CMU Shaft Height

[Rweave]

I am having a hard time understanding how to design a freestanding masonry elevator or stair shaft. I am looking at like 40 foot tall shaft that is going to access the ground floor and two elevated floors. After reading the code it makes it clear if I don't want lateral loads from the building going into the shaft then I should keep it separate. This being said a free standing 8 inch cmu shaft at 40 feet seems little odd, but I have seen it done. I am just not sure how to go about designing this without using a design software. Being an elevator and stair shaft the one side of the shaft will have door openings. I tried looking at this as stand alone building with shear walls on four sides, the side with the openings doesn't seem to work?

Little background info its a shaft about 8' x 7' x 40 feet tall constructed of 8 inch cmu. This shaft will have a steel deck and beam enclosing the roof.

 

[KootK]

You might have to span the walls horizontally and treat the shaft as a three sided building at substantial openings if you want to pursue a stand alone approach.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Rweave]

I thought the only way that you can consider like a 3 sided open structure is if you have a rigid diaphragm????

 

[KootK]

The main point of classifying a diaphragm as rigid or flexible is so that you can ascertain the distribution of load to the various lateral resisting elements. With a three sided building, the load distribution is known automatically so the whole rigid/flexible thing becomes moot for all intents and purposes. Besides, if you go horizontal spanning with the walls, it kinda stops being a diaphragm building anyhow and more resembles a perforated tube under bending and torsion. It's actually quite complex without the diaphragm connections at each floor. Good candidate for some ETABS modelling is you really want to chase the behavior down.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.