Masonry Elevator Shaft in Wood Framed Building

[hdn32]

Hello,

I was asked/assigned to design an elevator shaft in a wood framed building with 10'-6" floor to floor height. The building lateral resisting capacity of the building is provided entirely by roof/floor diaphgragms and shearwalls. The building is under Seismic Design Category B (per IBC).

Dimensions of the elevator shaft are 8'6"x6'11" (inside)x 34'6" in height (from the top of the reinforced concrete pit to top of CMU shaft). 8" CMU wall thickness is proposed by the Architect.

Since I am not familar with Masonry structure, could anyone please point me to any references/direction regarding the design, detail of the above structure?

Following are what we have at the office:
- Design of Reinforced Masonry Structures by Narendra Taly, P.E.
- Building Code Requirements and Specification for Masonry Structures (TMS 402-08/ACI 530-08/ASCE 5-08).

Any input will be appreciated,

HN.

 

[msquared48]

What kind of shearwalls? Wood... Concrete?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[msquared48]

If you have access to it, Jim Amrhein's book, "Reinforced Masonry Engineering Handbook" is the bible for this.

Good backup is his "Masonry Design Manual".

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[BAretired]

The Elevator Branch in the Province of Alberta outlawed the use of masonry for elevator shafts a number of years ago. The reason was the difficulty of getting a good connection between the elevator hardware and the masonry.

I don't know if the ban is still in effect, but personally, I prefer cast-in-place concrete or timber for elevator shafts.

BA

 

[SLTA]

That's really interesting, BA - down south that's pretty much the standard, and will often be the only CMU in the building. What about the connection was difficult?

 

[hokie66]

A reinforced concrete masonry elevator shaft is not difficult to design. The 8" wall proposed by the architect should do it. Use your references, but be practical. Reinforce the wall in both directions, and grout all cores. That way, there will be solid masonry for all the fixings required to support the floors and the elevator rails, etc.

 

[Brad805]

BA, we put a masonry shaft in Bonneyville, AB a couple of years back so I think the ban ended. I am surprised to hear you mention preferring wood over masonry? I know quite a few elevator companies that do not like wood shafts because they have to come back and adjust too many times.

Brad

 

[BAretired]

slta, The difficulty, as it was explained to me was fastening bolts through the face shell of block. Too many cases of fracturing the face shell due to improper installation.

hokie, I would agree that masonry cores should be concrete filled all around.

Brad, masonry wasn't really an option, but if the ban has been lifted, I would certainly consider it now. Maybe the face shell could be removed where attachments are to be made so that the fasteners are made in solid concrete.

BA

 

[hdn32]

@ Msquared48: They are wood shearwalls.

@ Everyone: Thank you very much for your prompt response.

 

[msquared48]

OK.

By mixing a masonry core with external wood franing, you are going to have to deal with differential shrinkage of the wood floor to floor relative to the masonry that will not shrink.

Don't forget this aspect in designing the connections.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[msquared48]

And, obviously, the masonry core will add to the seismic forces seen, and tend to suck up more load than the wood shear walls if you have a rigid diaphragm. If it is flexible, no worries.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[hdn32]

@Msquared48: Thank you.

Those are flexible diaphragms. As far as connection, I am planinng to use metal straps/ties (by Simpson or equivalent) embeded into CMU walls at floor diaphragm levels.