Company to start building "standardized" small industrial buildings.....

[ARS97]

The company I work for has decided to try and build "standardized industrial buildings" that will primarily be used to house electrical panels and will be small enough to be shipped whole. (Let's ignore the fact that they have been building them for some time now without any engineering review whatsoever......that's a whole other issue.) The buildings are about 35' long x 10' wide x 10' tall at the gable. They'd like to use small HSS tubing for all members. The primary structural frame is essentially two (2) end walls with typical gable "moment frames" spaced at about 4' along the length of the building. The buildings will have a floor in them, but the building will usually be sitting on a slab. Pretty basic, right? Well, there's a few issues that I'm trying to address:

1) In a typical gable moment frame like this where the column bases are "pinned", there are three (3) "rigid" joints - two on the sides where the sloped roof members meet the columns, and one in the middle where the sloped roof members meet. Well, in an effort to save money, some of the owners have come up with a lovely connection detail using thin bent plates instead of mitered joints with a full penetration weld. (See attached sketch) This allows them to square cut the ends of the tubes, slap on the thin bent plates, and throw some weld on it. I am arguing that the rotational stiffness of this joint isn't something that is documented anywhere and I believe that we'd have to perform some type of testing to verify the stiffness. This joint would fall somewhere in between a "pin" and a fully-restrained MC. AISC does touch on the topic of partially-restrained moment connections (PR MC), but it mainly just provides flexible moment connections (FMC) as an alternative. Any suggestions on how to handle this? Personally, I'm leaning towards being a hard*** and just telling them to miter the joints if they want my stamp on the drawings. However, I'm open to new ideas....

2) It's been discussed that the steel sheeting (not decking) on the roof & sides could possibly be used as a diaphragm and help resist the lateral load effects. I don't deal much with diaphragms, but for these "economical" buildings, I may be forced to become familiar with their design. My guy feeling is that relying on light gage steel sheeting probably isn't a terribly reliable way of load transfer, but I suppose there would be SOME strength. Thoughts?

 

[TLHS]

Using the roof as a diaphragm is likely fine unless you foresee equipment being installed or removed by cutting out the roof in the future. I'd be really careful about using siding as a diaphragm in an industrial building, though. People *will* come along and cut holes in it in the future without realizing they're compromising the structure. If you decide to go that direction, I'd suggest doing some checks to see what happens if someone cuts out a portion of the wall to run new facilities into the building.

If at all possible, I'd default to throwing in some tension rods or angles as bracing instead. They're less likely to get cut into (although it certainly still happens). If you can't do it, just make sure your shear wall and diaphragm are designed to be a little more robust to account for future openings.

 

[ARS97]

I'd rather not rely on the sheeting whatsoever. As of right now, they have a "design" that they'd like to stick with and I'm trying to find reasons as to why it won't work. In regards to the sheeting acting as a diaphragm - if the manufacturer doesn't have any strength data for this type of function, then it seems like I'd be out of luck.....

 

[BAretired]

1) Square cutting and adding thin plates doesn't work unless small web plates are included in which case, I doubt that it is an economical solution.

2) Steel sheeting may be adequate for diaphragm or shear wall action if it is thick enough, but usually, it is too thin to be relied upon. Like TLHS, I would favor a structural system independent of the sheet material.

BA

 

[BUGGAR]

Based on your sketch, I think the top plate could buckle under the compression load (unless a thick plate), and the lower plate would be subject to "zipper" tearing of the welds along the sides. There is no weld access to the upper side of this plate and the side welds will tear before the plate end weld gets into the action.

I stand behind you as the Engineer of Record refusing to stamp anything you won't stand under. Lawyers can find other work.

 

[TLHS]

Is their problem with a more conventional HSS connections the possible full penetration weld? The easier way to make a connection like this in HSS is to make sure your widths don't line up. So make sure your roof beam, for instance, is less wide than your column, miter the corner and then just run a fillet around the outside. You don't need a penetration weld and you don't have to deal with the irritating flare bevel weld at the radius of the HSS.

You obviously have to watch that you don't punch through the larger HSS wall.

 

[Brad805]

I think by the time you make the building assembly stiff enough to handle with a crane without the need for complicated lifting arrangements much of your lateral load concerns will resolve themselves. There are not many design tables for using cladding as a diaphragm that I am aware of. The ones I have found typically indicate screwing all around the perimeter of each sheet. This is a lot of extra work, and there are other options that are more cost effective (and reliable) in this case.

I do not believe their peak connection detail will save them anything by the time you get done adding in whatever plate stiffeners you need to keep those plates a reasonable size for the axial and shear forces. A simple miter detail is not difficult.

Have you searched out what others do? This is a simple skid shack and there are lots of them on the market. I do not see a lot of need to re-invent the wheel for this simple structure.

 

[ARS97]

BAretired - agree 100%.

BUGGAR - I agree. In addition, I have no idea how I would accurately represent the fixity of such a connection. Due to the complete lack of any bracing, I need this frame to ACT like a moment frame, and those connections won't produce that effect.

TLHS - due to the small loads involved, I'm sure I can get away from full penetration welds. They're just looking at making these things as cheap as possible. Even the miter cut is being frowned upon. For goodness sakes.....we have a beamline......it's a piece of cake.

Brad805 - the problem is that they're trying to copy a competitor who isn't producing an "engineered" product either. When you copy junk, you get junk. I agree with your assessment about the lifting scenario and the difficulty in producing a reliable steel sheeting diaphragm.

Very frustrated.........

