Design of tensegrity structures using parametric analysis and stochastic search

Abstract

Tensegrity structures are lightweight structures composed of cables in tension and struts in compression. Since tensegrity systems exhibit geometrically nonlinear behavior, finding optimal structural designs is difficult. This paper focuses on the use of stochastic search for the design of tensegrity systems. A pedestrian bridge made of square hollow-rope tensegrity ring modules is studied. Two design methods are compared in this paper. Both methods aim to find the minimal cost solution. The first method approximates current practice in design offices. More specifically, parametric analysis that is similar to a gradient-based optimization is used to identify good designs. Parametric studies are executed for each system parameter in order to identify its influence on response. The second method uses a stochastic search strategy called Probabilistic Global Search Lausanne (PGSL). Both methods provide feasible configurations that meet civil engineering criteria of safety and serviceability. Parametric studies also help in defining search parameters such as appropriate penalty costs to enforce constraints while optimizing using stochastic search. Traditional design methods are useful to gain an understanding of structural behavior. However, due to the many local minima in the solution space, stochastic search strategies find better solutions than parametric studies.

Design optimization and dynamic analysis of a tensegrity-based footbridge

“…The equilibrium between tension and compression forces is responsible for the structural stability and load bearing capacity of tensegrities. Previous studies have found that the self-stress level initially introduced in tensegrity members before applying loads have a direct impact on both the weight and the deflection of the tensegrity footbridge [26,27]. This suggests that initial self-stresses, together with the cross-sectional areas of tensioned and compressed members are the key design parameters that affect the structural performance and cost of a tensegrity structure.…”

“…Recently, Motro [25] proposed a new family of tensegrity modules called "tensegrity rings" that can be assembled in a "hollow rope". As shown in previous work [26,27], the concept of "hollow rope" shows promise for architecture and civil engineering applications such as footbridges. Few studies on design and optimization of tensegrity structures have been observed to be of practical significance.…”

Design Aspects of a Deployable Tensegrity-Hollow-rope Footbridge

“…Moreover, designing a tensegrity structure is a challenging task due to a complex coupled nonlinear behavior that is closely related to the topology explored. Furthermore, there are no generally accepted design guidelines for tensegrity structures except a few studies underlying critical parameters of their structural behavior such as self-stress and the strut-to-cable stiffness ratio [9,10]. Due to the complexity of the design task, the use of stochastic search methods or other optimization techniques has been explored [10,11].…”

“…Furthermore, there are no generally accepted design guidelines for tensegrity structures except a few studies underlying critical parameters of their structural behavior such as self-stress and the strut-to-cable stiffness ratio [9,10]. Due to the complexity of the design task, the use of stochastic search methods or other optimization techniques has been explored [10,11]. However, no study takes into account shape changes such as deployment and actuation schemes for the design of the tensegrity structure.…”

Mechanism-Based Approach for the Deployment of a Tensegrity-Ring Module

“…Although tensegrity rings are composed of a single strut circuit, their deployment can be completed without strut collision. The "hollow rope" concept shows promise for architecture and civil engineering applications such as pedestrian bridges (Rhode-Barbarigos et al 2010b;Rhode-Barbarigos et al 2010a). However, its application for a deployable footbridge has not been explored.…”