huangyhg

aci:what are the factor of load cases in analysis of piles
hi all,
i am working in project designed by aci.
with members of the body structural part( slab, beam, column) i used combination with factored load (these combination are shown detailly in aci).
to calculate the numbers of pile, i want to use allowable stress design (in which force at top of pile compared with allowable capacity of pile), and use combination with unfactored loads. but i can not find provision showing detailly about these combination in aci.
could you kindly please give me a detail table about these above combination, for example:
1. f1d+f2l;
2. f3d+f4l+f5w;
3. f6d+f7l+f8e;
...
with f1=; f2 = ...
i am looking forward to hearing from you


d + l
d + 0.75l + 0.75w
0.6d + w
d + 0.75l + 0.75(0.7e)
0.6d + 0.7e
with these load combinations, a 1/3 increase in allowable capacity is not permitted.
daveatkins
thanks daveatkins!
your counsel are highly appreciated.
one more question:
i found in ibc that "when having more than two or more transient load act simultaneously with the dead load,ibc 1605.3.1.1 permit a 25% transient load reduction-> have factor = 0.75 in these cases. and i found the same in aci standard;
but: about a 40% reduction of dead load in combination (0.6d+w, 0.6d+0.7e), i only found in ibc, did not in aci;
could you kindly show me:where in aci say about this reduction or where in aci permit use ibc code (because in my project i have to use aci code)
i look forward to hearing from you
ose,
chapter 8 (of aci318-08), section 8.2, defaults to asce 7. chapter 2 of asce7,"combinations of loads" calls out the basic combinations in 2.3.2. ibc section 1605.3 is similar to asce7.
i hope that this answers your question.
ose,
in the two cases you asked about the 0.6d does not represent a 40% reduction in dead load. rather it is a 40% reduction in the stabilising effect of the dead load against the wind or earthquake load. in other words, watch the signs.
aci would not have a 0.6 factor anywhere, because concrete is designed using ultimate strength design, not allowable stress design.
daveatkins
dear all,
thanks for your answers. they make me understand clearly about load combination.
i wish that we can discuss more in future.
with very best wishes,
ose

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