Some standard content:
ICS65.040.30
Machinery Industry Standard of the People's Republic of China
JB/T10288-2001
Multi-span greenhouse structure
Multi-spangreenhousestructure2001-06-22Published
China Machinery Industry Federation
Implementation on 2001-10-01
JB/T10288-2001
This standard is one of the greenhouse series standards formulated for the first time. This series of standards includes: 1. Greenhouse structure design load
2. Greenhouse ventilation and cooling design specifications
3. Greenhouse engineering terms
4. Multi-span greenhouse structure
5. Sunlight greenhouse structure
6. Wet curtain cooling device
7. Greenhouse heating system design specifications
8. Greenhouse electrical wiring design specifications
9. Greenhouse control system design specifications
Among the above standards, the first two are national standards, and the rest are industry standards. This standard is a newly formulated industry standard.
This standard is proposed and managed by the National Agricultural Machinery Standardization Technical Committee. The drafting units of this standard are: Environmental Engineering Equipment Research and Development Center of China Agricultural Mechanization Research Institute, Shenzhen Lvpeng Agricultural Facilities Engineering Technology Co., Ltd., Hebei Langfang Jiutian Agricultural Engineering Co., Ltd., Yangling Qinchuan Water-saving Irrigation Equipment Engineering Co., Ltd., and Cangzhou Limin Machinery Factory, Hebei Province.
The main drafters of this standard are Wan Xuesui, Chen Zhimin, Huang Fenggang, Zhang Minqiang, Gao Xiwen, Shi Zeying and Wang Li. This standard was first issued in June 2001.
1 Scope
Machinery Industry Standard of the People's Republic of China
Multi-span greenhouse structure
Multi-spangreenhousestructureJB/T10288—2001
This standard specifies the technical conditions for the skeleton structure, covering materials and foundation of multi-span greenhouses, and establishes the test methods, inspection rules, packaging, transportation and storage methods of the main components of multi-span greenhouses. This standard applies to industrially produced metal structure multi-span greenhouses (hereinafter referred to as greenhouses). 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were all valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards: GB/T 700—1988
GB/T8451985
GB/T2410—1980
GB/T 2517—1981
GB/T26801994
GB/T3091—1993
GB/T3880—1997
GB/T 5237—1993
GB/T5285—1985
GB/T 63881986
GB/T 6723—1986
GB/T 67251992
GB/T 67281986
GB 9969.1—1998
GB/T11981—1989
GB/T126151990
GB/T133061991
GB/T13793-1992
GBJ9-1987
3 Models and specifications
3.1 Models
Carbon structural steel
Cross recessed pan head tapping screws
General results of light transmittance and haze test methods for transparent plastics Hot-rolled steel plates and strips for structural use
Determination of visible light transmittance, direct sunlight transmittance, total solar transmittance, ultraviolet transmittance and related window glass parameters for architectural glassGalvanized welded steel pipes for low-pressure fluid transportation
Aluminum and aluminum alloy rolled plates
Aluminum alloy building profiles
Hexagonal head tapping screws
Transport packaging delivery and receipt marks
Dimensions, shapes, weights and allowable deviations of general cold-bent open steel sectionsTechnical conditions for cold-bent steel sections
Cold-bent steel sections for structural use Hollow steel dimensions, shape, weight and allowable deviationsIndustrial product instructionsGeneral rules
Light steel keel for construction
Closed oval head blind rivets
Straight seam electric welded steel pipe
Building structure load code
Approved by China Machinery Industry Federation on 2001-06-22Implementation on 2001-10-01
JB/T10288—2001
Gutter height, m
Span, m
Control type: Z-Intelligent, B-Semi-automatic, S-Manual Covering Layers
Roof Shape Features Code: G-Arch Roof, R-Double Slope Single Roof (Man-made), J-Zawtooth Single Roof, RR-Double Slope Multi-roof, J-Zawtooth Multi-roof
Covering Material Code: S-Plastic Film, B-Glass, PPC BoardMulti-span Greenhouse Code: The first letters of the Chinese Pinyin of "Lian" and "Wen"3.2 Specifications
3.2.1 Greenhouse Span
