Wood elevator shaft in renovated 5 story

[TehMightyEngineer]

There's a few topics around the forum on this but it seemed worth it to start a new one.

Got a project involving installing a new elevator in an old building that is being renovated. Existing building framing is in good shape. Elevator shaft to be wood framed walls/supports that span between the existing floors (12" by 4" rough sawn at 12" o.c.). One side of the shaft will be existing masonry wall. The elevator rail and hoist beam will be supported on heavy timber or LVL spanning vertically between floors. May have to substitute steel for this if the loads are too large (but then I'll have shrinkage issues between the wood and steel). There is quite a long span between floor framing, 140 inches clear. Low seismic region, but my hoist beam reactions and rail loads are around 5,000 pounds.

So, my question is what issues have people encountered in similar situations with wood framed elevator shafts?

I suspect my biggest problem will be the lateral deflection of the rail supports between floors. Thankfully the building had a service elevator in the location of the future elevator, so the existing elevator shaft only has to support itself and the framing is already setup for an elevator shaft. The pit design will be typical reinforced concrete, nothing special there.

Picture attached.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[racookpe1978]

Service power runs and instrumentation/motor and gear locations above the top of the shaft OK?

Electric loads Ok for the breaker panel and controllers?

 

[TehMightyEngineer]

Both are more or less outside our scope (we were hired for structural only). However, electrical contractors were in there today and I trust they have it in hand. There's a cable run depicted on the elevator drawings and we can accommodate that in the structure easily enough. Motor and gear locations above the top of the shaft is the only sticking point. There is no penthouse but we're using the 14 ft clear height to our advantage. The elevator drawings show minimum clearances and we're close but should be able to meet them.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[Ron]

TME...look at fire resistance and fire code...not sure you can do as planned.

 

[KootK]

In 2x6 walls, I've used deep parallam columns on the flat for rail support. It eases coordination issues a bit.

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.

 

[BadgerPE]

I agree with Ron that fire code should be checked before you go much farther.

Man I love those old floor joists! I worked on a project several years ago that had 3"x16" at 12" o.c. spanning like 18-20' and in great condition for being 125+ years old.

 

[TehMightyEngineer]

TME...look at fire resistance and fire code...not sure you can do as planned.

Very good point which I forget to mention. Architect called for a 1 hour fire rated wall to surround the actual elevator shaft framing, so two walls adjacent to each other. You are right that this could derail the project so I'll clear this up with my boss who is much more versed with the fire code than I am. I will also follow up with the architect on and find out how he plans to accomplish this. I'm mostly concerned about the fire rating at the roof given our plan to try and fit the hoist beam and accoutrements in the ceiling of the top floor.

In 2x6 walls, I've used deep parallam columns on the flat for rail support. It eases coordination issues a bit.

This was my initial gut feeling. PSL or LVL turned flat for the rails, anchored well into the floor/roof timbers with simpson hardware. Plus, being engineered lumber will help a lot with shrinkage issues as I suspect dimension lumber would be far too prone to pull away and distort as it dries out.

Man I love those old floor joists! I worked on a project several years ago that had 3"x16" at 12" o.c. spanning like 18-20' and in great condition for being 125+ years old.

I'll definitely look into the fire code issues, see above. I'm going over ASCE A17.1 right now to see if that has any guidance as well on flammable walls for elevator shafts.

The floor beams and structure is in remarkable shape. I can see why they want to renovate this building. I've attached a picture of the unrenovated exterior, it's going to be a nice place. Mercantile on the first 1st floor, storage in the basements, and medium end apartments in the remaining floors.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[TehMightyEngineer]

Hmmmmm, architect called for a 1 hour fire rating on the enclosure yet my reading of the 2009 IBC section 708.4 seems to make it quite clear that a 2 hour fire rating is required. If the shaft is sprinkled then does this go down? I thought it did but don't see this exception.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[BadgerPE]

2 hour seems right. We did a 3 story hospital and I seem to remember a 2-hour shaft being required.

 

[Archie264]

Mr. Mighty Engineer, congrats on passing the 16 hour Bataan Death Exam.

 

[TehMightyEngineer]

Thanks Archie, that was by far the most difficult thing I've ever done. Makes designing an elevator shaft a piece of cake.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[ergus]

we did one recently. I lined the inside of the shaft with 3/4" plywood for structural purposes covered this with 5/8" Type X gypsum board for fire rating. We also used LVL on the flat to support the rails.The Building Inspector accepted it.