Inflatable structures: the new playground for architects – Lily in the 20hby TF1
It is a monument able to rise in seconds, thanks to a simple fan. A refectory, an artist's studio or even a golf practice, the inflatable structures are rediscovering a new life. The details in picture in the video below. This topic was broadcast in the television news of 20H of 22/06/2019 presented by Anne-Claire Coudray on TF1.
Technical creativityby Anton Miserachs et Pilar Navarro
TP Architectura i Construccio Tèxtil is a company that has been exploring for 30 years the technical possibilities of inflatable and textile architectures. Companies at the origin of the manufacture of inflatable projects AZC, they tell us their evolutions and their rejection of standardized projects in favor of a "technical creativity".
TP Arquitectura i Construcció Tèxtil is a family business specialising in textile constructions. We were set up 30 years ago by Ton Miserachs and Pilar Navarro in Catalonia. Our aim has always been to offer a personalised service. By refusing to manufacture in series and turning down projects for standardised constructions, we have been free to concentrate on technical creativity, with each new project a new challenge.
We are constantly looking for new materials and technical innovations that allow us to respect architects’ and designers’ designs while proposing technical improvements. From the outset we have worked closely with Professor Ramon Sastre, PhD, Architect, and the Universitat Politècnica de Catalunya. These relationships allowed us to benefit from the very first software for the calculation of tensile and inflatable structures, WinTess, developed by Ramon Sastre. As the software has been improved and refined, he has involved us in every stage of its development. From being a system that required new calculations for every stage of the process, WinTess has become a genuine design and construction tool (CAD/CAM) providing support for our skills.
With the benefit of experience, technical improvements and an increasingly qualified team, we have been able to diversify our activity. Now working alongside some of our children, we began developing a series of renewable energy solutions in 2009, specifically in the biogas sector under the brand Upbiogas. Once again we recognised the importance of innovation and, in collaboration with the university and Ramon Sastre, have developed the world’s first software for calculating roof structures for biogas digesters. We have managed to rationalise and reduce risk in the calculation and dimensioning of every element for the development of single- or double-membrane roofs for digesters. The software is very complete, offering calculations based on stresses, anchorage, storage volume, gas pressure and pattern-cutting for particular roof geometries.
As the company has developed, our research has particularly concentrated on managing the energy consumption of the pumps used for inflation. As a result, we have rejected stitching in favour of high-frequency welding, often double welding. A testing system currently under construction will allow us to test resistance and air-tightness before installing a roof. This process will enable us to increase the resistance and durability of the welding, but also to control internal pressure because there will no longer be any air lost via the holes made by stitching. So we are producing inflatable structures that are more or less airtight, with pressure control. Air pumps will function only when necessary. In this way, the volume of air inside the structure is not affected by external loads and tension, which is essential for withstanding wind or snow. Being able to control all these parameters means that we can precisely define coefficients and the limits of resistance and establish a security protocol. We work with textiles that are 100% recyclable, even at the end of their life. Following the establishment of the Texyloop system, even the smallest pieces can now be recycled. What motivates us at TP Arquitectura i Construcció Tèxtil is the creation of one-off pieces that are lasting and safe, the product of our long years of experience.
We originally came across pictures of the Bouncing Bridge on social media. We were really impressed with AZC’s project and naturally wanted to track them down to congratulate them and to propose our collaboration. It is unusual for people outside of the world of textile constructions to conceive a project that is striking in its design and almost entirely realisable. AZC’s reply was immediate and we quickly got to work making a first prototype at 1:10 to test the behaviour of the inflatable structure and the trampoline mesh. A second model at 1:3, produced thanks to updates to WinTess, confirmed the viability of the project.From the first picture we saw of the Bouncing Bridge we were certain that this project was realisable. There was plenty of work to do and technical issues that needed resolving before that could happen, but most importantly the design fitted with the materials to be used. The Bouncing Bridge adventure has introduced us to two architects who, in their experience and professionalism, share our attitude to life and work. They are in touch with the child in us all. They’re driven by their emotions, which allows them to listen to their craziest ideas – like the one to build a bridge for bouncing on. A trampoline bridge? Why not!