Refers to the width of a greenhouse roof in the direction perpendicular to the ridge. For multi-span greenhouses, it is the distance between the center lines of adjacent gutters. The span of the greenhouse is selected according to the following values: 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 12, 15m3.2.2 Greenhouse Bay
Refers to the distance between two adjacent columns under the gutter. The greenhouse span is selected according to the following values: 3, 4, 5m, and special-purpose greenhouses are not subject to this limit. 3.2.3 Ridge height
The ridge height of the greenhouse is generally controlled within the range of 3.3~6.0m, and special-purpose greenhouses are not subject to this limit. 3.2.4 Slope
The slope of the double-slope roof is expressed as the angle between the slope and the ground plane. In the southern areas without snow, in order to save roofing materials and reduce greenhouse costs, it is recommended to select 20°, and 25° in other areas. 3.2.5 Number of consecutive spans and bays
The number of consecutive spans and bays of the greenhouse is mainly determined by the width and length of the land on site. 3.2.6 Lower chord height
refers to the height of the lower edge of the main frame of the greenhouse roof from the ground, which is usually approximately equal to the height of the beams and gutters from the ground. The lower chord height of the greenhouse: when the span is 6m, it should not be less than 1.8m; when the span is 7~8m, it should not be less than 2.4m; when the span is 9~10m, it should not be less than 3.0m; when the span is 12~15m, it should not be less than 3.6m. 4 Frame
The frame of the multi-span greenhouse is a geometric invariant composed of various components made of light materials (currently mainly light steel pipes) connected into multiple units. It supports the greenhouse covering materials, operating facilities and all auxiliary equipment installed on it, and is the carrier that bears the self-weight and other loads of the greenhouse.
4.1 Greenhouse design load
The loads borne by the greenhouse structure include permanent loads (constant loads), variable loads (roof uniformly distributed live loads, construction and maintenance concentrated loads, wind loads and snow loads) and accidental loads. The design load of the greenhouse structure shall meet the relevant provisions of GBJ9. When greenhouse structures and components are subjected to the most unfavorable possible design load combination, the stress generated in the components shall not exceed the allowable stress of the materials used, and no serious accidents such as collapse, overturning and roof lifting shall occur.
Because the structural weight of most greenhouses is relatively small, special attention should be paid to preventing the upward pull caused by wind. The foundation of the greenhouse should be firm, and guy wires can be added when necessary.
In snowy areas, there should be at least 3.0m between adjacent greenhouses to prevent the sliding snow from piling up too high and damaging the side wall covering materials.
4.2 Requirements for greenhouse construction
4.2.1 Orientation of greenhouse
The orientation of the greenhouse refers to the direction of the greenhouse roof ridge, that is, the direction of the gutter. The tidal direction of the greenhouse should be considered in combination with the local latitude and the main wind direction. Generally speaking, in most latitudes in my country, the orientation of the greenhouse should be north-south, so that the lighting in all parts of the greenhouse is relatively uniform. If conditions are limited, the east-west direction must be adopted, because the shading effect of the gutter and frame components often causes certain local locations to be in the shadow for a long time, and insufficient light is obtained, thus affecting the normal growth and development of crops. Indoor corridors and cultivation beds should be properly arranged, or appropriate local artificial lighting measures should be taken to ensure that the crop cultivation area has sufficient light. 4.2.2 Greenhouse location environment
The greenhouse should be located at a sufficient distance from the buildings and trees on its south side (sunny side) to ensure the lighting of the greenhouse. Attention should also be paid to the shading of obstacles on the east and west sides, and the requirements can be relaxed compared to the south side. The north side of the greenhouse should be convenient for ventilation, installation and maintenance. 4.2.3 Greenhouse size
