4-Storey concrete & steel midrise (or low-rise I guess :-) apartment
with two elevators rated for 3500 and 4500 pounds. Can a 2000lb milling
machine with a 3'x3' footprint be safely placed on one of the upper floors?
What if no other object is positioned within 8 feet?
(40psf * 8 * 8 = 2560). Don't know what actual design limits
of structure are or how to find them. Current owner doesn't
know builder. Would the blueprints be on file at city hall?
I guess I'm thinking the answer will be:
A.) No way, don't even try it,
B.) I need to see the blueprints/design specs, or
C.) Based on modern (i.e. 2004) construction techniques, you
should be OK
Without any information about the nature of the floor design, column spacing, wall locations, materials strengths, etc. etc. the answer can only be "B".
If you consider that the 2000 lb item that you are talking about would be placed on 9 sq.ft, the basic loading is over 200 psf (10 kPa for those that care). Most floors are designed for much less than that but they are also designed to be applied over much larger areas. So while the floor as a whole can potentially accommodate very large total loads resulting from small unit loading, smaller areas could suffer local failure under high unit loading.
__________________
Member of the SSPIA Senior Committee. Have a question? Go pester Tony.
I'll try to see if the city has records on that building so I can contact the builder,
but looks like I'll need the actual blueprints rather than just the loading numbers,
since the XX psf loading can be exceeded for small areas without danger. (A 250lb
man standing on one foot generates a load of > 750lbs per square foot.)
I feel pretty strongly that putting in a 4500 limit-marked elevator was pretty foolish if
the structure will punch through at half that amount. Sort of like leaving a car
with the keys in the ignition if you ask me. Of course, I want it to handle that load!
The specified capacity of the elevator does not imply any kind of guarantee about how the floor is designed. It only certifies the lift for that particular load.
Even so, a 4500 lb lift is probably about 5' x 7' ... or a "measly" 125 psf if one tried to empty the full load onto an equivalent space on the floor
__________________
Member of the SSPIA Senior Committee. Have a question? Go pester Tony.
I'll try to see if the city has records on that building so I can contact the builder,
but looks like I'll need the actual blueprints rather than just the loading numbers,
since the XX psf loading can be exceeded for small areas without danger. (A 250lb
man standing on one foot generates a load of > 750lbs per square foot.)
I feel pretty strongly that putting in a 4500 limit-marked elevator was pretty foolish if
the structure will punch through at half that amount. Sort of like leaving a car
with the keys in the ignition if you ask me. Of course, I want it to handle that load!
a 250 pound person does generate a 250 point point load if they are standing on their tippy toes, but you could not fit enough people into a normal space to reasonably generate 750 pounds per square foot, thus the generally accepted live load for an aseembly space (the most heavily occupied space) of 100psf. since it is highly unlikely that the structure was designed for 225 psf live loads, one cannot assume that the milling machine can be supported without further information. the capacity of the elevator is completely irrelevant.
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