CMU Wall Max. Length

[iv63]

I am designing stair tower made of 12” thk CMU. It is a free standing vertical box 23’x9’x45’ with 4 walls (please see attachment). Tower is located inside of existing warehouse in California. I am planning to have bond beams at every stair landing. Section 2109.4.1 of CBC or IBC says: “Masonry walls shall be laterally supported in either the horizontal or vertical direction at intervals not exceeding those given in Table 2109.4.1.”
Question is what is max. length or height for this tower? Is it distance between bond beams or full height? Also what type of construction these walls are-bearing or non-bearing walls?
Thank you very much,
IV

 

[seny]

from point of lateral support in your case requirements are satisfied by floor to floor high. you need to check shear for placement of shear reinforcement accordingly. in case of heavy shear i prefer to have bond unit (bond beam if you want) for good placement of shear reinforcement where necessary, instead of having bars in between CMU courses.

 

[msquared48]

It depends here...

A. If there are floor or roof diaphragms that tie into the wall, lateral support points can be assumed here with proper connections.

B. If not, then you will have to look at the stair landing configuration to see if some logical argument can be made for restraint there.

If not, then full height, but I do not think that this will have to be the case. There could also be a combination of A and B considering the fact that there are four walls, probably with different lateral support situations.

Mike McCann
MMC Engineering

 

[SteelPE]

Doesn’t table 2109.4.1 fall under the empirical design of the code? Could you possibly engineer the stair tower using either section 2107 or 2108 and not have to worry about this table?

I know this doesn’t answer your question but it is another option.

 

[sandman21]

Can you even use empirical design? Take a look at section 2109.1.1

 

[JLNJ]

Your 12" CMU likely can span the 23'. It's just a simple shaft.