How to account for East and West wind in both +ve and -ve directions?
Please see the following AutoPIPE help section: Help > Contents> Contents Tab> Bentley AutoPIPE> FAQ> FAQ #24.
In order to account for a negative wind direction: add an additional wind load case specifying the Inclined direction to be opposite of the initial wind direction.
For instance:+X axis only : Wind direction = Global X-X axis only : Wind direction = inclined, Dx = -1, Dy = 0, DZ = 0
Modeling "Wind" - Load Case