薄膜承载力及其对日光温室结构稳定性能的影响

Load-bearing capacity of films and its effect on structure stability of Chinese solar greenhouse

为研究薄膜对日光温室结构抗灾害垮塌性能的影响,采用ANSYS有限元分析软件,模拟了单片薄膜受风雪、冰雹荷载作用情景,分析了薄膜厚度、尺寸(长度×宽度)、预张力和外荷载对单膜承载力的影响,建立了日光温室结构单榀拱架、无膜空间整体骨架、覆膜空间整体骨架3种计算模型,得到了风雪灾害下日光温室结构破坏全过程以及覆膜日光温室结构空间系数,探讨了薄膜厚度、弹性模量、预张力等参数改变时,薄膜张拉刚化效应对日光温室结构稳定性能的影响。结果表明:薄膜尺寸(长度×宽度)和厚度是影响其承载性能的主要因素,同时应适当考虑薄膜长宽比影响;0.2mm厚的薄膜可满足特强冰雹的防灾要求;薄膜张拉刚化效应有助于提高日光温室结构抗风承载力,对抗雪承载力影响不大;各分析参数中,薄膜弹性模量对日光温室结构空间系数的影响不明显。研究结果为覆膜日光温室结构抗风雪、抗冰雹灾害设计提供参考。

Besides offering space,appropriate temperature and humidity for animals and plants,greenhouses should also bear all kinds of loads,including the loads induced by improper operation and extreme natural disasters,such as heavy snowfall,high wind and hail.The safety of greenhouses covered with film depends mainly on the film used and greenhouse structure.The mechanical properties of film and their effects on greenhouse structures covered with film are very important to prevent the whole collapse of the greenhouse structure under extreme natural disasters.In order to investigate the effect of plastic film on anti-collapse behaviors of solar greenhouse structures under disaster loads,the numerical simulation on mechanical behavior of single film under wind load,snow load and hail load was carried out by using finite element analysis software ANSYS.The effect of film thickness,film span,film pre-tension and load on load-bearing capacity of the single film was analyzed.At the same time,three computation models of solar greenhouse structures,including single hinged arch structure,whole frame structure without film,and whole frame structure with film,were made.The overall failure process and space coefficient of solar greenhouse structure were obtained.The effect of tensioned film on the solar greenhouse structure stability was discussed with parameters such as film thickness,film elastic modulus and film pre-tension changing.The results showed that film dimension and thickness are the main factors affecting its load-bearing properties,and the ratio of film length to film width should also be considered appropriately.Film at 0.2mm thick can prevent disaster caused by extra heavy hail.Tension film was used in favor of wind resistance for solar greenhouse structures,but is not effective for snow resistance.The space coefficient of solar greenhouse structures is least effected by film elastic modulus in all analyzed parameters.The ultimate bearing capacity of the whole frame structure without film is higher than that of the single hinged arch structure under wind and snow loads.The reason is that the stiffness out of plane is enhanced by purelines.Film also plays an important role on improving the ultimate load bearing capacity of greenhouse structures.The fruits are useful to the wind,snow and hail resistant design of solar greenhouse structure covered film.