Structures exposed to the most destructive effects against seismic forces are constructions where irregularities are present. In this study, torsional irregularities were investigated by creating different slab openings on 5 three-dimensional reinforced concrete floor diaphragms. Except for slab openings, the configurations of the slabs were the same. The aim of this study was to investigate the effect of torsion on the relationship between the mass and rigidity of the center position and diaphragm behavior in reinforced concrete bearing systems. During the experiments, measurements were taken from points at the top of the carrier system columns by means of total station and the displacement changes at these points after each cycle were determined. Thus, structural geometry changes, torsion direction, and angles were drawn separately in the plan for all diaphragm models. In symmetric buildings where the mass center and the stiffness center overlap, torsion is not expected when there is no asymmetricity induced during nonelastic behavior and where there is no wave-passage or coherency effect of the soil. However, in cases where the diaphragm behavior is not rigid, different results can be obtained. As a result, even if the mass and stiffness centers overlap in the structures, the results of this study show that torsional irregularity can be seen in cases where horizontal rigidity is not enough.