A load-supporting structure comprises a plurality of similar longitudinally extending truss members each having upper and lower spaced-apart chords and intermediate joining members. The chords and joining members are constructed of rectangular tubular members, the joining members being arranged to overlap adjacent side surfaces of the respective chords which, in a preferred embodiment in which the tubular members are constructed of fibre-reinforced plastics material, provides large bond areas resulting in a strong lightweight structure.The load-supporting structures of the invention find particular application in forming the individual trackways of a temporary bridge structure, means being provided for attaching structures end-to-end and to suitable ramp portions.