Combining numerical analysis and engineering judgment to design deployable structures

Abstract

Deployable structures are prefabricated space frames that can be stored and transported in a compact folded configuration and then deployed rapidly into a load bearing configuration. The structures are stable and stress-free in the folded and the deployed configuration, but exhibit a highly nonlinear behavior during deployment. Therefore, their design process should include simulation of their response in two phases: in the deployed configuration under service loads, and during deployment. The first phase involves linear analysis while the second one requires a geometrically nonlinear finite element formulation. Both simulations can be very demanding in terms of computer storage requirements as the number of degrees of freedom increases. In addition, the nonlinear analysis is quite expensive because of the large number of load steps that are necessary in order to trace the complete load-displacement path. This paper first describes a set of numerical models that were used to simulate the exact structural behavior using the finite element program ADINA. Then, some simplified analytical and numerical models are proposed that can be applied in the preliminary design stage, or even for final design, in order to obtain approximate but satisfactory results at a much lower cost.