Concrete anchor help! (1 Viewer)

[MrMoMo]

Ok folks, I need some wisdom here. Installed a hoist in my garage and I am really having trouble with the anchor bolts. I have 5 anchor bolts per hoist foot - hoist instructions say to torque them to 125 ft lb. I'm having trouble getting them to 60 ft/lb, and I just pulled one all the way through... Holes are the correct size (3/4"). They just seem to pull up, they are not rotating, just continually moving up (some of them are working properly, but 3 of them I really don't feel comfortable with. The holes are drilled all the way through the concrete, which in some places is about 8" thick, other places its only about 4" thick. Hoist stated it needs 3-4", so I have enough.

My question is - why are they doing this - and how do I fix it? I don't want to put my cruiser on the hoist and destry everything in my garage... I really want to get this done ASAP so I can install my OME the easy way!!!

Thanks!

Oh, and what is the reccomended method for getting out old anchors - so I can make them all work, instead of just some of them (don't say cut 'em off with a torch - I really don't want to do that)

 

[Capt. Jim]

Couple questions Bruce:

How old is the concrete that the bolts are pulling through?

What type of bolts are you using? Expansion bolts? Lags?

BTW, 3" to 4" thick concrete seems too thin for the concrete slab beneath your lift posts.

 

[wfd175]

sorry for being the devils advocate

Sounds like the concrete has a little too much air entrainment for the anchors too work. It may be too brittle, who really knows. You're talking about some serious point loads here.

When you say hoist I'm presume your talking about a lift. 2 post or 4? I'd be more the leary installing a 2 post lift on un-tested garage floor. Espescially if it's only 3" thick. Depend on the base course, you possibly could have air voids etc.. underneath. Who knows? Is this a residential garage?

Since you're dealing with a pre-manufactured hoist?, I'd contact the manu. about the installation problems.

Some applications can use an epoxy anchor

Like thisWilliams Form Engineering Corp. - Wil-Bond Epoxy Concrete Anchor System

Unfortunately, the concrete may not have the compressive strength to handle the loading of a hoist. Are there any other mounting options available?

A core sample from a local engineering company is probably a good idea at this point to verify if the concrete is able to handle the load. The fact that the anchors are not working correctly could be a sign of a larger problem with the floor. Not that it doesnt' function perfectly to park cars on.

I'd hate to see something bad happen.

 

[osagecruiser]

hilti epoxy anchors....basically epoxy all thread into the concrete and add nuts and washers....i am sure anchoring the lift is to stabilizer the lift....4 inch concrete should be plenty for the lift and anything you put on it....the sky is not falling!...i have had trouble with expansion anchors in new concrete 10 " thick....good luck

osagecruiser

 

[Toyo FJ40]

I have an 9000lb 2 post Atlas lift and it said 4" concrete was fine. I put it on a 6" slab of 4000psi concrete and had 2 of the anchors pull up about an inch with torquing it to 90 pounds (what Atlas calls for) The problem was even though they say drill down 4 inches by the time the anchor's collar pulls tight it's lifted an inch. I drilled the rest at 5" and then it was fine. Did your anchor pull out? If it did did the steel collar pull through? If the ring is still on the bolt I would think that maybe your hole was drilled too big. I would look into the epoxy system, it can be done in place without moving the lift and should be strong enough to get the torque you need (125 pounds sounds high but mine had 6 bolts per post)

Kevin

 

[3_puppies]

if it were me, I'd cut out the section of concrete, at least 2 times you footprint or more, and dig down and make a nice footing, with "J" type anchors, then fill the rest up and level off. plenty of rebar also!

having a rig up on a lift and one of the posts start to lean over is a scary event.

happened to a friend back in the early 90's, thankfully no one was hurt and no damage, the lift was in for over a year before this happened, same thing the anchors were pulling thru the concrete floor.

 

[Capt. Jim]

I'm with 3-Pups above. A lot more must be taken into consideration other than the # of bolts and thickness of the concrete at the bearing point.

