When it comes to truss modeling software...trust!...but verify! ;-)

Seriously, how can I test that GRAPE gives accurate results? Roy Diffrient helped out here by providing an equation that describes the stiffness of a typical, 8 member truss.

The deflection is calculated by the formula

Deflection = W L^3 / (c^2 A E)

where

W = load (including one-half the truss weight)

L = truss member length

c = base spacing between members

A = cross sectional area of the material in a member

E = elasticity modulus

Comparing results of this equation with GRAPE gives agreement within two percent. This does not test all cases, but helps show that the software is at least reasonably accurate, and that I'm learning how to use it properly.

For other information, see:

http://astro.umsystem.edu/atm/ARCHIVES/APR00/msg00974.html

and

http://astro.umsystem.edu/atm/ARCHIVES/APR00/msg00921.html

and Sky and Telescope magazine, February, 1994, page 93 for an article on truss analysis.

and

http://physics.uwstout.edu/StatStr/indexfbt.htm

All feedback is encouraged!

email: t-k-r-a-j-c-i-@-s-a-n-.-o-s-d-.-m-i-l (remove the dashes)

Last update: 27 Dec 2002