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Re: Expansion Anchors in Masonry

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FredT5(--nospam--at)aol.com wrote:

> Some expansion anchors have slipped right out of their holes in past
> earthquakes.....  I am glad to see
> ICBO adopt a go slow approach on approving building systems such as these
> which appear to be quite sensitive to cyclic loading. They have learned their
> lessons from the Northridge Earthquake.
> Fred Turner

I am not advocating the immediate approval of expansion bolts for seismic loads,
however, I must say that one of the lesson I learned from the Northridge
earthquake from repeated observations is that standard "J" bolts cast in concrete
pull out during seismic loads also.  Based on visible failures, I am not sure
that cast-in place bolts do any better than expansion bolts.  There are many
quality control procedures that must be followed to get proper performance from
standard cast-in-place bolts.  Many of the "J" bolts I saw fail were very close
to an edge, or had poor consolidation right around the bolt.  Properly designed
and installed, I suspect that both types of bolts will perform properly.  But we
do need some test data to back up my suspicions.

Lynn