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Re: Simple connection eccentricity on columns

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Thanks for finding that. I like Charlie's answer.
 
 
Will

 
On 7/25/06, Jason Emoto <jemoto(--nospam--at)lava.net> wrote:
There is a discussion of this topic on AISC's website in the FAQ section:

http://www.aisc.org/PrinterTemplate.cfm?Section=Steel_Interchange2&Template=
/CustomSource/Faq/SteelInterchange.cfm&FaqID=2110

Jason Emoto


-----Original Message-----
From: Will Haynes [mailto: gtg740p(--nospam--at)gmail.com]
Sent: Tuesday, July 25, 2006 1:14 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Simple connection eccentricity on columns

I have picked out of the tables many times myself. I was recently reviewing
some HSS column sizes that RAM had generated and it was making more of a
difference than I had expected, particularly at the typical perimeter of the
floor (only one beam framing into the column in one direction). I need to
check to make sure it is sizing them correctly with the 4.5" or so
eccentricity it is estimating for the connection with 35kips of load.  What
I had figured by the table could easily be an HSS 4x4x1/4, it was generating
HSS 6x6x1/4's.  (It is a small access level floor, hence the small columns).



Will Haynes


On 7/25/06, Jordan Truesdell, PE < seaint1(--nospam--at)truesdellengineering.com> wrote:

       I'll be honest - I usually don't.  The amount of eccentricity in an
       unbalanced column is usually very small compared to the allowable
moment
       capacity, and tends to make a very small difference in the design. I
       usually leave a bit of headroom on any column picked out of a table,
       because hand calcs are just not that accurate. Leaving 10-15%
capacity
       "on the table" also puts in a little future capacity should the
usage
       change.  It rarely increases the weight of the column appreciably,
and
       I'd rather have the stability.  Also, the amount of time to hand
calc
       the full solution on a small job rarely justifies the potential
savings
       in steel.

       This is, of course, subject to engineering judgment.  My background
is
       such that I feel I should be able to calc most common things in my
head,
       on the fly, to within 20-25%.  It comes from reviewing presentations
in
       meetings.  Knowing simple mass properties, CTEs, common
emissivities,
       etc. can quickly identify if someone has slipped a decimal place,
goofed
       an in-ft dimension (factor of 3.5 or 2.3 off)  or fouled up their
units
       completely (frequencies are often off by 386.4^0.5, or about a
factor of
       20 by young engineers). If I get out of a tight range of shear
offsets,
       I'll check it just to make sure, though it might just be a scribble
in
       the margin of a calc sheet or a number run in the memory of my HP48.

       Oh, and I'm not an "old guy" - not even 40 yet -  though my hair is
a
       bit grayer than I'd like. I've just done a lot of calcs by hand, and
       have gotten to work with some pretty darned smart folks over the
years
       and was able to pick up some of their tricks.

       Jordan



       Will Haynes wrote:

       > How many of you (that do not use RAM or other software that
calculates
       > it automatically) actually figure the eccentricity of a simple
beam to
       > column connection and add that moment to the column design? I know

       > when I first started, the older guys would always pick a column
out of
       > the AISC concentric load tables without regard to the moment from
the
       > actual connection eccentricity.
       >
       >
       > Will Haynes


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