How to implement a threshold for dry friction ?

[bourinax]

Hi

I'm using bullet to simulate Keva planks (also known as kaplas) structures collapsing, like in this video :
http://www.youtube.com/watch?v=OBzBfhrjx5s.
My problem is that the structure is unstable. A perfectly stable structure (in the real world) collapse by it-self after several seconds of simulation. Here is what my structure looks like :

The higher the structure, the faster it collapses. There must be a solution to tackle this issue, hence the big building shown in the youtube video.

I think the problem comes from the "static" behavior of the kaplas. In a real world there is a threshold for dry friction, under a certain force a solid does not move. This doesn't seam to be the case in my bullet simulations, the structure never stabilizes. What bullet classes/physics settings can be used to fix this problem ?

Thanks.

[bourinax]

Maybe I should pose the question more directly : how do I change the default dry friction coefficient ? or the "bouncing" coefficient ?
Is there any possibility to define separate static friction and kinetic friction coefficients ?