] [Thread] [Date] [Author]

["Jeff Barrett" <jbarrett(--nospam--at)peaofsc.com>]

Chuck...we are reading it as yes we do have to change our ways, and the 1/3
increase is no longer an option (with the exception for wood).  I wish we
could still take it, but we haven't found anything that will allow it.  If
somebody knows of a loop hole, please show me where I can find it in the
IBC.

Jeff Barrett, P.E. S.E.


----- Original Message -----
From: "George Richards P.E." <george(--nospam--at)borm.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, October 29, 2001 4:59 PM
Subject: RE: 2000 IBC v 1997 UBC code question


> Chuck and Jeff:
>
> I also understand that the factors for wood are based on the load
duration.
> I have been told that this is also the case for other materials.  Then
again
> I have heard it argued on this list-server that that the 1/3 is only for
> cases where multiple loads apply to account for the fact that max dead,
live
> and wind are unlikely to occur at the same time.  Sort of a simplified
> probability analysis.  What ever the history though on the Left Coast we
now
> take the 1/3 on everything even seismic only load cases.  Do we have to
> change our ways?
>
> George Richards, P. E.
>
> -----Original Message-----
> From: chuckuc [mailto:chuckuc(--nospam--at)pacbell.net]
> Sent: Monday, October 29, 2001 1:35 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: 2000 IBC v 1999 UBC code question
>
>
> Jeff-
> My understanding is slightly different regarding wood.  I thought the 1/3
> increase for wood had to do with the fact that wood's test capacity is
> highly
> rate dependent.  The 1/3 increase is used for dynamic loads like seismic.
> The Simpson values should come from tests in wood, and would therefore by
> allowed the increase--however, I'm not sure that is in fact how they test.
> I'd
> bet a nickel that the very close nail spacing on some of their straps
would
> split the grain.  I don't think ICBO does a very good job of monitoring
the
> test
> setups used (and or permits dubious calculation methods to be used to
derive
> the
> loads ratings for some hardware).
> Chuck Utzman, P.E.
>
> Jeff Barrett wrote:
>
> > George:
> >
> > To answer your question...it is my understanding that the 1/3 stress
> > increase never had experimental data to back it up.  It simply was
"always
> > done that way".  Now, the IBC has taken that option out even though the
> > individual referenced standards allow it (AISC, ACI, etc...)  Wood is
> still
> > allowed because it is unlike the other materials because in its design
> > criteria the allowable stresses are low and then bumped "up" by factors
> such
> > as 1.15 and 1.6 depending on the criteria.  This is due to the fact that
> > every wood member is different.  Other materials such as steel start
with
> > higher stresses (because of the better quality control of the material)
> and
> > are reduced.
> >
> > To answer your question regarding the Simpson ties...you better ask
them,
> > but my feeling is most of those connectors are governed by the
connection
> > (nails, screws, etc...) and the failure is in the connection to the
wood.
> > Consequently, for wood connections, these Simpson would not need to be
> > reduced since the stress increase is allowed for wood.  However, if you
> were
> > using these connectors in light gauge steel design, they would have to
be
> > reduced.
> >
> > Jeff
> >
> > ----- Original Message -----
> > From: "George Richards P.E." <george(--nospam--at)borm.com>
> > To: <seaint(--nospam--at)seaint.org>
> > Sent: Monday, October 29, 2001 1:51 PM
> > Subject: 2000 IBC v 1999 UBC code question
> >
> > > Fellow Engineers:
> > >
> > > I am reviewing the impact the IBC will have on how we design out West.
> > >
> > > Using 1997 UBC Alternate Basic Load Combination 1612.3.2 we are
allowed
> a
> > > 1/3 stress increase for wind or seismic only loading regardless of if
> the
> > > material is wood, steel, or concrete.
> > >
> > > Using 2000 Alternate Basic Load Combination 1605.3.2 we are NO LONGER
> > > allowed a 1/3 stress increase for wind or seismic only unless
> specifically
> > > given in the material section.  This means wood only.
> > >
> > > First question:  Did I read this correctly?
> > >
> > > Second question, {mostly for those of you in Texas where I know that
> every
> > > home is Engineered :)} where the IBC has been adopted are you still
> using
> > > Simpson numbers or since they have also included a 1/3 increase on
steel
> > are
> > > you down grading them?
> > >
> > > Thanks in advance.
> > >
> > > George Richards, P. E.
> > >
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