Study On New Polyhedron Spatial Frame Structures

A new polyhedron spatial frame structure was created by the engineers of ARUP in Australia in 2003, and was used in National Swimming Center "Water Cube" which is among the three most important projects of 2008 Beijing Olympic Games. This structure is new, there is no study on mechanics behavior of this structure so far. This thesis systematically analyzed and studied geometric constitution, static and dynamic behavior and ductility of this structure.The basic cells of this structure are polyhedrons derived from foam theory, which fill three dimensions efficiently and are formed by two dodecahedron and six tetrakaidecahedron. This thesis presented the basic cells in the new polyhedron spatial frame structures - semi Weaire-Phelan polyhedrons. Both graphoanalytic method and analytical method were adopted to study the geometric constitution of polyhedron cells, exploring an important character - the shape of this kind of cells is controlled by a single independent parameter called shape controlling parameter c. The relationships between c and the total member length, the number of member lengths were found. This structure is formed by combination, array, rotation and cutting of the semi Weaire-Phelan polyhedron cells. It is different from the traditional spatial structures which are usually formed by simple array of basic units. Therefore, the shape and dimension of units, the axis of rotation, the angle of rotation and the position of cutting planes are the important parameters which significantly impact the geometric constitution of the structure. By analyzing these parameters, this thesis presented the optimization rule for the geometric constitution of polyhedron spatial frames, and provided theoretical basis and feasible method for establishing various polyhedron spatial frame structures with high efficiency and reasonableness. Subsequently, this thesis illustrated the application of the proposed optimization rule and method in National Swimming Center "Water Cube".This thesis studied the simplest type of this structure--plate polyhedronframe structures to explore mechanics behavior of this structure. The results indicatethat this structure is geometrically changeable when the members and nodes are hinged, so the connection must be rigid so that the structure can be subject to external load, the member internal forces include axial force, biaxial bending moment,biaxial shear and torsion moment, the later two items are small enough to be neglected.This thesis analyzed static behavior of plate polyhedron frame structures. The distribution rule of member internal forces was found by comparing with plate grid structures. This thesis also discussed the influence of span and boundary condition on steel weight,stiffness and internal forces.This thesis also analyzed dynamic behavior of plate polyhedron frame structures. The comparing with plate grid structures indicates that plat polyhedron frame structures are more flexible, seismic dynamic response of which is less remarkable. This thesis also discussed the influence of boundary condition on dynamic characteristics.This thesis presented the concept of ductility and three important indexes to measure structural ductility, and interpreted their importance. The constitutive relationship of steel members and performance points based on SAP2000 were provided. The ductility indexes of plate polyhedron frames and plate grid structure by static elastoplastic analysis were obtained, the comparing of them explored themost important character of this structure--good ductility. As a example, thepushover analysis of National Swimming Center was provided.At the end of this thesis, some valuable conclusions were reached, some fields that need to be further studied are put forward so that this new structure is widely accepted and used.