From: "Laurence B. Oeth III" <viacalx(--nospam--at)europa.com>
Date: Thu, 06 May 1999 17:28:39 -0500
Lynn H wrote:
> If you run the numbers, in one direction the plywood
> diaphragm does in fact calculate out to be rigid.
> In the other direction, it calc's out as flexible.
> This is another thing engineers have never had to
> deal with before, a diaphragm flexible in one
> direction, rigid in the other.
> Answer me this, if the diaphragm is rigid, then it
> will distribute loads by rotation to walls
> perpendicular to the forces if the center of gravity
> and center of rotation are not coincidental.
> However, the as in the other direction the diaphragm
> is flexible, it is not not capable of transmitting
> the loads by rotation. The design theory breaks
> down at this point.
> How in the world to you figure this one? One can or
> worms after another!!
You answered your own question. Take a package of plastic drinking
straws down to the building dept and demonstrate what will happen to the
non-isotropic diaphragm by laying a dozen or so alongside each other.
Now push horizontally across the straws, but off-center and see if the
mass rotates. Rigid one way, flexible the other (OK, I'm using
primarily shear deformation rather than flexural to make a point).
I'm open to better demonstrations.