Abstract: An automated weldless inter-locking grating assembly for bridge decks and the like which includes a plurality of primary load-bearing members located laterally, a plurality of transverse secondary load-bearing members and a plurality of trimorphic load-bearing members. Secondary load-bearing structural members are inserted sideways into apertures of primary load-bearing members and trimorphic load-bearing members. Thus, when a horizontal force is applied to alternate primary or trimorphic load-bearing members or any combination thereof, rotation of secondary load-bearing member or members occur to efficiently and automatically lock secondary load-bearing member or members into primary and trimorphic load-bearing member or members completing assemblage thereof into a rigid structural form.