Roof Pressure in Design Wind Load Cases
Roof Pressure in Design Wind Load Cases
(OP)
Reference ASCE 7-05 Figure 6-9 "Design Wind Load Cases", specifically Cases 3.
They do not mention roof wind. In Case 3, are the roof suctions additive such that the roof would be designed for (0.75 + 0.75)P = 1.50P?
They do not mention roof wind. In Case 3, are the roof suctions additive such that the roof would be designed for (0.75 + 0.75)P = 1.50P?






RE: Roof Pressure in Design Wind Load Cases
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Roof Pressure in Design Wind Load Cases
I cannot remember who suggested it, but I will proceed with Case 3 as if wind was coming at 45 degrees to the building. Roof pressure will start at that windward corner and get lower as it moves across the roof, NOT adding the roof pressure that would result from the two orthogonal directions.
RE: Roof Pressure in Design Wind Load Cases
After getting design wind pressures on the walls and the roofs using Fig 6-6 for each of the directions X and Y, do combinations of wind loads using cases 3 & 4 of Fig 6-9. These combinations are applicable to both, the walls and the roof.
RE: Roof Pressure in Design Wind Load Cases
RE: Roof Pressure in Design Wind Load Cases
If Case 1 is WX, Case 2 is WY, then Case 3 is 0.75 WX + 0.75 WY.
You would have to use the method above even if you are interested in calculating pressures along the diagonal of the building for MWFRS purposes.
For designing the roof elements, it would be C & C pressures as per Fig. 6-17.
You may also refer to commentary on page 297.