huangyhg

elevated swimming pool
i am trying to design an a swimming pool at second floor supported underneath by pretensioned/ pt beams.
aci specifies to use to add 1.4 x f ( water load) to every load combination with live load.
-wht live load should i use ( the people swimming ??) how much??
- do i have to consider impact load ( a person jumping to the pool?? if yes , how do i distribute that
- if i have to consider siesmic on my load combination do i have to add the water load with the dead load ...
- any good reference book/code i can refer
i really appreciate for your much needed answer to my qstns?
bennie
check out our whitepaper library.
i would include a live load - perhaps 50 psf to 100 psf.
no impact.
seismic - sloshing water is an issue - but i'm not sure about those requirements -
a swimming pool = fancy tank- so look up tank information. you should be able to find info for circular or rectangular- odd shaped, variable depth, perhaps not.
in tank design, part of the fluid is assumed to act rigidly with the tank and part of it moves at a much slower period due to the sloshing (considering the sloshing is usually a reduction in loading, not an increase as might be expected).
the building codes also have some wording about tanks supported by buildings- check into those sections.
when designing water bearing or retention structures like a swimming pool, i would strongly advise using a multiplier of at least 1.7. as a matter of fact, aci 350 says to use an extra multiplier of 1.3 (1.7 x 1.3 = 2.21) for bending stresses.
agree with jedclampett. while a swimming pool is not strictly an environmental concrete structure, it does contain liquid, so i would use aci 350, including the so called "durability" factor.
aci 350.3 covers seismic design of liquid containing concrete structures.
i would ignore live load of swimmers, as people weigh less than water, and have the same beta factors, under aci 350.
when people enter the pool the water level will rise (archimedes principle). if the pool overflows and the water is piped "away" the weight of the contents of the pool (water + people) will remain essentially the same (people have a specific gravity very close to 1 ... some "sink", some "float")
if the water level rises, but the pool does not overflow, the weight of the pool contents (again... water + people) will increase by an amount more or less equal to the weight of the people. this is true whether the people are standing up (touching bottom) or swimming (not touching bottom).
however if compare the weight of the water with the weight of the water + people the difference is small. you did not mention the size of the pool, hypothetically say that it is 60' x 20' x 5' (average depth). weight of water = 374 kips.
say that there are 50 people in the pool with an average weight of 160 pounds. weight of people = 8 kips.
that 2% increase (if the water does not overflow) will be "lost in the shuffle" of your other calculations (this simple comparison ignores the weight of the pool / supporting structure).
i agree with the others to consider sloshing. have never designed a swimming pool, but have designed foundations for tanks in a high seismic area. we used the american petroleum institute (api) codes as a guide - load consideration for sloshing was tremendous.
funny note on the design of swimming pools. our firm designed a pool with an observation room for a local high school several years ago before i was employed there. the shockwave from the first person to dive into the pool shattered the glazing in the observation room, nearly emptying the pool.
a swimming pool could actually help for seismic, acting as a liquid damper.
the load factors in aci 318-05 have u=1.4(d + f) in eq 9-1. the other combinations have u=1.2(d + f + t) + 1.6(l + h), eq 9-2. only using appendix c - alternative load and strength reduction factors shall the 1.4(f) be added to all loading combinations that include l (and the higher phi factors for shear and torsion).
it will not fall down using higher load factors or "durability" factors of aci 350 but the owner may protest the added cost from the the code required minimums and engineering judgement is no protection to "errors or omissions" suits in a court
slideruleera
every pool i've been in (i swim laps for exercize) has a spillover that limits the high water level. i was assuming this pool has such a device.
civilperson
strength is not the rational for the durability factor of aci 350. it's watertightness. the factor is introduced to limit crack widths under service loads.

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