usable height

例句：

1. 1.The building has a usable height of 20 meters.
   这座建筑的可用高度为20米。
2. 2. The new elevator can reach a usable height of 30 meters.
   新电梯的可达高度为30米。
3. 3.The tallest tree in the forest is 15 meters high, which is just above the usable height for many people.
   森林中最高的树高达15米，对于许多人来说，这已经超过了可利用高度。