ASCE 7-05 Wind Load GCN Values - Monoslope Roof
ASCE 7-05 Wind Load GCN Values - Monoslope Roof
(OP)
Hello,
with regard to determining the pressures acting on a monoslope roof of pitch = 0°, Components and Cladding provisions direct me to Figure 6-19A to which I am given two distinct gust coefficient (GCN) values for each zone, one positive and one negative. I am having difficulty in understanding the following note given on the page:
Plus and minus values signify pressures acting toward and away from the top roof surface, respectively.
Does this mean I have two possible load cases in which the wind force is either positive or negative?
OR
Does this mean I apply both negative and positive forces concurrently and the resulting force is the sum of the two?
I apologize in advance if this is blatantly obvious to a seasoned structural engineer, my background is mainly mechanical.
Alex
with regard to determining the pressures acting on a monoslope roof of pitch = 0°, Components and Cladding provisions direct me to Figure 6-19A to which I am given two distinct gust coefficient (GCN) values for each zone, one positive and one negative. I am having difficulty in understanding the following note given on the page:
Plus and minus values signify pressures acting toward and away from the top roof surface, respectively.
Does this mean I have two possible load cases in which the wind force is either positive or negative?
OR
Does this mean I apply both negative and positive forces concurrently and the resulting force is the sum of the two?
I apologize in advance if this is blatantly obvious to a seasoned structural engineer, my background is mainly mechanical.
Alex






RE: ASCE 7-05 Wind Load GCN Values - Monoslope Roof
RE: ASCE 7-05 Wind Load GCN Values - Monoslope Roof
Thank you for the clarification. I must confess though I did make an error in posting the wrong note as that one was from Figure 6-17a, the note I should have typed is:
1. CN denotes net pressures (contributions from top and bottom surfaces)
This one implies to me that they act concurently, or am I missunderstanding?
Alex
RE: ASCE 7-05 Wind Load GCN Values - Monoslope Roof
RE: ASCE 7-05 Wind Load GCN Values - Monoslope Roof
But that clears things up, thank you.
So in essence do these two pressures cancel each other out to a degree (as in they are opposing each other) or would the load be a summation of them acting in the same direction? From the code it suggests that positive means acting toward the surface and negative means acting away. I know I may have just answered my own question there but if they do combine the resulting load does seem overly onerous in my particular application.
Alex
RE: ASCE 7-05 Wind Load GCN Values - Monoslope Roof