A SYSTEM OF TRUSS STRUCTURES FOR INTERMEDIATE AND HEAVY LOADS FOR FORMING, SHORING, SCAFFOLDING OR THE LIKE, comprising a set of metal double T beams, each beam having a length (a-f), a height (w,y) and a width (r), and being made up of opposing C-shaped metal profiles with bent flanges and parallel webs separated and coupled by reinforcing cross-members, equidistantly spaced, defining openings or separations (20, 30) in the beams, wherein: - the set comprises two beams having two different heights, one heavyweight and one lightweight, which compensate and are complementary to one another but have different heights (w,y), and are arranged in different lengths (A to F) respectively; wherein - the heavyweight and the lightweight beams have the same width (r) and are made of metal sheet; wherein - the lightweight beam has through lightening holes in the webs of a diameter of 60 mm arranged in one row centred and aligned with the longitudinal axis; and wherein - the two beams (1, 1a) are closed at their longitudinal extremities by means of rectangular end plates (24,31) having heights (w,y) and widths (r) corresponding to the respective beams, lightening holes (25,35) coinciding with the openings or separations (20,30) in the beams and fixing holes (25, 36); the system being CHARACTERISED in that: - the heavyweight beam has a height (w) of 420 mm and the lightweight beam a height (y) of 200 mm; wherein - the metal sheet of the heavyweight and of the lightweight beam have a thickness of 6 mm and of 5 mm respectively; wherein - the heavyweight beam has through lightening holes with a diameter of 60 mm in the webs arranged in two rows, aligned with the longitudinal axis of the beam, transversally spaced in relation to said axis and longitudinally paired, a plurality of fixing holes with a smaller diameter being situated around these lightening holes with an equidistance between them equivalent to 110 mm occurring both transversally and longitudinally; wherein - the bent flanges of the two beams (1 and 1a) have fixing holes situated equidistantly; and wherein - said reinforcing cross-members which are fitted in the openings or separations (20, 30) of the two beams (1, 1a), are secured in slots cut in each one of the webs, in which embossments of the cross-members are fixed by means of welding, or of forming welding nodes, around which there are sets cf fixing holes in an orthogonal arrangement. - the set comprises two beams having two different heights, one heavyweight and one lightweight, which compensate and are complementary to one another but have different heights (w,y), and are arranged in different lengths (A to F) respectively; wherein - the heavyweight and the lightweight beams have the same width (r) and are made of metal sheet; wherein - the lightweight beam has through lightening holes in the webs of a diameter of 60 mm arranged in one row centred and aligned with the longitudinal axis; and wherein - the two beams (1, 1a) are closed at their longitudinal extremities by means of rectangular end plates (24,31) having heights (w,y) and widths (r) corresponding to the respective beams, lightening holes (25,35) coinciding with the openings or separations (20,30) in the beams and fixing holes (25, 36); the system being CHARACTERISED in that: - the heavyweight beam has a height (w) of 420 mm and the lightweight beam a height (y) of 200 mm; wherein - the metal sheet of the heavyweight and of the lightweight beam have a thickness of 6 mm and of 5 mm respectively; wherein - the heavyweight beam has through lightening holes with a diameter of 60 mm in the webs arranged in two rows, aligned with the longitudinal axis of the beam, transversally spaced in relation to said axis and longitudinally paired, a plurality of fixing holes with a smaller diameter being situated around these lightening holes with an equidistance between them equivalent to 110 mm occurring both transversally and longitudinally; wherein - the bent flanges of the two beams (1 and 1a) have fixing holes situated equidistantly; and wherein - said reinforcing cross-members which are fitted in the openings or separations (20, 30) of the two beams (1, 1a), are secured in slots cut in each one of the webs, in which embossments of the cross-members are fixed by means of welding, or of forming welding nodes, around which there are sets cf fixing holes in an orthogonal arrangement. - the heavyweight beam has a height (w) of 420 mm and the lightweight beam a height (y) of 200 mm; wherein - the metal sheet of the heavyweight and of the lightweight beam have a thickness of 6 mm and of 5 mm respectively; wherein - the heavyweight beam has through lightening holes with a diameter of 60 mm in the webs arranged in two rows, aligned with the longitudinal axis of the beam, transversally spaced in relation to said axis and longitudinally paired, a plurality of fixing holes with a smaller diameter being situated around these lightening holes with an equidistance between them equivalent to 110 mm occurring both transversally and longitudinally; wherein - the bent flanges of the two beams (1 and 1a) have fixing holes situated equidistantly; and wherein - said reinforcing cross-members which are fitted in the openings or separations (20, 30) of the two beams (1, 1a), are secured in slots cut in each one of the webs, in which embossments of the cross-members are fixed by means of welding, or of forming welding nodes, around which there are sets cf fixing holes in an orthogonal arrangement.