(2) The single building greenhouse can be divided into two types: arched round type and roof type. Single-arch circular greenhouse is widely used in Beijing suburbs, which has the advantages of easy construction, convenient material acquisition, firm structure, easy film fixation, wind resistance and snow pressure resistance, and convenient maintenance and operation. Roof style has many shortcomings, which are rare in the suburbs of Beijing.
(3) Semi-arched greenhouses have developed rapidly in Heilongjiang, Liaoning, Jilin, Shandong and other provinces. The wall is built in the north and the arch is set in the south, which is half-arched, equivalent to the sunlight greenhouse (plastic greenhouse) in Beijing. This kind of shed has good lighting, heat preservation, wind resistance, convenient heating and curtain pulling device, which can be used for seedling raising, seedling separation or direct cultivation.
According to the materials that make up the big signboard, it can be divided into the following categories:
(1) The bamboo-wood structure greenhouse is a big signboard with wooden poles as main columns, bamboo as arch poles and pull rods, connected and fixed with lead wires to form a skeleton, and covered with films. This is a simple and basic form. Its disadvantages are that there are many columns, which cause shade, inconvenient operation, poor firmness, and the wooden columns buried underground are easy to rot. But the cost is low and the materials are convenient, and the cost per mu of skeleton is only about 2000 yuan.
(2) The main column of the greenhouse with bamboo-cement mixed structure is cement column, and bamboo is used as arch and pull rod to form the skeleton. Compared with bamboo shed, it has firm structure and strong ability to resist wind and snow. False columns can be added between columns, which can reduce the number of columns, improve working conditions and overcome the shortcoming of perishable embedded parts with wooden columns. The cost is slightly higher than that of bamboo shed, which is economical and applicable. This type is more common in the suburbs of Beijing.
(3) The welded large support with key rib structure can be welded into a single coffin frame with different types of round steel, buried underground through cement foundation, with the spacing of 1.20cm, and fixed into an arch frame with key ribs, steel pipes, rabbit keys, etc. , or three round steels (diameter 1.2- 1.4mm) are connected by wire rods to form a triangular flower beam structure. In order to make the fixed arch bar firm, the top end is welded with gold-shaped iron. Arch bars are mostly made of bamboo. Steel bars have no columns or a row of movable columns. Put it down when it is windy and snowy, and lift it at ordinary times. The sign has good ventilation and light transmission, convenient operation and easy installation of double-layer thermal insulation curtain. However, the amount of steel used is large, the investment is large, and its own weight is large. It is easy to deform when encountering strong winds and heavy snow, and it will collapse when it is serious. Moreover, the steel bars are seriously corroded, and the suburbs of Beijing have rarely been developed in recent years.