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RE: Hardy Frame, between code changes

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Ernie, some good questions. I spoke with Gary Hardy today and discussed some
of the same issues with him. Please see my comments embedded in your text:

Dennis Wish PE
La Quinta, California
ICQ# 6110557

"Silence is the virtue of fools."
Francis Bacon

|-----Original Message-----
|From: ErnieNSE [mailto:ErnieNSE(--nospam--at)]
|Sent: Friday, March 27, 1998 10:22 PM
|To: seaoc(--nospam--at)
|Subject: Re: Hardy Frame, between code changes
|I saw a similar narrow shear wall type light gauge steel braced
|frame with a
|continuous wood header on top at a website but I forgot what brand
|it was and
|what the website was. It's got truss like diagonals between end vertical
|members. I don't know if it has ICBO or L.A. City approval.

I suspect you saw the Hardy Frame web site. I had seen it before as well,
and just did not take notice until now. I could not tell if the diagonal is
rigid, but believe it would need to be since it occures only in one

|There must be other similar products out there. My questions or doubts are:
|1. What seismic factor do we use. (Rw=? for braced frame?, for lightgage
|tension braced frame?, not specifically in the code so use Engineer's
|judgement?) Do we use the seimic factor for this wall line only or for the
|whole building or for this direction only?

Don't have an answer on this one, however, I would think the system is still
a boxed system. In a box system where plywood shearwalls are not used, the
Rw is equivalent to 6. I would think that this is adequate since we apply
the save Rw to steel stud construction which uses braced panels as an
alternative to plywood shearwalls.

|2. OK, if it's got approval, it passed some kind of test. But how will they
|perform in the long run, maybe 5, 10, 20 years from now. (Remember the
|continouous threaded rod anchor from foundation to third floor holdown that
|got loose?) How was the test conducted?, who conducted the test,
|what are the
|things to consider in determining if the product will meets its
|purpose, what
|is the passing criteria?

The only real question I would consider relevent is the differential
shrinkage in the wood compared to the steel under gravity loaded conditions.
I would doubt that there is sufficient shrinkage vertically since both
materials are under constant loading. This is not much different than having
steel columns in a stud wall supporting a beam perpendicular to a bearing
wall. I don't recall seeing the top of a double plate shrink away from the
top of beam elevations. I would think that this is insignificant.

|3. Do they need special inspection or structural observation to
|install. Even
|if we think they are too simple to install with a clear
|instructions from the
|manufacturer, we are not the ones to install them and you know
|what those guys
|out there are capable of screwing up, especially on a new product.

According to Gary Hardy, this system elimates the need for SO unless the
building official specifically requests it (or the EOR). The reason is that
there is no nail inspection to be done.
The frame resists uplift the same way as a shear wall - with conventional
Simpson PHD pre-deflected holddowns that screw into the vertical sides of
the frame. I have used these holddowns in both wood and steel and perfer
them to conventional HD's or HDA's. They do not have to be perfectly
centerend to work well, there is no need to worry about installing with
oversized washers and nuts in a tight space.
Hardy supplys all templates for the placement of the hold down anchors -
taking much of the guesswork out of the system.
The connection to the top plate is the same as I use for connecting wood
drag trusses to steel stud walls. I screw up through the top track into the
truss with as many #8 screws as is needed to gain the capacity I need. I
also use this method for connecting wood blocking to the top track of a
steel stud wall. It's much easier and a better connection that toe-nailing
blocking to a wood plate.
The best part of screwing the connections is that even a layperson can do
it. In our low income housing plans, the homeowner provides 40 hours per
week constructing their home. This is why we went to screw type
connections - the homeowner finds it much easier than swinging a hammer.

|4. We have to trust the  product's engineer's calculations, assumptions,
|loading conditions, member sizes, specifications and connections,
|etc. Because
|if something goes wrong, we cannot just blame the other engineer.
|we are the
|EOR you know. We have to review the product's calcs and drawings very

This is a great question and one that bothered me most of today. How do we
know that the testing proceedures followed are correct or adequate? I think
the answer is that ICBO has reviewed their data as did the City of Los
Angeles. I would assume if there was a question regarding the adequacy of
their research it would have come out from these groups.
This doesn't excuse the EOR of learning as much about the product as they
can and reading the ICBO reports. I do this often, because I found that most
suppliers and contractors use an ICBO report like a get out of jail card in
a Monopoly game.
For example, a contractor contacted me yesterday to substitute a Rawl
Injection Epoxy for the Simpson SET adhesive. The Rawl Epoxy is actually the
Sikadur Injection Epoxy. I had his supplier fax the ICBO report to me. The
report did not provide the answer I was looking for - namely the tensile
strength (working stress) value of a 7/8" diameter threaded rod embedded 5
1/2" into concrete - 2 1/2" from the edge of slab. Simpson provides the
reduction formulas based upon the edge distance.
I ended up calling Sika and talked to a service tech who was simply not
knowledgable enough to know that the capacity of the connection needed to be
reduced when installed closer than 11 inches from edge of slab. After about
20 minutes I decided that based on Sika's values as close as I could get
them, their Adhesive was equivalent to the Simpson ET adhesive NOT the SET
My client had to special order the SET.
My point is that no engineer should take the claims at face value. It's each
one or our responsibility to seek an understanding of the materials we use
in practice. Not really much different about the way we use computer
software. Do you assume that your analysis program is 100% correct?

|Only after these questions and concerns of mine are answered will
|I use these
|products with total peace of mind. In the meantime, I'll stick with plywood
|shear walls, steel columns with fixed base or steel rigid frames or braced
|Ernie Natividad

I'll second you there, Ernie! For the looks of it, the Hardy Frame is a good
product. I intend to do some serious learning about it because I would like
to see it work in these low income homes - saving the owners labor dollars
and at the same time improving the performance of the structure.