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Re: length to be used for tension bracing kl/r

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While going through examples in the seminar, I noticed
that the limiting slenderness ratios were never used
in determining the allowable stresses. When I
questioned, Dr. Yura, about the existing requirement
on limiting slenderness ratios, he said that they are
not relevant. Perhaps, the committee on the code
provisions decided to retain the minimum kl/r
requirements.

Rajendran
--- Rick.Drake(--nospam--at)Fluor.com wrote:
> 
> The latest LRFD Specification (December 27, 1999)
> will be bound in the next
> LRFD Manual, 3rd Edition, later this year.  Section
> B7, Limiting
> Slenderness Ratios, remains unchanged.  Preferable
> slenderness ratios are
> still 200 and 300 for compression and tension
> members respectively.
> 
> New LRFD Specification Section C3, Stability
> Bracing, reflects Yura's
> excellent work in defining the required brace
> strength and stiffness for
> the stability of the braced member or structure. 
> These requirements are in
> addition to the long-standing slenderness
> preferences.
> 
> Rick Drake, SE
> Fluor Daniel, Aliso Viejo, CA
> 
> ***********************
> 
> 
> 
>                                                     
>                                                     
>          
>                     Padmanabhan                     
>                                                     
>          
>                     Rajendran            To:    
> seaint(--nospam--at)seaint.org                                   
>              
>                     <rakamaka@yahoo                 
>                                                     
>          
>                     .com>                cc:        
>                                                     
>          
>                     06/28/01 11:58                  
>                                                     
>          
>                     AM                   Subject:   
>  Re: length to be used for tension bracing kl/r     
>          
>                     Please respond                  
>                                                     
>          
>                     to seaint                       
>                                                     
>        . 
>                                                     
>                                                     
>          
>                                                     
>                                                     
>          
> 
> 
> 
> 
> Less than a month ago, I attended a seminar on
> "Bracing for Steel Structures", conducted by the
> international authority on the subject, Dr. Yura. 
> The
> limitation of kl/r (200 for compression members and
> 300 for tension members) are not required. The
> bracing
> members should satisfy only the "stiffness" and
> strength requirements. Future editions of AISC
> Manual
> (ASD or LRFD or some hybrid form) will include
> detailed sections addressing bracing.
> 
> Rajendran
> 
> --- Ken Peoples <kspeoples(--nospam--at)yahoo.com> wrote:
> > I seem to be constantly coming up with bracing
> > member sizes that are
> > controlled by kl/r instead of the force in the
> > member.  I have been
> > using the full length of the member when
> evaluating
> > kl/r.  My question
> > is this: for X-bracing angles that are designed
> for
> > tension only with
> > the kl/r<300 recommendation, is it reasonable to
> use
> > a length of 1/2
> > the actual length when the angles are bolted
> > together at the center.  I
> > know that the other angle wouldn't give it much
> > lateral support to
> > prevent buckling in one of the directions if I
> were
> > designing for
> > compression, but to satisfy the l/r<300
> > recommendation for tension
> > members, I would think that it might be OK.  I
> > understand from the AISC
> > 9th ed. commentary on B.7 that the recommendation
> is
> > made to "afford a
> > degree of stiffness such that lateral movement
> > ("slapping" or
> > vibration) will be avoided. What approach do most
> > engineers use?
> > Thanks for your thoughts.
> > Ken
> >
> > =====
> > Kenneth S. Peoples, P. E.
> > Lehigh Valley Technical Associates
> > 1584 Weaversville Road
> > Northampton, PA 18067-9039
> > ph: 610-262-6345
> > fax: 610-262-8188
> > e-mail: kpeoples(--nospam--at)lvta.net
> >
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