Plumbing a 12 ft. steel colum using shims

Threaded rod is inserted into the concrete while wet. After curing, hex nuts are used on either side of the base plate to level the device. Then grout under the base plate.

This method works very well. Eliminates settling and is very strong. Do not embed any shims in concrete it will not work if you really need the jib to be plumb.

Mike

Shims are not embedded in grout. Grout is placed around shims. While holding the column vertical, pack in the grout all around the shims. Best of all methods!

This is a great method when working above "perma frost" to anchor a piece of equipment like a pump or tank but a jib could flex and loosen the anchors. Large threaded rod is the most secure method.

Place a pack of shims on the concrete under the center of the baseplate. Place column and baseplate over the anchor bolts, resting on the shims. Brace the column in two perpendicular directions using 2x4 lumber or cables. Plumb the column and fasten the braces so column remains plumb while you work. Now grout. Let dry. Tighten nuts on anchor bolts. Remove braces. Bob's your uncle.

Have a look here, there is a lot of discussion including my own comments from days of installing Roll Formers, shims are a pain, use jack screws.

http://cr4.globalspec.com/thread/25730#newcomments

Try to express yourself in a clear, concise way so that we can all understand what you are attempting to say.

So far as I am concerned, when you are installing a single column, not tied to anything else, a central shim and column bracing are by far the easiest and best method to use.

I have put up quite a few light poles, posts or whatever you might want to call them and the one thing that I can say is this: make sure the bolts that are going to be on the bottom of the plate (on the bottom of the column) are all level. Check them left to right and then diagonally...

Next, as it is a column and not a light post, I would look for a few steel shims that could be used to "fine tune" as needed after the bolt pattern had been torqued down.

Mortar, would be the filler that would be put in after everything is done... Just make sure to clean out under the column, 'k? You do not want to have any extra filler in there that can possibly cause issues later on - vacuum it, blow it whatever and then do your mortar thing. Want it to look cool? Build a wooden trough around the base of the column (about 1-1 1/2 inches wider on each side) and then pour your grout in. After letting it set for awhile, take the wood off and then use a trowel to put a 45degree edge on each side. This looks really, really cool indeed. They are doing it around all of the columns and supports where I am working (currently building a power plant). After you have cut the 45's, place some plastic and 2x4's over the edges so the mortar can cure and hold its shape. Leave it on for the remainder of the day and then uyou will be good to go.

Good luck carina 01

Ferris

Thanks for the advice:

What I'm installing is a 3 ton jib boom. It sits on a 12 ft. 18" dia.column(mast)

It has a 4 ft. dia. base plate which is 1/4 " thick.

It will be placed on top of a 8ft square block of concrete that is 4 ft. high.

12 bolts 3 ft. long will be cast into the concrete in a 42" dia. circle.

Questions:

1. What do you use for shims? Do you place them near the bolts? I assume you start with 1" shims all the way around and increase as necessary to plumb the column?

2. Do you hand tighten the nuts before grouting? Do you wait 24 hrs to torque the nuts after the grout has set?

3. One person recommended that I coat the bottom of the base plate with roofing tar(compound) before erecting to protect it from rust and corrosion.

Carina01

Did you say 1/4" thick? That doesn't seem adequate to transfer moment at the base. Suggest you have it checked by a structural engineer before proceeding.

Please see post #1. You must allow the "anchor bolts" to cure before applying the loading. If you follow the correct procedure there is no need to worry about the grout as it has no structural purpose. However, if you insist on depending on the grout to carry the load, you are going to be sorry. Your crane will fall over.

If the grout has no structural purpose, then why use it? Grout has a compressive strength at least as high or higher than the concrete it sits on, so it does have a purpose.

Over the last fifty years or so, I have designed a few jib cranes. All relied on grout to transfer the compressive stresses to the foundation. So far as I know, none have failed so far. Tensile forces, needless to say, must be carried by the anchor bolts. The best anchor bolts are threaded rods with double nut and washer buried in the concrete. The anchor bolts should be firmly held in place with templates before pouring concrete around them.

In the present case, the column is 18" in diameter. The baseplate is 48" in diameter by 1/4" thick. I don't know the size of the anchor bolts, but these proportions are clearly wrong! The diameter is excessive and the thickness is inadequate. It should be reviewed by someone who knows what the heck he is doing.

"I don't know the size of the anchor bolts"

Exactly or even if there are any anchor bolts. Please don't reply to me as I do not have the information either. Suggest you reply to the OP. Maybe he knows. I have unsubscribed from this thread.

The grout does its job and just makes the installation look really, really bitchin'

Hello carina01,

I found the L.K. Goodwin Co. FS300 Base Plate Mounted 3 Ton Capacity Jib Crane on the Internet. This seems to be about the size you are talking about and I note that the base plate is reinforced with six gusset plates.

1. If you use leveling nuts under the base plate, you would not use shims at all.

2. Select three bolts 120 degrees apart (a tripod) for leveling the base plate. Mark the bolts with chalk for easy identification. Screw the other nine nuts a little below the underside of base plate so they don't get in the way. Then set the mast on top so that the holes match with the bolts. Place the upper nuts on the three bolts with leveling nuts and tighten with a wrench. Make sure the mast is plumb, then tighten the remaining nine bottom nuts up to the underside of base plate to a snug fit. Place upper nuts and tighten with a wrench.

Now you are ready to grout. Use a non-shrink dry pack grout placed in accordance with the manufacturer's recommendations.

