In recent years, China's photovoltaic industry has developed rapidly, but recently under the siege of European and American developed countries, it has been difficult and can only be turned to the domestic market. At present, only adopting new ideas, new designs, and new materials to provide domestic users with safe, economical, reliable, and versatile steel frame supports can provide a broader application space for the comprehensive promotion and development of photovoltaic power generation in China.
Introduction: With the rapid development of China's green economy, monocrystalline silicon / polysilicon photovoltaic power generation and thin film BIPV technology is maturing. Compared with other structures, steel structures have great advantages in terms of function, design, construction, and overall construction cost. Therefore, it is of great significance to actively develop and produce a new steel structure photovoltaic stent system to replace the existing angle steel stent system.
1, solar steel bracket steel type
At present, in view of the simple structure and small size of solar photovoltaic supports, light steel and small section ordinary steel structural steels are mainly used in the selection of steel materials.
Lightweight structural steels: Lightweight structural steels mainly refer to round steel, small angle steel and thin-walled steel. Among them, when the angle steel is used as a support member, the strength of the steel material can be better utilized, and the installation of the entire bracket is facilitated. However, when the angle steel is used as a bending and compressing member, the generated deformation is relatively large. At present, the angle steel of the national standard is relatively small compared to the solar energy bracket. Therefore, more small angle steel models are needed to adapt to the rapid development of the solar energy market. The thin-walled steel girder components generally use thin steel plates with a wall thickness of 1.5 to 5 mm, and are made into thin-walled steel products of various cross-sectional forms and sizes after being cold-formed or cold-rolled. Compared with hot-rolled section steels, in the case of the same cross-sectional area, the radius of gyration of the thin-wall section steel can be increased by 50-60%, and the moment of inertia of the section and the moment of resistance can be increased by 0.5-3 times, so that the materials can be reasonably used. The strength, but because the processing of thin-walled steel is mostly in the factory, the need for high-precision drilling can be matched with the screw hole behind the photovoltaic panel. After the factory processes the drill, it can be galvanized and rust-proof; when it is shipped to the site for installation, due to the small steel section, the tool is difficult to operate and the construction is difficult. At present, most of the battery panels in China cannot be directly connected to thin-walled steel, and they all require other auxiliary fixing structures (such as briquetting, etc.).
Ordinary steel structural steel: Ordinary structural steel often uses carbon structural steel or low alloy steel that is easy to smelt, and has low cost. There are many kinds of cross sections. The commonly used photovoltaic includes I-shaped, H-shaped, L-shaped and various design requirements. Profiled section. The processing methods are also varied. Among them, the welded steel is made of steel plates of different thicknesses, and the steel is processed and welded at the factory according to the design requirements. This molding method can be calculated according to the force of different structural parts of the photovoltaic engineering project and taken differently at different locations. The thickness of the steel plate is more reasonable than the hot-rolled one-step molded product, which is more suitable for on-site installation and can also save steel materials.
2. Requirements for the performance of steel brackets for solar energy The steel of solar steel structures should have the following properties:
1) Tensile strength and yield point. The yield point height can reduce the section of the steel section, reduce the weight of the structure, save the steel, and reduce the overall project cost. High tensile strength can increase the overall safety of the structure and increase the reliability of the structure.
2) Plasticity, toughness and fatigue resistance. Better plasticity can result in greater deformation of the structure prior to failure, which can enable people to find and take remedial measures in time. The better plasticity can also adjust the local peak stress. In order to adjust the angle, the solar panel installation is often forced to install. The plastic properties cause the structure to produce redistribution of internal forces, so that the stress in some of the original stress concentration parts of the structure or component tends to Uniform, improve the overall bearing capacity of the structure. The better toughness can make the structure absorb more energy when it is destroyed under external impact load. Especially for desert power plants and rooftop power stations with large wind power, the wind vibration effect is obvious. The toughness of steel can effectively reduce the degree of danger. The better fatigue resistance also allows the structure to have the ability to withstand repeated changes in wind load.
3) Processing performance. Good processing properties include cold workability, hot workability and weldability. The steel used in photovoltaic steel structures must not only be easily machined into various forms of structures and components, but also require that these structures and components not be adversely affected by excessive strength, ductility, toughness, and fatigue resistance.
