Study On The Design Theory Of Multi-Span Plastic Greenhouse Structure And Engineering Applications

Multi-span plastic greenhouse is one type of modernization greenhouses, it has lots of advantages compared with one-span plastic greenhouse, such as high the ratio of soil using, fine performance of heat preservation and low heat consumption, large space of protected horticulture and convenience for mechanization, etal; Comparing with multi-span glass greenhouse, it has lower cost of construction and better capability. In 1980's, multi-span plastic greenhouses are widely applied for our country protected horticulture with the developments of factory agriculture. In the year of 1996, the State Science Committee organized a "Project of High Efficiency Factory Agricultural Demonstrative Engineering", and invited public biding on the commonness key technical such as "optimization design and implement for structure and control establishment of greenhouse". Zhejiang university agricultural bio-environment engineering institute submitted a tender on "the optimization design and implement for structure and control establishment of East-China type greenhouse".Modernization multi-span plastic greenhouse, its course of development has only ten several years in our country as one trade. Up to the present, we have not yet produced special greenhouse structural safety standards which suit the situations of our country for multi-span plastic greenhouse. At present, greenhouse structural design mostly refers to industry-civil architecture standards and some foreign standards , owing to lacking uniform design standards, greenhouse structural designs are so disordered that we can't unify to supervise production specifications, quality, performances and the extension of applications, which not only lead to the wastes of resources and capitals, but also affect severely the benefits of producer and developments of greenhouse industry.Making a comprehensive view the development courses of greenhouse industry from developed countries, we have found out if greenhouse become an industry, first of all it must have a series standards from design, construction & installation and management. Aimed at the situations of theory research which is not enough systemic for multi-span plastic greenhouses structural designin our country, based on the contrast analysis of standards provided in foreign and Chinese standards, through digestion and absorption , then innovation, a suit of multi-span greenhouses structural design method and theory will be summarized in accordance with the specific conditions of our country, which helps to the establishment of greenhouses structural safety design standards in the tenth five-year plan periods.No heating in winter is design demand for series East-China multi-span plastic greenhouses. The climate characteristic of East-China is : low temperature, raininess, few shine and often heavy snow in winter and spring; high temperature, high humidity, more typhoon and rainstorm in summer and autumn, it concentrates all the disadvantageous factors for multi-span plastic greenhouses design. Therefore, it has common significance and adaptability for study on the design theory of multi-span greenhouse structure which takes series East-China multi-span plastic greenhouses for research object.Multi-span plastic greenhouse structure design theory has been studied systemic which include design loads, design methods and system optimization designs aimed at the situations above-mentioned, meanwhile, theory analysis and designs have been completed for series East-China multi-span plastic greenhouses in accordance with the local climate characteristic. Some elementary conclusions are summed up:(1) In the aspect of multi-span plastic greenhouse structural design loads researches, based on the contrast analysis of loads provided in foreign and Chinese standards, analysis and discussion are mentioned about the definition loads, the estimation and load cases for multi-span plastic greenhouse structural design in details, Some conclusions are summed up first:I, Wind load: Under the present conditions, it is unne...