By this stage, I have conducted a fairly substantial amount of research and investigation into most aspects of the construction process that I am proposing – a cement-free concrete, cast onto fabric formwork, supported by living bamboo formwork, in compressive vault forms. I've been bringing these ideas together in drawn form, as a series of phased sections, and have been using Rhino and Grasshopper modelling a lot as well, as a good way of testing how these types of forms may begin to occupy the site.
As I have placed so much emphasis on physical modelling, and have found it so rewarding, I don't want to lose that as I move into the later stages of this project. For this reason, I have carried out this latest physical test.
As well as giving me the final form of a column at 1:10, the process to get there also serves as a kind of proof of concept. Each of the key steps of the process are documented below. The step of striking the falsework and formwork, which I found to be one of the best parts of this physical modelling process, is shown in the timelapse video below.
Striking the falsework and formwork of the column
Planning and creating the base
First, I used Grasshopper to generate a compressive form at the correct scale and then used this to work out the heights of each of the bamboos. I arranged them so that they would form tension rings, so that I could test that element of the strategy.
Grasshopper/Rhino model
With the computer phase completed, I then laser cut the pieces for the base, with all of the bamboo locations. Then, I cut the correct number of bamboo pieces of each length, ready for slotting into the base.
Sketching out locations and heights of bamboo, gluing the laser cut pieces of the base, cut pieces of bamboo grouped into heights
Bracing the bamboo falsework
Next, I stapled the middle of the fabric into the middle of the base, as otherwise this could have been tricky once all of the bamboos were in place. Then I put the bamboos in place, starting from the centre ring and working outwards.
As I went, I braced each ring of bamboos together with wire wrapped around, so that each ring was rigid and would resist the tensile forces of the fabric, which would otherwise push them outwards.
Building up the bamboo forest, bracing them into tension rings along the way
Applying the fabric formwork
Once all of the bamboos were in place and braced, I pulled the fabric out from the middle and stretched it out over the tops of the bamboo. I pinned it to the side of the base in the corners and rolled up bits of excess fabric and clipped them out of the way, so that I could get good photographs of its form at this stage.
Fabric being stretched into place, showing the indenting effect of the bamboo tops which will be left as a negative version in the final cast column
The photo below is a composite created in photoshop, to demonstrate how it would look at this stage with the column module repeated so that arches and vaults were created.
Composite photo of the fabric stretched to form several vaulted spaces
Applying the cast material
Then it was time to undertake the casting process. Because this was just one column, rather than an arch made of two or a vault made of four, I knew that it would probably require some reinforcement (the form is cantilevering out and not meeting the other side of an arch or vault which would strengthen it and form a complete compressive system.
Based on my reinforcement tests and their respective levels of success, I elected to use modroc reinforcement. I brushed on a layer of plaster first, then added overlapping layers of modroc, and then applied more plaster, leaving a thin but reinforced cast form.
Applying plaster, modroc reinforcement, and then more plaster
Striking the falsework and formwork
Once fully dried, I embarked on the process of striking the falsework and formwork. I could probably have simply cut the fabric where it was stapled at the base and the lifted out the cast, if I were only interested in the final form of the model, but I thought that trying to recreate the process as closely as possible, albeit at 1:10 scale, would be a useful exercise. This took over an hour, using a junior hacksaw to cut each bamboo as near to the base as possible and wire cutters to cut the tension rings off. In reality, the tension rings would be made of natural rope and would simply be undone, unwrapped from around each culm, and stored for future use. There would also be guy ropes periodically, which would be of the same natural rope and would be similarly collected for re-use.
Once all the bamboo pieces were cut away, I peeled the fabric off, leaving the final cast form.
The photos shown here are stills from the timelapse video which is embedded near the start of this blog post.
Stills from timelapse of the striking the falsework and formwork process
Finished cast column
I am pleased with the final form of the model as an object in and of itself, as a form that demonstrates the architectural language that I am proposing. I am particularly pleased that the bamboo has left a memory of itself in the cast form, as a series of indentations, as this is exactly what I had been envisaging. Because I have used small bamboo that is about 10% of the diameter of full-size culms, this really is an accurate 1:10 representation, which is so useful to have as a reference object. I have created similar forms, including the indentations, in Grasshopper, but they do not have the elegance and beauty of this, so it is reassuring to see that the physical process is exactly what I had in mind.
Finished cast column
I also hope that I am able to combine photos from this with some of the computer model work and drawings, to create hybrid drawings to convey the forms being proposed. One example of taking the model photos and manipulating them to convey more of what the project will look like is shown below – compositing two photos of the column together to show an arched, vaulted space.
Composite image of an arched/vaulted space
Reflection
I am delighted with this both as a final object and as a process that I have managed to document fairly comprehensively.
As a process, it demonstrates the cut bamboo being braced, the fabric formwork being stretched into place, and the casting material being applied. Then, once the cast material had dried, it demonstrates the bamboo falsework being harvested from beneath it and the fabric formwork being peeled away.
As a final object, I consider it to be a beautiful thing, and an accurate representation of what I have been designing.
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