huangyhg

design load criteria for old cotton mill
somewhat of a different question . . .
i am looking at a building that was constructed in 1917.
the concrete building was constructed as a three-story cotton mill.
the floor slab is 12" thick, has round columns in a 21' by 23' grid, with capitals and 3" deep by 8' square drop-heads.
the ceiling height is nearly 20', and i know the loading had to be in excess of the usual 250 psf for light manufacturing facilities, based upon the details.
does anyone have any old references that may suggest what the design loads for the floor might have been?
epr,
if you have access to "structural renovation of buildings" by alexander newman, he discusses that at the turn of the century there were quite a few proprietary concrete floor systems. i don't know what kind of information you may have available about the existing construction (drawings etc.), but this came to mind. if you had drawings that listed a type of floor system, someone out there may have some allowable load criteria for the floor system.
referencing a 1904 kidder-parker builders handbook that actually has somewhat of a design example for woolen/cotton mills. no exact loads are provided. the author states, "in store houses the story height should be low enough to prevent overloading." and "baled materials can be packed and stacked closer together than miscellaneous articles from floor to ceiling in defiance of building regulations, posted notices, and common sense." the author goes on to provide the 250psf load and then states once again that the designer should research the use and function of the building to determine more accurate loading conditions. sorry i can't be more assistance, but i bought this book a few years ago for a similar situation you are in, at least you will not buy this exact text in vain.
thanks to you both, shepherd and blake989.
the design of the system seems to be that which was common at the time.
this system consistes of radial and circumferential reinforcement, as the design contemplated circular design slabs. in lieu of the modern design theory of column and middle strips, the design was based on a pattern of circular slabs of three different designs. one circular slab was centered over the columns, one centered between and aligned with the columns in both directions, and one in the middle. these design sections actually used reinforcing oriented radially and concentrically with the design sections, and other bars to anchor the circles to each other. it was actually ingenious, when you think about it.
however, since i do not know the size or type of the reinforcing bars, i was hoping to get a range of possible floor loadings.
if anyone else has any information, i would greatly appreciate it.
epr,
sounds very much like the s-m-i slab system. according to newman it was very popular in the eastern u.s.. newman references a crsi booklet "evaluation of reinforcing steel systems in old reinforced concrete structures", 1981.

can you find a couple of holes through the floor slab where you might get a look at the rebar? then you might be able to back calculate the original design capacity, just for the sake of getting a feel for the design. you would have to assume that the building where in good condition, but it would give you a starting point and then adust from there.
it is always possible to take a few investigative core samples too.

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