Concrete block chimney

[BobNeng]

Hello all,

I know this is probably a pain, but I have a 42' free-standing (abutts a two-story porch) chimney 32"x72"and am looking for design examples etc. Does anyone know of any good resources for designing partially grouted cmu boxes? MDG-7 has in-plane loaded shear walls, but they're fully grouted. Doing mostly residential work, I usually only contend with simple out-of-plane wall loading so this is a bit more complicated. I was going to do the firebox out of poured concrete, but it would be nice if the rest could be block construction.

thanks

 

[hokie66]

A tall order, pun intended. I suppose you have reasons, but why so tall?

The design of a cantilevered reinforced masonry tube would be just like any other beam, just without the inside. The absence of the middle part should have little effect, I think.

Overturning will be an issue, so your footing/firebox design needs to cope.

I doubt you will find a design resource which will specifically address your problem.

 

[BobNeng]

Why so tall? Architects! I had looked at it tying into this two-tiered porch which has a steel moment frame for lateral bracing of the chimney AND porch, but the columns I was using are "too big" because they'll conflict with the remote control roll-down screens. Like I said: architects

Yes, the overturning is bad, 115 mph but it's exposure D. It does have stone veneer to help with the overall.

I had looked at it like a hollow beam (like you said, scooping out the middle should have little effect since I still have webs and flanges), but wasn't sure about fully-grouted vs. just grouted at the corners where my bars are.

I appreciate the insight Hokie66. My brother would say "you're getting wrapped around the axle" and pop might have said "you're going to drive yourself crazy" but if/when these things go south, you'd better be able to back it up.

thanks again

 

[hokie66]

Oh, I would definitely fully grout the cores of the blocks, and you will need a lot of reinforcement to withstand the wind loading. That is, if you can make it work, and I don't have an opinion on that without running some numbers.

 

[Tmoose]

Are the concrete blocks standard smooth faced blocks? It seems unlikely, but If so are they going to receive some kind of surface finish?

"Surface bonding" has fallen by the wayside for several reasons, but not due to poor performance.

http://www.masonryconstruction.com/_view-object?id=00000154-22da-db06-a1fe-73da22910000

 

[BobNeng]

Got it. I'll grout it all solid and bump-up everything accordingly.

These are standard blocks, yes. The whole thing gets stone veneer.