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Re: Standard Portal Frame Analysis

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Harold:

We learned how do perform lateral drift calculations in the '50's using moment distribution and other classical methods.  Our text book was "Analysis of Statically Indeterminate Structures" by Williams. (which I still have on my bookshelf today).   We had learned the graphical methods in our stress analysis class in our junior year.  I have both the Klienlogel books, "Beam Formulas" and "Rigid Frame Formulas". (Picked up in London)  Believe I "programmed" some of the frames in Visicalc.  

Our class (of about 22) all used slide rules - mine was a larger circular.  

Neil Moore, PE, SE
still with a passion for engineering like Harold and the rest of you.


On 11/1/2011 8:50 AM, Harold Sprague wrote:
Back in the 1970's, I was trained by engineers who did not know computers.  They used graphical methods and other approximate methods to calculate lateral drift.  I came in on my white horse and was going to teach the old hands how to calculate lateral drift the computer way.  They could do it faster by a long shot, and we were well within about 5% of my "modern" ways.  ...I was not worthy. 
 
I have collected many approximate methods in order to calculate lateral drift quickly with only a calculator (or even a slide rule). 
These are some additional very good tools:
  Kleinlogel had a book of formulas for frames in the 1950's
  Hool & Kinne wrote " Stresses in Framed Structures"
     and
  AISC "Single Span Rigid Frames in Steel" in 1948
  AISC published a really neat little one page frame drift tool in Modern Steel Construction, Steel Interchange in April 1993.  It was based on Kleinlogel.
 
I have used a similar method that you list below.  I think you will be surprised how accurate the approximate methods are. 

Regards, Harold Sprague
 
From: vicpeng(--nospam--at)telus.net
To: seaint(--nospam--at)seaint.org
Subject: Standard Portal Frame Analysis
Date: Mon, 31 Oct 2011 11:28:31 -0700

I’m doing stuff I should done in school J

 

1)      I am reviewing how to quickly arrive at sway in a rectangular (or any, for that matter) portal using simple portal frame equations.

2)      I calculate the moments from the std equations and then release the top corners to arrive at a flagpole concept tied at tops by a strut/beam.

3)      The resulting base moments are approx by iterative moment distribution.

4)      If I use a partial, or offset, load on the beam I expect sway.

5)      My question is, “Is it too simplistic to take the resulting moment difference at the bases and apply slope-deflection arithmetic to arrive at an estimate of the sway?”

 

Thanks

 

Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC, V8T 1Z1
Email:
vicpeng(--nospam--at)telus.net

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