This paper presents a numerical procedure to study the effect of interactions between slabs and ribs of a floor system using a combined finite element and finite spline strip method. The slabs and fibs are modeled separately by finite strip and finite element methods, respectively. The interactions between the slabs and ribs are calculated on the base of a flexibility approach. A computer program is developed and numerical tests are carried out to validate the procedure. The results can be used directly to assess the present design methodology of ribs that excludes an evaluation of force transfer at the connections between slabs and fibs.