The Study On Structural Systems Selection Of Greenhouse Public Buildings And On Joint Test

A large number of Greenhouse structures are designed for public use, such as eco-restaurant, eco-business, ecology housing and so on due to its low cost and novel figure. And greenhouse public buildings require more security but less on lighting and ventilation which are different from other horticultural structures. However, public buildings often require large space, the shortcomings of bent structure characterized by unidirectional transmission of force which is the traditional structural system of greenhouses are reflected. Thus, it’s necessary to improve it by spatial structures.Venlo greenhouse is applied most in rigid cladding greenhouses in the world and is used in PC board and glass greenhouse in China as well. In this paper, a standard Venlo greenhouse(2spans 12 bays 16m x 48 m, PC board) is built with PKPM, and member sections are drawn after checking and optimization. On the basis of this structure, a simplified Venlo greenhouse model, a grid-type folded plate structure model, an inverted triangle spatial truss structure model and an equilateral triangle spatial truss structure model are established using finite element software. By comparing behaviors under the vertical load, conclusions are reached: spatial structure can achieve greater span; the internal force of grid-type folded plate structure distributes uniformly and the integrity of spatial truss structure and its transmission of force are better than Venlo structure under the same steel consumption. Furthermore,under the same steel consumption,equilateral triangle space truss performs better than the inverted triangle truss system on torsional resistance and uneven load performance.Two equilateral triangle space truss specinen are designed then, and between them there is one with new docking nodes, the two specimens were tested statically under one-third point loading, the results show that:(1) Equilateral triangular space truss has a good capacity of bearing load and deformation; Complete specimen are better than the one with docking nodes;(2) The maximum total tension and compression stress of two structures are very close; For maximum axial stress, complete specimens is always smaller than the one with docking nodes; for the stress of the webs adjacent to the supports, complete specimens of the structure is always larger than another one, and the its rate gradually increases.(3) For the complete one, at the beginning, the chord bend to resist external loads, and then the stress converts into the axial stress to resist external loads; for the one with docking nodes, external load resistance is mainly provided by axial stress of the top chord, bending stress accounts for 40% at most,the condition of lower chord is close to the complete one.(4) Before the specimen with docking nodes yields, docking nodes is the main load-bearing part of the structure for the lower chord which mainly subjected to bending, while the docking nodes of the top chord bear axial force mainly; after the specimens yield, top and bottom chords itself carry greater stress( mainly axial stress).