n. 竖旋桥活动桁架

[ noun ]
a structure or device in which one end is counterbalanced by the other (on the principle of the seesaw)
<noun.artifact>

Bascule \Bas"cule\ (b[a^]s"k[-u]l), n. [F., a seesaw.]
In mechanics, an apparatus on the principle of the seesaw, in
which one end rises as the other falls.

{Bascule bridge}, a counterpoise or balanced drawbridge,
which is opened by sinking the counterpoise and thus
lifting the footway into the air.