Analytical Predictions Of The Snap-throughCharacteristics Of Deploy Able Structures

Abstract

The deployable structures investigated in this paper are prefabricated space frames consisting of straight bars linked together in the factory as a compact bundle, which can then be unfolded into large-span, load-bearing structural forms. During the deployment process incompatibilities between the member lengths lead to the occurrence of strains and stresses resulting in a snap-through phenomenon that locks the structures in their deployed configuration. The structural response during deployment is, therefore, characterized by geometric nonlinearities and, hence, accurate simulation of the deployment process requires sophisticated finite element modeling. In the present work, a simple analytical model is proposed that uses geometric considerations to predict the intensity of the snap-through phenomenon. The underlying reasoning is that snap-through must be related to the maximum shortening of the bars due to geometric compatibility requirements. The objective of this approximation is to minimize the number of finite element analyses during preliminary design. The proposed analytical model is validated through comparison to numerical results obtained by detailed finite element simulation. 1 Description of the Problem As mentioned above, this study deals with deployable structures that are prefabricated space frames. They consist of straight bars that are linked together in the factory as a compact bundle, and can then be unfolded into large-span, load bearing structural forms by applying forces on selected nodes. Because of this feature they offer significant advantages in comparison to conventional, Transactions on the Built Environment vol 21, © 1996 WIT Press, www.witpress.com, ISSN 1743-3509