The invention relates to the stiffening structure of load-bearing intermediate floor slabs in buildings, the framework of which comprises load-bearing columns (10); longitudinal sides (Sa) and transversal sides (Sb), a reinforced-concrete intermediate floor slab (9) in the area defined by the columns; on the longitudinal sides of the intermediate floor slab, longitudinal steel edge beams (Ia) or a combination of longitudinal steel edge beams (Ia) and longitudinal concrete-steel-sheet composite beams (3a), or longitudinal concrete- steel-sheet composite beams (3a); and on the transversal sides of the intermediate floor slab, load-bearing transversal steel edge beams (Ib) or a combination of load-bearing transversal steel edge beams (Ib) and transversal concrete-steel-sheet composite beams (3b). The intermediate floor slab rests on said load-bearing transversal edge beams. In the area of the columns (10), the stiffening structure of the intermediate floor slabs comprises effectively L- or Δ- shaped tensile stress transmission members (30), the first branch (31) of which is arranged in the direction of the longitudinal side (Sa) of the intermediate floor slab and fastened to said longitudinal edge beam (Ia) and/or said longitudinal composite beam (5a), and the second branch (32) is arranged in the direction of said transversal side (Sb) of the intermediate floor slab and fastened to said transversal edge beam (Ib) and/or said transversal composite beam (5b).