Elevator Guide Rail Supports Deflection Requirement

[ctb74]

I am tasked with designing some HSS members to support the elevator guide rails on a building with high floor-to-floor (24 ft). The elevator rails cannot span this distance on their own and so we would like to use HSS6x6 columns to support the rails. The issue is deflection. The elevator manufacturer states we need to limit deflection to 1/8". With a 24 ft span and a seismic load of nearly 4000 lbs, a HSS6x6 is not even close to working. My question is two fold:

1) Is anyone familiar with the elevator code and where the 1/8" deflection limit comes from and if this applies to the member supporting the rail?
2) Are the seismic rail reactions provided by elevator manufacturers at a factored level meaning we can divide them by 1.4 for deflection calculations?

 

[KootK]

ASME A17.1 I believe. Excerpt below. I believe that the loads supplied by the elevator folks are appropriate for deflection checks without modification.

Perhaps you could meet the requirement by attaching the rail high and low on the HSS's rather than at mid-height.

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.

 

[bookowski]

Usually intermediate rail supports would be supported off of a horizontal divider beam. You should have the reaction being applied to a beam spanning roughly 8ft (or whatever the shaft depth is) - much better than 24ft. That beam needs to frame into something that has horizontal stiffness (and strength obviously). Usually I see this as a vertical steel post that is then braced laterally to the core walls at that midheight, or you can provide an intermediate concrete beam that the divider beam frames into. The above is typical - most elevators will spec an intermediate support for spans > 14ft.

 

[ctb74]

Thank you for the input. In the 2013 CA Building Code, there is a table under "Retainer Plates" that gives limits for the maximum guide rail deflections relative to its supports but I do not see anything in the CBC that overwrites the 1/4" maximum deflection of the supporting member noted in KootK's response above.

 

[sandman21]

1616.10.22 applies to DSA-SS projects, such as state owned universities. The section does not apply to buildings that will not be reviewed by DSA. ASCE 7-10 13.6.10 which refers to ASME A17.1 and sections 13.3.1 and 13.3.2.

 

[MrHershey]

What I was given recently by Otis:
1/8" for non-seismic deflection per 2.23.5.2 of ASME A17.1
1/4" for seismic deflection per 8.4.8.2 of ASME A17.1

Believe they were referencing the 2010 incarnation, if that makes a difference.

These guys originally just gave me the 1/8" number similar to you and I asked them to clarify if that included seismic and they gave me the separate 1/4" value that KootK had indicated above for the seismic cases.