----- Original Message -----From: Dick_Roberts@oxy.comSent: Tuesday, November 01, 2011 10:57 AMSubject: RE: Standard Portal Frame Analysis
Back in the dark ages (before computers) we did a lot of these things graphically. Recently a engineer I work with had to check the
truss calculations that a intern did. I was looking at them and looked at my computer with AutoCAD and Microstation and said I could check them graphically faster than he could check them. It took my less than an hour to draw the truss and loads to scale and measure the stresses in ea member.
(I must confess it took me a lot longer to remember how to do it.
From: nma [mailto:email@example.com]
Sent: Tuesday, November 01, 2011 12:18 PM
Subject: Re: Standard Portal Frame Analysis
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"
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
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?"
Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC, V8T 1Z1
Tuesday, November 1, 2011
Re: Standard Portal Frame Analysis
It took me more than an hour to remember what I needed to write that posting to Thor last night.
H. Daryl Richardson
at 10:27 AM