Development and Application of a Crossed Multi-Arch Greenhouse in Tropical China

The arch bar of the floor-type round-arch greenhouse structure (Figure 1a) has a good mechanical performance and an easy-to-install structure [11]. However, there are also problems such as the difficulties in using and operating the area below shoulder height in the greenhouse or between greenhouses. Thus, an upright side wall type single arch greenhouse structure (Figure 1b) was developed during real production. This structure solves the problem of shoulder space use. To further improve the land use and make full use of structural materials, a multi-span round-arch greenhouse structure (Figure 1c) was developed [12,13,14,15]. This structure is spacious and has a high land use rate, which is being gradually developed into a major structural form of the current multi-span plastic greenhouse [16].

When the multi-span round arch plastic greenhouse is used in tropical areas such as Hainan, it has ventilation and rain protection problems. For example, when a sudden rainstorm occurs in summer and autumn, the roll film ventilation mechanism at the top of the greenhouse cannot be closed quickly, and the crops inside the greenhouse can thus be damaged by a rainstorm. Many users stopped using the roll film ventilation mechanism and covered the roof with roll film to ensure the rainproof performance of the greenhouse, the ventilation instead being solved by setting ventilation channels between the arches; thus, a multi-arch split structure model was formed [17]. This structure was first used in Sanya, Dongfang, Ledong, and other places in Hainan for cantaloupe greenhouses, and it quickly became the mainstream cantaloupe greenhouse type (Figure 2a) due to its simple structure (no need to consider the typhoon load; the column can be directly inserted into the ground without setting the foundation) and low cost because it is only used in winter and spring (no typhoon and fewer rainstorms). Inspired by this, structural designers made some improvements (Figure 2b) to the multi-arch split structure and used it for summer and autumn vegetable cultivation in Hainan. After years of practice, the structure has achieved good results. As it is mainly used for off-season production in summer and autumn, it is necessary to consider the resistance against typhoons. An independent foundation needs to be set up at the column, larger and stronger materials should be used, and the cost should be at least twice that of cantaloupe greenhouses.