【作者】 史晓君；

【导师】 于海业；

【作者基本信息】 吉林大学 ， 农业生物环境与能源工程， 2012， 博士

【摘要】 温室农业是农业生产中重要的种植方法，它通过人工设施控制环境因素，使作物获得最适宜的生长条件，从而加长生产季节，获得最佳的产出。温室的发展不仅可以减少耕地使用，同时也可降低水资源及化学肥料的使用量，是实现环境友好型农业的重要手段。温室结构形式的优劣直接影响到温室性能的高低,在提高温室的生产率和能源利用率,降低成本,保障安全稳定生产等方面具有重要的意义，因此，结构设计和技术应用是当前国内外温室研究和发展中的一项重要课题。目前国内外学者对温室结构研究主要集于光环境及覆盖材料、通风系统等可控环境性能的研究，在温室结构安全可靠性方面的研究还较少。我国温室，一方面受到地域性的限制，使得进口温室在我国大多存在着通风不足、抗雪载能力差、透光性较差等问题。另一方面，温室研究的主要精力集中于环境，忽视了对温室结构安全性问题的研究，使得目前我国温室存在诸多安全隐患。近年来的多起由于大风或大雪导致温室结构倒塌的工程事故，造成了很大的经济损失，亟需开展我国自产温室的结构设计理论和技术研究。本文通过研究仿生学在建筑中的应用，依照技术推进型的思路，结合现代温室技术、农业机械化工程、计算机技术、仿生学和数学等学科的知识，对自然界中蜻蜓翅膀力学特征进行研究，并建立基于仿生的新型温室空间结构体系，为建筑仿生的研究范围和温室结构设计方法提供理论依据与参考。论文的主要研究工作与研究成果如下：（1）蜻蜓翅膀结构刚度的力学研究。建立蜻蜓翅膀的脉络模型，分析模型在不同载荷条件下的变形规律，研究主、次脉对结构刚度的影响及蜻蜓翅膀模型在各向集中力和均布载荷下的整体变形协调性能。得出主脉为蜻蜓翅膀的主承力结构，次脉对结构刚度影响不大，主次脉相结合，可提高结构的整体强度和承载能力。蜻蜓翅膀脉络结构在各向集中力的作用下，没有局部大变形的产生。（2）结合蜻蜓翅膀空间结构的特征，从蜻蜓翅膀结构中，分离出四种基本的网格结构：四边形网格、交错四边形网格、六边形网格及三、五、六边形组合网格，分别建立有限元模型模拟蜻蜓翅膀的主要空间结构。结合蜻蜓翅膀飞行时所受最小升力，模型分别施加相同的荷载F=10000bN×(1,2,3,4,5,6,7,8,9,10)作刚度分析，研究蜻蜓翅膀的空间结构对刚度的影响：①蜻蜓翅膀褶皱结构的力学分析。根据主脉起皱的结构特点，取四边形和交错四边形两种网格模型，建立不同起皱高度（0,1,3,5,7,9,10,12dmm）的模型进行力学分析，可知在相同的起皱高度下，随着载荷的增加，变形也随之增加，但起皱高度越大，随载荷增大的变形量越小，受力相同时，交错四边形网格模型的变形量总是稍大于四边形网格模型；同时无膜网格模型的变形略大于有膜网格模型。②蜻蜓翅膀起拱结构的力学分析。根据蜻蜓翅膀双向起拱的结构特点，取六边形网格及三、五、六边形组合网格，建立不同拱高（矢跨比分别为0，1/8,1/7,1/6,1/5,1/4,1/3）的力学模型，模型分别施加相同的荷载F作刚度分析。得出相同载荷条件下，两种网格模型的结构刚度都随起拱高度的增加而增大；载荷及拱高相同时，有膜网格的变形小于无膜网格，刚度明显增强；无论有膜、无膜，相同载荷条件下，六边形网格的变形总是大于组合网格模型，因此，网格密度越大,刚度就越大。（3）温室仿生结构的设计研究。基于蜻蜓翅膀结构的刚度特性，从翅膀结构力学性能的基本原理出发，结合现有的温室结构及尺寸特征，建立三种温室的新型仿生空间结构，温室结构的整体形状是以六边形网格构成的起拱结构，在起拱的基础上，用四边形网格起皱，形成主框架。通过对三个仿生结构在各种工况作用下的比较分析，可知模型二在空间结构的分布上较模型一和模型三更为合理，表现出良好的力学性能，因此选择模型二为确定的温室骨架结构，并对其进行进一步的力学设计：①材料及尺寸设计。采用不同的复合材料对模型进行模拟，结合温室结构的载荷组合情况，对模型二进行静力分析，比较模型二在不同工况载荷作用下的挠度及应力的变化情况。结构的骨架及壳体均使用复合材料后，挠度明显降低，杆件的应力值也下降很多，材料弹性模量的提高可以增加结构的弯曲刚度。分组定义梁的不同尺寸及壳体厚度，在模型上施加1000N/m2的均布荷载做力学分析。随着梁的管径及壁厚的增加，结构的刚度有所增加，结构所用材料也增加；壳体的刚度随其厚度的增加也有较小幅度的增强。通过以上分析，综合考虑结构刚度的保证及原材料的节约，确定出温室结构适宜的材料及几何尺寸。②应力刚化对结构刚度的影响。在模型二上施加1000N/m2的均布荷载，比较它在三种静力分析下的力学性能，可知在考虑应力刚化效应下进行小位移静力分析时，结构的最大挠度值降低了0.027m,仅为不考虑应力刚化效应时挠度值的89.5%，说明壳体受拉后对结构弯曲刚度有较大幅度的提高。大位移静力分析时挠度值略大于不考虑应力刚化效应的小位移静力分析。对结构分别施加F=200N/m2×(1,2,3,4,5,6,7,8,9,10)的均布载荷，做出挠度随载荷的变化曲线，分析曲线可知，随着荷载的加大，应力刚化效果也更加明显，结构挠度的降低幅度也越大。因此在结构设计时刚度不益过大，结构在一定的变形下，才会使梁和壳体共同作用下提高结构刚度的性能更好的发挥出来。③约束条件对结构刚度的影响。对模型二增加两个支柱，进行竖向的位移约束，比对模型在不同的工况组合下，增加约束前后的最大挠度值和应力值的变化情况，可知结构增加约束后挠度值仅为原来的10%左右，最大拉、压应力也按照近似的比例大幅减小。可见，温室结构中支柱的增加可能减小结构的整体变形，对刚度的提高起着重要的作用。因此设计时，在结构尺寸保持不变的基础上，可以通过增加结构的约束来减小变形，满足安全性的要求，同时发挥结构的应力刚化效果，节约原材料。（4）连栋温室仿生结构的设计研究。对模型二沿长、跨方向进行镜像，建立对称的仿生模型Ⅰ，通过力学比较，可知在相同工况下，无论结构是否增加支柱约束，模型Ⅰ的最大挠度都小于模型二，两部分对称结构可互相牵制、协调，增加结构的整体刚度。综合利用对称结构及蜻蜓翅膀自身的结构优势，设计出两种新型大跨度连栋温室仿生结构，应用时可根据土地条件和实际需求，设计具体的连栋个数并增加支柱约束，以满足刚度的要求。本文创新点如下：（1）针对国内外温室结构设计的理论及技术研究，提出温室结构仿生设计的思路，对蜻蜓翅膀的整体刚度和空间结构性能进行了研究；（2）设计了三种温室仿生空间结构模型，并对仿生结构的力学性能进行了进一步的探索和研究；（3）对温室仿生结构的研究进行拓展，建立了对称的大跨度温室仿生结构，进行连栋温室结构的仿生设计研究。本文所提出的基于仿生的温室结构设计方法的研究，为设施农业的发展提供了新的思路和技术支撑。更多还原

【Abstract】 Agriculture in greenhouse is an important planting method. It controls environmentalfactors through artificial facilities, helps crops obtain suitable growing conditions, thusextends their growing season and achieves best output. The development of greenhouse cannot only reduce the use of arable land, but also reduce the use of water resource andchemical fertilizer. So it can be an environmentally-friendly planting method. The Quality ofgreenhouse structure has direct effect on the performance of greenhouse. So the quality ofgreenhouse structure is of great importance