“Innovative membrane structures: water and membranes",
Research unit ADE, Technische Universiteit Eindhoven, April 2009- October 2009

The aim of this thesis is to investigate the innovative combination of water and membranes for temporary architectural applications.
Water can be useful, as a construction material, for three different purposes.
First of all, thanks to its thermal mass, it can be used as a medium for cooling down or heating up buildings;
secondly, water is uncompressible and, in combination with air, it can be used as part of a structural elements;
thirdly the mass of water could work as a sound barrier so it can be used as sound insulation material.

The following pages will focus on the second and the third use of water in architectural applications. The research in both structural
and sound insulation fields was carried out in the laboratories of Technische Universiteit Eindhoven, The Netherlands. The materials
and the mock-ups were provided and built at Buitink Technology, The Netherlands.

The research investigates innovative applications of water in architecture and for this reason an empirical approach was required.
Just few researches have been carried out about sound insulation properties of water and almost no literature have been found by the
author about structural properties of water. In fact, at present time, water is considered nor a structural neither an insulation material for
architecture. For this reasons standard computation software8 can not deal with it.

Thus, the research was based on the tests of two mockups. The first prototype concerns a 200 mm thick panel filled with water.
The airborne sound insulation of this panel was measured in accordance with standard ISO 140-3. Results show that the single number
rating for the airborne sound insulation Rw for an average water layer thickness of 200 mm is 48 dB. This value is comparable to the one of
a 150 mm brick wall or 100 mm concrete panel. Predictions about sound insulation of the same system at different thickness and possible
applications such as highway sound barrier or construction site sound barrier are presented in the following pages.

The second prototype is a “waterbeam” of 2 m span.
Starting from the Tensairity® technology principle developed by Airlight, the purpose of the test is to replace the iron struts with a membrane
chamber filled with water. Water, incompressible, works well in compression even at low pressure and air prevents buckling. The result is a
rigid structural element made by non-rigid material (water, air, membranes and cables) with a significant reduction of weight and cost of
transportation compared to the traditional iron beam but also compared with the Tensairity® system. Different bending tests were carried out.
In each test, the two chambers of the beam were filled with air or water to understand the material behaviour. The comparison between the
results shows that water works slightly better than air (stiffness increase of a range of 8-12% in the elements filled with water).

Water application in architecture showed promising results. Further investigation (pure compression tests on columns, multiple layers sound
barrier) should be carried out. These results could give architects new design opportunities and solutions, concerning temporary building,
emergency sheltering and moveable architecture.
Moreover companies and building construction industry could develop innovative structural elements and new insulation components.

Key words
Lightweight structures, membranes, pneumatic beam, sound insulation, Tensairity® system, water.

Roberto Maffei,
Sep 29, 2010, 8:34 AM