Experimentation by producing three-dimensional samples for understanding the seismic behaviour of a structure takes a significant amount of time and these experiments may be highly complicated. Based on literature, the seismic behaviour of structures with slab openings usually was represented by analytical assessments instead of three-dimensional experimental studies. Moreover, the limiting values of slab openings vary greatly between earthquake regulations. This variability has made it important for experimental studies. For this purpose, a total of 5 reinforced concrete carrier system models, with different slab opening ratios, were produced at 1/2 scale. As a result of the study, it was observed that in cases where there were 25% or more openings in the slab, rigid diaphragm behaviour decreased in the structure. It was recommended that for analyses of these types of building systems that the finite element method, based on the assumption of an elastic diaphragm rather than the assumption of a rigid diaphragm, be used.