Study On The Topology And Mechanical Behaviors Of Grid Shells

Grid shell is a new type of single layer latticed shell,especially suitable for glass roofs. Compared with common single layer latticed shells, nearly all meshes are planar quadrangles, which can be easily fabricated and can also increase the transparency. Each quadrangular mesh should be braced by cables in order to increase the planar shear stiffness. In other words, grid shells are composite structures formed by flexible cables and stiff bars. At present, there is little research on this type of structures, as well as the practical projects. However, with the development of space structures, this type of latticed shell will be applied in the near future. So that, the method of model creating, the basic static mechanical behaviors and the static stability behaviors will be studied in this paper, which is supposed to supply advices for applications. This paper includes main contents as follows:The parametric strategy of grid shells and the meshing method of planar quadrangular meshes are deeply analyzed. Translation surface method is adopted to realize the nets-meshing of complex surfaces, based on the above work.A typical grid shell, paraboloid over a circle, is analyzed by using a common finite element analysis software ANSYS. Some parameters about static mechanical behaviors are adopted, such as, area of steel bars, area of cables, prestress of cables, ratio of rise to span and different load cases are considered, in order to investigate the relationship between the maximum axial stress/the maximum nodal displacements and the parameters above. The analysis results presents that, there is a optimal ratio between these parameters.Based on the static mechanical behaviors, nonlinear finite element method is chosen to investigate the static stability behaviors of the paraboloid mentioned above. Area of steel bars, area of cables, prestress of cables, f/d and different distribution of loads are considered. The results show that, the critical capacity of grid shells is sensitive to the scale of imperfection. Little imperfection can reduce the critical capacity of grid shells seriously. Another investigation shows that, the static stability behaviors of grid shells includes two kinds of different modes, the elastic stability and the plastic stability.