Tensile fabric structures are supporting fixtures that became popular in the second half of the 20th century. These are tensioned structures made of technical textiles, which offer a light, elegant and often extremely economical solution for covering spaces due to the used materials and solutions. In the past decades, serious research has been conducted in order to resolve the mechanical problems in relation to tensile fabric structures.
The main tasks are the determination of the shape, the design of the cutting pattern and the non-linear analysis of structures. The Budapest University of Technology and Economics undertook a serious role in this work: the lecturers and researchers of the Faculty of Architecture and the Faculty of Civil Engineering actively contributed to the scientific results achieved nationally and internationally, and also took part in the construction of numerous structures.
There are well usable solutions for most mechanical problems. By now, there are only two main tasks left to resolve. One of these is to create an appropriate material theory for textiles with very non-linear behaviour, the other is the oscillation analysis of structures. The planned research is aimed to the latter.
Membrane structures are very light, therefore these tend to oscillate due to the exciting effect of wind. Irritating and frightening movements, loads causing fatigue and forces causing damage may happen due to oscillation. The aim of the planned research is to examine the effect of the wind and the reaction of the structure, moreover, the development of a strategy to prevent oscillation.
The planned research is closely related to the research being conducted on the Department of Mechanics, Materials and Structures of the Budapest University of Technology and Economics; it has been going on for nearly two decades based on the traditions of the 1950s and 1960s. Currently, Dezső Hegyi, Orsolya Gáspár and Eszter Fehér deals with the shape definition of tarpaulin structures, the analysis of the structure, the non-linear behaviour of the material and the waving of the material, and they had numerous publications regarding these problems. Based on these, the examination of the oscillation related problems can be realistically achieved.
The measurement method used
Digital Image Correlation is one of the most advanced measurement methods of the modern age, which can be used for measuring spatial shapes, deformations and elongations on the surface. It is especially suitable for the testing of tarpaulin structures, as there is no need to fit measuring instruments onto the sensitive textile, and it is suitable for measurements covering every point of the tested surface, not only averages.
In the wind tunnel tests within the planned research, this device is intended for the measurement of deformations, and it would be necessary for the recording of the material principles of the materials used. The latter is especially interesting as the behaviour of tarpaulin materials is very non-linear, and there are no data sheets available for the various makes that could be effectively used. The regular processes are unsuitable for accurate calculations, even though it is a requirement for the examination of oscillation to be aware of the accurate material theories.
We have a positive experience in relation to the use of DIC: As a visiting researcher at the Space Structures laboratory of the Caltech University (California, USA), Dezső Hegyi successfully used such measurement system for the measurement of deformation of foils.
DIC is a universal measurement method, which makes numerous researches easier. It is expected that the purchased equipment will assist in new scientific achievements in the long term.
Involved researchers and departments
Hegyi Dezső PhD | BME Faculty of Architecture | Department of Mechanics, Materials & Structures
Recent publications of BME on the subject
Hegyi Dezső, Sergio Pellegrino: Viscoplastic tearing of polyethylene thin film. MECHANICS OF TIME-DEPENDENT MATERIALS 19: pp. 187-208. (2015) – journal rank: Chemical Engineering (miscellaneous) 79/268 (Q2)
Title image: The St. Augustine Amphitheatre (Florida, USA), the wind tunnel test of which was performed on behlaf of Span Systems Inc. at the BME Theodore von kármán Wind Tunnel Laboratory.
Establishment of an Atmospheric Flow Laboratory 