girder:A horizontal beam, as of steel or wood, used as a main support for a building or bridge.大梁:一水平的铁制或木制的桁条,用来作为建筑物或桥梁的主要支撑物.beam:A squared-off log or a large, oblong piece of timber, metal, or stone used especially as a horizontal support in construction.梁、栋梁:建筑中用作水平支撑的,多为切成方形的圆木或长方形木材、金属或石头.