noun
horizontal structural member
Technical term in architecture and building engineering for beams, girders, and other horizontal load-bearing elements.
横架材の設計には、建物の荷重を十分に考慮する必要がある。
When designing horizontal structural members, it is necessary to fully consider the building's loads.
桁 specifically refers to a girder or a beam that supports a floor or roof, a subset of 横架材.
Compound of 横 (horizontal) + 架 (erect, span) + 材 (material, member). The term is a modern technical coinage in architecture and structural engineering.