Anchorage Design for Basement Elevator 1

[mikek396]

I am looking for some help with design of anchorage for a basement elevator machine replacement. The current machine has (4) 3/4 anchor bolts, and not in the correct locations for the new machine. New design loading will be approximately 26k sustained tension load on the anchor bolt group. Attached photo of 1 of 4 ABs and the machine overall (couldn't figure out how to rotate the images - sorry). I also attached an example bolt group layout from one particular machine, not necessarily the machine that will be used here - the manufacturer specifies that bolt F should be designed for 60% of total load - or ~15.6k tension, this is the most critical bolt. Option A would be to install anchor bolts in the locations A-F to directly handle the loads, Option B would be to install anchors in different locations and add some grillage assembly to which the machine will be mounted. Option A if preferable because it doesn't require additional steel, and doesn't add to the height of the new machine.

View attachment IMG_6400.jpg
I have extensive experience in elevator design, and specifically basement elevator design. For new construction this is easy, even for most modernizations it is straightforward to reuse the existing anchors, but this will be new anchors in existing concrete, so definitely not my forte. Right now I am looking for conceptual help, not free design. When the time comes I'll need a stamped anchorage design (NY) that I can use and I will be more than happy to pay for. TYIA

 

[lexpatrie]

I could use a basic description of how this even works, I take it there's no hoist beam at the top of the shaft?

Basement elevator design is a new one to me.... it's got a cable that's being pulled down on to lift the elevator?

Skipping past that, generally a new anchorage is going to involve drilling, special inspection, hole prep and adhesive anchors. Constant tension sounds a lot like the issues with the big dig hanging heavy precast panels from the ceiling, (they've done research since, as i recall, to prevent this kind of failure fro recurring).

These loads don't sound like a mechanical anchor would be viable, either.

You'd rather not have unused holes left in the substrate as all the testing I know of involves "solid" concrete, not perforated concrete.

You probably need to rotate the photo before you upload it, that's how my photos work, and phone photos are always goofy versus normal digital cameras. Just saying.

 

[mikek396]

@lexpatrie

The basic concept is that instead of the machine being at the top of the shaft, there are a set of sheaves (pulleys) that the cables wrap around and then go to the bottom of the shaft to wrap around the machine. There's a pretty good diagram at this link https://www.schumacherelevator.com/elevators/passenger/traction/basement-set/

Regarding the loads: it is true sustained tension, as the weight of at least the empty elevator and counterweight are always pulling up on the machine. Albeit, the actual load is much less than the required design load, as the elevator code calls for calculating the up-pull as double all cable tension less the machine dead weight - I usually just use double cable tension as an added margin of error.

To make things slightly more complicated- there is also basically a constant vibration when the machine runs, although I know this is never truly considered when these calcs are typically run.

 

[driftLimiter]

What do you have to anchor to? 26k isn't small potatoes. How much concrete is resisting there load? That's are big important questions.