ibc code

huangyhg

ibc code
according to ibc code,
if i am designing a stair case
it say's for top rails use 200# or 50 #/ft which ever is max.
does 50#/ft loading has to be continuous...
or do i have to find out the max moment or reaction it will prroduce considering various cases
such as for 3 span:
case 1 : 50# /ft through out
case2 : 50#/ ft at end
case 3: 50 #/ ft across 2 contionous spans..
check out our whitepaper library.
design the guardrail to resist a load of 50plf (continuous) applied in any direction at the top and to transfer this load through the supports to the structure.  also, design the guardrail to resist 200 pounds applied in any direction at any point along the top and have attachment devices and supporting structure to transfer this loading to appropriate structural elements of the building.  the greater of the two controls.
word continous can be taken as
in 3 span: continous on first two spans , and no load on the third.
if you see the guard rail is loaded continuous on first two spans.
if we can load the concentrated 200# at center, ends (for cantilever condition), why not the uniform loading.
if you see the asd/ lrfd manual page 2-309 for 4 span loading,if we compare fig 39 to fig 37
we can see that fig 37 has a moment that is 200% more than fig 39. if my section can bear bending stress (with 1.33 overstress included) for fig 39 will it not fail in fig 37 case loading..
this is a question that i have thought about before as well. handrail posts are typically 4'-0" apart. for this case a 200# load will be equal to a 50plf load for the design of any one handrail post.
however, a 50 plf over the entire length will control for other cases compared to a 200# load. i have heard reasons that the 200 # load could be from a person falling over who is trying to hold on from falling over. the 50 plf is more for people exiting during a emergency or some such event.
it is also interesting to note that you are allowed a 1/3 increase in stresses in the florida building code, however in a hvhz (high velocity hurricane zone), no stress increase is allowed. to me a enclosed stair is independent of whether it is in the middle of a storm or in vaccum.
your thoughts are welcome.
i don't think that the requirement for alternating "live loads" in the ibc applies to the 50 plf load at all.  make it continuous over all the spans.  the 200 lb load is the force that takes into account one single force on one location and not on other segments of the rail.
thanks for the comment,
slickdeals, jae, stevemort and other..
2006 ibc also allows a 1/3 stress increase for asd of handrails (1607.7.1.3).  i agree with jae, i don't think the alternate loadings are required here.  i can't say i've checked it, but i'm not sure if it would make that much difference.