Browsing by Author "Li, Jian-Min"

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Open Access
Form-finding of grid shells with continuous elastic rods
(2011) Li, Jian-Min; Knippers, Jan
Grid shells with continuous elastic rods have the advantages to generate curved spaces with uniform members and joints. However, finding the boundary conditions, including the grid pattern and bearing positions, which lead to a specific geometry, is not an easy task. Designers have to keep equal grid lengths, minimise the residual forces and ensure the smoothness of geometries simultaneously. In this paper, we present a new numerical method which can derive the grid pattern and bearing positions in accordance with a desired geometry. This is done by finding the least strain energy state of the elastic grid in the solution domain defined by constraints. This method can provide architects a grid pattern that satisfies all the geometrical demands. At the same time, a structure with less strain energy is favoured by engineers. This is especially important for elastic grid shells, whose structural stability is largely affected by the residual forces.
Open Access
Timber shell structures : form-finding and structural analysis of actively bent grid shells and segmental plate shells
(Stuttgart : Institut für Tragkonstruktionen und Konstruktives Entwerfen, Universität Stutgart, 2017) Li, Jian-Min; Knippers, Jan (Prof. Dr.-Ing)
Shell structures are structurally efficient but difficult to manufacture and thus expansive. Actively bent grid shells and segmental plate shells could be alternatives. The first kind utilizes bended members to form a continuously curved geometry and thus reduce the complexity of the joints. The second kind utilizes the stability inherited in trivalent geometries to be able to build a shell without using bending stiff joints. Both these two types of timber shell structures could largely reduce the construction cost. That is why they are chosen as the research topics. The dynamic relaxation method (DR) is applied in this research as an important numerical method. It is used as the fundamental base for developing the form-finding tools of both actively bent grid shells and the segmental grid shells. A solver capable of the structural analysis of beam system is also developed here based on DR. Through the text, we show that DR could handle not only form-finding problems but also geometrically nonlinear analysis. The dissertation consists of four parts. Part I is the introduction. Part II and Part III present both the form-finding and analysis techniques of these two types of timber shell structures. The last part is the conclusions.