narrower concept I-beam Concept beam Concept beam grillage Concept belfast roof truss Concept box girder Concept cantilever beam Concept composite girder Concept connection point Concept glued girder Concept glued timber girder Concept laminated beam Concept nailed truss Concept nodal point Concept plain beam Concept plain truss Concept prefabricated beam Concept steel structure Concept truss Concept truss girder Concept wood beam Concept