The Peace Pavilion
The Peace Pavilion benefitted greatly from the tests carried out for the Bouncing Bridge. We were already aware of the capabilities of each of the project’s participants. That allowed for a real dialogue to be established: the designs were developed as the technical team modified and checked them. This time we knew that we wouldn’t be able to make any test models. WinTess was very useful for conceiving this project. Following his experiences on the Bouncing Bridge, Ramon Sastre developed the software’s capabilities, tailoring it to requirements. Despite its apparent simplicity, the Peace Pavilion demanded a rigorous approach because the beauty of its shape stems from the infinite variety of perspectives it offers. One never knows with an inflatable structure whether one has succeeded until it is inflated. During manufacture it is little more than a pile of fabric. Once the design is defined, we have to be meticulous in the organisation at each stage of the manufacturing process. The roof of the Peace Pavilion, a surface area of 49.8 sq m, was made from 132 pieces. It was a real challenge to calculate this canopy, made in pre-tensioned PVC. The shape’s complexity required precision to the millimetre to avoid any folds. Thanks to the performance of the pattern-cutting software, the precise cutting by numerical control and the quality of the welding, we achieved the perfect dimensions. In textile architecture, pre-tensioned PVC usually deviates by 0.5%. That means that the roof needs to be 0.5% smaller than the structure so that it will attain the correct dimensions when it is under the necessary tension. Unfortunately, at the pressure required for the structure, the diameter of the tube increased by 1% and required us to modify the dimensions of the roof. Using the final dimensions, we tested various loads in order to verify rigidity and define the dimensions of the roof in pre-tensioned textile. The Peace Pavilion is a jewel. Its design is very beautiful, very simple, and very delicate. Realising it required the most advanced technologies and all the skill that comes from many years of experience.
The Flower Pavilion
The Bouncing Bridge and the Peace Pavilion are both integral objects. To build them requires the assembly of a number of different pieces but once constructed they become one single element – an inflated tube – that is both horizontal and vertical, wall and roof. The unity and apparent simplicity of the object make both these projects very appealing. The Flower Pavilion is a more architectural project. It takes its inspiration from nature – a flower – to which it adds a material dimension while maintaining the feeling of a natural shelter. Our design needed to be stable, easily disassembled and transportable. To convince the client of the project’s feasibility, we decided to make a prototype. The project’s complexity derived in part from the assembly of the vertical posts with the horizontal roof, each having a different function in terms of forces, and in part in designing the metal structures that encircle the inflatable modules of the roof. Curved structures, like the petals of the pavilion roof, require a particular level of precision because the deformation forces they are subject to are more complex. Plus we had to consider the affect of air pressure on the petals when they are inflated, particularly because the climate in Berlin would require a high-level of air pressure. In order to be able to fit the different petals together and anticipate water run-off, we had to minimise any deformation. Although the shape of the petals themselves was good for working in compression, we nonetheless planned for a thick frame to ensure minimum deformation. When we inflated the various petals, the forces were incredible and we had to reinforce the metal joints that linked the frames because they were deforming by several millimetres more than anticipated. Following adjustments to the pressure and the thickness of the frames, we were able to get the roof right.
In addition to its technical success, the project generated immediate enthusiasm. During testing near our premises, the children of the neighbouring village, intrigued by this flower, quickly came to join us. We made the most of their energy to test the solidity of the pavilion by getting them to bounce on its inflatable roof. And an engineer friend who teaches agronomy at the Institut la Garrotxa in Olot, wanted to use the project for the Temps de Flors festival, which each year fills the city of Girona with flowers.
Textile, stretched or inflatable structureby Ramon Sastre
Ramon Sastre, PhD in architecture, lecturer at the Polytechnic University of Catalonia and consultant in textile structure, has been interested since the 70's in these architectures. He notably participated in the technical development of Bouncing Bridge with the software he created: Wintess.
I’ve been interested in textile structures, tensile or inflatable, ever since 1973, the year I graduated as an architect. That year, a friend from my graduating class, Francesc Albardané, translated a book about Frei Otto into Spanish. We were fascinated by the work of this German architect, and became immediately passionate about lightweight structures. In 1978 Albardané and I had the chance to work together on the design for an inflatable roof for a swimming pool in Sabadell, Spain. It was then that I understood the gaps in my technical knowledge, and I decided to pursue a doctorate in this kind of construction. While working on my thesis, which I submitted in 1981, I developed the first version of the Tess computation software, which, with the advent of Windows a few years later, became WinTess. Ever since, I have continued my research into the development of software for calculating tensile and inflatable architecture.
Bit by bit I have specialised in the design and calculation of these structures, which to start with were unusual but which have become more and more commonplace. At first I worked as an architect, designing and building my own projects. Over the years, other architects have sought me out as a consultant. WinTess, initially designed for private use, has become a piece of commercial software, so my work as a consultant has gradually taken over.
Concurrently, I teach at the architecture school at the Universitat Politècnica de Catalunya. It is important for students to learn about these structures because they are the source of so many pieces of playful, contemporary architecture for sports or industry. We also dedicate one semester each year to lightweight structures. Few architecture schools offer this programme and I am regularly invited to teach or lead workshops at other architecture schools in Europe and the Americas.
