Numerical Simulation and Experimental Study of a Deployable Footbridge

Abstract

Spatial structures with bars have been used in different fields since the beginning of the 20th century. These were first used in aerospace industry to obtain lightweight structures and it was as of 1930 when their use in construction became widespread, especially in roofs with big spans. Deployable structures can be considered a special case within the broader class of spatial structures. They can be transformed from a closed compact configuration to a predetermined expanded form. There is a wide range of applications, such as temporary construction and roofing systems, or for movable elements in the aerospace industry. This article describes a deployable structure that has been patented by researchers of San Pablo CEU University and Eduardo Torroja Institute of Madrid, Spain. The presented invention optimizes the material needed to fulfil the safety requirements according to the span it covers. It has a folding and unfolding system that makes transport easier and cheaper. It is versatile, since it adapts perfectly to many different uses with a reduced number of elements and it also reduces the cost by making the best possible use of the materials. Specifically for space deployable structures the main challenge remains to ensure high reliability in deployed geometry, stiffness and function. The goal of this article is to simulate different options to reduce the axial stress and the deflection of a 40-meter span deployable structure. Firstly, the basic elements that define the system will be described; secondly a first analysis on software SAP2000 will be shown; finally, this paper presents the procedure and methodology to improve the shape of a structure through optimization, and to control the deflection at mid span by means of post-tensioning.