LOCATION. Sydney, Australia
SAAC Pavilion is a full scale prototype of a sustainable hub with an aim to tour major cities in Australia to educate city dwellers on how to live their urban existence in a more sustainable manner. The brief called for the development of a 12 metre wide deployable structure that would be: durable; self-supporting; waterproof; (dis)assembled within three hours; 70% recyclable material; lightweight; adaptive and inexpensive, lots of boxes to tick.
Looking through a number of precedents on deployables, the minimal surfaces, yurts, tensegrity structures and geodesics were a recurring theme that we desperately wanted to avoid. Alternatively, we were interested in hybrid structures that had no retrospective connotations, therefore we looked at structural principles and respective rule sets to develop an adaptive parametric model within grasshopper.
Utilising the geodesic's load transferring organisation, we employed two force agents that would influence the structural nodes, similar to that of an isostatic surface's operation. This initial sketch model allows for the exploration of multiple spaces to emerge from the structural matrix whilst other parameters such as member density and agent influence provides feedback on material lengths and structural performance.
One of the most powerful techniques available in grasshopper that most other parametric softwares do not have available is the ability to drag / drop / connect any number of components or organised algorithms onto an existing GH definition. We built a number of explicit definitions that perform specific routines (tessellate, goal seek, optimise, etc.) From a library of definitions that we have been compiling the above is an example of our new and improved unfold script which then flattens a list (or datatree) of parts into two dimensional maps which can be then used to asses material layouts and ultimately to deliver fabrication templates. The form was scripted to extract the points as a series of banded strips that could each be laser cut, requiring only one connection per band (as a periodic strip) and three or four connections between each band.
Using this script we outputted a matrix of laser cut models of which 1 hour of cutting and 2 hours of taping the strips exemplifies the potential of parametric > fabrication methods.
In terms of design, fabrication and construction, there were a number of important factors that implemented in order to create an efficient structure. Maximum structural lengths, membrane offsets, membrane stretch and clash detection were all applied as coded subroutines optimised for the organization and construction of the structure.
Due to the minimal 1.25mm thick walled circular hollow section recycled aluminium tubing, the maximum spans of 6.5 metres meant that each node location could adapt its position with respect to neighbouring node locations, providing a relaxation of the network. The same script could be applied to the membrane, adjusting for percentage of stretch inherent in the material qualities before creating the unfolded cutting template.
With 102 structural members in total, the part layout and stack order of each node required a large number crunching exercise to resolve intersecting geometry within a 1mm tolerance allowed by the structural engineer. There are 46 nodes across the pavilion with up to 7 stacked parts on each connection (7 connecting members produce 7 x 6 x 5 x 4 x 3 x 2 x 1 = 5040 permutations of stack orders) meant a large amount of possible combinations per node to review and resolve clashes between an unbelievable amount of variations when dealing with the entire 46 nodes.
After writing the clash detection and permutation script, the entire structure can be optimised and stack arranged within 2.1 seconds clearly demonstrating the power in scripting and parametrics and exhibiting the level importance that these techniques carry when faced with complex problem solving.
The structure only took the two of us to layout and assemble on site. It then required one person on each node to lift it to the correct height in order to fix the perimeter structure. Once in place we made our way around each node tighten all the bolts and spigots in order to form a ridged structure. Once in place the canvas skin was dragged over the frame and pegged around the perimeter in order to complete the requirements for wind loading.