2 post lift pulled lags, what to do now?

[Crock]

Ok...to start off, it was totally my fault and a stupid mistake on my part. I bought a older Mohawk lift and picked away at the install over about a month. I had the cylinders rebuilt and bled the whole system. I had a problem with the raise switch sticking so I ordered a new switch. While I was waiting I gave it a fresh coat of paint and removed the the two top limit caps on each post to paint them too.
When the new switch came I was pretty excited to try lifting my car. Lifted my car about three feet and everything was really solid. The next day I lifted the car all the way up and since I forgot to replace the top limit caps, the top of the drivers side carriage came out and the car dropped about 1 1/2 ft on the drivers side until the carriage jammed against the post. We got the car down with some damage, but not too bad. It could have been way worse. I got the carriage back in the bearing track and everything looks ok, except the post lags pulled up about 1/2”.
I don’t know what to do from here. Do I pound them back down and re-torque or do I need to move the posts and drill new holes and use new lags?

 

[pattenp]

I wouldn't pound the lags back down. I would torque them where they are. A half inch isn't that much as long as they don't pull out anymore while being torque.

 

[Chevy-SS]

I would call a lift company, perhaps the manufacturer. They would have a tech line, and could likely get you back to 100% safe. You want that thing ROCK SOLID. You only get one life, and some people (working alone) have died slow, agonizing deaths when vehicles fall on them and they can't move.

 

[sberry]

Agree, see if they tighten securely.

 

[Crock]

Good idea. It called for 5” lags bolts and I used 6”, but still kinda nervous. I will see what Mohawk says.

 

[nadogail]

IMHO, Longer, Stronger & Deeper will be better.

But I will not argue with the Manufacturer's Tech Support.

 

[wssix99]

Good idea. It called for 5” lags bolts and I used 6”, but still kinda nervous. I will see what Mohawk says.

Then you are just fine to tighten them down as-is.

These bolts develop strength through a stress cone in the concrete:

Your lift has a spec, calling for a cone made by a 5" deep anchor. (Including a factor of safety.)

With your 6" bolts pulling out 1/2", you still have a 5.5" cone and are perfectly safe! (The holding power in the concrete is proportional to the surface area of that cone - so you develop exponentially more strength as you go deeper, due to the shape.) With the force you just put on them, they probably have quite a bite in the concrete, as well!

 

[sberry]

I agree, they are well bit, make sure the nut doesn't shank out, put a couple washers on them. Obviously the human factor trumps the mechanical one. Mohawk has a huge footprint. I saw one with the pads lodged on the frame, had a car on it, no bolts.

 

[theegovernor]

I am a lift installer. In the case of anchor pullout, I would recommend getting some grade 5 3/4 threaded rod and some wej it all weather inject tite epoxy. This combo when installed properly still meets inspection requirements

 

[wssix99]

I am a lift installer. In the case of anchor pullout, I would recommend getting some grade 5 3/4 threaded rod and some wej it all weather inject tite epoxy. This combo when installed properly still meets inspection requirements

Why would you recommend this when the OP still has (by far) sufficient embedment of the wedge anchors?

 

[Robert Haas]

you folks need to give some thought before offering advice on such an important issue.

Why would a properly torqued wedge anchor pull 1/2" ? How is it even possible?

Something had to give way. The tensile strength of the anchors themselves could not possibly have 1/2" of stretch in them, so what moved? If the concrete fractured there could be a whole different issue at play and something that would need to be inspected.


So how do you inspect it?

Sadly the only way possible is to disassemble and lift the column off the anchors and test the concretes integrity. A visual inspection might reveal spalling or cracking at the penetrations however that is not guaranteed. X Ray or ultrasound inspections of concrete up to 24" thick is possible but very expensive. A simple bore test where a small masonry drill (non percussion) is used to determine the density of the concrete near the existing penetrations would be valuable however it would take a deft and trained "hand" to evaluate the process.

I am a licensed general contractor with many years of experience in pouring slabs and using anchors and I would not be qualified to to give a clean bill of health for this situation.

One option would be to drill 4 new anchor locations in the base and and reinstall it with 8 evenly spaced anchors clocking 90 degrees from the original.


This is the internet and this advice is worth exactly what you paid for it.

 

[sberry]

I have installed a few of these bolts too, lots of them in nuke. With hoists they get installed every day by the thousands in common concrete, most of it wit little to no QC by common labor and cured in very uncontrolled environment.
I will agree they didn't stretch, would be worth a look to see if they tighten. If this was uber critical we would need on site engineer, testing and qc for every hole instead of the crews that often install these. Not all but often simply general labor with little to no real training other than a little hand to mouth or hand me down experience.

 

[sberry]

The economy was in the capper when I had mine done, I paid for install. The guy asked me all proud. How long you think I been doing this. I didn't answer, he said,, 6 months, my guess would have been 2 weeks. I mentioned to sales I had a pour over a pour, they were to include some longer bolts for the outside. They were not the least concerned with any of this.

