There was discussion recently on one of the lists I read about
installation of lifts, maybe it was this list.
In my dad's shop he has 2 small lifts and one larger lift, all of them
are cantilevered 2-post lifts. (He said the larger lift is rated for
16,000 pounds). He has been in business for over 50 years, and bought
an existing building to get started, which he says was originally part
of a cotton gin. He has rebuilt the building itself twice since then,
once because of a fire, but using the original floor slab. He noticed
that his bigger lift was pulling the bolts out of the floor so he
decided to remove a section of his slab and repour it.
I happened to be there last weekend when they sawcut out the section of
floor slab. The old slab was about 5" thick, with no reinforcing of any
kind in it. 24 hours later he had his new slab in place. I didn't find
out what reinforcing he put in it but they did reinforce it. They
poured a thicker slab and thickened the sections under the lift poles
even more. They used wedge bolts to install the lift originally, and
when they broke out the concrete it liberated some of the bolts. I
measured them and they didn't extend far enough into the slab for proper
anchorage.
In my business I get to see the latest bolts from Hilti, Simpson,
Philips and Powers, so I recommended that he use a threaded bolt such as
the Simpson Titen. These look like a tapcon concrete anchor, but much
larger. I called him today and he said he got framework of the lift
reinstalled today. They still have to run the cables and connect the
hydraulics, and install the cantilevered arms. I told him to test it by
putting a truck in there and picking up the front end of it by using
just the front arms and not having any of the load on the back arms.
This would put the most pullout on the anchor bolts as a test.
Whether you use the old type wedge bolts or the newer anchors such as
the threaded Simpson Titen, they have to extend far enough into the
concrete to be effective. A large anchor just 2" or 3" into the
concrete will not get its full capacity and will fail by pulling a chunk
of concrete out right at the anchor. With that same style anchor
extended 5" or more into the concrete and it will get a lot more pullout
capacity. I was looking at manufacturer's specs for some anchors and a
properly installed 3/4" diameter wedge bolt should have a pullout
capacity at failure of over 15,000 pounds. If you use the threaded
anchors then you may have to use one size smaller so that the threads
will fit through the holes in your base plates. The manufacturer's
specified capacity for the 5/8" diameter Titen at failure is a little
bit above the capacity of the larger 3/4" diameter wedge bolt. (If
anybody out there is trying to engineer their own connection, these
anchors are typically used with a factor of safety of 4, so the
allowable tension on the anchor is closer to 4,000 pounds each.)
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