Studies On The New-style Large-span Roof System By Bionic Modeling Of Dragonfly Wings

Firstly, the high resolution pictures of dragonfly wings from sample tests were studied, the unique feature of the reticulate vein structure and the details of dragonfiy wings were figured out. Then several computational models based on dragonfly wings were proposed, beam 189 and shell 93 elements in ANSYS were used respectively in modeling of the veins and the membrane to ensure the compatibility between the veins and the membrane at a deformed state. For comparison reason, the planar and spatial models based on a forewing structure were analysed, it is shown that the cambered corrugation in the wings can improve the flexural stiffness of dragonfly wings effectively; the veins distribution and their size variation in different zones are quite reasonable. The wing models with/without membrance were studied respectively, it demonstrates that the tensile stress in membrane can improve the stiffness of the wing structure greatly. Several models of the joint were evaluated, it illuminates that the joint can alleviate the stress concentration and suppress the quivering effect of the wing.Secondly, a forewing and a hind wing were compared with each other. It is shown that the distribution of their veins were similar; and both wings tend to be much stiffer under upward loading than under downward loading; the area of a forewing is smaller than that of a hind wing from the same dragonfly; and the structural performance of the forewing is superior to that of the hind wing. Several models with different cambered corrugation were evaluated, it demonstrates that the wing becomes stiffer with the increase of the cambering and corrugating magnitude of the wing structure, while the material consumption of the wing and its deadweight increase at the same time. A model with larger vein grids is much stiffer than that with smaller grids, but the latter is more economical in material consumption. Thus, it is significant to have a well-chosen magnitude of the cambered corrugation and well-defined grid sizes in a new-style structural system to arrive at a balance between material consumption and satisfying stiffness.Finally, three models of new-style large-span roof systems with different grid forms and grids arrangement were analysed, and an optimal one was figured out, thereafter its member sizes and material properties were optimized further. The linear/nonlinear behaviour, dynamic performance and buckling capacity of the new-style structural system were evaluated, respectively, subsequently, three new-style large-span roof systems were generated by mirroring this optimized model, these models demonstrate even superior performance and more elegant appearance than the original one. Composite material was adopted to replace steel to lower the contribution of the deadweight to the deflection of these bionic structural models.