I see what you mean - it's really the formation of a plastic hinge that leads to the instability long before the top pin reaches the level of the foundations.
I don't think the glu-lam beams will show that much plasticity before the roof caves in.
Thanks for the explanation, Paul.
Today, I believe that I established that the foundations need to be anchored in rock, with a key to resist lateral thrust. The client and the rest of the design team have come on board. So thanks everyone for your encouragement.
On 10/11/07, Paul Ransom <ad026@hwcn.org> wrote:
Ooops.
I dropped a decimal in my calcs. That should be:
33 in^2, 113 plf, 7 in dia solid rod, increase for load factors.
Paul
> Kevin,
> In your case, the lateral foundation stiffness at each support must be
> 800 k/in +/- to hold a 1" foundation separation. That's 1/2" displacements at
> each support. Load factoring not considered.
> (quick calc tie rod: 330 in^2, 1131 plf, 20" dia solid round, 200 ft long at
> each arch - increase for load factors - how much does the arch weigh after the
> first design pass?)
> Regards
> Paul
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