# In Search of Lightweight Deployable Tensegrity Columns
## 1 Introduction  
Recently, a growing interest in deployable systems has been observed. Such systems have been constructed for use in space, as well as on Earth, where they can be applied in various fields of mechanical and civil engineering. Among the systems designed for space applications, the most popular are antennas, masts, and solar arrays. There are two main factors that need to be taken into account while creating such systems: a very compact and lightweight stowed form and the ability to automatically deploy in space [1; 2]. In the present paper, the authors focus on deployable structures aimed at civil engineering applications, specifically columns. The design of such structures is focused on large shape and geometry changes with the simultaneous assurance of the stability, stiffness, and desired load carrying capacity of the deployed system. Although the environment in which civil engineering structures are used does not resemble the one in space, deployable systems constructed for earthly use, such as columns considered in this paper, should also meet some of the criteria defined for astronautical applications. They should have small sizes in a folded form, and the deployment should be possible without or with the limited participation of humans. The weight of the structure is not as important here as in space; however, it can become a key factor from the point of view of transportation, mobility, possible applicationscenarios, and deployment. Having all these factors in mind, the authors searched for lightweight systems that could be used as deployable columns aimed at temporary applications. There are in fact very few structural systems that meet the described criteria. One of the most popular are structures based on the scissor mechanism, which is relatively simple from the mechanical point of view. An interesting work was presented in [3], where the author focused on showing a variety of shapes possible to obtain from the pantograph mechanisms. He presented spatial structures of pyramids, a tower, a bridge, a chair, an arch, plates, a vault, a dome, and even a boat. Another example is a mobile scissor bridge aimed at emergency use in remote disaster affected areas [4]. Among other lightweight deployable systems, mechanisms based on air-filled elements deserve attention. In [5], tensairity structures applied as deployable roofs and temporary bridges or buildings were presented. The work [6] focused on deployable tensegrity systems with inflatable compression members. In [7], inflatable roof systems were proposed. While discussing the deployment, the analysis of bridges under construction [8] should also be mentioned. They are not directly related to deployable systems; however, studies of the behavior of bridges during the construction stages resemble in some aspects the analyses of the deployment scenarios. An interesting group of lightweight structures suitable for deployment are tensegrity systems [9; 10]. They can be defined as pin jointed systems that consist of cables (elements in tension) and struts (compressed members) and have infinitesimal mechanisms, which are balanced with self-stress states. Tensegrity systems have a very good stiffness-to-mass ratio and are prone to structural control through an adjustment of self-stress forces [11]. The parameters of the unfolded structure, as well as its deployment can be controlled using only selected, so-called active members, which are a big advantage, as they reduce the number of actuators. An example of a deployable tensegrity footbridge was presented in [12]. Scientists from the Swiss Federal Institute of Technology in Lausanne constructed a prototype, which was formed by four pentagonal tensegrity modules with a total span of 16 m. In [13], a deployable tensegrity mast was presented. Its structure was based on the system developed by [PERSON] [14]--a mast constructed from overlapped regular simplex modules.