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Re: Beam design

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To be precise, the switch to the "sliding" phi factor, previous referred
to as the "Unified Design Method"  (i.e. determining if it is
tension-controlled or compression-controlled as Mr. Fu put it but
really determined by the strain levels) has been in the ACI code for
quite a while.  It is true that it was moved into the main body of the
code recently, but this actually happened in the ACI 318-02.  Prior to
that, this method was in an appendix for at least a couple of cycles.  In
the 2002 edition, this method was placed into the main body of the code
and the "old" method was placed into the appendix.  I will note that you
are still permitted to do it per the old method since it is still
contained in an appendix (Appendix C to be precise), unless the locally
adopted code or model code specifically states an exception that disallows
the use of that appendix (ACI 318 allows it, but can be "over-ridden" by
the legally adopted code or a model code the references ACI 318).

Regards,

Scott
Adrian, MI


On Tue, 10 Jan 2006, TJ Fu wrote:

> We know R.C. beams always subjected to some kind axial loads and bending moments. It doesn’t matter whether that beam is horizontal or vertical, you have to design the beam for whatever loads you have along the beam according to ACI 318-05 9.3.2 thru 10.12.3.2 based on (1) stress and strain compatibility or (2) using ACI 10.3.6 approximate equation.
>
>   Due to beam self-weight, for horizontal beam, you’ll have additional beam moment (M) to consider along the beam and for vertical beam, you’ll have additional axial load (P) to consider at the bottom.
>
>   We used to apply strength reduction factor differently where you treat that member as beam (0.9) or column (0.70 tied or 0.75 spiral).
>
>   New ACI 318-05 has all these factors built in. You don’t need to worry if it is a beam or a column now. You only need to determine if it is tension-control or compression-control based on the applied factored loads (Pu & Mu). It also tells you how to apply the reduction factor if you have in-between situation. Please note that the strength reduction factor for compression-control sections has been reduced from 0.70/0.75 to 0.65/0.70.
>
>   I have use MathCad to come up a Beam-Column design procedures per ACI 318-05 for rectangular section subjected to axial load, uni-axial or bi-axial bending. It is free if you like to try that out.
>
>   T.J. Fu
>   Louisville, KY
>
>
> Santhosh Kumar Yedidi <sant527(--nospam--at)gmail.com> wrote:
>       I am sorry, I am not getting the replies.
>
> What I meant was, Generally members lying horizontally are designed as
> beams, ofcource but columns are defined as those members irrespective
> of its direction if there is some significant axial load acting.
>
> So in my case if the beam is subjected to axial load then we cant use
> the beam theory to design it.
>
>
>
> On 1/9/06, David Fisher wrote:
> > Gerard:
> >
> > Thanks for saying that...
> >
> > When I see questions like that, it really gives me the creeps.
> >
> >
> >
> > David L. Fisher SE PE
> > Senior Principal
> > Fisher + Partners Structural Engineers inc
> > 372 West Ontario
> > Chicago 60610
> >
> > 312.573.1701
> > 312.573.1726 fax
> > 312.622.0409 mobile
> > www.fpse.com
> >
> > David L. Fisher SE PE
> > Director
> > Head of Design and Construction
> > Cape Cod Grand Cayman Holdings Ltd
> > 75 Fort Street
> > Georgetown Grand Cayman BWI
> > mobile 312.622.0409
> > www.ccgch.com
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: Gerard Madden, SE [mailto:gmadden(--nospam--at)maddengine.com]
> > Sent: Monday, January 09, 2006 10:53 AM
> > To: seaint(--nospam--at)seaint.org
> > Subject: RE: Beam design
> >
> > Is this on the midterm? What material? Is it open book?
> >
> > Good luck.
> > -gm
> >
> > -----Original Message-----
> > From: Santhosh Kumar Yedidi [mailto:sant527(--nospam--at)gmail.com]
> > Sent: Monday, January 09, 2006 1:41 AM
> > To: seaint(--nospam--at)seaint.org
> > Subject: Beam design
> >
> > How to do beam design with axial forces acting.
> >
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