The influence of wind load on greenhouse and prevention points
Published:
2023-02-18 10:49
With the rise and development of greenhouse, the demand for large-span, large-size, high-efficiency and standard type of greenhouse structure increases, and the stronger anti-disaster ability of facility greenhouse becomes the focus of attention.
As a common form of greenhouse, plastic greenhouses are affected by wind load more frequently, and the disaster degree is heavier, which may lead to greater economic losses.
Wind force characteristics of plastic greenhouse
The force of plastic greenhouses on wind is mainly suction and pressure.
The first force of the greenhouse is the surface maintenance structure, when the maintenance structure reaches the wind limit damage, the second force is its internal skeleton structure and materials.
The main skeleton of the plastic greenhouse is mostly fabricated galvanized steel pipe, the spacing is 4.00 ~ 5.00 m, the span is 6 ~ 12.8 m. Steel pipe, film and film line together form the main body of plastic greenhouse and envelope structure.
Plastic greenhouse under the action of wind load, the film floating up and down, the force is transmitted to the card slot, the film belt, different thickness of the film and different sections of the film line can withstand different loads.
Greenhouse film is a flexible material, does not have external stiffness, can only withstand tension, film damage is generally bad.
Film flexibility is good, high strength, no sharp, hard things into the general will not destroy. So plastic greenhouse structure calculation is mainly skeleton calculation.
As shown in the figure, wind load of 20m/s under finite element analysis is indicated by wind pressure stress blowing through the side and front respectively
1. On the left side of the vertical ribbon, the color from blue to red under normal conditions, represents the stress value from small to large, the two ends of the maximum and the lowest peak.
2. The color displayed on the right part is consistent with the color band on the left. The redder it is, the higher the stress value will be.
For facility plastic greenhouses, wind load is a complicated dynamic load in the total load. Wind load may cause a large area of shed film and the overall structure instability and overturn, the consequences are serious.
In order to avoid loss and better protect the internal load-bearing skeleton, it is necessary to do a good job of windproof work in plastic greenhouse. Windproof points include:
1. Build greenhouses with strong wind resistance.
Designed by professional and technical personnel, the wind load must be calculated. The wind resistance of greenhouses is positively related to the stability of greenhouses, which is closely related to the construction quality, skeleton material, canopy surface radian and span of greenhouses.
2. In the greenhouse site selection, try to avoid tuyere.
Under the condition of ensuring light, try to build greenhouses near buildings with wind barriers.
3. Raise the awareness of windproof and estimate the windproof ability of greenhouses.
Make frequent assessments in windy weather so that appropriate windproof measures can be taken; Timely repair of damaged shed film, vent and shed door, especially in strong weather, to check the condition of greenhouse, found that the damaged shed film should be repaired in time, to prevent damage degree force mouth, timely replacement of old aging plastic film.
4. The key parts should be taken care of.
The lower vent of greenhouse: this part due to the shed film often rolled up and down, the film pressing line is weakened accordingly; The part on the tuyere is the key protection part, and the greenhouse on the tuyere is the key protection greenhouse.
5. Slow down the wind speed acting on the greenhouse.
To construct permanent or temporary wind barriers, wind barriers are ventilated or semi-ventilated walls designed on the windward side of greenhouses to block or reduce wind power. Attention must be paid to the wind barrier must be strong, to prevent strong winds from blowing down the wind barrier, the greenhouse. The wind barrier built on the lee side of the greenhouses can significantly reduce the negative pressure film lifting effect of the wind on the windward side of the greenhouses.
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