upper beam

例句：

1. 1. The engineer carefully measured the length of the upper beam before cutting it.
   工程师仔细测量了上梁的长度，然后才进行切割。
2. 2. The upper beam was used to support the roof and prevent it from collapsing.
   上梁用于支撑屋顶，防止其坍塌。
3. 3. The construction crew had to reinforce the upper beams to withstand the weight of the building.
   建筑工人必须加固上梁以承受建筑物的重量。