Public timber elastic gridshell

Project

302074

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Submitted

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NEW EUROPEAN BAUHAUS AWARDS: existing completed examples

Project title

Public timber elastic gridshell

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Description

Our university collective is working on a concept of design, studies, and construction of elastic gridshells of all sizes for a public use, in order to :

- Improve the environment of the inhabitants in the cities;

- Build with less material, and with bio-sourced and local materials such as wicker and ash timber.

It has been experiments thoughts pavilions in the public park of the Butte du Chapeau Rouge in Paris. We now want to conduct research to make this architecture even more effective.

What was the geographical scope of your project?

Does your project address mainly urban or rural issues?

Does your project refer to a physical transformation of the built environment or other types of transformations?

Has your project benefited from EU programmes or funds?

Has your project won an EU prize?

Your project is fully completed?

When was your project implemented?

How did you hear about the New European Bauhaus Prizes ?

On whose behalf are you submitting the application?

Please provide a summary of your project

An elastic gridshell is an experimental structural typology truly effective in terms of material consumption by span ratio. Our project want to use those architecture to provide to citizens a new kind of covers and equipment, usable in public spaces and help to reconnect them with nature.

Because the consumption of raw materials is a current and important issue for the planet, we want to optimize those pavilions, make them even more effective and with a maximum use of local ash-timber instead of other greenhouse gas emitting materials.

But the apparent complexity of this building method makes that typology a subject area restricted to researchers or engineers and still too inaccessible for architects. Our goal is also to make those concepts understandable and reproductible for everybody. We so build, from nothing, the set of necessary tools for the form-finding, dimensioning, fabrication and assembly of a full-scale elastic gridshell in post-formed bending.

In order to popularize those notions, we engaged in different works:

• The development of a complete, generic, open-source and ergonomic algorithm, usable by all, for form-finding, dimensioning and optimization of elastic gridshells using dynamic relaxation.
• The realization of guide in order to let everyone built its own gridshell.
• The practical application of our study by constructing a full-scale public pavilion, in partnership with the municipality of Paris on the belvedere of the Butte du Chapeau Rouge park (Paris XIX).

Pavilions are exposed here : https://www.construire-l-architecture.com/echelle-1

Please indicate the main themes of your project with 5 key words

Please give information about the key objectives of your project in terms of sustainability (including circularity) and how these have been met.
Please highlight how the project can be exemplary in this context

Architectural covers, whether for large facilities or small public pavilions, often use materials with high greenhouse gas emissions. For example, we can think about concrete or steel. For building large architectural shells, some projects are designing gridshells with carbon fiber or glass tubes. Two other large GES emitting materials.

When we talk about covering, or crossing, we can imagine using a beam. In architecture, only 10 to 15% of the material constituting a reinforced concrete beam actually works. The rest is there for filler purposes. This is not an efficient structural element. A steel beam is not much more efficient, except when made with a truss which can exceed 50% efficiency.

But that solutions still let a rather wide margin for improvement. Elastic gridshells are among the most efficient crossing methods and they far exceed the efficiency of the elements mentioned above.

To reduce the impact on the planet, optimizing the material is a solution. Building with biosourced materials with low greenhouse gas emissions is a second solution. Our project makes it possible to take benefit from both! This type of construction method (the grid is built flat then bent on site to form a vault) requires a material that is both flexible and resistant. Ash, a very common type of timber in Europe, meets these criteria perfectly. In the end, one square meter of concrete slab, for a standard span, weighs among 500 kg. In steel construction, it will take more or less 100 - 350 kg. In wooden construction, 80 - 250kg. A gridshell will be at most around 30 - 120 kg. And the timber construction provides medium-term carbon storage solution.

Please give information about the key objectives of your project in terms of aesthetics and quality of experience beyond functionality and how these have been met.
Please highlight how the project can be exemplary in this context

During and after the inauguration of the pavilion, many inhabitants of the district, relatively underprivileged in Paris, took up the pen to tell to the City of Paris how much they were happy with our project.

Both in terms of aesthetics and functionality. Because the architecture allowed by the timber gridshells is very free, airy and following natural curves, but it is also useful to cover large span without damaging the landscape's aesthetics.

People of the district have invested this place, creating themselves their own uses. It is not uncommon now to see Feng Shui lessons in there, or photo shoots by the neighborhood craftsmen  who are creating African jewelry. It is a poetic place, the project reasons with the nature of the park and offers it a gentle use.

Please give information about the key objectives of your project in terms of inclusion (equal opportunities, public participation, citizen engagement, co-design, universal design, accessibility, affordability, etc.) and how these have been met.
Please highlight how the project can be exemplary in this context

From a local point of view, these pavilions respond to a clear request addressed to the Paris City Hall by the relatively underprivileged population of the district who asked to revitalize this park and to benefit of new exhibitions and new uses who respect the natural environment in which they take place. Citizen can freely adress us request make the pavilion to evoluate.