3. Roofing tar should not be used under the base plate. It would compromise the bearing of grout against steel. It is normal practice to leave steel surfaces in contact with concrete uncoated.

I trust that helps.

The plans are just about identical.

The nuts (12 ) that are provided are quite thick (I'm at home so I can't measure them but I think they are about 2" thick).

They are provided with lock washers.

I would think I could get thinner nuts (maybe 3/4" to 1" thick) to put on the bottom.

This would keep me close to 1" for the grout.

What do you think?

Carina01

Thanks for the info on roofing compound.

A thinner bottom nut would be okay. It isn't carrying much load. If necessary, you could increase the grout thickness a bit. It is common practice to use 1.5" thick grout under column base plates. I don't think there should be a problem with 2" if you use a non-shrink grout.

You know honestly, I watched some guys on another crew putting up Iron and they struggled at it... As we are electricians, this is not a real surprise - we are not Iron dogs that are used to it... To answer your question, they used (at first) a half inch shim on each side (I regress, there was only about an inch-an inch and a half between the bottom of the column and the top of the concrete) and then stacked more in place to suit their needs. I have watched the Iron workers on the job do the same thing... You build it up accordingly

1 Level the bolts before the steel is erected (remember - side to side and then in a cross pattern in order to 100% sure of your level)-these would be the bottom bolts...

2 Set you steel and then place your bolts. DO not torque. Hand tight at first

3 Get a LONG level (like a 4' level in order to good a GOOD read on your plumb) and then check all four sides for level; especially, checking up high where the plumb is most important, not to mention most obvious.

4 Set your shims in place and add in increments on the sides as needed. You are going to need a pretty heavy duty hitting utensil to do the blasting into place of the shims as they get tighter and tighter (a 22 ounce hammer won't cut it.)

5 When you are happy with your plumb, I am hoping that you are going to have enough threads on top of the plate, get a lock washer in place and then 2 nuts for each of the "bolts", first tighten up the bottom bolt and then get a wrench that can be blasted by the hemmer mentioned above (they make 'em with a box end and a SOLID rectangular bottom that can be blasted whatever size hammer you preference) and then beat the upper bolts into place so that they are jammed in and will not be moving AT ALL

Again, goodluck with my limited info... Stay safe where Gloves and eye protection

Ferris

I have a 20' jib boom in my shop that is probably the best thing I ever installed. I would advise against using nuts on the bottom of the base plate but rather shim the plate level and then pull down snuggly, grout with a non shrinking grout and after grout has set tighten the base plate tight so that the load is spread out. I would also suggest using stainless steel shim material. I have always been under the impression that this was the proper way to install a column and it has proven to work for me for many years. If you use nuts on the under side of the base plate it will be easier to level but all of the load will be on the nuts and not on the grout as it should be. I think some states have codes that will not allow nuts to be used under a base plate. I worked on the construction of a new paper machine in Texas a few years back and and we were not allowed to use nuts underneath the many hundreds of columns we installed. I was under the impression that it was in the industrial building code there although I could be wrong.

pipewelder

"all of the load will be on the nuts and not on the grout as it should be"

Not true. Once the grout gains strength (after 7 days it should have 60% of it's 28 day compressive strength) it will take the load.

Please do not load the crane early until said grout has achieved strength. Shims can also share the load so use them too.

It can be done either way. My first choice was a steel shim centered under the mast because, in the case of building columns, that seems to be the choice of the majority of steelworkers I have encountered. Most do not like leveling nuts. With building columns, the tops of columns are tied together and the structure is cable braced while plumbing the columns. That was why I suggested temporary braces for the mast while plumbing.

I agree that each nut under the plate tends to act like a "hard spot" trying to hog the load, but if the grout is non-shrink or even expansive, I think there will be a satisfactory distribution of compression under the plate.

By the way, the Goodwin crane which I found on the internet has 12 bolts of 1.25" diameter. According to my steel handbook, the nut depth is 1 ³/₃₂, so I don't think a reduction in nut thickness is necessary or advisable.

I found the same drawing when I designed the crane in my shop. I used it to get the basic idea but my crane is a 2 ton with a 20 ft' beam and a 16" pipe pedestal. the beam on my crane is a 15' off the shop floor. rather than having an "under-slung" so to speak gusset I utilized a cable and turn buckle on the upper side of the beam. The foundation on my crane is 6'x 6' wide x 6' deep. One foot from the bottom of the foundation I set a 48" wide x 1" thick octagon base plate that matches the base plate on my pedestal base with (8) 2" OD 7' long threaded rods welded into it and a double 3/4" re bar mat on 12" centers attached. Also the footer re bar for my shop perimeter foundation is tied into 3 of the threaded rods on the back side and I used 10' hair pin re bars around the other threaded rods that radiate out into a 5" thick fiber reinforced floor slab. The base plate on my pedestal is reinforced with a (8)1" thick gusset plates 30" high welded in line with each bolt hole. Now I am not saying this is the proper way to do this and do not recommend my design to anyone else. This is just the way I did it and what I feel comfortable with. I am very careful on who I will let operate the crane and how it is loaded. Because it has been so helpful in my work I really can't afford to loose it because some idiot overloaded it. Although I have had 2 tons of load on the crane I do not routinely try and test it with this kind of load way out on the 20 ft beam. I think it is a must to use common since with this sort of thing.

pipewelder

I am not plumber expert but I want to participate this forum not to give an advice but to pick up some ideas from the other guests,and luckily I got some ideas.thank you for open up this topic on this forum.

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