The plan size of a greenhouse is determined by the geographical environment, production scale, technology and management requirements, as well as energy and financial conditions. As for the greenhouse itself, it is recommended that the building area of each greenhouse should not exceed 5000m2 in South China and 10000m2 in other regions, taking into account the ventilation, heat dissipation and cooling, and logistics and transportation conditions of the greenhouse. For greenhouses equipped with wet curtain fan cooling systems, in order to reduce the temperature difference in the greenhouse, the length or width should not exceed 40~60m. Otherwise, forced air circulation measures must be taken in the greenhouse. For larger greenhouses, effective measures should be taken to ensure the performance of the greenhouse in terms of heating, ventilation, cooling, and logistics and transportation. 4.3 Skeleton structure type
4.3.1 Arch roof [Figure 1a]
This type of greenhouse is the most common type. It has a simple structure and is easy to construct. It is often used in greenhouses with single-layer or double-layer plastic film as the roof light-transmitting covering material, and can also be used in greenhouses with single-layer plastic corrugated sheet as the roof light-transmitting covering material. 4.3.2 Double-slope single roof [Figure 1b]
This style originated from traditional dwellings. The roof is in a herringbone shape and spans between each row of columns, with one roof per span. The roof has an appropriate slope to facilitate the sliding of rain and snow. This greenhouse has good lighting, relatively uniform indoor lighting, a tall structure, a greater impact of wind load on the structure, and a greater demand for heating load. It is more suitable for greenhouses with translucent panels (glass, multi-layer hollow plastic structural panels) as roof translucent covering materials.
4.3.3 Double-slope multi-roof [Figure 1c]
This is a small roof double-slope greenhouse, which is the most widely used structure of a glass greenhouse. Due to the use of smaller roofs (each roof is 3-4m wide), each span is composed of two to four small roofs, and the total height of the greenhouse is limited, thereby reducing the impact of wind load on the structure and reducing the demand for heat load. However, it still has the best lighting effect, which is particularly important for greenhouses in high-latitude and short-day areas.
4.3.4 Sawtooth single roof [Figure 1d]
JB/T10288—2001
Each span of this greenhouse has a partially rounded arched roof and a vertical ventilation window to form the roof. The two roofs are connected by a gutter to drain rainwater from the roof. The vertical ventilation windows of this structure can be rolled, inflated, flipped, and pushed and pulled, and have a large height difference with the side wall ventilation windows, which is conducive to natural ventilation. When designing, it is necessary to avoid the windward side of the winter cold wind, and to make it located in the downwind direction of the dominant wind direction in the local high temperature season, so as to use natural wind to generate negative pressure ventilation. At the same time, the gutter should have sufficient drainage capacity to prevent the water from overflowing into the greenhouse due to untimely drainage. 4.3.5 Sawtooth multi-roof [Figure 1e]
This shape is an improved version of the sawtooth single roof. The purpose is to increase the roof slope, improve the sliding effect of snow, and increase the area of vertical ventilation windows to facilitate natural ventilation. At the same time, it also limits the height of the greenhouse building to an appropriate range. It is more suitable for naturally ventilated greenhouses with larger spans and covered by film. a) Round surface
b) Double slope single surface
t) Double slope multi-surface
dynamic) Saw-shaped single roof
e) Sawtooth multi-roof
Greenhouse building shape
4.4 Shading grid structure type
JB/T10288—2001
The shading grid is a part of the frame of the multi-span greenhouse, which supports the shading net and its retracting and stretching mechanism. The shading grid is divided into external shading grid and internal shading grid.