The Bouncing Bridge
TP Arquitectura i Construcció Tèxtil, a Spanish construction company specialising in textile and inflatable structures that I have known for many years, came to see me one day to show me the Bouncing Bridge project. They had come across it on the Internet and had contacted AZC to propose making it. The architect in me was immediately seduced by the bridge’s design and I was sure it would spark a lot of interest. On the other hand, as an inflatables specialist I saw the incredible challenge such a project would pose if realised for everyday use. I had never built anything on water – it’s not an architect’s usual environment! Even less so when it’s moving water. So first of all I concentrated on static studies, saving the dynamic studies for a later stage.
The project has two key elements: firstly the ring shape, which constitutes both structure and foundations, and secondly the stretched membrane, a secondary structural element but essential to the function of the bridge. It quickly became clear that a certain number of questions could only be resolved empirically. For financial reasons and to improve analysis of the results, we made a first prototype at a scale of 1:10, approximately three metres in diameter, which we wanted to test for structural behaviour, stability on the water and feasibility of construction.
The shape is not created by simply twisting a ring, but, similar to a sewing pattern, by joining lots of different pieces that together will generate a curved, three-dimensional form. Working on a small-scale prototype created a considerable amount of extra work for us when devising the pattern. The number of pieces had to be the same as for the full-scale bridge, so that we would be able to judge the smoothness of the curves. Geometric design was very slow because we had not yet developed the necessary software. We did, however, finally manage to build the first prototype and to test it. First of all in dry conditions, testing it with different loads and under different pressures. We had to take into account the proportional relationship between the 1:10 prototype and the full-scale object, so that we could analyse manufacturing details for the object (behaviour of the materials, dimensions, joints) and the reactions to the tests (how much it would move when in use). The model’s behaviour lived up to our hopes, as WinTess had predicted. Next we tested its stability on water in a domestic swimming pool. We were satisfied with the results, but the size of the prototype did not allow us to test the impact that bouncing on the trampoline membranes would have on the bridge.
This was why we built a second prototype, this time at 1:3, measuring 10m in diameter, which would allow us to test the project’s behaviour on water but also to observe how the trampoline would work under real conditions. A swimming pool would no longer suffice, so we took the model to Banyoles Lake. The tests on the water, with several people jumping on the trampolines at the same time, were a success.
After this we were very keen to build the project full scale, 30 metres in diameter. But we also needed to evaluate the tests we’d carried out in order to improve our method. Principally in pattern cutting – I wanted to be able to put together this kind of tubular structure more efficiently. And in fact, a new project came along that allowed us to do just that!
The Peace Pavilion
The Peace Pavilion is a smaller scale project, with limited civil liability but of a more complicated design. Its beauty stems from the different perspectives afforded by the twists of the ring, a fairly complicated 3D structure.
Thanks to our experience with the Bouncing Bridge, we did not need to build a prototype, because we already knew that the principal difficulty would be in making the tube, more specifically designing the pattern. The curves for this project were more complex than those of the rings for the bridge.
Designing the pattern manually with the help of WinTess, as we had done for the bridge, would have been very laborious considering the number of pieces required by the structure. Each change to the design would have meant redesigning all the pieces. So I created a new module for the software that was able to define the tubes in 3D and to automatically set out the pattern. This was a lengthy task but the result was spectacular: we were able to create various patterns for this type of tube in seconds! This allowed us to adapt the shape of the pieces in order to optimise the amount of material used and to precisely define the curves of the final object.
Unlike the bridge, the pavilion’s structure would not have to withstand significant dynamic loads, but just carry a simple, waterproof, transparent canopy. However, it is far from straightforward designing a canopy for such a complex three-dimensional structure, requiring parametric structural modelling software rather than geometric. We were therefore able to use WinTess.
The result entirely lived up to our expectations: the images speak for themselves.
For the Peace Pavilion, the next challenge would be to design a more permanent structure. For a temporary event we were able to ignore the effects of snow or wind, the characteristics of the ground or the durability of the project. But for a permanent structure, all these considerations would be primordial. We look forward to an opportunity to prove that this is possible.
In the case of the Bouncing Bridge, we have not yet realised AZC’s project for three 30m-diameter inflatable rings. Moreover, if the project needed to be permanent or semi-permanent, its structural complexity would be greater and we would have to study the implications of different locations, a calm or fast-flowing river, a lake or a canal. However, I am certain that we could successfully develop this trampoline bridge.