Progress in my dissertation has been hampered by the Basil Spence project but thankfully inroads are being made, starting with my boob model.

As I made clear previously my dissertation is not spline stressed membrane structures. Instead it is a study of 3-way spanning batten gridshells. Normally (pinned) gridshells are 2-way spanning with cable bracing, such as the Weald and Downland Open Air Museum gridshell. The Savill Building, recently awarded the Supreme Award for Structural Engineering Excellence, is also 2-way spanning but is braced by a skin of plywood. I hope to do away with the need for bracing by the addition of the third grid, which, if you like, is the bracing.

A ‘grid’ in this context is a set of parallel (ish) lines, and so a ‘2-way grid’ gives a surface with four sided shapes, and a ‘3-way grid’ gives a surface with three sided shapes (when the grids are in plane).

It is hard enough to construct a 2-way spanning gridshell so imagine the fun and games to be had constructing a 3-way beast! Or is it harder? The real problem with 3-way spanning gridshells is that all 3 grids will not intersect with regularity. In other words there will not be a regular array of nodes to pin the three grids together. Therefore the third grid is not properly working to “brace” the structure. The three grids will not align over a three dimensional surface as they do on a plane surface because the battens have to follow geodesic paths. Following a geodesic path was explained to me by Mike Barnes as wrapping tape over a curvy surface so that it does not crease (i.e. shear). There are further analogies to be had with dress making and svelte figured women.

So what am I to do? Well, a 3-way spanning gridshell will still have nodes with all three grids passing through and so I am looking at the patterns of local stiffness and instability, and so on, in the hope of shedding some light on this complex and rather case specific form finding problem. I hope to do a bloody good job, learn loads including how to create dynamic interactive C++/OpenGL programs, and create pretty pictures.

For the mean time I give you boobs: