PEMB's & Upgrades

[ToadJones]

I know this has been beat to death here, but do you guys handle engineering/ upgrades to PEMB's?

I have a customer who wants to upgrade crane capacity to a a crane runway that is on brackets on a PEMB moment frame.
I have no experience to PEMB frames.

I can handle everything up to and including the bracket but from there should I inform the owner that he must contact the PEMB manufacturer?

I want nothing to to with analyzing the PEMB frame (not the first time I have been down this road either!)

Thoughts are much appreciated.

 

[SteelPE]

I call my PEMB expert engineering buddy and give him the job. He used to be the chief engineer at one of the large PEMB companies until he went out on his own. He loves that stuff.

 

[ToadJones]

Steel-
You give him the entire job or hire him to analyze the frame?

 

[dcarr82775]

Oh come one, its a challenge. Adding load to a building designed to a demand capacity ration of 1.05 including a 10% bump on the specified steel yield is always a interesting project. (to be clear, that is written in sarcasm font)

 

[ToadJones]

dcarr-
I am guessing you have been asked to do this many times as well eh?

 

[SteelPE]

Toad

Depends on the project. I have had times where I have included his part of the design on my drawings (this happens very rarely). Other times I will tell the customer to call him direct. I guess it just depends on how entailed the project is and how much responsibility I want to put on my own shoulders.

 

[ToadJones]

I need a guy like this....

 

[SteelPE]

What part of the country are you located in?

 

[Lutfi]

I suggest adding new and independent column and relying on the frame to take the lateral loads which still wild require checking for adequacy. Obviously you need to work on the foundation capacity. I have learned through the years that PEMB guys design to stress ratios that are close to 100%. That is why they are cost effective.

I also would check with the client to see if he planned for this growth when he first purchased the building, some folks are forward thinkers and do not mind spending small upfront monies to account for future growth.


Regards,
Lutfi

 

[ToadJones]

Steel-
Pittsburgh area

 

[ToadJones]

Steel....I/we do work all over.
The building in question is in the Chicago/Milwaukee area.

 

[SteelPE]

I don't think my guy would want to go that far, and I am not even sure if he is still registered in that area anyway. Sorry. If you know the original mfr you may want to contact them to see if they can help you.

 

[JedClampett]

Listen to Lutfi. Add a completely independent system to support the crane. If you try to analyze the PEMB, you'll be obligated to tell the client it not only won't work for current codes, it didn't work for the code when it was built.
And remind the client about all the money he saved by buying a PEMB.

 

[ToadJones]

That was my first thought anyway...
Thanks SteelPE

 

[ToadJones]

Jed-
I agree with you 1000%.
However, when I suggest this it usually starts a wild pissing match and quite frankly, I'm tire of them. This comes up a lot and the bosses and owners don't usually like to hear that the best option is (and was) a separate crane column.

In this case the runway centerline and the building centerline are very close so adding a new completely independent crane shaft will be tough and will require some creative upgrades to the footings as well since the PEMB frame has hairpins tied into the slab.

IMO PEMBs have no place in heavy industry unless for storage.

 

[msquared48]

Toad... Let me guess:

1. The PEMB manufacturer is no longer in business;

2. The design programs for the frames were proprietary;

3. There are no calculations to see if the crane load combinations were critical to the design of the frame;

4. Drawings are sketchy at best;

5. Certainly no fabrication drawings are available.

If any are true, just follow Lutfi's advice.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[ToadJones]

Mike-
Say I can convince the owner to add independent crane columns, do you think I could justify not checking the frame for current design loads...seismic, wind etc?
I would be drastically reducing the gravity loads and moments on the building frames by adding columns.

If not, then I am in the same boat as far as having to deal with a PEMB frame which I do not want to do.

As far as adding new columns I know I am going to run into problems because I will need to add footings right near or on top of the existing and I do not know what the best approach is there.

 

[msquared48]

Toad:

You said in an earlier post that the runway centerline and the building centerline were very close. I guess I do not understand how any existing footings would be affected here if the Mainframe spans the width of the building without a center column as is normal. Perhaps it is not free-spanning?

Can you post a plan sketch of the building arrangement?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[ToadJones]

see attached (sorry about the bad sketch)

 

[ToadJones]

Mike-
now that I look at my own sketch, columns will probably fit.