To: atm{at}shore.net
From: tkrajci{at}san.osd.mil
Reply-To: tkrajci{at}san.osd.mil


> From: "Roy Diffrient" 

> - - Unless I missed something, there seems to be no allowance for the
weight > of the truss itself in your examples....

Yes, the software allows that, and I'm learning how to use it.  Initial
results...truss deflection for all truss types increases by factor of
approx. 2.5.  The 'ranking' of what trusses are stiffest does not seem to
change.  I'll post corrections to my website when I'm done with all
analyses.

> - - I didn't see the standard truss listed in the results table, but the
> deflection for that design can be easily calculated, and that could be a
> good check on the FEA software, setup, etc.  The deflection is
calculated by
> the formula W L^3 / (c^2 A E), where W = load (plus half the truss
weight,
> as above), L = truss member length, c = base spacing between members, A =
> cross sectional area of the material in a member, and E = elasticity
modulus

That begs the question.  What exactly is the 'standard truss?'  Once I know
the node configuration I can plug it into GRAPE and see if its model
matches the equation you provided.

Thanks in advance,
Tom Krajci

--- BBBS/NT v4.00 MP