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Re: MATRIX ANALYSIS

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Gentlemen,

        I'm so glad to read that someone is actually thinking of checking The Computer!  I was beginning to think that checking The Computer was regarded as heresy!!

        Lo . . . I was beginning to fear people like me were in the minority, destined to die because some technician thought the Bata angle in The Computer beam entry form related to the slope of the underside of the I beam flange, or some left handed architect thought that the right hand rule relating forces and axes was a nuisance that didn't apply to him (or her).

        On a more serious side, my own opinion is that not checking The Computer output is the same as stamping someone else's work when you don't even know how the work was performed or if the programmer is, in fact, a qualified engineer.  I have seen otherwise qualified engineers using a program which has been much maligned on this list and accepting solutions that included compressive forces in guy cables.  The same engineers also accepted first and second modes of vibration a fraction of a Hertz apart when, in fact, they had two approximations of first mode in each of X and Z directions.  They could also have had an infinite number of other first modes about an infinite number of axes of symmetry since the structure was axisymmetric and they wouldn't have known the difference because The Computer gave the answer and The Computer can't be wrong!

Regards.

H. Daryl Richardson
(computer literate but not always computer friendly)

Mark Hickey wrote:

 

Chris
Excellent comment.
There is no program at any level that can "design" anything.
Understanding is important
On any analysis,  check reactions check deflection magnitudes,  check equilibrium.
On any unfamiliar software,  carryout verficiation testing.
NAFEMS has good background data for benchmarking www.nafems.org

Cheers
Mark Hickey
Brisbane Aust

-----Original Message-----
From: Christopher Wright [mailto:chrisw(--nospam--at)skypoint.com]
Sent: Thursday, May 01, 2003 12:41 PM
To: ?
Subject: Re: MATRIX ANALYSIS

>I am checking a matrix analysis program for a structure. I don't feel
>confident that the forces I am getting for member design are right.
Check three things--
Force equilibrium overall
Member force equilibrium
For a few selected joints, check the force balance on the node points.
Also check a few of the members for proper displacements.

The reason you don't want to check it against another program is that you
can never be sure which one's right. If the program accords with first
principles of elasticity and the equations of motion, you know it's right.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw
 

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