Abstract
The self-excited vibration of long shell type roller gate is observed at the small gate opening in under flow condition. The relations between water depth and discharge can determine its occurrence. Namely its region is that the water depth in upstream is higher than the depth of maximum discharge under the gate arises. This discharge must be calculated by taking account the deflection of beam. In this paper, the results of field test in the gate of Himekawa No. 6 power station are shown as comparing the unstable conditions in both designed stage and after constructed stage. The results of field-tests shows good co-relations to the unstable conditions determined by the maximum discharge conditions.
