Lateral design of mixed timber and masonry

[steelnz2003]

Hi,
I am working on this job. The building consists of 2 units, but they are not on the same level, which makes it tricky.
The basement floor is reinforced concrete first slab is an infill concrete, and the top one is a timber Bondek.
The lateral system is RC masonry wall for basement and then GIB bracing for the other 2 floors.
There is a boundary RC masonry wall between the units.
I am requested a diagram ceiling to make things easier, that building can easily fall in an acceptable solution if floors at the same level
I do not see any issue for the gravity, but thinking of the easiest way to model it just to prove no torsional or unexpected mode.
Any suggestions for simple verification model? I used a u of 1.0 as elastic
Any ideas or comments?

Many thanks

 

[r13]

Any program can handle 3D model will work. I don't think you can easily eliminate torsion, but to minimize by adjusting support rigidity. Lateral load analysis will be very tricky though.