| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 94 === Link structures could be highly useful to the form finding of shell structures. With boundary conditions controlling and elements management, link structures could generate many types of shells with different geometric appearances. Such shells also have great advantage in material efficiency because of extremely low bending moments of witch.
The final stable state of the unstable link structures must be found by the iteration of the joints’ positions. In this research, the displacement of the particular joint in one iteration will be calculated under the specification that the other ends of the elements connected to the joint are taken as fixed points. And the displacements acquired above need also to be reduced by half to make sure the iteration convergent.
Since the element’s stiffness of the system is directly proportional to the iteration number, we can develop a time saving method by adopting the system with low-stiffness elements to simulate the system with high-stiffness elements. The method developed here can be used to calculate truss structures and cable structures, because these two structures are also in the category of the link structures. We will show how this method and that of SAP2000, the commercial software of structural analysis, have the results in common for both small displacements cases and large displacement cases.
Generally, every element’s length of one link structure’s initial state must be equal to their original length. However, it is not easy to determine the joints’ positions of such kind of initial state. Our iteration method could be run under such condition as every element’s length of the initial state is not equal to their original length. Thus, we could make an initial state with all the joints’ positions in one plane. And this property will be very useful to the shells’ form finding of the site with particular geometric shape.
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