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'97 UBC Design Question

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How is a "U" shaped building (with a courtyard) or one that is "V" shaped 
("U" shape with sloped legs) modeled if the roof  diaphragm exists at 
multiple elevations. Is the center of mass and rigidity calculated on the 
entire structure or on each block consisting of boundaries of shear elements?
Going a bit further, assume the structure is broken into separate blocks and 
each adjacent block contributes to the same line of shear. Is it reasonable 
to analyse each block for CM and CG an to calculate the rigidity of the 
shearwalls based upon the combined shear from each side of the walls 
(adjacent blocks)?
If this is valid, how do you treat the combination of blocks in the other 
direction where  two or more blocks (with varying elevations of roofs and 
directions of framing) contribute shear to the same grid lines. 
Do you accumulate the total shear from all blocks and distribut them into the 
grid line considering all walls in the grid to be tied by the plates and 
therefore balance them by rigidity?

Finally,  If you isolate the two legs of the "U" shape, you are left with a 
block with two open sides. How is the shear calculated at the two open sides 
and draged back into the exterior walls (courtyard) of each of the legs?

If anyone is willing to send me an example of a U shaped design i would be 
greatly appreciative.

Dennis Wish PE