Integrated analysis of kinematic form active structures for architectural applications: Experimental verification. (15th September 2016) - Van Craenenbroeck, Maarten
Highlights: The research illustrated the feasibility of prestressed kinematic fabric structures. The experimental results confirmed strain predictions made by the numerical model. Variations in fabric strains are minimal during the transformation of the structure. Permanent straining should be taken into account in the computational model. Abstract: Technical textiles used in lightweight tensile fabric structures are inherently highly flexible, which makes these materials very suited to, for instance, make lightweight adaptable façade or roof systems. Until now, however, kinematic fabric structures are mostly designed to transform between a prestressed, structural state and a compact state where the fabric becomes untensioned using fixed geometrically determined paths. The goal of this research is to design and validate the structural behaviour of a kinematic fabric structure which remains prestressed in all its possible geometric states by taking advantage of the out-of-plane flexibility of the material rather than the high stretchability. To make the design and the use of such a kinematic fabric structures possible, we investigated the material properties of a standard polyester-PVC fabric. Afterwards, we implemented these properties in a computational model and performed a parameter study to come to a conceptual design of a kinematic prestressed fabric structure where its geometry follows the reorientation of forces rather than restricting its movement to a geometrically determined path. Finally, the designed kinematic structure was built and tested as a prototype, comparing reaction forces and strains to the ones predicted in the computational model. This paper describes this experimental validation by comparing the experimentally obtained results to the values predicted in the computational simulations using a cable-net approximation and a linear elastic orthotropic material model. Although this comparison showed some deviations in the absolute values of the forces and strains, the general behaviour of the prototype was correctly predicted using a standard analysis method. The majority of the deviations could be contributed to the fact that the strains in the computational model do not take into account the compensation applied to the prototype and the high permanent straining of the boundary belts. The investigated prototype thus showed both the potential and the difficulties of using lightweight, highly flexible fabrics as structurally stable, kinematic elements.