Reduce the size of column Pre-Eng Building

[nilaypathak]

Hello,

What are different conceptual methods can be review to change columns from Tapered to Straight in PreEng building.

Is it possible to reduce the column sizes significantly?

Thanks,

 

[Ron]

Why? Most tapered columns are for single span bents. Straight columns are often used when the bent is multi-span.

Are you designing a PEMB? The manufacturers usually have dedicated software for their proprietary designs, which are difficult to replicate.

 

[rowingengineer]

column size normally dose not reduce if the same plates are used for the flanges and webs.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[nilaypathak]

Thank you all,

This is process-industrial and clear span buidling. Other deciplines desing aussumed the straight coulmn and model the duct and piping, which are now clash with actual column size, No doubt!!.

Thus, I am trying to see if I can reduce the column size to avoid the rework.

RS

 

[msquared48]

If the column is not taking a moment from frame action, there is no reason to taper it.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

Who would make an assumption that a pre-engineered building did not have tapered columns? The tapers are there for a reason. Sounds like a problem for the other disciplines. By the way, how did they get the sizes for the straight columns which were assumed?

 

[ajh1]

PEMB's are regularly designed with straight columns, although as everyone has indicated the tapered column is the preference. Depending upon the restrictions placed upon the depth of the column, the change can be done for anywhere from minimal cost to a very large added cost as the column depth gets smaller. There may also be issues associated with sidesway for shallow column depths.

 

[dhengr]

You are taking on responsibilities and liabilities for a building which has more than likely been designed to a FoS of 1.001 and maybe not even seen the worst load combinations it could see in its lifetime. You have no access to the original design, don’t know many of the details of the existing structure or the exact materials used and how they interact on this tight a design. What you are proposing is not a simple design problem. Don’t even offer to do this. Just getting started on what you are offering to do will take longer than redoing the Mech. designs. And, all this because some Mech. designers did a poor job in their original modeling and decision making. Why not tell them to move the ducts and piping 6" or 1', good original modeling should allow that fairly easily. You’ll still have plenty of hassle in justifying the new hanging loads on the existing structure.

 

[ajh1]

I perhaps missed the original point. I would not recommend redesigning an existing tapered column to replace it with a straight column. For new construction that has not been erected, it is certainly possible for the metal building manufacturer to provide a straight column for a price.

 

[JedClampett]

Once again be sure to remind all the powers that be, as they're rerouting all the pipes and ductwork, how much money they saved using a PEMB.
Could this mistake happen with a custom designed building? It happens all the time. But you would have the information at hand to make a technically sound decision.
I totally agree with all the posters above in not redesigning the columns. Even if you have the calculations, it's a losing proposition. How are you going to transfer the moments at the knuckle? How about deflections? Will the baseplate work?

 

[JennyNakamura]

Sounds like a coordination issue between the architect and the PEMB guys. PEMB suppliers have a responsibility to coordinate their work with the architectural and MEP designers, just as the SE does on a "regular" building. After all is said and done, either the PEMB design can be modified or it can't. If it can't, then MEP guys gotta work around it and the architect may have to make some adjustments. In my experience, the SEOR designs the building foundations based on some assumptions regarding the final PEMB, but is not responsible for helping the PEMB engineers engineer their final product. Or maybe I am just missing something here?

 

[audeuce02]

Why does everyone jump straight to this issue being due to negligence from the PEMB? We work from Contract Documents and follow the Code just like any other SE group, so why should I be labeled as a bad engineer. There is a lot of good information shared here, but there is also a lot of witch hunting of an entire industry sector due to some perceived short comings.

 

[hokie66]

audeuce02,
Everyone? In rereading the posts above, I couldn't find anyone suggesting negligence on the part of the PEMB engineers...maybe in some other threads, but certainly not in this one. A bit sensitive, are we?

 

[ToadJones]

There was the suggestion that the building was designed to the gnat's ass....this is likely what has annoyed Audeuce20.

 

[hokie66]

Maybe, but I thought PEMB designers considered that sort of comment as complimentary. Negligence? Bad engineer? Nobody said that.

 

[ToadJones]

True

 

[audeuce02]

I apologize. Its just a culmination of all threads regarding PEMB.

 

[JedClampett]

Maybe I'm the one perceived as taking shots at PEMB engineers. That's not the case. I consider them very good engineers within their charter, squeezing every last psi of capacity out of their buildings. And ther's nothing wrong with that. My real issues are:
*Lack of documentation. I'm one of the schmucks who get called when someone needs a window, a load increase, a hole cut in the roof, a monorail. The calculations (we always ask for them, never really get them), are indecipherable. We might get a couple of pages of summary, no interactions, no tributary loads, no section properites, no nothing. I know the calculations are done. How about someone figuring out a presentation that can be followed after the building is built?
*As far as the retrofit projects, the PEMB supplier is never any help. Just once, I'd like to get a contribution (or a call back)from them. How is it that every PEMB supplier has lost every calculation every done? I've heard that there were floods, fires and every other kind of pestilence imaginable. I don't think it's the engineers fault. I think that the PEMB companies see follow-on service as just an invitation for litigation.
Once again, I think that PEMB engineers are very good. They do good work. But for god's sake, think of the other guy. We're trying to make our client's happy, too.

 

[paddingtongreen]

@audeuce02,
I, and I think others, don't dislike PEMB designers. just the product. We have some spare capacity on our designs that often allows us to respond to small changes and answer questions quickly, your buildings do not, add to that that they are proprietary so we cannot answer peremptory demands to know if we can increase the weight of dome object or another. Your product comes out of a black box, we can try to analyze it with a regular program but it almost never says yes, but your companies say it does work but they can't prove it because the design basis is proprietary. It is like buying a pig in a poke. Would you buy a car from a man who won't let you look under the hood.

Additionally, those of us are/were called out to evaluate building failures, under wind or snow load, find that the damaged building is a PEMB.

I repeat, I don't have anything against you or your colleagues, I'm sure you just as honorable and ethical as the rest of us but i do hate your product.



Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[hokie66]

And there you have it. What say you to Jed and Michael's comments, audeuce02? Maybe it's not good enough anymore for us to just rely on "caveat emptor"?