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RE: Hold-down eccentricity

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Seems this would add support to Simpson's claim that the "system" performed
better than the sum of its parts. What do you think?


-----Original Message-----
From: RShreenan(--nospam--at) [mailto:RShreenan(--nospam--at)]
Sent: Thursday, February 17, 2000 9:03 PM
To: seaint(--nospam--at)
Subject: Hold-down eccentricity


I recently attended a techinical seminar by USP Lumber Connectors on shear
wall cyclic testing on various " site-built " shear walls with numerous
of commonly used hold- down connectors.

The tests were done at UC Irvine under the direction EQE International.  Los
Angeles City shear wall testing was also done there.  The wall panel,
hold-downs and post configurations were selected to accentuate performance
the hold-hardware.

The  results were interesting in that out of 27 tests to plywood fastening
failure, only one 4 x 4 post broke and that was due to a natural defect in
the wood ( a knot ).  The posts were D.F. Larch #1.  Calculated bending and
tension interaction indicated gross inadequacy in all samples.  Anchor bolts
were also over stressed but there was no sill plate failure

The maximum deflection of one 2:1 aspect ratio shear wall was 3/4" due
primarily to the crushing of the sill plate (3/8").  All groups of wall
panels achieved UBC allowable shear values for the plywood and fasteners
prior to reaching yield limit state or the code allowed drift.

Perhaps one way to reduce deflection in a shear panel that has large axial
post loads due to seismic is to put a galvanized light gauge, post sized
plate on the bottom and set the post down on the concrete.  Install the sill
plate  between the end posts instead of under them.

Ray Shreenan