Tensile-compression ring: A study for football stadia roof structures

Introduction A tensile-compression ring structure is derived from the spoke wheel principle. The general shape of the ground plan of a regular football stadium, which is more oval or rectangular shaped, is in contradiction with the spoke wheel principle. The goal of the thesis is to investigate the use and attractiveness of the spoke wheel principle for football stadia Research The thesis consists of an analysis and design component. The spoke wheel principle for the use for bicycles and for roof structures have been analysed. By designing a roof structure more insight is gained and conclusions can be made regarding the use of the spoke wheel roof structures for football stadia. Analysis The strength and stiffness of the wheel depends on the amount of ring action in the structure. When a tensile load acts on the ring, the ring becomes compressed and ring action arises. This principle can be applied for roof structures. The more ring action can be provided, the more efficient the roof structure will become and more material will be saved. The amount of ring action in a spoke wheel depends on four key factors: strength of the ring, loads, translation and curvature. To come to a design, the influence of different design variables on the key factors have been investigated. Design For the study of the use of the spoke wheel principle for stadia roof structure, two types of roof structures are investigated: Non-pretensioned spokes In a spatial truss system beam action will play an important role in the total stiffness of the roof structure. By directly transporting the loads to the ring elements that possess sufficient curvature, the ring action is used at full extend. The results confirm that the efficiency of the structure increases. By optimizing each single element in the roof structure, using parametric modelling, a lot of material can be saved. Pretensioned spokes A cable structure is not able to provide stiffness by beam action. The stiffness of the roof structure depends on the amount of ring action in the structure. The results showed that the reference stadium possess not enough curvature to provide an efficient spoke wheel roof by means of a cable structure. Further research is needed to use the available ring action at a greater extend for cable roof structures. Conclusion Research showed that a spoke wheel roof structure is an attractive type of structure for stadia use. The amount of curvature in the roof is crucial whether it is possible to come to an efficient structural design. When there is a lack of curvature a spatial truss structure is able to provide extra stiffness to the roof. Cable structures are very dependent from ring action, it is advised to use this type of structure only for roofs that possess curvature in the complete roof. To increase the application of the cable roof structure more research is needed.