(1) The column is the bearer of the main load of the greenhouse, bearing the pressure of the greenhouse arch, shed film, rain and snow, and the gravity caused by wind pressure and crosswind. Therefore, the column should be strong, and the direction of the column should correspond to the direction of pressure as much as possible. The magnitude and direction of pressure in different parts of the greenhouse are different, and the thickness or density and direction of columns in the corresponding parts should also be different, so as to make the best use of each column and give full play to the role of each column and make the greenhouse durable.
Greenhouse columns are mostly made of cement reinforcement members, bamboo poles, wood and other materials. The columns should be as thin as possible, which can reduce the shading in the shed and facilitate the field work in the shed. The column should be buried about 50 cm deep to avoid the greenhouse from sinking, pulling up or deformation. The bottom of the column should be provided with column footstones or cross bars to increase the stability of the column.
In the greenhouse with steel or steel tube skeleton, columns can be omitted, and the arch can bear the whole weight of the roof and itself. This greenhouse has no columns, which is beneficial to field lighting and agricultural operation.
(2) The arch bar, also known as the arch frame, is the skeleton supporting the shed film. It is horizontally fixed on the column and has a natural arch shape. Both ends of the arch bar are inserted into the ground or fixed on the cement-based column to avoid the decay of bamboo and wood arch bars and the corrosion of steel arch bars, so as to prolong the service life (Figure 1-9). The arch-pole spacing varies greatly according to the type, strength, elasticity, span and height of greenhouse, local rain and snow load, wind pressure and the presence or absence of grass cover, ranging from 1 m to 3 m. In practice, it should be used according to the material, not only to ensure the firmness of the greenhouse, but also to save materials, reduce costs and reduce shading.
Figure 1-9 Bamboo and Wood Greenhouse
1. Arch Bar 2. The third column in the middle. Sidebar 4. Top tie rod 5. Side tie rod 6. Cement base column
The arched rods can be made of the same or different materials. When selecting the same material, you can also use different specifications or models of arch bars in a greenhouse. For example, the mixed use of steel arch bars and bamboo arch bars, thick and thin bamboo bars as arch bars, and single-pole arch frames and triangular arch frames in steel frame greenhouses. Different types and models of arches can be mixed in greenhouse, which can give full play to the advantages of different arch materials.
(3) Pull rod The pull rod horizontally connects the column and the arch rod, or only connects the arch rod. The material of the tie rod is mostly the same as that of the arch rod, and the tie rod plays an important role in fixing the relative spacing of the arch rod, avoiding the inclination of the column and the integrity of the whole shed. There can be an upright post under the pull rod, or there can be no upright post, which is only connected with the arch rod. The position of the tie rod should be above the column and below the arch bar. In addition to the pull rod above the central column, there are more small struts between the pull rod and the arch rod on both sides of the greenhouse, so that a gap of 10 ~ 20cm is left between the pull rod and the arch rod, that is, the length of the small struts is 10 ~ 20cm, so that there is room for the film pressing line to tighten the plastic film.
If the film is fixed in the greenhouse by using the compression bar instead of the film pressing line, there is no need to set up small columns, which is labor-saving and convenient, and can make the greenhouse more stable.
(4) After the laminated greenhouse is covered with plastic film, one or more thin bamboo poles are added between the arch poles, and the film is flattened, compacted and fixed. The compression bar must be combined with the pull bar to fix each other and the membrane. Without the tie rod, the press rod can't be used in the greenhouse. In the galvanized iron pipe assembly shed, the film is often fixed by the film pressing line, or the film is clamped by the long groove without the film pressing line. The long groove fixing film is not easy to damage the film, and the quality of the fixing film is also good.
Iron wire is also useful in production, for example, using No.8 iron wire instead of film pressing line and pressure bar. It is very convenient to press the film with iron wire, and it is not easy to puncture the film, and the effect is very good.
(5) Plastic film is a transparent covering of greenhouse, which plays a dual role of lighting and heat preservation. Plastic films in greenhouses are generally PVC and polyethylene films, and the thickness is about 0. 1 mm ... Multiple films can be ironed into the required tent cloth with an electric iron, or two films can be stacked up and down without ironing, and the film pressing line is firmly fixed. The overlapping width of the two pieces should be between 25-35cm, which can be pulled up and down when ventilation is needed, and then put together when ventilation is not needed. This film connection method is more flexible and convenient than thermal connection method, and it is easy to ventilate, but the sealing and heat preservation performance is slightly worse.
About 30 cm of film should be left around the film shed and buried in the soil to fix the shed cloth. Around the film buried in the soil, the fixing method should not be permanent, because in high temperature season, the film should also be ventilated.
(6) Doors and windows shed doors are set at one end of the shed as access and vents. In cold season, a simple buffer room can be set outside the door to avoid the direct invasion of cold air when the door is opened, resulting in obvious cooling. The ventilation of greenhouse usually adopts the method of scraping the seam at the overlapping place of two films, or uncovering the vent at a certain distance around the greenhouse film for ventilation, cooling and dehumidification. Generally, there is no extra ventilation window. In the design of multi-span greenhouse, vents should be specially set for ventilation and cooling.
(7) The gutter gutter is a trough-shaped water storage device arranged at the joint of multi-span greenhouses. It collects rainwater that flows into the valley of multi-span greenhouses during rainfall and walks side by side. The gutter should have a certain slope to prevent water accumulation. The water collecting tank should not be too big or too heavy to avoid excessive shading and excessive greenhouse load.