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Re: Tension Tie of floor framing to masonry wall

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Dennis,
 
I have used this type of detail several times in exactly this condition.  I have used LTT19 and 20 and at times the PAI8 and 24 ties.  It has been successful with spacings at about 5' +/-.  Spacing has been determined by assuming a UDL pulling off the wall and thus anchoring that to the floor/roof.  Here in Canada we have to ensure that if the wall is a firewall, then we make sure that the floor/roof can rotate in such a way that the wall is not pulled down with any loss of floor/roof capacities.  I believe that these ties will not hamper such behaviours.
 
For joist parallel to the wall, I block out from the wall at tie spacings for a distance that I calculate is necessary to distribute the tie load into diaphragm shear.  I add MST, or similar, straps where necessary to extend the tie length.
 
The capacities available for the tie are determined by the masonry pull-out capacity in most cases.
 
I have also applied them to the sides of roof and floor truss/joists, but as close to the diaphragm as possible.
 
For retrofit cases that have space restrictions side-mounted are probably the easier to install.

Thor A Tandy P.Eng
Victoria BC
Canada
e-mail: vicpeng(--nospam--at)sprint.ca
----- Original Message -----
Sent: Monday, June 25, 2001 9:31 PM
Subject: Tension Tie of floor framing to masonry wall

I know this has been discussed a number of times, but I have not had time to search the archives. I am connecting a wood framed mezzanine to an 8-inch reinforced masonry wall via a 3x ledger. The CMU wall is reinforced with solid grouted cavities (as confirmed by the contractor).  I have to make the tensile tie of the framing to the wall and to avoid cross-grain bending of the 3x ledger (cross-grain failure).

Simpson shows an LTT19 nailed to the top of the joist and secured with a 5/8" threaded rod into a concrete wall with their ET Epoxy anchor. While Simpson provides values for tension in masonry, their literature for the LTT anchor only shows its use in concrete.

Considering this is a retrofit, it might be difficult to drill the hole
for the anchor because the "leg" of the LTT is short and the centerline
of the hole too close to the sheathing to get a drill bit comfortably in
place. This is my impression and it could be wrong. Has anyone had
experience in this type of connection?

Can I use the LTT flush nailed to the side of the joist and drilled
through the ledger to secure into the masonry with an epoxy anchor? I'm
sure this must be a fairly common detail and would appreciate it if I
can obtain a copy of a detail from another office familiar with this
(DWG please).

Some CMU information:
 
Only 7-feet of diaphragm tributary is connected the the wall - the rest
is bearing on interior stud bearing walls which are designed for shear.
The length of the ledger at the edge of the diaphragm is only 14-feet on
one wall and about 30-feet on the other wall (one side is open, the
fourth side is a wood stud wall).  The masonry wall is 8" with 12x18
pilasters at 20-feet on center - the mezzanine is not connected to the
roof. The 14-foot ledger is bolted to a wall that is about 80-feet long
and the 30-foot ledger connected to a cmu wall 160 feet long. The shear
contributed by the tributary area of the mezzanine connected to the
masonry wall is much less than 2% of the existing demand to be virtually
insignificant. The CMU walls are virtually solid (about 80% solid in the
long direction and 100% in the shorter direction).

While the lateral contribution of the mezzanine is insignificant, I
still have to consider the effect of the mezz to pound the wall if it
comes free. Therefore, I need to make the tension tie which I believe
still has to be equivalent to 200-plf or 30% of the tributary wall area
(at least it was in past codes). Can anyone clarify this for me to save
me a few minutes of searching the code?

Any suggestions for a tie connection would be greatly appreciated.

Regards,
Dennis S. Wish, PE
Structural Engineering Consultant
mailto:structures(--nospam--at)engineer.com
(208) 361-5447 E-Fax