The invention provides a damping-capacity-adjustable passive
shock absorber for bridge construction. The passive
shock absorber comprises a bottom plate, a mounting cavity is formed in the bottom plate, a motor is arranged in the mounting cavity, a top plate is arranged above the bottom plate, and a
piston rod is fixedly connected with the upper surface of the bottom plate through a bolt; throughthe arrangement of the motor, the
piston rod, a rotating rod, a first through hole, a
piston, a shell and engine oil, the interior of the shell is divided into two oil cavities through the piston, when a bridge is vibrated, the shell is extruded downwards to slide relative to the piston, vibration energy is absorbed under the
pressure difference effect of the two oil cavities, the motor is started, the motor drives the rotating rod to rotate, the overlapping area of the first through hole and a round hole in one side of the rotating rod is changed, then the flow of engine oil between the two oil cavities is changed, the
pressure difference of the two oil cavities is changed, damping is regulated and controlled, the passive
shock absorber can adapt to different using environments conveniently, and the service life of the bridge is prolonged.