Friday, 23 November 2007

FEM Analysis...

AKT has run an initial FEM analysis on the roof structure, and well...we've got a bit of work to do.
Though significantly lighter than conventional concrete, the Fibre-C is still concrete, and the self-load of the material is a bit more than our geoemtry can handle at the moment. Basically, with the tilt/lean of the roof structure, the self-load of the structural material, and the non-continouous nature of the structure....our notch joints are taking a hell of a load. The moment forces that these joints are taking is very high. We are also experiencing high stresses and deformation in the profiles due to bending in their weak axis. AKT has told us we need to reduce the stresses by a factor of about 6 (no stress factor has got to be +100 these days).

We've got a few options for reducing these stresses, but it looks like it's going to be a combination of them all:

1. Decrease the tilt angle of the roof structure. By reducing the angle by 15 degrees we gain a factor of 2. We also lose some of the dynamic formal movement and drama of the structure.

2. Introduce bracing, especially at the sides of the pavilion. This could be done by infilling flat sheets of fibre-c stiffeners between profiles at various locations. This could also detract from the visual and structural purity of the pavilion.

3. Add more primary ribs at the side faces. This might alter the visual effect of the moire pattern, but could also be interesting if done as a gradient of spacing. I also find it interesting to architecturally express where the structure is performing the most.

4. Increase thickness of material at primary ribs to 13mm, and decrease thickness of material at secondary profiles to 10mm (reducing the self-load).

As I said, we've got some work to do. All of these decisions need to be looked at before we can make a call on them. We need to maintain our design concept, while finding a structural solution that suits. But in particular...we need to so so ASAP!

Here's a look at the revised wire model with spliced profiles and intersection nodes we sent over to AKT today for a quick analysis. In this version, we have reduced the tilt angle by 10 degrees on the front face, and 5 degress on the back.
On another note, once again we have also revised the bench geometry again. Don't worry, it won't be the last time. As you can see below, we are using the 3.6m x 1.2m standard sheet size of Fibre-C as the module for sizing our profiles.
In light of this, we have now lowered the height of the seatback/counter, so that it drops within the 1.2m width of the sheet material. this allows us to cut the entire bench profile in the primary direction, in one continous piece. this is a very minor change, but one which saves us huge amounts of hassle and detailing.

Tuesday, 20 November 2007

joint details

We've made some progress on the joint detials over the last week. The two models we were looking at use silicone gaskets to provide a cushion between the interlocking profiles and here are the two mock-ups back from the RP lab. Thanks to Jeroen for all his help.

After a design team meeting, we've decided to go with the second option because it can deal with a variation in angles in two planes; it acts as a rotational stiffener once in place, and it will provide a locking resistance against vertical shear.

The assembly process has been reduced to a minimum - a pair of gaskets will be bonded to the notches on the primary concrete profile in advance. On site, the cross profile will be inserted and then the remaining pair of gaskets can be mechanically fixed with one pin each to lock the joint together.

Monday, 19 November 2007

bench in progress...

more revisions to the bench profiles. the original competition entry had the profiles revolving with the geometry of the bench, however this poses problems with how we slot the bench profiles with the deck underneath. now, we are continuing the primary profiles of the roof and floor into the bench. for the cross-members we are looking at taking the sections in one direction for the vertical surfaces of the bench (horizontal sections) and another for the horizontal (seating) surfaces of the bench. we still need to work on the density and spacing of the profiles, but i think we now have the principle in place.

as the deadline approaches and the complexity of joints is exposed, we are basing many decisions on the infamous "KISS Principle".

however, as usual, all sections are completely planar, but never parrallel...

more from theverymany...

here's a few more images from Marc Fornes of theverymany, and his entry into the DRL10 pavilion competition. Marc is doing some fascinating generative geometries in RhinoScript. This entry explores the use of a Danzer Tile, which is an aperiodic tiling system. Check out his site for more. As seen in previous posts, Marc has generously been supplying us with coding support to help us automate the process of producing the documentation for our pavilion.

Sunday, 18 November 2007

more joint options

work in progress...

the bench profiles are slowly beginning to take are some screen shots from today's progress...