Study On Morphogenesis Technique For The Free-curved Tree-like Brace Structures

Excellent buildings not only has the reasonable function, good art effect, also need to guarantee the safety, economy and practicality and it requires that the architecture is harmonious and unified with structure. In the large space structures, tree-like structure worked with free-form surface reticulated shells, will provide the architectural environment that human can have harmonious coexistence with the nature, has a broad application prospect. How to create a reasonable form of a tree-like structure can effectively support free-form surfaces, and can reflect a variety of needs in the actual engineering design, is an urgent research subject need to solve, is also a problem to achieve harmonization of architecture and structures.According to these, this paper carried out the following several aspects of research work.Considering the various restrained conditions and architectural requirements that exist in the practical engineering, proposed a method to generate a free boundary and any free-form surfaces. General construction has complex boundary conditions, directly using the spline function is very difficult. To solve this problem, researched a number of times’ curve to generate different curves for each curve, extended the functionality of the spline function,made it can be used in the complex and diverse boundary conditions.This paper adopted the method that generated b-spline curved surface in the external rectangular area of the building plane,used the Delaunay triangulation technology to triangulate graphic design aera, projected onto a B-spline surfaces,Formed free surface to meet the construction requirements.Since the up structure is a shell elements, while the below tree-like structure is rod unit, a single finite element analysis techniques can not be used for analysis.this paper used the same characteristic of rod unit and shell unit, prepared shell- pole hybrid finite element analysis program, expanding the finite element analysis capabilities. In addition,studied the sensitivity of strain energy and nodes, exported free-form surface restraint bar node sensitivity and free movement node sensitivity.In this paper, start from the relationship between strain energy and the shape of tree structure, constructs mathematic model of free-form surface based on dendritical structure,proposed the creation method of free-form surface structures with a tree-like support structure. By moving constraint node on the up free surface and the below free node to gradually adjust the shape of the below tree-like support structure, ultimately minimizes strain energy. The paper also discussed the characteristic shape of the tree-like structure and Strain energy、axial force and variation of moment in the process of minimizing strain energy, Summarized the characteristics of the method and the mechanical properties of the resultant structure, discussed the shape variation in the evolution, and verified the effectiveness and feasibility of the method by simplecalculation example.The paper also discussed application possibilities of the method in actual engineering design by simulation project example, and proposed a practical application of engineering design methods. The calculation example shows that the blow tree-like structure mainly passed load by axial force, greatly improve the overall stiffness of the structure, improve the internal force distribution. On the other hand,the resulting structure is not only can realize big span, and combined with the flexibility of free-form surfaces reflect good architectural renderings, the proposed method has better practicability.