in improving the productivity and energyutilization, reducing the cost, guaranteeing the safety and stabilizing the production. Becauseof this, the structure design and technology utilization have become an top topic in domesticand foreign greenhouse research and development.Now, all scholars focus on the research of luminous environment, covering material andventilation system. There is little research on the safety and reliability of the greenhousestructure. On the one hand, most imported greenhouse in China has deficient draught, poorsnow load stress, and poor light transmission; on the other hand, our research on greenhousepays close attention to the environmental factors, rather than the structure safety, whichleaves much potential safety hazard. During recent years, many engineering accidentshappened due to strong wind and heavy snow, which took a heavy toll. It urgently needs thetheory and technology research of greenhouse structure.From the utilization of bionics in architecture, according to the thought of technologypropeller, combined with modern greenhouse technology, mechanization of farming, ITtechnology, bionics and maths, this essay will study the mechanics of dragonfly’s wings,establish new space structure system of the greenhouse, thus offer theoretical foundation andreference for the bionics research and structure design of greenhouse. The main researchwork and results are as follows:(1) Mechanical research on the structural rigidity of the dragonfly’s wings. We willbuild finite element modeling, analyze the deformation regularity of the model, the effect ofmain vein and secondary vein on the structural rigidity, and the deformation compatibilityperformance of the model of dragonfly’s wings under different load pressure. Our result is:the main vein is the main load-bearing structure of the dragonfly wings, secondary veinshave little effect on the structural stiffness. Primary and secondary veins combining canimprove the overall strength of the structure and carrying capacity. Under the uniform loadand concentrated force, the dragonfly wing structure occurs only to the overall deformation,but the grid shape does not change.(2) Combined with characteristics of the spatial structure of dragonfly wings, we candivide into the four basic cantilever grid structure: quadrilateral mesh, staggeredquadrilateral mesh, hexagonal mesh and three, five, hexagonal combination of networkgrid as to the dragonfly wing structure. Respectively, we establish the spatial structure of thefinite element model to simulate dragonfly wings. Bearing the smallest lift, when combinedwith dragonfly wings’ flying model, we separately applied to the same load F=10000bN×(1,2,3,4,5,6,7,8,9,10) for the stiffness analysis, and study the effect of their wrinkle structureand bagging structure on the structural stiffness:①The mechanical analysis of the dragonfly wings fold structure. According to the structuralcharacteristics of the main vein wrinkling, we take the quadrilateral and staggeredquadrilateral mesh to create different z fold (wrinkle height of0,1,3,5,7,9,10,12dmm)mechanical model separately applied to the same load F for large displacement staticanalysis. The observation z to the structural deformation maps and extract the maximum zdisplacement, structural analysis model in different folds. Coming to the same uniform load,the greater wrinkling of the height, the smaller the structural deformation; if corrugationheight is the same, with the increase of the load, deformation also increases, but the greaterthe wrinkle height, the smaller the amount of deformation load. At the same time, thestiffness of quadrilateral mesh structure is slightly larger than the cross-quadrilateral meshstructure; under the same load, the deformation of the membrane mesh structure is alwaysless than the membrane grid structure.