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RE: Out-of-plane forces on concrete tiltup, or masonry walls

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Dan, see my comments below.

Barry H. Welliver
barrywelliver(--nospam--at)earthlink.net


> -----Original Message-----
> From: Dan Goodrich [mailto:dang(--nospam--at)karren.com]
> Sent: Thursday, January 17, 2002 9:14 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Out-of-plane forces on concrete tiltup, or masonry walls
>
>
> Under the 1997 UBC code, we used equation 32-2 from
> UBC 1632.2 to determine the out-of-plane force on
> concrete and masonry walls under seismic loads.  The
> coefficients Rp, and ap were taken from Table 16-O.
>
> Utah has now adopted the 2000 IBC.  The seismic stuff
> appears to be straight out of ASCE 7-98.  I thought I
> could use equation 16-67 for the out-of-plane force
> on the walls.  However, this equation is in the architectural,
> mechanical, and electrical component detailing section.
> Table 1621.2 and 1621.3 do not have any values for
> Rp and ap that fit a load bearing concrete or masonry
> exterior wall.

There is a publication by ICBO and SEA National Council titled "2000 IBC
Structural Application Guide" which appears to give some interpretation to
this matter. In a nutshell it says using table 1621.2 Item 4.a, ap = 1.0 and
Rp = 2.5 is appropriate when designing one-story masonry or concrete walls
for out-of-plane seismic forces. There is further discussion about z also.

We struggled with this a bit in the SEAU Seismic committee when reviewing
the 2000 IBC. I guess I still don't know how wall elements are considered
non-structural in this example, perhaps others can enlighten us. I'm looking
forward to some commentary on this code!
>
> Has anybody else dealt with this problem, or I am
> tying to use the wrong formula?
>
> Also, equation 16-64 of the IBC is used to determine
> the anchorage of concrete or masonry walls to flexible
> diaphragms.  This appears to be substantially higher
> than what was required under the UBC.
>
> Any input would be appreciated.
>
> Thanks,
> Dan Goodrich, P.E.
>
>
>
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