unit cross-sectional area

例句：

1. 1. The engineer calculated the unit cross-sectional area of the beam.
   工程师计算了梁的单位横截面积。
2. 2. The construction company needs to measure the unit cross-sectional area of the building.
   建筑公司需要测量建筑物的单位横截面积。
3. 3. The carpenter measured the unit cross-sectional area of the door frame.
   木匠测量了门框的单位横截面积。