Flush/In-Wall Pilaster & Masonry Wall Design
Flush/In-Wall Pilaster & Masonry Wall Design
(OP)
Hi All,
I am having difficulty in designing a masonry wall to work for my given situation. I am very green when it comes to masonry construction and am quickly finding out that it is not as simple as I originally thought it to be. I have the following situation, 8" cmu walls that are approximately 17.06' tall and are taking a horizontal pressure due to wind of 35.68 psf. The pilasters to take the wind loads are 13.45' on center, therefore the 48" wide in wall pilaster is to take a 480 plf line load located at the center along with an axial load of 9k. With that, the pilaster is to take a pressure of 480/4 120 psf. This of course describes the worst case. My wind loads are quite high as I have a high basic wind speed of 155 mph. Please see attached diagram for clarity. I am under the impression that an 8" cmu wall is not going to work even grouted solid with vertical reinforcing at 8: o.c.. As always, any and all help is greatly appreciated.
Thanks,
Shaylon
I am having difficulty in designing a masonry wall to work for my given situation. I am very green when it comes to masonry construction and am quickly finding out that it is not as simple as I originally thought it to be. I have the following situation, 8" cmu walls that are approximately 17.06' tall and are taking a horizontal pressure due to wind of 35.68 psf. The pilasters to take the wind loads are 13.45' on center, therefore the 48" wide in wall pilaster is to take a 480 plf line load located at the center along with an axial load of 9k. With that, the pilaster is to take a pressure of 480/4 120 psf. This of course describes the worst case. My wind loads are quite high as I have a high basic wind speed of 155 mph. Please see attached diagram for clarity. I am under the impression that an 8" cmu wall is not going to work even grouted solid with vertical reinforcing at 8: o.c.. As always, any and all help is greatly appreciated.
Thanks,
Shaylon






RE: Flush/In-Wall Pilaster & Masonry Wall Design
RE: Flush/In-Wall Pilaster & Masonry Wall Design
I am still struggling with my problem as noted above. One piece of information that I failed to mention is that I cannot use the roofing material for any shear transfer, therefor I do not have a diaphragm. I have been working on this on and off for the last three weeks now and still am not knowing how to get this to work.
hokie66, I don't quite understand how spanning the wall vertically to a bond beam to transfer the load back into the pilaster. I'm sorry, I am very green when it comes to masonry design.
Thanks for everyones help,
Shaylon
RE: Flush/In-Wall Pilaster & Masonry Wall Design
You can never use "roofing" for a diaphragm, although structural roof deck is often used in that manner. Roofing is to shed water.
You have to have a way to tranfer lateral loads at the roof level. Perhaps a horizontally spanning truss? As you have only talked about the wall itself, it is difficult to give advice on the whole structure.
RE: Flush/In-Wall Pilaster & Masonry Wall Design
I'm sorry, I misread your previous post about the horizontally spanning member. What you are saying makes more sense to me now.
I must also apologize for misspeaking about using the "roofing" material as a diaphragm. I guess what I should have said is that I am not able to use the metal deck system being used on this project as a diaphragm. We are using a 4in thick isulated "sandwich" panel which does not include any allowable shear values in the tecnical data.
Please see the attached framing plan to give you a better idea of how the structure is laid out.
Thanks,
Shaylon
RE: Flush/In-Wall Pilaster & Masonry Wall Design
You might consider a two way spanning wall for the wind loads here - as in a two way flat slab - with both CMU pilasters and steel WF wind beams.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Flush/In-Wall Pilaster & Masonry Wall Design
RE: Flush/In-Wall Pilaster & Masonry Wall Design
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Flush/In-Wall Pilaster & Masonry Wall Design
I have a qz = 45.17 psf with my current configuration. 35.86 psf is the worst case on any portion of the wall once the internal/external pressure coefficients and the different zones are under consideration.
Thanks,
Shaylon
RE: Flush/In-Wall Pilaster & Masonry Wall Design
Thanks for the suggestion though,
Shaylon
RE: Flush/In-Wall Pilaster & Masonry Wall Design
RE: Flush/In-Wall Pilaster & Masonry Wall Design
RE: Flush/In-Wall Pilaster & Masonry Wall Design
RE: Flush/In-Wall Pilaster & Masonry Wall Design
And by the "sandwich" panel term you mention, I assume you have 1/2" CDX ply on both faces with foam in between with edge 2X splines for nailing attachment?
Professionally, I would not use these panels in a commercial application, only residential, and only with tested and rated systems, both for shear and vertical load.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Flush/In-Wall Pilaster & Masonry Wall Design
Your way was about where I was going, but I’ve been accused of having some trouble with serious commitment. Oh... that’s a different subject.
RE: Flush/In-Wall Pilaster & Masonry Wall Design
The "sandwich" panels I am refering to are made of two metal panels with some insulating material in between them. See the attached PDF for the system we are using.
hokie66,
I am working on getting your method to work. I like this idea.
Thanks everybody. When I get something figured out or need further assistance I will post on this thread again.
Thanks again,
Shaylon
RE: Flush/In-Wall Pilaster & Masonry Wall Design
1. The screws used to transfer any shear are awfully long and seeing a lot of bending. I'm not sure how much restraint, if any, can be clunted on from the foam layer.
2. The upper level of metal decking, dut to the high rib, may not offer much lateral resistance. that may be concentrated in the lower layer, depending on its gage and the ability of the screws and foamm to contain it from upward movement.
I still stand by my original comments here.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Flush/In-Wall Pilaster & Masonry Wall Design
I think Mike was referring to projecting pilasters and not internal pilasters that can be used on 10" or 12" walls. The projecting vertical sections are often objectionable for interior function purposes and external architectural purposes, but they do define control joints although they can be hidden by a good architect/detailer. - One of benefits for thicker walls in some markets where unit weight is not cost detriment.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Flush/In-Wall Pilaster & Masonry Wall Design
then X-brace with cable or steel rods across the roof. This is
like a prefab metal building roof and would not depend upon the
panels for shear transfer. There is no way you will get 8"
CMU to work at your wall height. Might just as well figure 12".
10" is almost impossible to find these days.