Abstract
This paper described a field experiment result and its examination on flow-induced vibration of a two-step roller-gate installed in one estuary barrage in Japan. In the experiment, the vibration was measured at a center and both sides of the gate span, by varying the upper weir position when the lower weir was laid on the river bed. As results, the vibration was observed under limited conditions of up/downstream water levels and overflow height, and it was found that lower weir vibrated around the bottom edge like an inverted pendulum, at frequencies of 0.2 to 0.3Hz, with amplitudes of over 30mm. Moreover, after calculating the lower weir's moment of the hydrostatic fluid force and gate's gravity around the bottom, the water level conditions for the vibration occurrence coincided with ones for when the moment nearly equals zero, that is, the gate stands vertically without any rollers.
