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my interests & thoughts as a Part II student
Tag Archives: Hyperbolic Paraboloid
Large Scale Fabric formed HP: The Process
Previous [Tested] Formwork:
+ Simple
+ Sufficient (it worked!)
+/- Re-usable/not adjustable
– Not lightweight enough(timber panels)
– Fabric strength (undesirable sagging)
– Piercing of fabric(attaching edging and fabric to formwork)
Scaled up Formwork:
[Remembering Initial Intentions]
> Re-usable
> Adjustable
> Simple Construction
> Lightweight (minimal rigid elements)
Re-usable:
+ All elements, except jersey cotton top layer
+ Adjustable – can be re-configured
Simple construction:
+ ‘Nut and bolt’ connections
+ Clamp fixings throughout
Lightweight:
+ Skeletal formwork arrangement
+ Minimal volume of concrete used
Large Scale
Once the timber primary structure was complete, the first(structural) layer of fabric with stretch tabs attached was fixed to the structure. First at the two high points and then at both footings. This was done with clamps so that as the fabric was stretched it could be counter stretched/adjusted.
We worked our way round increasing the tension at each clamp point until the fabric reached it’s tensile capacity.
The stretch tabs were then stapled into place, maintaining the structural integrity of the fabric.
All clamps were then removed and the process was repeated with the red(jersey cotton) fabric.
This piece of material was not stretched to it’s full capacity because it was merely the sacrificial layer for the concrete application. This meant that there was no need for stretch tabs and it also meant that bolts for the “connectors” could be pushed through without loss to the fabric strength.
The secondary “shuttering boards were then applied. These were made out of ply with a waterproofing PV layer. These were cut to be 50mm wider than the primary struts- this meant that they could be held flush with the struts and clamped in place. By protruding they formed the guide for the edge thickness when concrete was applied.
The timber struts were removed after a couple of days- leaving us with the simple task of peeling the fabric!
Developing small scale HP…..all in the formwork!
The Formwork
I initially developed a form work with the following parameters in mind.
- Quick construction
- Easy to dismantle
- Re-usable
- Access to the underside of the fabric
- Adjustable end point heights
The first prototype, a basic square shape with simple plywood sides rising uniformly to two high points provides the shape for the fabric(in this case netting) to react to. Notice the hole in the base (access to the underside of the fabric) and the extended uprights(for adjusting the high points/shape of the HP).
In a nut shell this was a very crude adjustable formwork that could be re-used!
The Shape
We discovered that the shape of this kind of Hyparbolic Paraboloid(HP) is effected by a number of factors, edge condition, the type of fabric and the way in which the concrete is applied. We experimented at a small scale and developed our understanding of these factors.
With small variations it was possible to manipulate the outcome with some interesting but varied results. We highlighted some of the key positives and issues at an early stage.
These helped to define our thought process as we developed the idea/formwork.
Edge conditions
The high level of control over the “edge condition” meant that we could produce some very free form, double-curvature shapes with exceptional ease. This meant that as illustrated in the sketch above, two or more HPs could be formed with precise edge connections. This could lead to easy prefabrication of individual elements or ease in construction through a simplification of the formwork.
The Fabric
The fabric was initially the only part of the formwork that was not re-usable. The fabric although sacrificial acted as the translator between us and our formwork. The concrete could be said to be the language…..
At the small scale it was immediately apparent that the composition of the fabric was important. The stretch meant that we could create a smooth, creaseless surface for the concrete.
At this stage the texture left behind by the fabric itself was of more interest than it’s actual composition. This is something that would change!
Fabric formed Hyparbolic Paraboloid
My First Hyparbolic parabola in concrete!
The first crude/simple form being removed from the form work with Keith. The peeling of fabric from the concrete was like being a kid again….slightly unsure of what I had made and completely unsure of it’s strength!
Free-form fabric…….The Hyperbolic Paraboloid
I have recently been involved in a couple of small-scale projects in Kenya, where the clients were interested in freeform/organic shapes. Tented/canvas homes are quite common due to the climate. With this in mind I set about designing and fairly quickly stumbled on a very freeform shape that could be manipulated with ease. The double curvature and its potential for lightweight construction caught my interest.
At this stage I had no idea what it was called or how complex it was to create using other materials. Until I stumbled into the Disruptive Technologies module that Remo Pedreschi and Chris Speed run at ESALA.
Remo covered some very free form structures in his early lectures, namely structures by Eladio Dieste, Pier Luigi Nuevi , Felix Candela and Heinz Isler. One thing that was common to see throughout, was the complex formwork used to create these beautiful shapes. It was obvious that extreme precision and craftsmanship were neccesary and of course the mind of one of the greats mentioned above!
My initial thoughts were back to my experience of how easily fabric moved into similar shapes. Isler had used fabric to develop concept models at a small-scale. I wanted to explore using fabric as the primary formwork to create a more permanent Hyperbolic Parabaloid. The following posts will document my journey.
Works by Candela showing extreme complexity needed to produce such shapes(especially in the formwork)
The Philips Pavilion- Le Corbusier
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