on which a concrete floor is poured in the usual way but when the concrete has set the shoring structure is not dismantled but is caused to slide bodily horizontally until clear of the floor on top of it it is then lifted by crane and laid upon an upper floor so as to be ready to shore another concrete floor without delay since the flying shoring structure has to be lifted substantially at the limit of the crane 39 s reach it is very important that the structure should be light and the strength to weight ratio of the beam of the invention is very good as compared with prior art beams the stress in a shoring structure whilst it is being flown from the crane can cause the structure to distort the ability of the beam of the invention to receive cross braces or bridging braces between the beams means that the structure can easily be given the required stiffness that it needs to survive the flying operation without damage other refinements of the beam of the invention include the provision of the beads 53 57 at the extremities of the base 50 these beads receive clamping clips.