Wind pressure and suction on roof
Wind pressure and suction on roof
(OP)
I would like to get an idea of who adds wind pressure and suction to the roof for lateral frame strength checks and drift checks. I don't mean for the roof infill beams, but when checking the LFRS (a odd shaped moment fram in my case), would add the resultant roof suction and pressure in with the lateral wind forces for the wind load case?
I don't believe the program that we use does this (RAM), but it seems to me that it should be added.
What does everyone else do?
I don't believe the program that we use does this (RAM), but it seems to me that it should be added.
What does everyone else do?






RE: Wind pressure and suction on roof
"I don't believe the program that we use does this (RAM), but it seems to me that it should be added."
That is a scary statement coming from you, dont you think you should know what the program accounts for. Easy to check by checking the sum of the reactions.
Anyway, the suction on the roof will increase the moment at the windward eave connection.
RE: Wind pressure and suction on roof
RE: Wind pressure and suction on roof
RE: Wind pressure and suction on roof
Never, but never question engineer's judgement
RE: Wind pressure and suction on roof
RE: Wind pressure and suction on roof
For taller buildings the effect is minimal, and in my opinion can be safely ignored.
For one or two-story buildings, yes it is appropriate to use MWRS roof pressures when checking the lateral force resisting system as the effect could be significant. This can be performed in RAM by creating snow load zones that allow negative pressures to be input to approximate the effect of the wind and creating custom load combinations that combines this effect properly with the other wind cases.
Alternately, just create a simple 2-d model of one of your frames and see how much a difference there is with and without the roof pressures added to determine if its worth the trouble of applying to the entire model.
RE: Wind pressure and suction on roof
RE: Wind pressure and suction on roof
As far as RAM support goes, we have got some very lame answers from their support staff when we have had questions. Good luck with them. Their support is so terrible that my firm has considered looking for a new program.