Masonry Stair Tower C&C Loads
Masonry Stair Tower C&C Loads
(OP)
When designing an 8"cmu 21ftx15ft exposed stair tower, five stories tall, how would i go about reinforcing the wall for C&C loads on the 21ft face in a 90pmh wind zone? it would seem that i would have to place bond beams every other course to span horizontally.
i'd rather not reinvent the wheel here, so i'd appreciate any suggestions.
i'd rather not reinvent the wheel here, so i'd appreciate any suggestions.






RE: Masonry Stair Tower C&C Loads
RE: Masonry Stair Tower C&C Loads
RE: Masonry Stair Tower C&C Loads
If you do tie the wall to the stair landings, I would think that you would get a lot more two-way action than spanning simply from landing to landing.
RE: Masonry Stair Tower C&C Loads
RE: Masonry Stair Tower C&C Loads
RE: Masonry Stair Tower C&C Loads
Can you talk the Architect into allowing a steel girt at each floor? I mean, on the inside of the CMU.
DaveAtkins
RE: Masonry Stair Tower C&C Loads
You may have to look at several locations to determine the maximum wall height. You may still have to reinforce the walls vertically depending upon the floor to floor height.
Good luck!
RE: Masonry Stair Tower C&C Loads
What I have done in the past, not necessarily for stair towers (and I agree that it is not the best solution - masonry contractors hate it and it tends to slow construction down) is to provide horizontal concrete bond beams at whatever spacing is required. You can play with the concrete strength as required to get your spans and strength required. Just recently, I used it on a High School Fine Arts Theatre where the CMU walls were 50 feet tall. I spanned horizontally between pre-cast concrete pilaster/columns spaced about 22' apart using concrete bond beams at 48"o.c. vertically. In my case, the exterior auditorium walls were to be painted and the Architect used the bond beams as accent stripes at various levels.
RE: Masonry Stair Tower C&C Loads
I have encountered this situation several times in the past.
My method is to design the section of the wall between landings to span horizontally. By assuming a span from edge of landing to edge of land (in plan view) I get a span somewhere around 14 feet or so. This is doable with 8" bond beams. Don't forget to include the are of steel in your joint reinforcing in your calculations. It is small, but every little bit helps.
I then design vertical 'strips' the width of the landing to carry the load vertically between the landings.
This assumes that the landings can either transmit this horizontal force into the larger floor slab diaphragm (at the landing at floor elevation) or can carry the horizontal load into the masonry wall that is on the short side of the stair tower at the intermediate landing by some means of attachement.
This method appears rational to me.
Regards.
RE: Masonry Stair Tower C&C Loads
Your description didn't mention it but I assume that you then put a large vertical element at the end of landing (where the stairs connect) to carry the reaction component from the 14 foot horizontal span. The vertical element needs to transfer those forces to the landings above and below.
I prefer to have the wall continuously connected to the landings and stairs with intermittent clips. I then don't have to deal with trying to span the wall horizontally.
RE: Masonry Stair Tower C&C Loads
RE: Masonry Stair Tower C&C Loads
Yes, at the edge of the landings are vertical spanning elements (bars in adjacent cells) that carry the reaction from the 14' wide horizontal spanning section vertically between the landings.
RE: Masonry Stair Tower C&C Loads