4) Service life. Since the design life of solar photovoltaic system is more than 20 years, good corrosion protection performance is also an important indicator to measure the quality of the support system. If the stent has a short life span, 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) In accordance with the above conditions, the steel for photovoltaic steel structure should also be easy to purchase, produce, and also cheaper.
3. Technical analysis of new solar steel structure bracket
At present, the use of angle steel solar brackets is subject to more and more restrictive conditions. The most important reason is that the quality of steel products is uneven and installation requires a large number of on-site drilling. However, after drilling, steel is easily rusted, so it is necessary to use new types of brackets. Replace these angle brackets to reduce corrosion and extend the service life.
The main structure of the new solar stent: 1) Shaped cold-formed thin-walled steel stent structure system. Special-shaped cold-formed thin-walled steel is a prefabricated light steel structural system that can be mass-produced, assembled quickly, and completely dry. It has the characteristics of less steel consumption, time-saving construction, and labor saving. The main domestic manufacturers are Hilti and Haimai. The structural steel frame of the deformed cold-formed thin-walled steel structural system is formed by prefabricating cold-formed thin-walled steel at the construction site with bolts to form a structural skeleton, and then installing battery panels to form an overall photovoltaic array. 2) Factory prefabricated integral steel bracket system. The factory prefabricated steel frame with purlins needs only to be assembled and fixed at the construction site on the site of the support module, and then the entire photovoltaic array is formed by installing the solar panels. The construction speed is fast and it is suitable for large-scale power plants. This kind of steel structure has extremely high requirements for installation. The steel used generally has the best quality, and the surface treatment process is extremely excellent. Moreover, it is necessary to fully communicate with the PV module manufacturers in the early stages in order to achieve perfect assembly and cooperation.
3) Beam-column frame curtain wall photovoltaic bracket structure system. The photovoltaic curtain wall is suitable for beam-column frame steel structure support system. The structure is light in weight and reliable in structure. Due to its low lateral stiffness, when the height of the structure is high or the height of the layer is large, lateral support is required to form a supporting frame structure. In the design of high-rise photovoltaic curtain walls, the commonly used steel structures and cast-in-situ embedded parts form a hybrid structure, which enhances the overall structure's ability to resist lateral movement and reduce the amount of steel used, thereby reducing the total cost.
4, new cold-formed thin-wall solar bracket parts installation:
1) Connection of steel structural members The new type of cold-formed, thin-walled solar supports are assembled from pre-fabricated steel-plastic hybrid connectors. These types of steel-plastic hybrid connectors are available in a wide range of types to suit different installation conditions. Choosing the connection form and mode of the hybrid component is an important part of the overall structural design.
2) Bracket and foundation connection The new cold-formed thin-wall solar bracket is lighter in weight and has more holes. Generally based on an independent basis, if necessary, need to add reinforced concrete coupling beams. For places with poor geological conditions, strip foundations or crisscross foundations may be used, and the raft foundation may not be used as much as possible. All the upper legs are hinged, while the embedded part is available with insert legs or pre-embedded bolted waterproof concrete. Both of these column legs are easy to process, easy to construct, and perform well.
3) The brackets are connected to the mounting node in three forms: rigid, articulated, and semi-rigid. All three types of connection methods are ready to use. The articulated structure is simple, and the manufacturing and installation are most convenient. However, in areas with large winds, horizontal support or bracing is required to make the parapets withstand horizontal loads and provide additional rigidity. When the bracing is not set, the joints between the beam and the column should be made to be connected. The semi-rigid connection is simpler than the just-connected construction and has better performance than the articulation. Because the force is hard to control, it needs to be combined with experience before it can actually be adopted. At present, it is basically not used. The on-site connection is generally the first use of bolted joints after the two ends of the field welding.
5. Concluding remarks
Relatively speaking, the new cold-formed thin-walled steel bracket structure system can significantly reduce the project duration, to meet the needs of solar photovoltaic buildings, in particular, its superior corrosion resistance, recyclability, reflecting the comprehensive cost of steel structures Advantages; The direct economic benefits of the new cold-formed, thin-walled, solar-powered structure are mainly derived from the advantages of shortened construction period and reduced maintenance costs. With the extension of the number of years of use, the benefits will increase significantly. Xiaorong Rong believes that it is an inevitable trend to vigorously develop a new type of cold-formed, thin-walled steel bracket structural system.
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