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Re: ASD steel composite beam design

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Harold,

I appreciate your response.  I have briefly attempted to sort the composite beam design approach in the 13th ed.  Based on that, the floor joist I am looking at would just require 8(!) weld studs vs. the 70 I would need for a fully composite beam per ASD green book.  That's a huge difference, and this is a mild understatement...  Time is also a factor right now as this is a design-build job on the fast-track, and the sections have been ordered.  In due time, I will reacquaint myself with the LRFD approach.  But, for now, I'm going to follow the nice design examples in ASD 9th, and err on the conservative side.

David A. Topete, S.E.



"Harold Sprague" <spraguehope(--nospam--at)hotmail.com>

09/15/2006 09:17 AM

Please respond to
<seaint(--nospam--at)seaint.org>

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seaint(--nospam--at)seaint.org
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Subject
Re: ASD steel composite beam design





You really need to look at the 13th Edition for ASD composite design.  I do
like the color highlights.

The big argument and material advantage for going to LRFD back in 1986 when
the LRFD first Edition hit the streets, was to reduce beam sizes and stud
quantities.  The issue was more in that there was research that manifested
itself in the LRFD, but the ASD was never updated by the research that fed
into the '86 LRFD.  Prior to 2006 and the 13th Edition, the ASD composite
design was predicated on composite research and design practices developed
in the 1970's.

Beams and concrete did not know or care if you were designing in ASD or LRFD
so the results should not have been as divergent as they were.  With the
current 13th edition ASD, the resulting members are not as divergent (ASD vs
LRFD) although I have not done any formal study and analysis comparison.

The only thing that I know for sure is that the research and design
methodology in ASD composite beam design took a 30 year leap with the 13th
edition.

If I am way out of line, I am sure that Charlie Carter or other AISC smarter
than me guys can correct me.

.... I remember when the 7th edition was baby blue and new.  It came out in
1970.  The year I graduated from high school.  ...bell bottoms and the draft
was something more than a cool breeze.

Regards,
Harold Sprague


>From: David.Topete(--nospam--at)wildman-morris.com
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: <seaint(--nospam--at)seaint.org>
>Subject: Re: ASD steel composite beam design
>Date: Fri, 15 Sep 2006 08:31:03 -0700
>
>No, it doesn't.  The non-composite section is at full allowable bending
>capacity, and is defelecting about 2" under total load.  I would think
>that if Iuse the 1/4 Vh value, I greatly reduce the number of weld
>studsdeflections are still within allowable limits.  Just reading through
>the ASD spec, it almost seems as if it's all or nothing if the reduced
>horiz shear Vh' doesn't calc to at least 1/4 Vh.  Actually, reading the
>paragraph on 5-59 as you've pointed out kinda answers my question.  Thanks
>Will.
>
>David A. Topete, S.E.
>
>
>
>"Will Haynes" <gtg740p(--nospam--at)gmail.com>
>09/14/2006 05:42 PM
>Please respond to
><seaint(--nospam--at)seaint.org>
>
>
>To
>seaint(--nospam--at)seaint.org
>cc
>
>Subject
>Re: ASD steel composite beam design
>
>
>
>
>
>
>By page 5-59 it looks like you do have to meet the 1/4 minimum if using
>any composite action. Does the beam work without studs at all? I have used
>non-composite beams on a floor where the rest of the beams were composite.
>
>
>
>Will H.
>
>
>On 9/14/06, David.Topete(--nospam--at)wildman-morris.com <
>David.Topete(--nospam--at)wildman-morris.com > wrote:
>
>Following the examples for composite beam design in the ASD 9th edition,
>when economizing by taking advantage of partial composite action, does Vh'
>have to be at minimum 1/4 x Vh?  I ask because for a fully composite beam,
>I would need a total of 70 weld studs.  But, when computing for partial
>composite beam action, to economize on the weld studs, the calculated Vh'
>is a hair above 0kips.  Intuitively, I would guess that the intent of the
>1/4 Vh is to have some horiz shear force to design for, although it is not
>explicitly stated in the spec or commentary...
>TIA for any clarification provided.
>
>David A. Topete, S.E.
>

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