Well...I hate to differ...but
Generally the comments above are correct - the sidewall pressures don't normally come into play. But there are certain structural systems where they do:
[blue]Say you have a one story, warehouse type of structure with wind blowing in the North-South Direction.
The sidewalls are on the west and east sides.
The structural system is steel columns and beams/joists using some type of concentric brace system, or a moment frame. Some of the side wall columns could be part of the lateral force resisting system and receive stresses from the North-South wind pressures - this due to lateral shears in the plane of the sidewalls and these would be either axial forces for a concentric brace, or bending and axial for a moment frame.
But if those same columns also supported horizontal wind girts, the columns would be recieving load from the MWFRS North-South wind pressures (windward and leeward) and ALSO the columns would be recieving bending outward due to the MWFRS sidewall pressures. [/blue]
Thus, the sidewall wind pressures can come into play in a necessary, code-required design check.
This is not to be confused with C&C loading as that would be a separate check for those side wall columns, independent of the MWFRS loads brought into the columns as part of a brace.