4.4.1 External sunshade grid
The external sunshade grid bracket is installed above the gutter at the column position or at the top of the sloped roof. The side brackets on both sides can be installed above the gutter at the side column position, or a separate pillar can be set up. The external sunshade support wire should be 300-500mm higher than the highest point of the roof. The retracting and stretching mechanism should operate flexibly, and the transmission should be balanced and reliable. No part of the bracket structure should scratch the sunshade net. The retracting and stretching transmission mechanism of the external sunshade net can be installed on the side bracket or pillar. The cooling effect of the multi-span greenhouse using an external sunshade structure is better. 4.4.2 Internal sunshade grid
The internal sunshade support wire can be directly fixed on the column, side column or lower chord. This structure saves materials and is easy to construct. 4.4.3 Steel frame sunshade grid
For both external and internal sunshade forms, they can be designed as steel frame rigid brackets. This structure is similar to the main part of the greenhouse frame and is basically a fixed and invariant body. The retracting and stretching mechanism of the sunshade net can adopt a rigid push-pull translation mechanism (the transmission shaft is driven by an electric motor, and the gear on the transmission shaft drives the rack to translate). This mechanism is stable and reliable, but it consumes a lot of raw materials and has high requirements for processing and installation. 4.5 Skeleton structure and materials
4.5.1 Main load-bearing components of the skeleton structure
The main load-bearing components of the skeleton structure of the multi-span greenhouse are columns, side columns, wind-resistant columns, gutters, longitudinal beams, cross beams, arch rods and lower chord rods. The main load-bearing components of the skeleton structure must be subjected to force calculation to ensure that the components have sufficient strength, rigidity and stability. 4.5.2 Materials for main components of the skeleton structure
The main load-bearing components of the skeleton of the multi-span greenhouse are all made of carbon structural steel Q235, and the chemical composition should comply with GB/T700. The round tube can use a straight seam electric welded steel pipe, the outer diameter shall not be less than 22mm, the wall thickness shall not be less than 1.2mm, and the mechanical properties and specifications shall comply with GB/T13793. Low-pressure fluid delivery welded steel pipes that comply with GB/T3091 can also be used, and the nominal diameter should be above 25mm. In addition to round tubes, the main load-bearing components of the multi-span greenhouse frame can also be made of special-section steels such as square tubes, rectangular tubes, cold-formed equal-edge channels, cold-formed inner-curled channels and cold-formed outer-curled channels. The steel sections and materials used should comply with the relevant provisions of GB/T6723, GB/T6728, GB/T6725, GB/T2517 and GB/T11981.
All steel pipes or steel sections should be hot-dip galvanized or spray-coated before leaving the factory. Before and after galvanizing, there should be no cracks, interlayers, burns or other defects that affect strength on the components. The weight gain after galvanizing should reach 6%~13%, and the coating thickness is generally not less than 0.01mm. The outer wall surface must not be leak-plated. The outer surface should be smooth, and only one non-inclusive local rough surface with a length of no more than 100mm is allowed per meter. The maximum protrusion height shall not exceed 2mm, and it shall not affect the installation. When the pipe wall thickness is greater than 2mm, it is allowed to use the outer wall surface anti-rust paint treatment method instead of hot-dip galvanizing, but the rust must be carefully removed before painting. Each painting must not be less than two times, and there should be a complete paint layer, and no missing paint. After the greenhouse is put into use, the anti-rust paint should be re-applied every 35 years.
In order to reduce the weight of the structure, aluminum and aluminum alloy profiles are also commonly used in greenhouse construction. The aluminum and aluminum alloy profiles used should comply with the relevant provisions of GB/T3880 and GB/T5237.
For the support and pressure wires of the external sunshade, it is recommended to use stainless steel wire or high-strength polyester wire. The connecting bolts of the external sunshade net frame are stainless 5
steel bolts.
4.5.3 Connectors of the skeleton structure
JB/T10288—2001
The connecting structural parts of the skeleton of the multi-span greenhouse should use special fasteners, special bolts and standard bolts. The design and selection of all connectors must meet the use strength requirements. The surface should be hot-dip galvanized, and the thickness of the galvanized layer shall not be less than 0.01mm. Connectors are mostly made of carbon steel, and there should be no obvious burrs on the punched edges, and there should be no obvious crushing and scratches on the surface. The connection between the plate and the skeleton member is allowed to use cross-slot pan head self-tapping screws that comply with GB/T845 and hexagonal head self-tapping screws that comply with GB/T5285. The diameter and spacing of the self-tapping screws must meet the connection strength requirements. You can also use closed flat round head blind rivets that comply with GB/T12615 and connect them with a rivet gun. The specifications and spacing of the rivets should match the connected parts to meet the connection strength requirements. 4.5.4 Doors
Doors specifically used for operators to enter and exit shall not be less than 1.8m in height and 1.2m in width. The height of the equipment entrance and exit door shall generally not be less than 2.2m, and the width shall be at least 0.4m larger than the width of the largest equipment passing through. 4.5.5 Installation requirements for skeleton structures
In each structural plane (such as side walls, end walls, each row of columns and roof, etc.), appropriate diagonal supports or cables must be installed to prevent parallelogram deformation.