 

[Ron]

Your company is certainly not the first to take this shot! Such buildings are built in every region of the country, many without any engineering or code overview. I've been asked to evaluate before as part of litigation. In most instances, they don't comply with building codes and cannot even come close to withstanding high wind loads and snow loads. They do; however, make money for the producers!

If you are going to sign and seal the drawings (which will be used multiple times over to get a placement permit locally), then YOU require what you want. It is difficult working for a company that is run by non-licensed people because they rarely understand the importance of having to comply with licensing laws and the building codes that are applicable to these buildings. I've seen building departments exempt such buildings (wrongly), only to have the next municipality over require complete compliance with their code.

 

[ARS97]

Ron - I couldn't have said that any better. In my case, our electrical department is typically where these buildings get "designed". (Designed = makes sure it's big enough.) This specific building was fabricated and sent out to a site where it sat on elevated piers (6' tall) and footings. Of course, the foundation wasn't engineered either (they just threw some rebar in it), and now the code official is requiring a building permit and stamped drawings. This is going to turn out to be an expensive lesson for everyone involved.

 

[dik]

There are many issues for small ‘pre-fabbed’ electrical buildings or EBuildings. We’ve had numerous clients require that they be used and we try to dissuade them due to problems we have encountered.

They are typically flimsy and the installation is usually uncoordinated with other parts of the work.

Depending on jurisdiction, they may require a fire-resistance rating or may simply be non-combustible. The client may have certain requirements.

They have to be designed for current climatic loads (snow and wind), and possible seismic.

They have to be capable of supporting snow load accumulation from adjacent buildings.

They may have to have a fire-resistance rating on the outside skin for spatial separation issues for fire; this can be a local requirement.

With EBuildings, it may be necessary to have some strength to support electrical panels, etc. These can be supported from the floor with lateral restraint provided by the EBuilding. Also, there may be cable tray that has to be supported.

Anchorage of the EBuilding may be an issue. If anchor rods cast into concrete by others or may be possible to post install the anchorage. Anchorage may have to be coordinated with openings and trenches in the EBuilding slab.

Doors must be secured and sometimes larger doors to allow the installation of larger electrical equipment – starters, switchgear, breakers, etc.

Sometimes openings must be provided.

The building may require grounding for any metallic components.

The manner of hoisting it into location must be accommodated. If on a skid, it may require lifting lugs and or pulling lugs. A procedure should be provided in the event this work is undertaken by others.

And there are probably a few that I’ve missed…

 

[ARS97]

dik - as far as the environmental loads are concerned, we'd have to set reasonable limitations as to the areas in which the "standard design" could be used. I'm not going to design a one-size-fits-all building that can be placed anywhere in the US since there are widely variable wind, seismic & snow loads. But you're right.....all of those items you've mentioned would have to be considered. It's very difficult to come up with a cookie-cutter approach for something that has so many variables.

 

[ARS97]

On another note.........

I mentioned about the questionable "moment connections" that they've been using with those flimsy plates. These connections obviously aren't rigid, but perhaps they have SOME restraint. (I would also add web plates for shear transfer.) The question is - how much restraint do they provide? Part 11 of the AISC manual discusses partially-restrained moment connections (PR MC). How would one determine such restraint? Would this only be accomplished through testing of some sort? If so, has anyone ever performed such a test?

 

[TLHS]

Personally, I've had good experiences with vendor supplied electrical houses. Normally, though, the contract goes to an electrical equipment company that then procures the building from a reputable pre-engineered building vendor. The electrical company then goes through and integrates everything and delivers it as a unit to the site. I've also always made sure the client gets a stamped design and have included foundation and anchorage information as an early vendor deliverable so it can be integrated with the foundation design.

 

[BAretired]

You can google articles on semi rigid steel frames. I found the following links which may be of interest:

https://www.google.ca/search?q=flex...d+steel+frames&rls=org.mozilla:en-US:official

BA

 

[ARS97]

Thanks for the link.....I'll check it out. I also have an email out to AISC, so when I get a response, I'll post it.

 

[Brad805]

I know about the poor options on the market. You can go out to any oil field site and see numerous examples of the "by other" buildings. They do give you a good basis to start from. I believe this is going to turn out to be a challenging project if you continue down the path you are on now. I hear the comment, "but the other guys just do this," in your very near future when the reality of costs comes up.

Presumably your company plans to do the fabrication. I assume they have all the certifications to do so? If not, a pre-engineered solution may be a better plan. I trust Canam and they have reasonable system that might work for you (

http://www.canam-construction.com/en/products-and-solutions/econox-buildings).

I am sure Nucor has something similar, but I work with Canam normally (I am in Canada).

HSS is a neat and tidy option that makes for a nice clean interior look. It also makes for much easier connections when you are not setup to produce bolted connections quickly and reliably. From a cost perspective, it is not the best option.

 

[ARS97]

Yes, we'll be fabricating these buildings ourselves. The crazy thing is - they've been "designing" & fabricating these buildings for a few years now for our electrical department. It just so happens that nobody, until now, has asked for an official engineering review (stamped drawings).

As for the shop "certifications" - we have certified welders, but our shop isn't AISC certified. I'm not aware of any other special certifications.

I'm actually not THAT concerned about the sizing of the members, but rather the method in which they're connecting them. HSS profiles are great from a strength standpoint, but they are expensive. A preliminary analysis of the building frame is showing that the member sizes are fairly decent, assuming that the joint fixity is actually what I have assumed.

 

[dik]

YOu may want to look at the attached...

Dik

 

[ARS97]

dik - nice reference.............