Suspended Elevator Pit

[Galambos]

Two parts:

1. is anyone aware of special loading requirements in the US for an elevator pit that is suspended, rather than set on a foundation per ASME? My review of ASME A17.1 didn't turn up anything, but I want to make sure.

2. I have buffer reactions from my cutsheet below the counterweight and cab of about 30k apiece. Including live load and selfweight reactions from the rails, are there any loads I might be missing? Im thinking of reactions that the elevator manuf typically doesnt communicate.

Thanks!

 

[msquared48]

High rises have a lot of elevators that stop partway up and continue with another elevator run. This intermediate elevator would be the scenario I assume you are referring to here, ort something similar?

Mike McCann
MMC Engineering

 

[Galambos]

Yes, very similar condition.

 

[TDIengineer]

It is my understanding that the elevator show drawings should provide the buffer impact loads to your elevator pit slab. When you say suspeneded, I would guess that you have a structural slab on grade with piles?
Anyway, the pit needs to be designed for the self weights plus the reactions from the manufacturer. I don't think there is anything else.

I know the sheave beam and lateral supports limit structural deflections of 1/4". I don't think a pit support has those same constraints as the buffer loads are only applied if something fails in the elevator. I would check the pit slab for normal deflection limits.

 

[TDIengineer]

crum... elevator SHOP drawings.

 

[aaronPTeng]

galambos, I agree with TDI,

Check the elevator shop drawings, these loads can get high,
Where I am from I find the cheap lift companies always specified higher loads at the base.

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976

 

[Galambos]

yes, of course, elevator shop drawings, but as it always goes in the US, the elevator shop drawings have not been designed until well after the structural drawings are complete.

I have my buffer loads from the manuf's cut sheets. The cut sheets, for whatever reason, do not include the dynamic loads on the rails, as i am accustomed to receiving.

It's an interesting condition where we are suspending the pit from a new mild slab 35 feet down, past an opening in an existing slab.

 

[PUEngineer]

Elevator suppliers; the DIVAs of the building industry. I'm whole heartedly of the opinion that these should be sole sourced from the start of design. Especially with MRL elevators.

 

[archeng59]

I have contacted the elevator mfr's during design, explained the need for loads and received that information from them even if they don't have a contract with the owner/contractor for the project.

 

[PUEngineer]

That's all well and good for design, but my point is that not all elevators were created equal. And in my experience the manufacturers aren't flexible. So, getting loads upfront doesn't solve possible issues unless the actual elevator imposes similar loads to the 'basis of design'.

 

[TDIengineer]

Galambos,
I think I have normally seen the impact or dynamic loads to simply be double the static. Hope that helps.

 

[Galambos]

to close the loop, i spoke with the manufacturer, and it turns out that I had most of the information, but as I suspected some pieces were missing. Usually, my conversations with manufacturers are not all that helpful, but this one went well.

Hopefully, this will help someone in the future.

For the traction MRL TKE Synergy 500fpm models, there are three types of loads acting on the pit:

1. car buffer 41k +/- listed on the cutsheet
2. counterweight buffer 31k +/- listed on the cutsheet
3. Rail safety application force - missing from my information. 10k +/- a piece. not listed on the hoistway/pit cutsheet
4. the two buffers cannot act simultaneously with eachother (and if they did, it would be well beyond the listed buffer forces)
5. the rail safety force and counterweight buffer can act simultaneously with each other
6. the rail safety force and car buffer cannot act simultaneously.

Now one last question remains. IBC requires 100% increase for impact on elevator loads. However, these loads provided are already increased for dynamic forces by a factor of 2 or more. My thoughts are that there is no additional increase necessary to comply with IBC. Anyone agree?