The gutter is pressed and formed with galvanized steel plates. The joints and rivet holes or screw holes at the joints must be coated with sealant, and no dripping is allowed. The gutter groove can be fixed to the column through the coffin beam. For the gutter groove with coffin beam, the groove plate thickness shall not be less than 0.7mm. If the coffin beam is not used, the gutter can be directly supported between the columns, and the groove plate thickness shall not be less than 1.5mm. The cross-sectional size and installation slope of the gutter should be determined according to the intensity of local heavy rain and the length of the gutter. After the installation of the multi-span greenhouse frame, the overall structure should be compact and neat. The verticality error of each column in the vertical and horizontal directions shall not exceed 30mm, the straightness error of the beam shall not exceed 50mm, and the relative position error of the vertical hanger shall not exceed 50mm. 4.5.6 Frame life
The main components of the multi-span greenhouse frame shall be guaranteed to be used for at least 15 years from the date of delivery under normal conditions. 5 Translucent covering
5.1 Plastic filmbzxZ.net
The translucent covering plastic film materials used for multi-span greenhouses are mainly PE (polyethylene), PVC (polyvinyl chloride), EVA (acetic acid-vinyl acetate copolymer) and PEP (PE+EVA+PE three-layer co-extrusion) films, with a thickness of 0.08~0.2mm. The light transmittance (visible light) of the new film should reach more than 90%. For greenhouses that cultivate special crops (such as edible fungi), the light transmittance requirements can be reduced. The service life of plastic film for multi-span greenhouses must reach 3 years. The longitudinal and transverse tensile strength of the film shall not be less than 20MPa, the longitudinal tear strength shall not be less than 5gfμm, the transverse tear strength shall not be less than 8gfum, and the longitudinal and transverse elongation shall be more than 5 times. In cold areas, in order to improve the thermal insulation performance of the greenhouse, double-layer film can be used for covering, and air can be inflated between the layers to form an air insulation layer. The average thickness of the air layer should reach about 100mm. The inner film of the single-layer film and double-layer film should be drip-free film. The film surface with surfactant should face inward to reduce the condensation of water vapor into water droplets on the inner surface. Because water droplets will affect the light transmittance of the film and cause harm to crops. Multi-layer frame can also be used to support multi-layer film covering to obtain a more satisfactory thermal insulation effect. 5.2 Plastic Sheets
The light-transmitting plastic sheets used for greenhouses mainly include FRP (glass fiber reinforced polyester) sheets, FRA (glass fiber reinforced olefin resin sheets, PMMA (propylene resin) sheets and PC (polycarbonate) sheets.6
5.2.1 FRP Sheets
JB/T10288—2001
This material is a kind of glass fiber reinforced plastic. The sheets used in greenhouses are often made into corrugated shapes. The thickness of the sheets is 0.7~1.0mm. The light transmittance of the new sheets should not be less than 86%, and the thermal conductivity should not be greater than 0.128W/(m·K). The sheets must be treated with anti-aging treatment and their service life should reach 15 years. This material is prone to yellowing, which affects the light transmittance and needs to be repainted every 5~6 years.5.2.2 FRA Sheets
This This material is also called organic glass steel. The transmittance of the new board should reach 90%, the thermal conductivity should not exceed 0.233W/(m·K), and the service life should be more than 7 years.
