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Re: UBC Section 2213.51

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> Mark,
>
> The UBC section you allude to only applies to columns.  The member sizes
> you reference appear to be beams.

I realize this applies to columns, I had however applied omega to the
lateral load acting on my frame instead of applying omega to the axial force
in the frame column.

>
> I don't recall having to bump up the size of a column so much because of
> this code provision.  Are you aware that this is a strength expression
> and you need to factor your column load capacity by 1.7.

Yes, but this brings me to another question: The frame analysis from which
the column axial force is taken, is a result of which load combination? Am I
doing the following correctly:

1. Calculate load to the frame.
2. Use ASD load combination equation 12-9, 12-10 or 12-11 to analyze frame
(note E/1.4).
3. Take column axial load out of analysis results.
4. Check column axial capacity based on section 2213.5.1.

Here, I get hung up. The frame analysis was done with E/1.4. Now I have a
column axial load at service level forces to which I'm going to check
against ultimate capacity (Psc=1.7FaA) of section 2213.5.1?? I do need to
factor my column axial load by 1.4 prior to checking against Psc, don't I?

>
> Since it is the nailer transferring the shear to the frame, don't
> understand how the nailer capacity can be less than the design shear.
>
It can't, don't know what I said to give you that impression.

> Hope this helps.
>
Yes, thanks, it has somewhat but as can be seen above, I am still confused.
I have spent far to long trying to sort this fu$%ing code out and have just
about reached my limit.

You might be interested to hear a local building officials opinion on how to
design omrf under 97 code. "Design the entire frame for D+2.8E". Don't
divide E/1.4 and don't take any stress increases. He understood I was
talking about ASD design for the frame.

Regards,

Mark

> Jeff Coronado, S.E.
> West Covina, CA
>
>
> Mark Baker wrote:
> >
> > The load combinations of section 2213.51 are increasing the size of my
> > ASD OMRF members from W12x35 to W16x57.
> >
> > This frame is located at the end of a 65' x 40' structure, wood framed
> > with diaphragm @ 26' above fin. flr. The frame is also receiving load
> > from a 26' x 40' open canopy, wood framed.
> >
> > Section 2213.51 states the exception  "Axial load combination need not
> > exceed max. force that can be transferred to the column by elements of
> > the structure......".
> >
> > I interpret this to mean I can design the nailer/beam connection (for
> > example) for the applied lateral load (no more, no less) and proceed
> > with only meeting load combinations of 1612.3.
> >
> > If this is true, under what circumstances does one not "cheat the
> > code" by taking this exception and instead design for the load
> > combinations of 2213.51?
> >
> > Regards,
> > Mark
>
>