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RE: Non Professionals doing Engineering

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> ----------
> From: 	jerome.tan(--nospam--at)PAREURO.COM[SMTP:jerome.tan(--nospam--at)PAREURO.COM]
> Reply To: 	seaint(--nospam--at)
> Sent: 	Monday, January 25, 1999 6:58 PM
> To: 	seaint(--nospam--at); lhoward(--nospam--at)
> Subject: 	Re[2]: Non Professionals doing Engineering
> I trust the computer just as I would trust a stranger...with caution.
> But that's the way I should approach every project. Give an allowance
> to the answers, not too small nor too much but enough to be in good
> professional stead.
It is a good point, not to totally reply on the computer and software.
It is certainly not a good idea to do what computer says. For example,
the UBC has the following requirement for connections:

2227.1 Connections. Adequate strength of connections to withstand
calculated resultant forces and moments, and adequate rigidity where
such is required, shall be demonstrated by calculation or by testing in
an approved manner.

In the code, a connection must satisfy two conditions: adequate
connector loads (force, moment) and adequate rigidity (written in
stiffness). This is the basic concept in structural mechanics. The
problem is that most structural software cannot help engineers in
complying with the code, i.e., only outputs the connector loads. Under
this circumstance, many designs only consider the connector loads, but
never check if "the rigidity is adequate" because the computer outputs
nothing about the required connector rigidity. It is not appropriate to
design only the items computer outputs.

It can be realized that this problem is from the assumption made in
structural mechanics, i.e., joints of a rigid frame have a perfect
rigidity (infinite stiffness). All the output is under this assumption.
If a connection is without an adequate rigidity (too soft, not
sufficient large to be equivalent to an infinity), we can see what may
heppen. The internal forces and moments will be re-distributed,
different from the original analysis. Safe or not??