"J" bolts in fresh Concrete
Q_ed
[Q] Anyone have 1st hand knowledge of the 'holding/staying' power of :
a). pre_set "J" bolts in fresh concrete
vs
b) . pre_drilled, and, 'set', Anchor bolts ( expansion plug at hole
bottom )
Both "set" in 6000lb concrete slab, 6" deep, "spot" sub_foundation under
both.
I'm interested from the point of view of setting some steel support
columns
for a overhed steel beam, and , for the two columns of a 2_post auto
lift.
All 'above' require =firm= attachment to the concrete slab ...
non_loosening too mite be nice. :-)
The "Auto lift" guy says " ... drill, & use expansion bolts "
The Steel Fab guy says " ... sure, fine, swell, ... "J" bolts are good "
:-)
I do know that expansion bolts, holding 2-column 'auto_lifts',
=do= loosen, must be periodically re_torqued.
Not particularly "thrilled" with the loosening 'bit' ... suspect it
means "concrete powdering" in the drilled hole ... not nice.
I'd be grateful for any advise.
Ed Cook
Winchester VA
asf...@earthlink.net
the steel with the bolts. If you pull a j bolt out of concrete,
something is baddddd wrong! :) good luck.
Cecil
news:3A4E21...@shentel.net...
> "J" bolts vs Anchor bolts ... in concrete.
>
> [Q] Anyone have 1st hand knowledge of the 'holding/staying' power of :
>
> a). pre_set "J" bolts in fresh concrete
> vs
> b) . pre_drilled, and, 'set', Anchor bolts ( expansion plug at hole
> bottom )
I would go with J bolts set in wet concrete set to a depth of
about an inch from the bottom of the slab. I can't imagine
any stronger way.
gda...@aecconn.com
I can tell you that there are standards for the design of this stuff.
I'm an engineer and engineers don't just make up their recommendations,
they refer to standards. Unfortunately there are contractors out there
like the ones that have responded that don't mind shooting from the hip
on this stuff. I call it "the confidence that comes with ignorance".
First of all a J bolt has limited use. (I assume you mean a 1/2 inch or
5/8 bolt about 10 inches long with a 2 inch hook on it.) They are for
light weight low risk use, like mounting a cover over a pump on a
concret slab. If you are mounting a power lift, you need the help of
an engineer. I hope my next statement scares the hell out of all your
responents to date: Not only do you have to worry about the anchor
bolt pulling out but you have to worry whether or not the bolt is
sufficient to develop enough of the slab into providing resistance as
well. Many times a bolt will hold only to breakout out a 2 foot square
piece of concrete. So you just can't make up an answer. You have to
know what the load is. These two column lifters are usually designed
to be mounted on a 4 inch slab with expansion anchors. Good that you
have 6. Better if you put the bolts in when you pour the slab and tie
the bolts into some reinforcing steel. The standard I was referring to
is the CRSI (Concrete Reinforcing Steel Institute) design manual which
spells out standards for reinforced concrete (and anchor bolts). An
engineer will use this standard. And... the guy that says he would put
the anchor bolt in down to about 1 inch from the bottom of the slab
should know that reinforcing steel must be covered a minimum of 3
inches when next to soil (1 1/2inches if above grade)
Because this is a dynamic situation i.e. a lift that moves with a lot
of weight on it, you are going to need some safety factor. There is
protocol for that as well. Most of the time the lift manufacturers
will give you the data you need for the loads, but will not take any
responsibility for it. Get an engineer to help you, so that if you
have a car on a lift and someone backs another car into one of the
columns, you will have half a chance of avoiding a disaster.
As for whether or not wedge anchors or anchor bolts are better, anchor
bolts properly designed are always better. (You can expect a hook about
10 inches long instead of two and tied into reinforcing steel however).
If the concrete is already poured use an adequate expansion anchor
rather than cut out concrete to install the jbolts.
Retrofitting can be done with expansion/wedge/anchors or the newer
epoxy type installations providing that the loads are not exceeded for
that particular fastener and the slab can handle the load as well. I
prefer the epoxy anchors like those manufactered by Simpson. I trust
them over expansion anchors because they are more idiot proof. The
mfgs of the anchors publish the load capacities.
Good luck.
In article <3A4E21...@shentel.net>,
--
Glenn A. Davis, P.E.
www.aecconn.com/gad.html
gda...@aecconn.com
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res08hao
"Q_ed" <nan...@shentel.net> wrote in message
news:3A4E21...@shentel.net...
Fritz
place but using epoxy based anchors because the wedge anchors are pieces of
crap.
Now before any BS comes of this statement of epoxy vs wedge, I've already
performed pull tests on almost every kind of wedge vs Hilti 2 part epoxies
and the wedges WILL NOT perform as well. So there! And forget about the damn
glass vial epoxies, they're pieces of junk also.
I don't work for Hilti either. I do have 20 + years in industrial
construction though as a Union Ironworker.
Fritz