②The mechanical analysis of dragonfly wings bagging structure. According to thestructural characteristics of dragonfly wings bi-directional camber, we take a hexagonal gridand three, five, hexagonal combination of grid to establish different mechanical model ofvarious arch heights (vector span ratio of0,1/8,1/71/6,1/5,1/4,1/3), separately appliedthe same load F to the models for the stiffness analysis. We obtain that, under the same loadconditions, the structural rigidity of the two mesh increase with bagging height; when loadand arch height is the same, the deformation of the membrane grid is less than themembrane-free mesh, the stiffness is significantly enhanced; Whether with membrane orwithout membrane, under the same load conditions, the hexagonal network deformation isalways greater than the combination of mesh, we can see from that, the larger the meshdensity, the greater the stiffness.(3) Research on the design of the greenhouse bionic structure. Based on the stiffnesscharacteristics of dragonfly wing structure and the basic principles of the mechanics of thewing structure, combined with the existing greenhouse structure and size characteristics, theestablishment of three new bionic spatial structure of the greenhouse, the overall shape of thegreenhouse structure is a bagging structure of a hexagonal grid, on the basis of bagging, weutilize quadrilateral grid wrinkling to form the main frame. By comparative analysis ofvarious working conditions under the three bionic structures, we can see model two in itsspatial structure is more reasonable compared with model1and model3, which shows goodmechanical properties, and therefore is chosen for the greenhouse skeletal structure, andfurther analyzed mechanically:①The design of material and size. We use different composite materials to simulatethe model, combining with the load combination of the greenhouse structure on model two,make static analysis of it and compare its own weight, deflection, stress and weight plus external loads. It shows that the structure of the skeleton and shell use of composite materials,the deflection was significantly reduced rod stress drop, the improvement of the elasticmodulus can increase the bending stiffness of the structure. Grouping to define the beam sizeand thickness of the shell model imposed1000N/m2uniformly distributed load for staticanalysis. It shows that, with the beam diameter and wall thickness increase, the deflectionand stress of the structure decreased, but the unit area of supplies also increased; the increaseof the thickness of the shell can improve the bending stiffness of the structure, but not much.Through the above analysis, considering the stiffness of the assurance and raw materialssavings, we determine the appropriate material and geometry of the greenhouse structure.