Structural systems and elements therefor

A structural system comprises a set of elements including two or more plank members 10, which are preferably hollow and divided by interior partitions 12 into longitudinally extending compartments 13. The plank members 10 are open at each end, and are interconnected by connectors 20, comprising a stem 21, and two arrays of projections which may be aligned for in-line connection of the plank members, or set of right angles to form a corner, or have three arrays to provide a T-connection. The plank members 10 are connected vertically by rods 26 which pass through aligned apertures 14 in the plank members and notches 25 in the projections.