Formfinding and statical analysis of cable nets with flexible covers

Nowadays cable nets are built as roofs, enclosures for animals in zoos, facades, safety barriers in buildings, etc. Some of the advantages are high resistance against damage and high transparency. In the first part of this this paper the problems of the cable net calculation are described. The key problem is the generation of the assembly plan. This procedure is according to the cutting pattern generation process. In case of cable nets we have to create as big as possible fields. The reason for this purpose is the boundary patterning, this means: the patterns are restricted to the region along the boundary cables and equidistant rectangular meshes remain in the inner part of the fields. The calculation of the formfinding and the statical analysis of equidistant rectangular nets will be pointed out step by step. We also show the specific characteristic of small sized 60°-degree cable nets, produced e. g. by the German company Carl Stahl. This kind of cable net is characterized by a high flexibility and the adaptability to free forms. By the so called S-twist in the cable pieces between the clamps we have to consider special statical properties. The usage of physical nonlinear material laws and the node stiffness caused by the clamps will be explained. As opposed to the calculation of cable nets we have to consider additional material properties as shear- and crimp- stiffness for membranes and foils. The cutting pattern generation can be performed here as usual with surface seams. The disadvantage of cable nets is that an additional cover is needed if the usage requires a weather protection. In the last chapter we will show the calculation of the composite material cable net – membrane cover