 

[240sxguy]

How thick was the concrete? What are the odds the anchors went all the way through the slab? 6" seems pretty long.

 

[Robert Haas]

Look at these images and tell me what one was visible first?

 

[wssix99]

you folks need to give some thought before offering advice on such an important issue.

We did - and we also read the first post. The anchors took a dynamic impact beyond what they would see in regular use.

Sadly the only way possible is to disassemble and lift the column off the anchors and test the concretes integrity. A visual inspection might reveal spalling or cracking at the penetrations

This is a fair recommendation and would help confirm that the anchors just moved and didn't crack the cone.

however that is not guaranteed. X Ray or ultrasound inspections of concrete up to 24" thick is possible but very expensive. A simple bore test where a small masonry drill (non percussion) is used to determine the density of the concrete near the existing penetrations would be valuable however it would take a deft and trained "hand" to evaluate the process.

This shouldn't be necessary. If the thing moved 1/2" and the concrete cracked, it's going to be obvious at the surface or impossible to re-torque the bolt. If the hole is solid and there's no spaling then it's pretty certain things are fine.

... We also don't know what the torque was to begin with on the anchors. Some lifts specify very little and even then, the bolts can loosen over time or even move/loosen slightly with use.

 

[Robert Haas]

I honestly think that folks use wedge anchors with little to no understanding of the science or even the mechanical process they are designed to function in. Seeing people use rotary hammer drills improperly thus creating a non standard nor straight bore is troubling. Seeing wedge bolts driven into said bores and then tightened to full torque also is alarming.

Concrete is unlike a block of steel or metal, nor is it similar to wood or even resin. Concrete properly cured and reinforced with appropriate and consistent materials when poured has nearly zero compress-ability. That is the reason an anchor using a sacrificial wedge is so effective. The bolt pulling upward on the wedge achieves a near perfect platform to retain what ever is being attached. The reason being is the bolt is softer then the concrete by several factors. So a proper tension can be achieved that puts the bolt into enough tension to reach a yield point. Once it has reached that point further tightening would actually weaken the assembly even possibly cause a failure.

Clean straight bores using the correct equipment and using the correct techniques will achieve the desired results with the highest probability for a failure free life. ignore proper procedures and using shoddy or lazy procedures as has become the norm results in time bombs sitting in shops all over the world.

 

[Chuckster in NJ]

BEST ADVICE!........ CALL A PROFESSIONAL LIFT INSTALLER.


Your loss could be more than just financial.

 

[matt_i]

If the stud doesn't tighten right there, I'd keep pulling it up and go with the epoxy recommendation after throughly brushing and blowing out the hole.

Jib cranes rely on this same technology, its a high confidence setup because if the anchors in a jib crane fail some one's going to be very seriously injured to worse.

And they are all installed with epoxied anchors, pass proof tests (125% of rated) and are used for years on end.

For light duty stuff the wedge anchors are inexpensive and fast and make sense for many things. For systems when you are lifting overhead I would never go with the cheap + fast setup....

So why don't lift installers use epoxied anchors? I can think of 2 reasons. 1) they have to make 2 trips to the job...install one day...wait for epoxy to cure 24 hrs at 65F ambient, longer for colder conditions...before returning to apply final torque, makes the cost of the overall turnkey project higher....and 2) if the installer skips over brushing and blowing out the drilled holes multiple times to a superclean condition, the epoxy can have an installed strength lower than a wedge anchor. One can imagine pristine shop owners going nuts over an installer blowing out concrete dust from deep holes.

The suggestion to move over, drill new holes, is a poor one in my opinion. Wedge anchors are already trying to break out a cone and give them what amounts to a stress-riser (like a nearby expansion joint, void from casting or a previously drilled hole) and its a fast path to a big chip of concrete now separated and an anchor that has zero strength.

 

[leog]

Installed numerous anchors in a nuclear plant , to approved procedures, I have to agree with Mr. Haas how can we provide advice we new are not fully aware of all conditions. Pulling was reason for rejection by QC for any install. Ours were ferociously inspected after seismic events (earthquakes) and few were ever found to have failed. Should pull.

leog

 

[Wrench97]

How thick is the concrete you put 6" anchors in?

 

[sberry]

At the nuke we hit rods all the time, that was a challenge. The "installer" on mine drilled some crooked. Fortunately they were on the inside.

 

[wssix99]

So why don't lift installers use epoxied anchors?

They aren't fault tolerant like wedge anchors. When a wedge anchor bites, you get the full strength of the concrete because it bites at the bottom. (See picture above.) ... Or, the thing slips out and one knows clearly there is a problem.

When the adhesive anchors aren't installed properly and the lower part of the bolt looses it's bond, then the stress cone is smaller and the strength is much less. One only finds this out when it's too late...

^ Using epoxy anchors in critical installations takes training and a lot of careful work.

 

[ard]

Id start over.

Clearly needs a new garage....