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Re: 4" CMU walls with out-of-plane loads

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Ed,

I can't comment on the UBC right now...don't have it with me.  I do have
the 2002 MSJC (ACI 530-02) with me.

I don't see any restrictions for wall thickness for ASD.  For strength
design, there appears to be no restrictions for walls with a factored
axial stress of 0.05 f'm or less (section 3.2.5.4).  Nor are there any
restrictions for walls with factored axial stress between 0.05 and 0.2 f'm
_OR_ slenderness ratios under 30 (section 3.2.5.5).  Section 3.2.5.5 does,
however, requires walls with an axial stress of greater than 0.2 f'm OR
slenderness ratios exceeding 30 to be at least a minimum 6" nominal
dimension.

If I remember, I will look at the UBC when I can get my hands ont it.

HTH,

Scott
Ypsilanti, MI


On Thu, 13 Nov 2003, Ed Tornberg wrote:

> UBC 2107.1.3.1 (working stress) bans "bearing" CMU walls less than 6"
>
> UBC 2108.2.4.4 (strength) bans walls less than 6" for out-of-plane
> loads, when axial load is 0.04 f'm or less. (more or less non
> load-bearing)
>
> UBC 2108.2.4.5 (strength) says nothing for out-of-plane loads on walls
> with axial load greater than 0.04 f'm.
>
> What gives?  The working stress restriction is for bearing walls, and
> the strength restriction is for non-load bearing walls.  Have I missed
> something?  I suppose that the strength method has some limitation
> wrapped up in the formulas.  I've got some non-load bearing screens that
> the customer would like in 4" CMU, and working stress isn't quite
> cutting it.  I'm not interested in commentary on the practical
> difficulties of reinforcing and grouting 4" CMU - I'm intimate with that
> issue.
>
> For futher curiosity, does the IBC address this?  I saw nothing in a
> visual scan of ACI 530-99.
>
> TIA,
>
>
> Ed Tornberg, PE
> Blazer Industries, Inc.
>
> Aumsville, OR
> 503-749-1900
>
>
>
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