an elongated structural member of substantially triangular cross - section incorporating either one longitudinally extending continuous passageway of circular cross - section whose center is located at or near the center of the cross - section of the member or a cluster of passageways whose center is similarly located with a member so constructed employed to transmit forces in compression , tension , shear , bending , torsion and any combination thereof and the passageway employed as conduit for air , water , electrical wiring and the like and in the construction of buildings such members specifically designed to serve as beams , columns , or struts .