 

[Toyo FJ40]

On my lift they said not to use the L type anchors. I asked about it and they said because of the difficulty lifting a post on to it. I think it has more to do with the dimensions not being exact. you assemble the lift then drill the holes when it's plumb. With it installed mine's almost a 1/2" more between the posts because of the crossbar than the specs call for and both posts are plumb.

 

[bkfj40]

L type anchors are becoming a thing of the past. In testing scenarios, even with the L, the anchors are pulling up and out. This has been confirmed during high wind events as well. Most structural engineers (including myself) now specify anchor rods which is threaded rod with double nuts on the bottom and the plate between the nuts. This provides adequate prevention against pullout.

With your scenario, I would be using epoxy anchors as mentioned above. You will need to refer to the manufacturer's guidelines though as the hole has to be a certain size. Make sure you clean out the hole thoroughly to get the proper bond. Simpson Strong-Tie and Hilti both have epoxy anchors as do other manufacturers.

You should be refering to the anchor manufacturer for the maximum torque on the bolts. You didn't mention in your original message, but I can check when I'm at work next week on the maximum torque for the size of anchor bolt you're using and the max torque.

bk

 

[MrMoMo]

Thanks for all the replies guys.... The hoist manuf. is the one that states 125 ft/lb, and they only require 3 to 4" of concrete. I have 8" under one post, and about 5-6" under the other post. When the anchors pull through, (expansion type anchor) they leave behind the ring, and just pull through it. A Mech eng. buddy of mine did some calculations for me and said that the absolute minimum would be 28ft/lb, but there is a factor of safety (obviously) which is usually 4x, He said he would feel more comfortable if they are at least 60 ft/lb. The hoist is a 2 post, and it is a base plate hoist - so there is no top plate to stop the posts leaning in towards each other - but I am going to put one on!! I am also going to attach the tops of the posts to a cross beam in my garage - it's made of four 2x12's, so that should help stabilize it as well. This hoist is going in somewhat temporarily, as I am planning on a new floor in the spring - mine is not in the greatest of shapes. I managed to find some concrete adhesive (for anchor bolts) and I pulled the worst 3 bolts out (none of them got anywhere near 125 ft lb) I coated them with adhesive and pumped the hole with adhiesive, pushed them back in and I am going to wait 48 hrs before torquing them. If I can get them all to at least 60 ft/lb, and attach the tops of the posts -I'll be comfortable enough to operate it for the next few months until spring. (I'll re-check torque frequently!)

When I re-install it I am not going to use this type of anchor - and I will pour a deeper section where it is anchored. (8" at least) These anchors are set in holes drilled all the way through the concrete, the next ones will be glued in, in holes that don't go all the way through. And yes, Toyo FJ40 - you are right, it would not be fun to try to lift a post over existing studs! (especially when you only have about 4" clearance to the ceiling!

Thanks guys!

 

[Koffer]

I know when I got my lift there was a "big typo" on the install instructions that came with it to the point when I picked it up they had notes taped all over it saying not to tighten the lags to the 125#s listed in the book with it . It was more like 80# or something.
sound like you got it worked out

 

[MrMoMo]

WOW that concrete glue is the shiznit!! I think I'm going to pull the studs that don't have it and glue them all in!! amazing strength. All the ones I put the glue on I easily got to 80 ft/lb I will definately use that glue again when I re-do the floor and re-mount the hoist!! Thanks again for the help guys!

 

[MrMoMo]

Thanks guys!! it's working!

 

[Michael Hanson]

After 25 plus years of building I always engineered the slab Before we installed the lifts or heavy comercial equipment.That being said I would not trust the epoxy method. I would dig out the slab and put in the proper rebar,footings and beams and p.s.i. concrete.I know this is expensive but whats your life worth? This is only a free opinion. Mike

 

[MrMoMo]

That is what will be happening in the spring - I'll feel much more comfortable when that is done!

 

[sandcruiser]

good work on getting that in, What did you end up doing on the top to stabilize?