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# Re: Commercial Sign stru

• To: <seaoc(--nospam--at)seaoc.org>
• Subject: Re: Commercial Sign stru
• From: "Bill Allen" <BAllenSE(--nospam--at)pacbell.net>
• Date: Sun, 5 Apr 1998 11:42:32 -0700

```Good point, Roger. My first job out of school was with McDonnell Douglas
working on the DC-80. While I hated the job (don't flame me, I just don't
like working for large companies), I learned some valuable lessons from the
"old timers". It was pointed out to me that the DC-3 was designed using hand
calculations (slide rule-not even calculators-even before DOS). You would
take the design lift and consider the wings as cantilevers. You would take
the weight of the fuselage and consider it cantilevering off the wings. You
would calculate the section properties based on the diameter of the fuselage
and the properties of the longerons, etc. While this may seem archaic by
today's standards, there were over 10,000 DC-3s built and was a very
successful model. The point that the old timers were trying to make is that
a good engineer can/should check his/her computer output and be able to do
the analysis by hand. While there, I learned a lot of techniques to do
analysis that I still use today. There have been a lot of complicated 3-D
structures designed (well) without the benefit of computer programs.

It is kind of frightening how many engineers are willing to put data into a
computer program, take the results, design and detail the structure without
at least doing a global statics check of the input.

Regards,
Bill Allen

-----Original Message-----
From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
To: seaoc(--nospam--at)seaoc.org <seaoc(--nospam--at)seaoc.org>
Date: Saturday, April 04, 1998 11:25 AM
Subject: Re: Commercial Sign stru

>Jim Warne wrote:
>
>. > Why not just design a regular statically determinate frame - it doesn't
>. > have to be two dimensional -  and use statics and a calculator? Start
>. > with the loads at the source and follow them through to the foundation,
>. > resolving the components at each joint and making sure the sum of all
>. > forces and moments anywhere is zero.
>. >
>. > Or don't they teach that anymore?
>
>Apparently they don't!
>
>It seems that they teach students to look for a computer program written by
>someone they don't know, who may or may not be an engineer, who may or may
>not be college educated, who may or may not have structural engineering
>experience, and use that program and take the results as gospel.
>
>By the time they locate and obtain a program, they could have done the work
>by hand.
>
>A. Roger Turk, P.E.(Structural)
>Tucson, Arizona
>
>
>

```