Lateral Drift and Brick Veneer 1

[marinaman]

One of my architectural clients requested I design a building for him. It is single story, hipped roof, 76' wide and 160' long with an eave elevation of 14' and a roof slope of 4:12. The wind speed is 90mph per ASCE 7 and seismic forces do not govern. The building is veneered in brick over the full 14' eave height. I framed the building in conventional structural steel with tube braced frames.

Now, the owner has come back and stated he has a price from a metal building manufacturer to frame the building cheaper than conventional framing. It has been my experience that pre-engineered metal buildings typically have more lateral movement and vertical deflection than I'm comfortable with....especially since this building is clad in brick veneer and has offices inside (ceilings, lights, mechanical etc)

I was forwarded a set of prelim calcs by the metal bldg manufacturer for my review. I see that they're using H/60 for lateral drift allowance. This, to me, seems excessive,considering the building is clad in brick veneer. The building manufacturer is using rigid frames for stability.

I think this building should meet a maximum drift of H/400 or a max of 0.3". I want to limit the cracking of the brick veneer when the building is subject to lateral loads. What do you guys think?

 

[jike]

Absolutely! The Owner wants to by a cheaper product and you have a professional responsibility to inform him that the reason it is cheaper is because it does not meet the stiffness requirements to prevent the brick from cracking. Ask the PEMB to requote based on the recommended criteria from the BIA.

 

[msquared48]

I fully agree with you. Stick to your guns here. Don't stamp the plans unless your criteris is met.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[theonlynamenottaken]

I have had alot of experience in this matter. Most PEMB companies will be reticient to conform to higher drift limits, as their price will certainly rise accordingly.

The last few times I've encountered this problem it was solved by sending the owner a letter that stated that the PEMB as proposed was (in your case) over 9 times more flexible than recommended for supporting masonry.

 

[MiketheEngineer]

Don't seal them at all. Let the PEMB seal them and leave your card with the client. Tell them you will help them with their mess in two or three years...

 

[concretemasonry]

Dump the load on the brick veneer details and joints on his responsibility. If the architect or owner has selected a flexible building and chosen to use a rather rigid veneer there will be potential problems that cannot be be calculated with any program.

Cracks/moisture are visual "red flags" for early problems. Make sure the architect is responsible for the details, moisture barrier and administration.

 

[ishvaaag]

H/60 ... a tall traffic light to break the bolts. Not a house.

 

[SteelPE]

What does the architect think about the use of a metal building in this situation? I would think he would be on your side. You can both go back to the client and advise him that if a metal building is selected he should either increase the stiffness of the structure or change the exterior to a more flexible material.

 

[ishvaaag]

Convince the owner saying that for a two story house he is going to see his children in the bedroom when the walls go 10 cm inwards, then 10 cm outwards, then 10 cm left, then 10 cm right ... a banner house.