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Wrong design loads?

Wrong design loads?

Wrong design loads?

(OP)
I have a metal building that I have been asked to design the foundations on. Part of my review of the foundations loads is to make sure the design criteria used for the metal building were in compliance with the building code. From time to time I find discrepancies. I contact the client, supply the necessary code backup for my concern and the metal building manufacturer will make the change to his design.

In this instance the metal building company is refusing the make changes to their design. In this instance they are not using the amended wind speed tables. We have brought this to the attention of the building inspector who doesn't seem to really care. Where do we go from here? I am thinking about getting a letter from the BI stating that using the older winds speed is OK but I'm not sure if we should be appealing to a higher level or not.

RE: Wrong design loads?

I would be designing the foundations for the increased wind loads. Provide a letter to the client, PEMB, and BI stating what you have designed for, what the company is designing for, point out the discrepancies with code references. Then wash your hands of it.

RE: Wrong design loads?

What is the source of the wind speed change? Is this ASCE7-05 to ASCE7-10? If so, in many cases, the wind pressures dropped when switching to ASCE7-10, therefore the older wind speed might be OK.


I love your idea of asking the BI to provide a letter. Turn the tables on the inspectors that say "I'm OK with the field changes, just have the engineer seal a memo stating that it is OK"

RE: Wrong design loads?

(OP)
Not a switch from ASCE 7-05 to ASCE 7-10, just the jurisdiction switching the load tables around every few years. In thin instance the loads switched from 110mph to 115mph (allowable).

RE: Wrong design loads?

tell your client not to buy the building. I bet that gets the design changed.

RE: Wrong design loads?

You are legally obligated to design according to the adopted building code, as amended by the authority having jurisdiction. So, if the building inspector is willing to accept the another design wind speed in writing, then go with it. If he is not willing, then the wind speed in the adopted building code governs.

That being said, building codes are minimum standards. If you choose to design over and above the building code requirements, the only party that may have an issue is the owner since he is paying for it.

RE: Wrong design loads?

Maybe present it based on what you think may be wrong due to the incorrect loads? Going from 110 mph to 115 mph is a 10% increase in force per the code equation. That could mean a 10% overstress (maybe 15% overstress knowing PEMBs...) within the system that is not designed for.

And maybe the person who bought the PEMB may have the weight to throw at the PEMB company and should be brought in the mix, considering they are now buying a brand new non code compliant structure.

RE: Wrong design loads?

SteelPE:

Assuming the jurisdiction you're talking about has adopted chapter 1 of the IBC, they do not have the authority to "waive requirements specifically provided for in this code". See section 104, Duties and Powers of Building Official. I'd stick to the code or walk away.

Regards,

D. Uppgren

RE: Wrong design loads?

SteelPE, I'm a little surprised. Not that a PEMB engineer is being a stubborn pain in the rump. But from what I've seen they're pretty rigorous about using the correct loads. Not an ounce more, but they're correct. They plug a windspeed in a PEMB Design black box and it spits out the results.
Most of my issues with them have to do with them washing their hands of any foundation considerations (anchor bolt spacing; edge distances, sizes, etc.), rather than load problems.

RE: Wrong design loads?

(OP)
JedClampett

Really, I have have run into numerous problems with the PEMB companies not using the correct loads. The started when the local jurisdictions started adopting the IBC and then began amending the code with their own specific load tables. Ever since that switch, I have had problems. However, this may be because I am mostly working with contractors who don't know enough to spot the problem when ordering a building.

In regards to the bolts, up until recently I have only done work with one contractor who uses outset girts. This gives you a nice 10"-12" of clearance to outside face of foundation. However, as I branch out, I have a few clients who like to use inset girts, which drive me nuts as you can't put the bolts 2" from face of column as that is where the ties will be in the pilaster grrrrr. So something has to give.

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