Secondary support beam (1, 1A-1E), which is intended to be disposed between two primary beams (P1A-P1D) so as to form a modular support framework for supporting a slab formwork or the like, the secondary support beam (1, 1A-1E) extending along a first longitudinal direction (I-I) between a first end and a second end, and comprises: - a load-bearing upper surface which defines a load-bearing plane and is intended to bear the slab formwork or the like, - length adjusting means for adjusting the length of the secondary support beam, - a first connecting structure, which is disposed at the first end and is designed to be fixed to a respective primary beam (P1A-P1D) or to a shore (E1-E8), - a second connecting structure, which is disposed at the second end and is designed to be fixed to a respective primary beam (P1A-P1D) or to a shore (E1-E8), wherein: - the first and second connecting structures are respectively articulated to the first end and to the second end via a respective pivot connection (11, 12) allowing each of the first and second connecting structures to pivot about a respective first (IV-IV) and second (V-V) pivoting direction perpendicular to the load-bearing plane, - the secondary support beam (1, 1A-1E) having a maximum cross section which is defined by a height along the first (IV-IV) or the second (V-V) pivoting direction and defined by a width along a transverse direction (VI-VI) perpendicular to the pivoting directions (IV-IV, V-V), - the first connecting structure extends, widthwise, along a transverse direction (VI-VI) perpendicular to the first longitudinal direction (I-I) and to the first pivoting direction (IV-IV), along a distance greater than the maximum width of the secondary support beam (1, 1A-1E), characterized in that the second connecting structure extends, widthwise, along a transverse direction (VII-VII) perpendicular to the first longitudinal direction (I-I) and to the second pivoting direction (V-V), along a distance less than the width of the first connecting structure. - a load-bearing upper surface which defines a load-bearing plane and is intended to bear the slab formwork or the like, - length adjusting means for adjusting the length of the secondary support beam, - a first connecting structure, which is disposed at the first end and is designed to be fixed to a respective primary beam (P1A-P1D) or to a shore (E1-E8), - a second connecting structure, which is disposed at the second end and is designed to be fixed to a respective primary beam (P1A-P1D) or to a shore (E1-E8), - the first and second connecting structures are respectively articulated to the first end and to the second end via a respective pivot connection (11, 12) allowing each of the first and second connecting structures to pivot about a respective first (IV-IV) and second (V-V) pivoting direction perpendicular to the load-bearing plane, - the secondary support beam (1, 1A-1E) having a maximum cross section which is defined by a height along the first (IV-IV) or the second (V-V) pivoting direction and defined by a width along a transverse direction (VI-VI) perpendicular to the pivoting directions (IV-IV, V-V), - the first connecting structure extends, widthwise, along a transverse direction (VI-VI) perpendicular to the first longitudinal direction (I-I) and to the first pivoting direction (IV-IV), along a distance greater than the maximum width of the secondary support beam (1, 1A-1E),