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RE: (E) Masonry with steel upgrade

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The 1997 NEHRP Recommended Provisions and the 2000 IBC include a "Detailed
Plain Masonry Shear Wall" system that is permitted in areas of low and
moderate seismic hazard.  This system requires less reinforcement than does
a reinforced masonry shear wall system.  The R value is between that for
plain masonry and reinforced masonry.

Since the provisions noted above are for new (as opposed to existing)
construction you may run into other glitches in application.

It was not clear to me what you are calling a seismic-force-amplification
factor.  Would you please clarify?

**********
> -----Original Message-----
> From: merrick group [mailto:merrickgroup(--nospam--at)compuserve.com]
> Sent: Friday, January 21, 2000 11:04 AM
> To: Seaint
> Subject: (E) Masonry with steel upgrade
>
>
> I have an older building that has masonry
> steel ratios of .0008, .0009 and a total of
> .0017. I need .0007 min and a total of .002.
>
> How can I get this total ratio up?
>
> Can I allow the total number to be rounded
> up to 0.002? The code suggests a significant
> figure of one. I jokingly consider using the
> CMD97 program that allows the ratio.
>
> Shear capacities are from 1.5 times to 4 times
> that needed. Recall that the seismic-force-
> amplification-factor is 3.8. It would seem that
> adding extra reinforcement is unreasonable
> for capacity to demand ratio that is more than
> 3.8.
>
> Without any good recommendations, I am
> adding some steel pilasters that can carry the
> tributary lateral loads out of the wall?s plane.
> I will consider the pilaster as equivalent to a
> vertical bar of steel, at that location, to
> increase the effective steel ratio. The walls
> already have masonry pilasters every 14 feet.
>
> Less than minimum steel has been considered
> as having an equivalent ductility of masonry
> with no steel. How silly. I am request that the
> Seismic-rulers-of-the-code to consider a
> reduced minimum steel ratio that is
> dependent on an application of an adjustable
> seismic-force-amplification-factor.
>
> David Merrick, SE
> Merrickgroup(--nospam--at)compuserve.com