Company to start building "standardized" small industrial buildings.....
Company to start building "standardized" small industrial buildings.....
(OP)
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?
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?






RE: Company to start building "standardized" small industrial buildings.....
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.
RE: Company to start building "standardized" small industrial buildings.....
RE: Company to start building "standardized" small industrial buildings.....
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
RE: Company to start building "standardized" small industrial buildings.....
I stand behind you as the Engineer of Record refusing to stamp anything you won't stand under. Lawyers can find other work.
RE: Company to start building "standardized" small industrial buildings.....
You obviously have to watch that you don't punch through the larger HSS wall.
RE: Company to start building "standardized" small industrial buildings.....
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.
RE: Company to start building "standardized" small industrial buildings.....
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.........
RE: Company to start building "standardized" small industrial buildings.....
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.
RE: Company to start building "standardized" small industrial buildings.....
RE: Company to start building "standardized" small industrial buildings.....
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…
RE: Company to start building "standardized" small industrial buildings.....
RE: Company to start building "standardized" small industrial buildings.....
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?
RE: Company to start building "standardized" small industrial buildings.....
RE: Company to start building "standardized" small industrial buildings.....
https://www.google.ca/search?q=flexible+connected+...
BA
RE: Company to start building "standardized" small industrial buildings.....
RE: Company to start building "standardized" small industrial buildings.....
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-...). 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.
RE: Company to start building "standardized" small industrial buildings.....
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.
RE: Company to start building "standardized" small industrial buildings.....
Dik
RE: Company to start building "standardized" small industrial buildings.....