partition live load

huangyhg

partition live load
should the 20psf parition load be included when calculating live load reductions? if not, why would codes define it as a live load? i am working off of ibc 2000.
when things are steep, remember to stay level-headed.
-horace
partitions with the nbc of canada are considered as dl and they have the requirement that 20 psf be considered for partitions other than permanent partitions.  i normally don't consider them except as an added real load and stipulate on the drawings that "partitions shown are fixed permanent partitions.  no alteration, relocation or removal of these shall be made without prior approval of the engineer"
so far no problems... dik
i don't include the 20 psf in the live load reduction calcs.
neither do i... by code, it is considered as a dl
dik
so then you would also use the dead load factor for design instead of the live load (lrfd) factor.
in other words, you are still getting a break when you use factored design where i think i am supposed to be using full partition load and factoring it as a live load since it is listed under the live loads section.
sure... why not.  realizing that this is for fixed partitions.  with cmu partitions you pick a heavier dl <g>.  by code definition (in canada), the partition load is dead load... (i agree, it makes about as much sense as 20 psf... )  in many instances, the area displaced by the wall system somewhat accommodates part of the weight of the partition.  not using my abacus, a 4-1/2 wall displaces about 18 lbs of a regular office space loading... which is about 1/3 of the weight of the wall.. it takes a lot of partitions to make up 20 psf... and even more if you consider the displaced area of floor loading.  using a reduced partition load only applies to fixed partitions and you stipulate that those shown are fixed as my earlier note; many office floors do not have a partition layout...
one of the firms i used to work with used to design offices for ll=65 psf and no partition load... the 65 psf closely mimicing the 20 psf partition.
dik
haynewp-
for an office use, even though the code seems to say that the partition load is included within the live load when using > 80 psf ll, i treat it as a dead load and non-reducible.  this is probably conservative but on balance i will have little control over what partitions are put in over the useful life of the building.
believe that the statistical unlikelihood of actually ever getting a full live load on the floor is what drives the code to allow partitions to be included when designing with a higher live load. this is a nice idea in theory, but i think it is confusing in everyday practice.  (the old boca had the this same issue as the current ibc does now).
for example, if partitions are moveable this means that corridor locations can change.  code minimum office live loads for corridors (100 psf first floor, 80 psf upper floors) are higher than for just office space (50 psf).  i therefore usually end up designing the entire floor area that is going to carry moveable partitions for the corridor load. doing anything else will restrict how that portion of the building can be used, imho.  
so for example, for a non-composite steel framed first floor office, for gravity design i will use 80 psf as the reducible live load, but also add 20 psf to whatever the other dead loads are. i consider this as using the equivalent of a 100 psf ibc office live load.  if you have composite beams then the 20 psf is a superimposed dead load after the concrete is in.
i still design using asd most of the time, so haven't done this with lrfd load factors.  but if i was, would probably use the lower dl factor for the 20 psf partition load.

the other question this raises is how do you treat the 20  psf moveable partition load when calculating mass for seismic loads?  have to admit i usually don't include it, which perhaps is inconsistent. most of the buildings i work on are three stories max in low seismic risk areas, so there probably would not be a significant difference in the lateral shear if it was included.  but for a much taller structure in a higher seismic zone the difference in lateral load could be huge.  any one out there who does tall buildings out west care to comment further?
the best practice might be to always include the 20 psf partition load as part of the seismic mass, but i know of nothing in the literature that justifies keeping it in or out.  
good question.

in the 2003 ibc, section 1617.5.1, indicates that the effective seismic weight shall include the total dead load and other loads listed below: #2 states that "where an allowance for partition load is included in the floor design, the actual partition weight or a minimum weight of 10 psf of floor area, whichever is greater."
oldpapermaker-
that provision is also in ibc 2000, which governs here.  thanks for pointing it out.
sam:
i think the easiest thing to do is design the whole floor for the 80psf live load and make it reducible as you were mentioning. but i don't think i am going to go more conservative and add the 20psf to the dead load.
the reason for my decision on the 80psf reducible is that when i model the 50 + 20 in ram, i have a hard time defining the 50psf office load as being reducible while making the 20psf live load partition irreducible.
if i enter the partition load in just as a dead load with 50 live, i have to make sure camber is not figured in for the partitions and i don't think i am meeting code if using lrfd by factoring the partition load as a dead load instead of as a live load (ibc 1607.5 seems to make partitions to be treated minimally the same as a 20psf live load, or the other option is to just use 80 psf "specified" live load (i am figuring this to be reducible).
ibc section 1607.9 references table 1607.1 for reducible live loads but does not mention 1607.5, therefore i think the 20psf partition load is not up for reduction. i will just use 80psf live load reducible for now on for the gravity only design plus whatever dead load there is excluding partitions.