I've done a few tilt-up retrofitting per div. 91 & 95.
Here is some of my experience in response to your questions.
1. I doubled up sub-purlins as you have by nailing a new one to the
existing. I thought of using A35 or even glue to connect the new 2x
to plywood, but I abandoned the idea because I couldn't
decide how effective A35 would be using less than ½" long nail or
screws. Obviously I couldn't use longer nails to prevent damaging the
roof and I didn't have enough info. about glue. So, I specified
that each sub-purlin which receives wall anchor to be placed at the
panel joint which can easily be identified in the f field, since there
are 2 rows of panel edge nailing at that location. By doing this you
can use a higher shear value than 250#/ft which the code allows.
2. I usually carry the continuity tie across the building unless there are
some large openings wider than 24 or 32 feet and there are no continuous
In the direction parallel to girders, I use the girder as continuous
ties up to 48 ft spacing.
3. I've used wall anchors similar to holdowns that I've specially designed
for this type of work which are fabricated by LA City certified shops
on job to job basis. I couldn't use the propriety holdowns which were
available at the time, right after the Northridge Earthquake because
they had excessive deflection which was not
acceptable to LA City.Some contractors still use our home made holdowns.
I am told they are less expensive.
If the distance from the base of the holdown to the wall was small, I
specified double nuts but if it was more than 3" to 4" I specified wood
Anchor bolts are designed for tension, the compression force will not
affect the bolt if the framing is tight which is a requirement for
retrofitting but if there is any uncertainty you can calculate the
length of the bolt, which can take compression before buckling.
4. I don't think the City or the County would accept that logic. That sounds
like delayed design and incomplete work and I wouldn't want to be
responsible for that kind of retrofitting. As a general rule it is
easier to do retrofitting if the new roofing could be done at the same
J. Karim Hosseinzadeh
JAMKAR ENGINEERING, INC. Tel. 949 250 0522
Newport Beach, California Fax 949 250 1527
----- Original Message -----
From: Jeff Coronado <"jcse(--nospam--at)flash.net"@flash.net>
Sent: Thursday, May 04, 2000 7:15 AM
Subject: TILT UP RETROFITS
> For those of you who do a fair amount of LA City Division 91 and LA
> County Chapter 95 work:
> 1. We have typically doubled up the existing subpurlins that are to be
> anchored with new full length 2x subpurlins. The 2-2x subpurlins are
> supported at each end with a new hanger. The new 2-2x is attached to
> the diaphragm with A35 clips. I would be curious to know what some
> other offices are doing.
> 2. Do you carry the building continuity ties through the full length of
> the building or do you stop them by nesting subdiaphragms until a full
> width subdiaphragm can be justified?
> 3. Do you specify an arbitrary minimum end distance between the holdown
> and the end of the wood member even though the holdown is self-jigging?
> 4. A contractor has told me that what he sees some engineers do to
> reduce or eliminate subpurlin continuity ties is to reduce the depth of
> the subdiaphragm by increasing the subpurlin nailing at the time of the
> next reroof. Is this common practice?
> Thanks for the assistance,
> Jeff Coronado, S.E.
> West Covina, CA