A The mathematical model is occured with cracked section properties of the reinforced concrete structures shall be constructed for the sections to the purpose of determining seismic 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 accounted by using the 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 effecteffects. 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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