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RE: Shear Wall Tests - Static vs. Dynami

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No problem Roger. I think I'll wait for APA's response before acting. As
I've stated many times, I have seen very few failures related to the
shearwall (plywood connection to studs) failures at the panel nailing. I
have seen my share of failures due to oversized holes drilled in mudsills
which caused the plate to split. I've seen my share of failed connections of
holddowns to studs. Each of the last two conditions could be improved by
following the '97 UBC requirements for larger washers at bolted connections.
I've seen failures where plywood panels were not boundary nailed to the
mudsill causing overturning failure or shear failure in the panels.
Failure of the plywood panels and nailed connections are few and far between
(at least in the damage I've looked at). However, many of them can be traced
(I believe) to the use of sinkers rather than common nails - or improper
panel edge distance to the center of nail. The other types of panel damage
is over-nailing. These are more field quality control than code related
design issues.
Roger, I would not arbitrarily reduce the panels by 25% for another reason.
If you use an Rw of 8, you may have a point in zone 4 country.  However,
most engineers who I know use a more conservative Rw or 6 which equates to
18.3% base shear. Mind you, these are from plywood sheathed buildings - few
engineers are using gypsum as a shear element in zone 4 any longer. By using
an Rw of 6 you are essentially increasing the anticipated seismic load to
the panel by closer to 33% than 25%.
I think that most engineers are more conservative than UBC minimums. Because
of this I would say that we have instinctively been using more conservative
values as good engineering practice.

Dennis Wish PE
-----Original Message-----
From:	Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent:	Thursday, May 28, 1998 8:51 AM
To:	seaoc(--nospam--at)seaoc.org
Subject:	RE: Shear Wall Tests - Static vs. Dynami

Dennis,

The paper is not too long to fax (10 pages), but it is (horrors!)
*copyrighted*!  If there is a university nearby, their library might
have/get
the Journal (Journal of Structural Engineering, ASCE, June 1998, Vol. 124,
No. 6, pgs. 686 - 695).

Since a conclusion in the paper recommends a 25 percent *decrease* in the
UBC
allowable shear loads, I am going to implement this immediately.  If further
tests show that this reduction is excessive, then the design will be safe;
if
further testing shows that this reduction is not needed, the design will
still be safe.  It is a win-win situation.  On the other hand, if further
tests show that there should be a greater reduction in the allowable shear
loads, then I can say that I made use of the most recent and best
information
that I had.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

. > So, then the next question is why were the results different than those
. > done by APA in their Research Report 154 which justified the UBC
shearwall
. > values. This falls in line with Findleton's letter in the ICBO
. > publications "Building Standards" which Bill Allen Faxed to me.
. > Neither test was done cyclically.
. >
. > Is the ASCE report too long to fax? If it is, where can I obtain it?
. >
. > At what point would you revert to more conservative values such as the
. > ASCE's?
. >
. > Dennis
. >