Odd fabric building design with hoist

[Preeng1]

Hello:

I apologize in advance if my description is confusing:


I have a customer who wants us to erect a 50' x 325' x 18' arch shaped fabric building for them which has a concrete ballast block foundation system 4' high x 325' on one side (back wall) and each 50' end as the building has to be erected on wooden site mats at an oilfield site in northern B.C. and relocated within 4 to 5 months. No pilings or penetration of the site mats allowed.

The other side of the building is 13 doorways 25' wide for vehicle access and is to be framed using steel columns with I beam on top. The columns are 13' high and made from 6" x 6" x 3/8" wall hollow section and are 25' oc Each column has a plate welded with gussets on the bottom so that the column can be bolted to a "footing plate" that is 30" x 70" x 1" thick steel using 1" bolts.

Two 4,300 lb concrete ballast blocks will sit on the footing plates and be tied to it and the columns using steel ties with wedge anchors or epoxied anchors (that hasn't yet been specified)

The building frames which are welded truss frames 10' oc, are then mounted to the top of the concrete ballast blocks on the back wall but on the front wall are shorter to accommodate the door height of 13' so are to be mounted to a W10 x 49 I beam which sits on a plate welded with gussets to the top of the column and is atattched using 1" SAE Grade 5 bolts to connect the I beam to the column. The I beam is in sections and each section is connected using "fish plates"

The odd part is that they also have a 1,000 lb (max 2,000 lb) capacity chain hoist spanning the 50' width of the building on rails that run the entire 325' length on corbels which will be welded onto the face of the 6 x 6 columns to support the rails for the hoist. The back wall will also have the same columns with footing plates under the concrete ballast blocks in that wall to provide mounting for corbels on that side of the structure.

As each concrete block is 2' x 2' x 5' and weighs 4,300 lbs there is sufficient weight on the back wall which is continuous block except for a 24' opening at the mid point where an adjacent small fabric building ties into the other main building.

The back wall columns (supporting the crane only) will be braced easily as there are no restrictions except bolted construction and the small building opening that will be spanned by a small I beam to carry the load from the main building frames over the opening.

The crane rails will also be sectional as again the whole thing has to be moved in the not too distant future.

Pheew, finally, my question is what will the building or crane do if there is significant heaving in winter - spring thaw cycles or is that not a concern due to the weight - design of the building and foundation system ?

The vehicles which will be inside when the structure - crane is in use add about 10 tons per doorway to the site mat, block, I beam, columns, crane rails, crane and other weight.

The building is heated to just above freezing and when erected will be in continuous use until the proeject is finished when it will be dismantled, relocated and re-erected at another site for the same purpose.

Thanks in advance for any comments, input or thoughts



Bob
MBC International
Pre-engineered Building Systems

 

[BAretired]

Pheew, finally, my question is what will the building or crane do if there is significant heaving in winter - spring thaw cycles or is that not a concern due to the weight - design of the building and foundation system ?

They will move. It is a concern. Perhaps you should consider insulation under the foundations.

BA

 

[Preeng1]

Hi:

The nature of the site mats is that they are 8' x 40' and 3 layers of 3" thick oak plank fastened together. The mats are tied to each other. No insulation is allowed on site. they just go in flatten the ground surface then lay these mats down and that's it.

Bob
MBC International
Pre-engineered Building Systems

 

[BAretired]

In that case, they will have to live with the frost heave. Hopefully it won't be too much.

BA

 

[Preeng1]

I know that the winters are sufficiently cold in that area to drive the frost down very deep so it may be slow coming out in the spring time but coupled with moist soil conditions it is definately going to be a concern.

Mind you, I have concerns about the whole foundation - crane system anyway. Bear in mind I am not an engineer, just a building erector...

Bob
MBC International
Pre-engineered Building Systems

 

[dhengr]

Bob:
As a structural engineer, I am pleased to find a building erector who is concerned enough to pay attention to the details you are questioning. It’s really difficult to visualize many of the important details of your structure. You really should advise your customer, that they should get someone capable of designing the various parts to make this all work together in the suggested environment. They should provide you with explicit directions for erecting this bldg. and hoisting system under these conditions. Their analysis should include things like found. conditions and frost heaving; bldg. structure and fabric stability against snow and wind loading and the like. This should include some stability and load consideration of the hoisting system and door framing systems. You should probably not assume this responsibility yourself, as the erector.

