Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Composite Floor conventions

[Subject Prev][Subject Next][Thread Prev][Thread Next]
It appears that RAM outputs the total uniform number for the entire beam and this number gets imported onto the drawing.
 
 
Will Haynes

 
On 8/9/06, Carter, Charlie <carter(--nospam--at)aisc.org> wrote:
The number of studs on the drawings *should* be the total number
distributed over the segment, as the person who has to build it likely
does not know we calculate half the number. I'd get verification of that
from RAM, too, though.

There is a good discussion about lower percentage composite action on
page 16.1-311 in the 2005 Specification. There is no codified limit, so
you can use your engineering judgment.

Maximum spacing of studs is given in Section I3.2d(6) on page 16.1-88 as
6 times the total slab thickness or 36 in. Maximum spacing of deck
attachment (studs or puddle welds) to the beams is 18 in. per Section
I3.2c(1)(d).

Not sure where the 12" rule is from.

Charlie


-----Original Message-----
From: Jordan Truesdell, PE [mailto:seaint1(--nospam--at)truesdellengineering.com ]
Sent: Tuesday, August 08, 2006 10:28 AM
To: seaint(--nospam--at)seaint.org
Subject: Composite Floor conventions

It's been years since I've done a composite floor by hand - back when a
3/4" stud was comfortably assumed to carry 21kips. I'm knee deep in a
retrofit, and have managed to lose track of where things should go, and
where all the specifications are. Too many years relying on computers, I

suppose. Anyway...

On composite floor system drawings, it's common to label the beams with
end reactions and number of studs, which are equally spaced along the
length of the beam. This is the way RamSteel outputs the data, and it
flows right onto the drawings.  I cannot remember whether the call out -

which is normally labeled as "number of equally spaced studs" - refers
to the number of studs on each half of the beam, or on the entire beam.
Is there a consensus, and what is it (yes, I have a question in to RAM
as well, but that's from the software side).

It has come up because I have a retrofit job, and the beam in question
would probably calc in the normal load case with the 10 studs indicated.

Since its 28' long, 10 studs would meet the criteria for 36" o/c max
spacing.  It does not, however, meet the 25% composite "rule". Which
brings me to the next question: where is the 25% limitation written in
the AISC spec, or is it a guideline which is not written. I have gone
through the spec (13th Ed) and commentary and can't find it. I
understand the inherent problems with low-composite action beams, but
I'm looking for a specific limitation if it exists.

Last question...after rereading my course notes in advanced steel
design, I have several indications that the studs should "never be less
than 12" o/c".  And, now, almost a decade later, I can't remember if the

call out is for never placing studs closer than 12" (requiring double
rows), or never to have fewer studs on a beam than would be in place if
put on 12" centers.  I have a feeling it is the latter, but don't have a

definitive answer.  Does anyone else use the 12" rule?


--
Jordan


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org . Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********