The Baya weaver's nest study and the design of the pavilion has been made in collaboration with a large number of actors, among them :

• The Paris City Hall and the 19^th district City Hall.

• The ENSA of Paris-la-Villette.

• The Paris Centrale-Supélec school. 

• BM Montage and the Busson family which manufactures and gives us every year the metal pieces.

• The french Timber National Federation

Please explain how these three dimensions have been combined in your project.
Please highlight how this approach can be exemplary

Each point of these three dimensions have yet been widely described before, and also some kind of interaction between them. But the most important thing to remember is maybe that the architecture in general, and in the field of innovative structures in particular is a powerful tool to combine the three dimensions mentioned. Especially when offered to public space :

• Because architecture does not exist if it does not meet a need. Here, we answer directly to those of the people who live in the district, by offering them this pavilion which, we hope, meets the new uses they are asking for.
• Because architecture is an art, it speaks to the formal and spatial quality. And this is all the more pregnant when working on an innovative construction typology with free forms.
• Finally, because architecture is above all multidisciplinary, it is suitable for a largely transversal process and its design calls for the co-participation of citizens and the many trades and specialties.

Please give information on the results/impacts achieved by your project in relation to the category you apply for

At the request of the inhabitants of the district in need of nature, we built within the park of the Butte du Chapeau Rouge a cover that we would have; 50 years ago, made with reinforced concrete. We built it out of ash timber, the climbing plants from the containers will be able to grow on it. The framework is ultimately so fine that it poetically evokes the plant trellises of Renaissance gardens. The practice of Feng Shui that we saw being done in the pavilion leads us to think that we have somewhat reconnected urban citizens to nature.

Please explain how citizens and civil society were involved in the in the design and/or implementation of the project.
Please also explain the benefits that derived from their involvement.

Citizens regularly report to the Paris City Hall their request for a real animation of this part of the park, in connection with nature. The Town Hall transmitted to us a whole set of varied feelings, and we developed the project around a synthesis of all these. Regularly, the inhabitants come during the construction site and tell us what they think about it and what they would like to see more. This inspires us for the future projects, since we are offering to them a new pavilion every year!

Please explain what kind of global challenges the project addressed by providing local solutions

The main global challenge remains the uncontrolled release by humans of large quantities of greenhouse gases into the atmosphere. Our project does not solve it, of course. But by seeking to use more virtuous and bio-sourced materials and by making them operate at the maximum of their efficiency in order to save them, we hope to humbly add a small brick to the vast edifice that we must build collectively.

Please highlight the innovative character of the project as compared to mainstream practices in the field of the project.

Elastic gridshells can be describe as a post-formed elastic gridshell as the post-buckling shape of a flat grid subjected to imposed displacements of its supports.

Once the ends of the bars are in their final position, the bent gridshell, which is by nature very deformable, must be stabilized and rigidified by adding bracing to limit the deformation of the mesh and possibly by adding shear blocks. The final grid is very rigid and can cover a large span without intermediate supports, and this with very little material. But it generaly reming very slender !

It can be used for a private pavilion. But examples in public spaces remind relatively rare. Our gridshell is in a public park, we have to assure people's safety : our design is able to carry 168 kg/m² of loads while it weighs is less than 5 kg/m² (i.e. 3360 % of its weight) !! For comparison, a reinforced concrete slab of 500 kg/m² can only support 400 kg/m² in conventional spans (i.e. 125% of its weight).

Please explain to the potential of transferring the projects’ results or learnings to other interested parties and contexts.
Please provide clear documentation, communication of methodology and principles in this context.

As previously evoked, for each pavilion project and each innovative construction method proposed, and so for the ELASTICA project, we are carrying a real popularization work for the general public in general and for builders in particular. This has been developped around three axis :

• Our purpose is to transform a very technical and complex set of calculation and design methods into an ergonomic and open-source tool that can be used by everyone. So that everyone can reproduce our pavilions, or use the technique and design method to develop their own original pavilion, we are freely giving these tools available on our website (https://www.construire-l-architecture.com/07-elastica).
   
• In order to share of scientific work, we present it in an internationnal conference, for ELASTICA project it was at the international association shell spatial structures IASS 2021 in Surrey (UK) and publicated a scientific paper for the peers (this paper is joined to the application).
   
• Finally, each tool is accompanied by a 100 pages (or more) PDF manual (attached to the file, but in French only for the moment) which popularizes the scientific and architectural principle as much as possible and explain the making of our pavilion in order to inspiring him to develop his own.

Is an evaluation report or any relevant documentation available?

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