Floor beam pressurized aircraft

The invention relates to a beam (1) for pressurized aircraft floor comprising an upper sole (2), a vertical web (3) and a bottom flange (4), the bottom flange being provided with two oblique legs (7, 8 ) disposed on either side of the vertical web and having a bearing surface (14, 15) for supporting the membranes pressurized areas (9), characterized in that the bottom plate comprises a connecting member (10 ) connecting the two oblique legs, so that said bottom flange has a closed section. Such a structure can advantageously be made of composite material.