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Yes, you not need to consider the effect of cracking in sections. Following is an excerpt from ASCE/SEI 7-16 "A mathematical model of the structure shall be constructed for the purpose of determining member forces and structure displacements resulting from applied loads and any imposed displacements or P-delta effects. The model shall include the stiffness and strength of elements that are significant to the distribution of forces and deformations in the structure and represent the spatial distribution of mass and stiffness throughout the structure. In addition, the model shall comply with the following: a. Stiffness properties of concrete and masonry elements shall consider the effects of cracked sections." ACI 318, or equivalent guidelines, set the rules. Use manual calculations/excel sheet to investigate your beams. A single modifier can not be applicable to every x-section of beam. It better to use a low modifier for all beams (0.1 or 0.01), and then manually verify only those cross-sections who are failing the shear+torsion interaction as per results of ETABS.