Abstract: A self-supporting structural element and combinations of such elements in roof structures are provided in which each element has an upper beam and two side truss members formed by paired upper and lower longitudinal profiled ribs joined by the tie and strut members of a lattice framework, preferably exhibiting a trapezoidal cross section, and in which a plurality of the structural elements are joined in parallel relationship along the lower rib members. These structural elements are especially useful when combined into special roof structures for industrial, school or sport buildings.