Key to my design process has been a hybrid technological toolkit, amalgamating digital and analogue tools in interlinked programmes of virtual and physical prototyping, which feed into one another.
Grasshopper and Kangaroo, within Rhino, have been at the heart of the virtual prototyping. My initial capabilities with these were first acquired in Abstract Machine last year, but have been much progressed through intensive and varied use throughout this project. Grasshopper has allowed dynamic models to be created and continually adjusted in response to the findings of physical prototyping. Kangaroo is a sub-set of physics simulation components within Grasshopper, which have facilitated the form-finding of the optimal compressive vault forms used in the project.
Animation, film and photography have been other important digital techniques, with their different strengths adding value and context to each other. Animation has been particularly important for conveying and testing temporal elements of the project, from the site’s historical and future development, to the different stages of the construction sequence; the zoomed-out context. Film and photography, on the other hand, have been invaluable for documenting and representing the unique, imperfect and messy reality of the fabric formwork process, and bringing texture, tactility and the presence of the human to the fore.
Physical modelling and prototyping has been especially important for testing the many variables of the fabric formwork process. One adaptable rig created was used for five tests of different fabric materials, three vaulted space form-finding exercises, and three reinforcement strategies tests. Bamboo properties were also tested physically in a 1:1 bracing strategies model. These two strands converged in the creation of a 1:10 model of one column which brought many technological aspects of the construction process together and crucially facilitated the creation of a timelapse film of the striking of falsework and formwork to be created (fig.15).
Fig.15 – a catalogue of some of the key physically prototyping and modelling iterations
This does not show every single physical model or protoype made, but most of the ones which were key to the design development and the testing of its technological constraints. Geodesic models first tested bamboo as a strategy, then the living bamboo falsework was tested with rigid formwork, and then fabric formwork, reinforcement, bracing and striking formwork strategies.
Alongside my own primary research and prototyping, the input of several engineers has been vital in addressing technological issues of the design. In particular, Chris Matthews of Atelier One’s direct experience of working with bamboo allowed him to validate my proposed implementation of it by explaining its mechanical properties. For further industry knowledge on fabric formwork, the book Fabric Formwork and online lectures by Mark West of C.A.S.T. have been invaluable in confirming that my small-scale plaster tests can scale-up to full-size concrete forms.
To tackle technological issues in the design implementation, a period of full-size physical prototyping is scheduled to occur on the site in years 2 to 4 of the project. This will iteratively test and refine the strategies detailed below prior to the first structures for occupation being cast in year 5.
The chosen cutting strategy uses drones, linked to a geo-located computer model of optimal compressive forms created through Kangaroo form-finding (fig.18), to cut each bamboo culm to exactly the right height.
Fig.18 – a Grasshopper/Kangaroo formfinding iteration
This is one iteration of formfinding using a freeform plan rather than a orthogonal grid of column locations, demonstrating some of the different spaces that can be created, all in compressive forms and therefore viable for producing as thin concrete shells with minimal reinforcement (fibres will be used as a secondary reinforcement strategy).
Then, people brace the structure with a system of tension rings and guy ropes, using rope tensioned with trucker’s hitch knots (fig.17), and then stretch the fabric on top.
Fig.17 – bamboo bracing force diagram
By wrapping the rope around the culms rather than drilling through, the culm is loaded evenly and to its natural strength, instead of weakening it and having high concentration force points.
This hybrid process of the computer/machine and the human capitalises on the relative strengths of each, much like my own design process.
The fabric proposed is calico, based on my physical testing results. Its advantageous properties include its strength, inelasticity, permeablity, low environmental impact and low cost. The inelasticity prevents large, structural problematic downward deflections under the weight of the concrete, and the permeability allows excess water to leave the concrete mix, strengthening it. During the on-site prototyping, geotextiles, which have similar material properties, would also be trialled.
It is vital that any current or future architectural project is a sustainable as possible, with the 2030 RIBA Climate Challenge Targets (Appendix D) being one metric with which to compare.
Appendix D – RIBA 2030 Climate Challenge Targets
The project uses a concrete which fully replaces cement with 5% Cemfree activator from the DBG factory in Cambridge, 80% GGBS from the Outokumpu steelworks in Sheffield 15% bamboo leaf ash from the site, which majorly reduces embodied carbon (fig.16).
Fig.16 – material sourcing map
This shows the sources of the cement replacement materials, showing that they will not be contributing great amounts of carbon from travel distances either.
The growing of bamboo and crops on site further aids carbon sequestration, cleans the air on the site, and is a positive force in engaging local people in gardening for their physical and mental health. Potable water usage is reduced by collecting rainwater in the hollow columns and using it untreated for flushing toilets and watering the crops.
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