If I understand what your saying, for a case of independent frames/shearwalls in two orthogonal directions, the load on a particular wall has two cases to consider:
1. Torsional shear with accidental due to 100% load parallel to wall + 100% of the centroidal shear due to load parallel to wall...
I don't deal with seismic design in FL and trying to study up on some basics. ASCE7-05 12.5.3 talks about the combined seismic loading interaction for Category C and up.(ie 100% in one direction and 30% in the orthogonal. That said, section 12.8.4.2 states that the accidental torsion of 5%...