Wind pressures on semirigid diaphragms are calculated for each Windward and Leeward surfaces of the building. Then, these pressures are converted to uniform line loads and applied along semirigid diaphragm edges as shown in the following figure.

In the preceding figure, (A) shows a uniform load applied at Windward side of the building. If diaphragm type is rigid, then the program converts the uniform load into a concentrated load and applies it at mid-width location of story (B). If there is any eccentricity defined, the concentrated load is shifted to its location (indicated in the figure with b ), or associated moment (w×a×b) is applied at the mid-width location (C).

In order to account for eccentric loading on a semirigid diaphragm, uniform wind line load is represented with a trapezoidal load pattern ( Equivalent Loading Systems ). The following equations are solved for new load pattern:

And solving the above two equations, one can find

It should be noted that the trapezoidal load profile generates the same amount of total load as of the uniform load, plus it also generates the same moment (w×a×b). This is graphically portrayed in the previous equivalent load systems figure.

The following figure shows an example of eccentric wind loads on a semirigid diaphragm. Note that if there is no eccentricity defined (A), the loading profile is linear. Otherwise, it is converted to a trapezoidal profile (B) to reflect the effect of eccentric loads.