Based on ASCE code: 12.2.2 Combinations of Framing Systems in Different Directions. Different seismic force-resisting systems are permitted to be used to resist seismic forces along each of the two orthogonal axes of the structure. Where different systems are used, the respective R, C d , and Ω 0 coefficients shall apply to each system, including the structural system limitations contained in Table 12.2-1. 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. 12.2.3.1 R, C d , and Ω 0 Values for Vertical Combinations. Where a structure has a vertical combination in the same direction, the following requirements shall apply: 1. Where the lower system has a lower response modification coefficient, R, the design coefficients (R, Ω 0 , and C d ) for the upper system are permitted to be used to calculate the forces and drifts of the upper system. For the design of the lower system, the design coefficients (R, Ω 0 , and C d ) for the lower system shall be used. Forces transferred from the upper system to the lower system shall be increased by multiplying by the ratio of the higher response modification coefficient to the lower response modification coefficient. 2. Where the upper system has a lower response modification coefficient, the design coefficients (R, Ω 0 , and C d ) for the upper system shall be used for both systems. EXCEPTIONS: 1. Rooftop structures not exceeding two stories in height and 10% of the total structure weight. 2. Other supported structural systems with a weight equal to or less than 10% of the weight of the structure. 3. Detached one- and two-family dwellings of light-frame construction. 12.2.3.2 Two-Stage Analysis Procedure. A two-stage equivalent lateral force procedure is permitted to be used for structures that have a flexible upper portion above a rigid lower portion, provided that the design of the structure complies with all of the following: a. The stiffness of the lower portion shall be at least 10 times the stiffness of the upper portion. b. The period of the entire structure shall not be greater than 1.1 times the period of the upper portion considered as a separate structure supported at the transition from the upper to the lower portion. c. The upper portion shall be designed as a separate structure using the appropriate values of R and ρ. d. The lower portion shall be designed as a separate structure using the appropriate values of R and ρ. The reactions from the upper portion shall be those determined from the analysis of the upper portion amplified by the ratio of the R∕ρ of the upper portion over R∕ρ of the lower portion. This ratio shall not be less than 1.0. e. The upper portion is analyzed with the equivalent lateral force or modal response spectrum procedure, and the lower portion is analyzed with the equivalent lateral force procedure. This code converts the reactions of upper structure taken as an output of ETABS software and inserts the reactions to e2k file of lower structure.