Big Brick Cylinder

[tw]

Architect wants a 36 foot outside diameter brick cylinder that will be 55 to 66 ft tall (sloped edge at top). Roof is light steel structure supported by brick wall. The wall is 4 wythes thick (16”) and is to be solid masonry as it stands now. There is building around the lower 30 ft of the cylinder but there is no real structural attachment to it other than light stair framing and some small roof pieces. In other words the wall is not required to support or brace anything of importance other than itself. There will be some wind load on the exposed portion at top half, around 25 psf. The base of the cylinder has 4 equal arched openings each equal to 1/8 of the perimeter length, so the cylinder actually is supported by 4 “legs” each equal to 1/8 of the perimeter length.

By simple calculation the brick will always be in compression (within allowable) with wind and dead load.

Architect and engineer he talked to says that this will work without any reinforcing, but not having done any “brick only” structures I don’t have a good feel for it. I’d rather make interior 8” of wall reinforced CMU and use brick veneer, since I could do that easily. I also could reinforce the brick itself like BIA.ORG technical notes show. I’m not sure of relative cost.

Anybody have any similar structures experience?

tw

 

[JAE]

Seismic concerns? Where is it?

 

[tw]

It's in south/central Louisiana, so seismic shouldn't be an an issue, though I haven't done a calc for seismic with newer codes.

 

[JAE]

South LA has nominal values - Ss about 0.12 and S1 about 0.05. The key would be the site classification. With class D or E you'd get a SDC of B.

I think you'd fall under IBC 1621 in which case section 1621.1.1, Exception 2 might kick in and allow you to ignore Seismic altogether.

Any of you seismic CA guys out there have an opinion?

 

[Ron]

tw...the process you've described is how many older buildings were built in the 1700's and 1800's. Many are still standing. I know of one particular lighthouse along the SE US coast that was built almost exactly as you described and has withstood many wind events over the years. These structures had no reinforcement.

 

[dougantholz]

I have worked on renovating many unreinforced masonry buildings and what you are talking about will generally work but there are a few bits of advice.
1 - rule of thumb is thinnest portion should be 3 courses and you should add a course on the bottom for every 25 feet. So for a 60 foot tall structure I would have a 5 course (~21") at the base, 4 in the middle and 3 at the top.
2 - Joint reinforcing is a beautiful thing. Using 9 guage wire liberally would be a good idea.
3 - Connect at the base, as low as you can. The moisture and thermal expansion could be >2".
4 - If the architect doesn't really need a true "brick" structure how about creating a concrete wall in a gap between outer courses. Tie the brick faces together with full depth ladder joint reinforcing and then fill the middle with concrete/grout. Strong then brick and probably cheaper.
5 - pay good attention to your mortar and jointing since your high humidity will likely cause some lime leaching.

Just some food for thought.