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Structure with no anchor bolts

Structure with no anchor bolts

Structure with no anchor bolts


I work for a mechanical company that produces recycling equipment. A coworker of mine designed a support frame for a compressor and asked me if there was any code that allows him to build it without anchor bolts. He wants to know this because the client will be relocating this equipment from time to time.

The structure will be located in seismic zone 4. It is about 10 feet tall and 5 feet width. Located inside a building warehouse.

Since I'm only just an EIT I don't know what code would say, but from my general knowledge, I would say that as long as the uplifting force on any side of the columns doesn't experience full tension it, it will not overturn. However, There is nothing to hold the structure in place due to shear... so the structure would be able to move itself during a lateral load.

If I left any info out of the picture, feel free to drop a line and I'll get back to it asap.


RE: Structure with no anchor bolts

Compressors and such tend to vibrate, and will dance around on the floor if they're not tied down.


Mike Halloran
Pembroke Pines, FL, USA

RE: Structure with no anchor bolts

Look at ASCE 7, chapter 13. You are definitely required to anchor it.  

RE: Structure with no anchor bolts

If it operating equipment, it can be expected to move or "walk" around without any lateral restraint. Recycling equipment can be extremely unpredictable and possibly violent, depending on the process.

The equipment is normally developed and pre-tested using a mounting that is secure. Without a proper secure mounting the maintenance could be high and the reliability low. Any responsible manufacturer should supply mounting/hold-down information including bolt patterns, suggested weld points and applied loads from the equipment.


Engineer and international traveler interested in construction techniques, problems and proper design.

RE: Structure with no anchor bolts

We do quite a bit of equipment anchorage in our office and in a high seismic zone you will almost always need anchor bolts to resist shear and or tension.

Depending on the weight of your compressor it is possible that there is no uplift but I doubt it with 10' x 5' dimensions.

I would advise that anchor bolts be used.

There are anchors that allow easier replacement of equipment - such as mechanical anchors.


RE: Structure with no anchor bolts

If you don't "nail" it down - just say good-bye to it!!

RE: Structure with no anchor bolts

OSHA requires at least 4 anchor bolts for "columns" and at least 2 anchor bolts for "posts".  OSHA defines a post as a vertical member supporting 300 pounds or less; any vertical members with loads exceeding 300 pounds are defined as columns.

RE: Structure with no anchor bolts

Tell me how the bags of stuff suspended from cantilevered hoists don't produce an overturning moment.


Mike Halloran
Pembroke Pines, FL, USA

RE: Structure with no anchor bolts

Hilti came about for this exact reason.  Bolt it down and move on with life.  When they want to move, get out the torch and all will be well.

RE: Structure with no anchor bolts

JeffLam: as a side note, some of us here are not male.  Just a heads up.

I'd really suggest you draw yourself a basic free body diagram on this.  And, only being an EIT is no reason to not know the code! It's great bedtime reading material.

RE: Structure with no anchor bolts

Ignoring that last comment... bigsmile ...

Just tell the owner that it's OK by the code for him to move the equipment, but it is not OK by the code for the equipment to move itself.  We like to think that we are smarter than the machines.

Mike McCann
MMC Engineering

RE: Structure with no anchor bolts

Most codes and AHJ's will require that you secure the type of equipment you showed against overturning and moving laterally on the floor, with some FoS.  You potentially have vibrating equipment which could cause the frame to walk around, a lateral shearing load btwn. the bearing pads and the conc. slab.  You certainly have to consider earthquake loading and the various masses within your structural frame, both lateral and overturning.  And, you have the overturning moments from the lifting booms, and I'd consider both operated at the same time.  You could apply counterweights to the back side of the frame to balance this overturning.  They should be low on the framework to minimize their EQ affect, and of course, they add to the difficulty of relocating the entire frame, as you said you were want to do.  If you could relocate the two booms, one to each end of the structural framework you would lessen the overturning problem.  If you can limit the primary design bolt loads to shear btwn. the bearing pads and the conc. slab, low or no bolt tension, you might get by with expansion shields and bolts, self tapping bolts or epoxied bolts.  All of which are easier to install and remove when you want to move the equipment.

RE: Structure with no anchor bolts

Thanks for all your advice. Structure would be attached to skid mounts and I'm guessing that those skid mounts are anchored to the concrete.

@slta, I am familiar with some code such as ASCE and AISC, however not familiar with every type of structure... I have a grasp of the general aspect of what would be needed to stabilize a structure of this sort (stated above) such as a low center of gravity to prevent overturn and etc.

We contacted the client and was able to conclude that he would be responsible for hiring a professional engineering firm to handle this sort of business.
Our company is mostly manufacturing so I assume we were responsible for the production end. Overall I appreciate all of your input since I'm a structural EIT still learning and trying to grow everyday!

RE: Structure with no anchor bolts

Oh geez, Mike, yer in the gutter again...  

RE: Structure with no anchor bolts

No guessing is allowed here.  You have to know how it's going to be done and what the loads are or you don't know how to design your structural framework and skids.  And, if skids are what the client wants, they should be your design, so they can be properly integrated with your frame and equipment.  The client may install it, but you even recommend on that account too, given an assumed slab thickness and conc. strength.  Then let the client take it from there and make the required adjustments.  You better be able to show that the bolts pulled out of the conc. or sheared off below your skids if anything goes wrong or your company might still be footing the bill.  What they don't teach pre EIT is that in your designing you must be careful to protect yourself, your product, your company from what other darn fools might do to it.  And, how quickly an attorney will have you spending more than that piece of equipment is worth, to defend your design and equipment, and prove that the failure was not your fault.  Be careful and thorough in your design effort.

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