics of less steel consumption, time-saving and labor-saving construction. The main domestic manufacturers are Hilti and Haimai. The steel structure bracket of the special-shaped cold-formed thin-walled steel structure system is to connect the cold-formed thin-walled steel prefabricated by the factory with bolts at the construction site to form a structural skeleton, and then install the battery panel to form an overall photovoltaic array. 2) Factory prefabricated integral steel support system. The factory prefabricated steel structure frame with purlins only needs to assemble and fix the bracket module on the construction site, and then install the solar panel to form the entire photovoltaic array. The construction speed is fast and it is suitable for large-scale power stations. The installation requirements of this type of steel structure bracket are extremely high. Generally, the quality of the steel used is the best, the surface treatment process is excellent, and it needs to communicate fully with the photovoltaic component manufacturers in order to achieve a perfect assembly.
3) Beam-column frame curtain wall photovoltaic support structure system. The photovoltaic curtain wall is suitable for the beam-column frame type steel structure support system. The structure is light in weight and reliable in structure. Due to its low lateral rigidity, when the structure height is high or the layer height is large, it is necessary to provide lateral support to form a supporting frame structure. In the design of high-rise photovoltaic curtain walls, a common steel structure and cast-in-place embedded parts are used to form a hybrid structure, which enhances the overall structure's ability to resist lateral movement, reduces the amount of steel used, and thus reduces the total cost.
Installation of new cold-bent thin-walled solar bracket components:
1) Connection of steel structural members The new cold-bent thin-walled solar bracket is assembled from various steel-plastic hybrid connectors prefabricated by the factory. These steel-plastic hybrid connectors are of various types and can be suitable for different installation conditions. Choosing the connection form and method of hybrid components is an important part of the overall structural design.
2) The bracket is connected to the foundation. The new cold-bent thin-walled solar bracket has a light weight and multiple installation holes. It is generally based on an independent foundation, and reinforced concrete connecting beams should be added when necessary. For places with poor geological conditions, strip foundations or cross foundations may be used, and raft foundations are not used as much as possible. All the upper column feet are hinged, and the embedded parts can be selected as plug-in column feet or with embedded bolts and waterproof concrete. Both of these column foot forms are simple to process, easy to construct, and have good performance.
3) Bracket purlin connection installation node connection has three forms: rigid connection, articulated connection and semi-rigid connection. These three connection methods all have ready-made modular production methods of supporting nodes. The articulated structure is simple and the most convenient to manufacture and install. However, in windy areas, horizontal braces or diagonal braces need to be set to allow the parapet to bear horizontal loads and provide additional stiffness. When no braces are provided, the connection nodes of beams and columns should be made rigid. The semi-rigid connection is simpler than the rigid connection and has better performance than the hinge. Because its force is difficult to control, it needs to be combined with experience before it can be actually adopted. Currently it is basically not used. On-site connection is generally carried out by bolting and then welding the two ends on site.
Conclusion
Relatively speaking, the new cold-bent thin-walled steel bracket structure system can greatly reduce the project's construction period and meet the needs of solar photovoltaic buildings, especially its excellent corrosion resistance and recyclability, reflecting the comprehensive cost of steel structure. Advantages: The direct economic benefits of the new cold-bent thin-wall structure solar support system mainly come from the advantages of shortening the construction period of the structure and lowering the maintenance cost, and with the extension of the years of use, the benefits increase more obviously. The author believes that it is an inevitable trend to vigorously develop a new type of cold-bent thin-walled steel support structure system.
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