IBC 2003 Serviceability for Steel Buildings
IBC 2003 Serviceability for Steel Buildings
(OP)
We have a great debate waging in our office and I thought I would throw it out there to you guys to see what kind of opinions I get.
The whole issue began with the question as to whether a steel rafter supporting a drop ceiiling needs to meet a deflection of L/180 or L/240. Of course the drop ceiling would qulaify as a non-plaster ceiling putting it in the L/240 category. However, the argument has been made that the drop ceiling is a flexible system and could certainly bounce back from a deflection of L/180.
This of course led to other debates concerning the amount of snow load that needs to be considered for these deflection calculations. Is it DL + 1/2 50 year snow or DL + Full 50 year snow. There seems to be some disagreement here between AISC, ASCE and MBMA.
I'll leave it at that for now and see if you guys have an interest in discussing this topic.
~waytsh
The whole issue began with the question as to whether a steel rafter supporting a drop ceiiling needs to meet a deflection of L/180 or L/240. Of course the drop ceiling would qulaify as a non-plaster ceiling putting it in the L/240 category. However, the argument has been made that the drop ceiling is a flexible system and could certainly bounce back from a deflection of L/180.
This of course led to other debates concerning the amount of snow load that needs to be considered for these deflection calculations. Is it DL + 1/2 50 year snow or DL + Full 50 year snow. There seems to be some disagreement here between AISC, ASCE and MBMA.
I'll leave it at that for now and see if you guys have an interest in discussing this topic.
~waytsh






RE: IBC 2003 Serviceability for Steel Buildings
If the roof framing is concrete, creep must be considered. If the roof framing is steel, and is a low slope roof, ponding must be considered. I size steel joists for roofs for L/360 live load deflection, since I have found this tends to control ponding.
Oh, and I always use full snow load for checking deflection.
DaveAtkins
RE: IBC 2003 Serviceability for Steel Buildings
I design for the recommendations in the second edition of the design guide, which have recommended deflection ratios and maximum recommended deflections. They also say to use a 50 year snow. If the ceiling does hang up on a partition and there is some distress, you could get an irate call from the owner.
RE: IBC 2003 Serviceability for Steel Buildings
I would still be interested in hearing more opions both for or against as well as any relavent code mentions.
~waytsh
RE: IBC 2003 Serviceability for Steel Buildings
The codes just don't leave any out for anything but the L/240.