②The effect of stress stiffening on structural rigidity. If1000N/m2of uniformlydistributed load applied to model two, compared with the three kinds of mechanicalproperties through static analysis, we know that, considering the stress stiffening effects ofthe small displacement, the maximum deflection of the structure reduces0.027m, only89.5%of the deflection value without considering the stress stiffening effect, the shelltension dramatically increased the bending stiffness of the structure. We make largedisplacement static analysis, taking into account higher order terms, the deflection value isslightly larger than without considering the small displacement static analysis of the stressstiffening effect. F=200N/m2×(1,2,3,4,5,6,7,8,9,10) uniform load imposed on thestructure, respectively, to make the deflection with the load curve analysis of the curveindicated with of with load increase, the stress stiffening effect is more pronounced, thegreater the decrease of the structural deflection. The stiffness in the structural design shouldnot be too great. In a certain degree of deformation, the beam and shell together will improvethe stiffness, thus achieve the better performance.③The effect of constraint conditions on the structural stiffness. If adding two pillarsof the vertical displacement constraints to model2, the maximum deflection and stressvalues change in different operating conditions, we can see the deflection of the structure toincrease constraint is only about10%of the maximum tensile of the original, andcompressive stress also decreased substantially in accordance with the approximateproportion of the greenhouse structure with the pillar of the vertical displacement constraints.It can significantly reduce the deflection of the entire structure, and plays an important rolein improving the stiffness. The design, based on the structure size is unchanged by addingstructural constraints to reduce the deformation, to meet the requirements of security, andmeanwhile, makes the most of the advantage of the stress stiffening effect and saves rawmaterials.(4) The design of multi-span greenhouse of biomimetic structure. along the lengthand cross-direction of model two, we build its mirror symmetry. By mechanical comparison,we can see in the same condition, regardless of the pillars of constraints added to thestructure, the maximum deflection of model1is less than model2, two partially symmetricstructure can contain each other’s coordination, increasing the overall stiffness of thestructure. If we comprehensively utilize the symmetry of its structural advantages and dragonfly wings, and design two new large-span and multi-span greenhouse biomimeticstructure to meet the stiffness requirement, which should be based on land conditions, actualneeds, actual number of multi-span and the pillars of constraints.The innovation of this essay is: for domestic and international greenhouse structuraldesign theory and technology research, it puts forward the ideas of biomimetic design ofgreenhouse structure, and studies the overall stiffness of dragonfly wings and spatialstructure performance; designs several new types of bionic spatial structure of thegreenhouse and carries out further exploration and research on the mechanical properties;expands the biomimetic structure of the greenhouse, builds symmetrical large-span bionicstructure, and study the biomimetic design of multi-span greenhouse structure.The research on greenhouse structural design based on biomimetics offers new researchideas and reference for the development of industrialized agriculture.更多还原