5.2.3PMMA board
This material is also called organic glass board. The thickness of the board for greenhouse should be 3~4mm, the transmittance should reach 92%, and the thermal conductivity should be less than 0.2W/(m·K). This material is easy to deform when heated and is impact-resistant, but has low hardness and the surface is easily scratched. It can also be made into multi-layer hollow boards with a thickness of 8~16mm. The transmittance should be higher than 83%, the heat transfer coefficient should reach 3.5W/(m2·K), and the service life should reach 20 years. 5.2.4PC board
This material is used as a greenhouse covering material and often appears in two forms. One is a solid corrugated board, which is used for PC in greenhouses. Corrugated board, thickness 0.8~1.2mm, light transmittance should reach 88%92%, thermal conductivity not more than 0.20W/(m·K). The other is a multi-layer hollow board, commonly used are double-layer board and triple-layer board, light transmittance should reach 82% and 74% respectively, heat transfer coefficients are 2.7W/(m2·K) and 4.0W/(m2·K) respectively. It has good impact resistance and service life should be more than 10 years. PC board with anti-condensation inner material should be selected to ensure good light transmittance. Due to the excellent performance of PC board, it has been widely used in recent years. It can not only be used to cover the entire greenhouse, but is also often used in conjunction with plastic film as a light-transmitting covering material for end walls and side walls. 5.3 Glass
Glass has good light transmittance, chemical resistance, corrosion resistance, dust resistance and easy condensation discharge. It has excellent properties such as water condensation and is often used as a light-transmitting covering material for high-end greenhouses. Ordinary flat glass and float glass are commonly used in greenhouses with a thickness of 4~6mm, a light transmittance of 90%, and a thermal conductivity of 0.756W/(m·K). Its disadvantages are poor impact resistance, easy breakage, heavy weight, high investment, and high requirements for the greenhouse frame, so the application of ordinary glass is greatly limited. Glass can also be covered with two layers, with dry air filled between the layers and sealed at the edges to obtain good thermal insulation, heat insulation and sound insulation performance. In addition, tempered glass and heat-absorbing glass can also be used as light-transmitting covering materials, but due to their high prices, they are not recommended in production greenhouses without special requirements. 5.4 Covering material installation
5.4.1 The plastic film must be tightened and flattened in the longitudinal and transverse directions and then fixed in the card slot. Under the design wind load, the film must not fall out of any position in the card slot. There must be no cracks, scratches or holes on the covering film. In case of cracks and scratches with a length of less than 5m, or holes with a size of less than 1cm2, due to careless construction, there shall be no more than one crack for every 300m2 of surface area, and they must be repaired with adhesive tape. There shall be no gaps that leak air or rain.
5.4.2 When inlaying plastic sheets and glass, sealing strips or other sealing measures shall be used to prevent water leakage. 5.4.3 When using roll-up film ventilation windows, the roll-up film is located on the outside of the fixed film, and the two ends overlap with the fixed film by no less than 0.3m. Limiting and film pressing mechanisms must be set at both ends to make the roll-up film shaft close to the fixed part of the greenhouse to prevent fanning. 6 Foundation
The foundation is an important component that bears vertical loads to prevent sinking, bears horizontal loads to prevent tipping, and bears upward force to prevent lifting. 6.1 Basic requirements
JB/T10288—2001
6.1.1 The geometric shape, size and bottom depth of the foundation from the ground surface should be determined according to the ground bearing capacity, load, groundwater level and frozen soil depth. The minimum depth should be at least 600mm and below the frozen soil layer. 6.1.2 The foundation should be placed on the original soil layer (untilled), or on compacted backfill or cemented soil. 6.2 Common foundation types
6.2.1 Continuous wall foundation (Figure 2))
When the distance between columns is small, for example, less than 1.2m, a continuous wall foundation should be used. This foundation can be made of masonry or concrete. When building the wall foundation, the prefabricated parts for installing columns or other equipment should be accurately buried in the appropriate position. 6.2.2 Concrete Column Piles (Figure 3) Continuous Wall Foundation When the distance between columns exceeds 1.2m, it is more appropriate to use separate concrete column piles and footings as the foundation. 立档 Steel Plate Figure 3 Concrete Column Piles Pre-embedded Rebar 6.2.3 Concrete Square Piers (Figures 4 and 5) JB/T10288—2001 When the span of a multi-span greenhouse is 8~9m and the bay (column spacing) is 3~4m, under the general soil bearing capacity, the middle column can use the trapezoidal concrete square pier with a small top and a large bottom as shown in Figure 4 as the foundation, and the peripheral columns can use the rectangular concrete square pier as shown in Figure 5 as the foundation.
