A mathematical model with cracked section properties of the reinforced concrete structures shall be constructed for the purpose of determining member forces and structure displacements resulting from applied loads and any imposed displacements according to 12.7.3.
The effective section stiffness of the reinforced concrete structural system elements is taken into account by using the effective section stiffness factors given in Table 6.6.3.1.1(a), as described in ACI 318-19. Effective cross-section stiffness factors are applied only in the calculations under the loads included in earthquake effect. Effective cross-section stiffness multipliers are not used in the calculation under loads included in load combinations that do not have earthquake effect.
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