As BA suggested frost heaving is certainly likely, and I would add, that this sounds like a bldg. system which might tolerate that kind of movement, if done properly. Maybe you should be in contact with the manufacturers of the steel arches, door frames, and hoisting system and have them tell you how they are all tied together and supported, and what loads they are designed for under these conditions. You may want to talk with a GeoTech guy about the soil conditions at the site. Hopefully, it isn’t a permafrost situation where everything could sink out of sight in the spring and the mats will be sufficient as a base.

 

[Preeng1]

Thanks for the compliment. I have been at this for 30+ years and have seen a lot of different approaches to building design, some good, some just plain silly...

This design does seem able to handle heaving but my concern, even though a small hoist lifting a max 1,000 lbs the potetial for problems does exist....

I am told the whole idea is engineered but so far no stamp or further detail regarding who the engineer is.... saw that before with Cover-All buildings and look what happened there....



Bob
MBC International
Pre-engineered Building Systems

 

[dhengr]

Your contract should be for erection only, to their drawings, specs. and direction. And, there should be a certified letter, or some such, which states this and that you are not responsible for structural or foundation design, or the general adequacy of the entire system. Otherwise, your really don’t care who engineered it, if they relieve your of those responsibilities. You are right to be concerned, and are providing them good service and advice by bringing these issues up. They should not be saddling you with this responsibility. They may say, gee, this is just a temporary equip. maintenance bldg. at the site, and it won’t be up long enough to fail. But, that would not be good enough for your protection if it does fail under wind or snow loading. The hoist loading should not be any more severe on the mats than the bldg. framing system loads, but there must be proper bracing so it won’t just topple over when used.

Otherwise, the framing system is relatively flexible, to tolerate frost movement as long as this doesn’t cause secondary moments and stresses at connection points, etc. And, the covering is flexible enough to allow individual arch/frames to move independently, a good thing for this structure. The door frames have to be stable also, and tied into the structure in some way. They should not fall over under design loads, and I’m not sure what to say if a Cat or truck hits one of them.

Alternatively, you could provide GeoTech and Structural services as part of your total package, these would be your subs., but that’s a whole new ball game and set of cost through you to the customer. I understand their want for simple erection, 6-8 months, easy disassemble, and move to the next drilling site. And, all is well, until something goes wrong, which you had no control over. Someone has to be responsible and insure this project, and it shouldn’t be you unless you are compensated for it, and have some control over what’s done. That’s all the judge will understand, if and when.

 

[Preeng1]

You're aboslutely right, this is thier design and their building system.

One thing I do understand too well is liability and responsibility. That's why I take steps to cover "due diligence" amd document it all. I undertake the erection of their building package stamped by their engineers and follow manufacturers reccommended erection procedures.

Sadly I have learned the hard way to make sure I practice "CYA" and can actually say I have never had a building fall down or fail in any way including concrete with no failurse other than typical tiny hairline cracks... if anything I over build but in our climate temps rnge from 120 in the summer to minus 50F in the winter so I don't take any chances if I can avoid them.

Yet I want to ensure that my customer is getting value for the moeny they spend. Sometimes you can't always do that...
Sometimes they just won't listen...


Bob
MBC International
Pre-engineered Building Systems

 

[Gumpmaster]

Even if it's someone elses problem, our first responsibility is to public safety, so good on you, Preeng1.

Sounds like you do good work. I wish there were more concientious contractors like you.

Maybe put the question in writing as a formal RFI to the engineer.

 

[Preeng1]

Hi:

We do indeed do good work, too bad the economy has bumped everyone and projects the way it has. Like everyone we are only at about 50% capacity with so many jobs evaporating.

We warranty our workmanship unconditionally for 1 year and can say we have never had a warranty claim yet. As well we have not had a lost time accident in almost 25 years so we tend to be concientious and sometimes a little anal in how we do things, especially regarding safety but we have also never been turfed from a job site either



Bob
MBC International
Pre-engineered Building Systems

 

[dhengr]

Bob:
What’s this “sometimes a little anel” thing? In the previous post you said you were “CYA.”