AASHTO - Wind Load to Substructure

[DCKlyce]

I interpret in AASHTO standard spec section 3.15.2.2 that the area of the substructure for the end and front elevations should be calculated as set values. The 40 psf wind load should be resolved into an end and front component such that the resulant remains 40 psf. For example, for a 0 degree attack the components are 0 and 40 and for a 45 degree attack there are equal components of 28.3 psf to the end and front substr areas...and so on.Note the bridge is not skewed. Is this interpretation correct?