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RE: Concrete Strong Column/Weak Beam

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The purpose of this check is to ensure that at the connection, the plastic
hinge does not occur in the column vs. the beam. This is a local check so to
speak, whereas the stability affects the global capacity of the column. The
same check is required for steel frames and there also, The Z*Fy of the
column is compared to the beam flexural capacity.

Ben Yousefi, SE
San Jose, CA 

	-----Original Message-----
	From:	richard lewis [SMTP:rlewistx(--nospam--at)juno.com]
	Sent:	Thursday, June 21, 2001 11:52 AM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Re: Concrete Strong Column/Weak Beam

	That is what puzzled me, "the flexural capacity of the columns is
	affected by the coincident axial load".  Does it not matter how
slender a
	column is when you check the flexural capacity based on the axial
	capacity?  

	I take an interaction diagram, go up to the axial load and then go
across
	to the curve boundary to find the moment capacity.  If it were a
column
	design the moment capacity would be the magnified moment.  In this
check
	it is just the moment capacity of the beam.

	Rich


	On Thu, 21 Jun 2001 10:16:41 -0700 "Mike Valley" <mtv(--nospam--at)skilling.com>
	writes:
	> Slenderness and P-delta do not play a part in this calculation.
The
	> assumption is that flexural yielding will occur at every joint.  
	> The
	> purpose of the calculation is to assure that the columns have
	> sufficient flexural capacity to force yielding into the beams or
	> girders.  Keep in mind that the flexural capacity of the columns
is
	> affected by the coincident axial load.
	> 
	> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- 
	> -
	> Michael Valley, P.E., S.E.                   E-mail: 
	> mtv(--nospam--at)skilling.com
	> Skilling Ward Magnusson Barkshire Inc.              
	> Tel:(206)292-1200
	> 1301 Fifth Ave, #3200,  Seattle  WA 98101-2699      Fax:        
	> -1201
	> 
	> -----Original Message-----
	> From: richard lewis [mailto:rlewistx(--nospam--at)juno.com]
	> Sent: Thursday, June 21, 2001 9:58 AM
	> To: seaint(--nospam--at)seaint.org
	> Subject: Concrete Strong Column/Weak Beam
	> 
	> 
	> I have a question regarding using ACI 21.4.2.2 check for the
strong
	> column weak beam check.  How is column slenderness accounted for
in
	> this
	> check.  The ACI equation is :
	> 
	> sum Me >= (6/5) sum Mg
	> 
	> If I have a slender column, is Mg magnified somehow like in ACI
	> 10.13.3?
	> If I used a P-Delta analysis to get Mg, does it have to be 
	> magnified
	> for
	> this equation?  How does the effective length factor 'K' factor 
	> into
	> this
	> check?
	> 
	> Rich
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