According to Section 12.2 - Design Coefficients and Factors by Type of Structural System
Cd = Deflection amplification factor
Ωo = Overstrength factor
R = Response modification coefficient
12.2 STRUCTURAL SYSTEM SELECTION
12.2.1 Each seismic force-resisting system should be designed by users in accordance with the specific requirements for the system listed in Table 12.2-1.
184.108.40.206 R, Cd , and Ω0 Values for Horizontal Combinations
The value of the response modification coefficient, R, used for design in the direction under consideration should be selected the least value of R for any of the systems used in that direction.