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Re: Architectural Low Rise Projects (Lateral Stability)

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Rick:

I usually treat them as "ordinary moment frames of steel", but as I said, I try
to avoid them.  Further, I design my connections cognizant (sp?) of the failure
mechanisms.

I learned the "knee-brace" technique from an employer who obtained his
California SE (along with several other licenses) and feel confident in its use
for low lateral loads.  I avoid "compromises" such as these when lateral loads
are substantial.  (My usual litmus test is the roof diaphram.  If it takes
special design to get the roof to work, I pay closer attention to the vertical
system and loadings.)

--- Rick Burch <rburch(--nospam--at)conterra.com> wrote:
> Keith Fix wrote:
> > 
> > 
> > An option I try to avoid is "knee"-braced frames, which I generally treat
> as a
> > subset of moment frames.  
> > 
> > I'd appreciate comments on any of my thoughts.
> > 
> 
> > 
> > Keith Fix, PE (CA)
> > Little Rock, AR
> > 
> 
> 
> Keith,
> Are you in a non-seismic area (if there are any of those left now)?  If
> you have to design for seismic, when you determine your R factor, do you
> consider the knee-braced framed to be a moment frame? They seem to
> actually be a type of eccentric bracing, but they probably don't meet
> the multitude of code requirements for eccentric braced frames.
> 
> I used to use knee braces for industrial type buildings, but now I only
> use them occasionally for something like a minor platform structure,
> mainly because I don't know what they are considered, seismically
> speaking.
> 
> Rick Burch
> 


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