A beam (20) comprising first and second flanges (23, 24), the beam (20) having a first region (28, 30) extending between the flanges (23, 24) and a second region (26) extending between the flanges. The first region (28, 30) is designed to support an applied concentrated shear load and the second region (26) is designed to support a predominantly bending load. The first region comprises a fan-shaped truss comprising a hub (36) adjacent the first flange and a plurality of struts (37) which extend substantially radially from the hub (36), and the second region (26) comprises either a truss structure which is substantially regular in the longitudinal beam direction or a shear web. The beam may, for example, be used as a floor beam for an aircraft fuselage.