Keyboard
Acid board
Northern City
Trapezoidal concrete square pier
Head buried steel plate
Pre-buried steel
Rectangular concrete pier
Figure 5 Rectangular concrete square pier
6.3 Foundation construction
JB/T10288—2001
The foundation of the greenhouse is usually provided by the greenhouse manufacturer with construction drawings and specific requirements, and is built by the greenhouse owner himself. The built foundation needs to be cured for 7 to 10 days, and then the skeleton is installed. The location and elevation of the foundation must be exactly consistent with the drawings. The position error is not more than 10mm, and the elevation error is not more than 5mm
7. Test method
7.1 Test method for structural steel parts
7.1.1 The weight of the galvanized layer of hot-dip galvanized steel pipe shall be determined in accordance with the provisions of Appendix B of GB/T3091-1993. It is also allowed to determine the weight by weighing the weight difference of the steel pipe before and after galvanizing. 7.1.2 Test of the bonding strength of the zinc coating of hot-dip galvanized steel pipes. Under the condition that the room temperature is not lower than -10℃, the hot-dip galvanized steel pipes are bent slowly and continuously along a bend with a bending radius of 8 times the outer diameter of the steel pipe (for special-shaped steel, it is the normal dimension of the bending arc). When the bent side is turned 90°, the zinc coating is not allowed to peel or fall off in any direction on the surface of the test piece.
7.1.3 Test of the bonding strength of the zinc coating of electro-galvanized parts. Under the condition that the room temperature is not lower than -10℃, the middle part of the electro-galvanized test piece (length 100mm, width 30mm, thickness 0.5~1.0mm) is placed between two back-to-back elbows with a bending radius of 50mm and clamped on a bench vise. The test piece is bent repeatedly three times and folded into 90°. The zinc coating should not peel or fall off.
7.1.4 Place the hot-dip galvanized or electro-galvanized test piece in a thermostat and heat it to 180-200℃ for 1~2h. The zinc layer shall not protrude or fall off. 7.1.5 Hot-dip galvanized layer uniformity test
The test shall be carried out in accordance with the provisions of Appendix A of GB/T30911993. 7.2 Test method for light transmittance of covering materials
7.2.1 Glass
The light transmittance of glass shall be measured in accordance with the determination method of direct sunlight transmittance specified in GB/T2680. 7.2.2 Plastic film
The light transmittance of plastic film shall be measured with an integrating sphere haze meter in accordance with the method specified in GB/T2410. 8 Inspection and acceptance rules
8.1 Inspection rules
The inspection of various parts shall be carried out in batches, with each batch of 1,000 pieces consisting of continuously produced parts. 8.2 Sampling
For the test of the bonding strength and uniformity of the galvanized layer of parts, 0.5% of each batch shall be randomly sampled for inspection. If there is less than one batch, the sampling can be reduced, but it shall not be less than 2 pieces. If any test of a test piece fails, double the number of test pieces shall be randomly sampled for re-inspection. If there is still one failure, the batch of parts shall be unqualified. 8.3 Visual inspection of appearance
Under daylight or artificial lighting conditions (the light intensity on the surface of the parts should be above 200Lx), check the rods one by one with the naked eye. Rods with obvious cracks, flattening, twisting and deformation on the surface that affect the strength shall not be accepted. 8.4 All parts of the greenhouse shall comply with the provisions of this standard and shall be accepted only after passing the inspection. 10
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