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12.2.3 Combinations of Framing Systems in the Same Direction
Where different seismic force-resisting systems are used in combination to resist seismic forces in the same direction, other than those combinations considered as dual systems, the most stringent applicable structural system limitations contained in Table 12.2-1 shall apply and the design shall comply with the requirements of this section.
The intent of the provision requiring use of the most stringent seismic design parameters (R, Ω0, and Cd) is to prevent mixed seismic force-resisting systems that could concentrate inelastic behavior in the lower stories.
12.2.3.3 R, Cd, and Ω0 Values for Horizontal Combinations
The value of the response modification coefficient, R, used for design in the direction under consideration shall not be greater than the least value of R for any of the systems used in that direction. The deflection amplification factor, Cd, and the overstrength factor, Ω0, shall be consistent with R required in that direction.