masonry screenwalls

huangyhg

masonry screenwalls?
i have discussed this question with other engineers in my office and i can't seem to get a reasonable answer that sits well with me.
so i figured that many of you could provide me with a logically answer that has proof to it other than this is the way i have been doing it for years.
i recently was designing a masonry screenwall to go around some mechanical equipment outside. in asce 7-05 provisions for screenwalls and signs there is one equation for a force (f) in lbs. what is the purpose of calculating that force when in the equation f = q(h)*g*c(f)*a(s) you are first finding the uniform velocity pressure. from a design perspective it makes sense to calculate a uniform velocity pressure q(h) or q(z) in psf [and from my understanding q(h)=q(z)] to find the moment to design it as a cantilevered wall. once you have the moment then you are able to design the foundation for overturning.
i am not seeing why there is a need to find a force (f) in lbs when you could have an infinite length of screen wall. so that would mean you would have an infinite area a(s).
what good does it do? i am probably missing something here so any help would be greatful. it is sunday morning and this has been bothering me since friday.
thanks in advance.
andrew.
it's not really set up for a screen wall case.  you need to check the wall for a one foot (or whatever) wide unit section and design the whole wall for those per foot moments and forces.
the only complication is that when you got to the values of cf for the sign/wall case, you'll need to use the maximum value of l/h on the table.  don't use the unit width you picked for "l" or your analysis will be too conservative.
i don't know why the asce 7 presents it like that.  almost everything is done using a unit width analysis.