Instability of an Idealized Tainter-Gate System without Damping Caused by Surface Waves on the Back Water of Dam

抄録

Many Tainter-gates are being used with increased frequencies also in Japan, in order to control the water level of reservoirs. In this type of gate system, the effect of mechanical frictions is much less than in the type of vertical-lift gates, therefore providing a small hoisting load and a smooth operation of the gate. Though Tainter-gates have such great advantages, these facilities of the mechanism yield a fear that Tainter-gates may oscillate owing to some fluid-induced structural load, i.e. the operation of Tainter-gates may tend to become unstable. In this study, the stability of an idealized Tainter-gate system without damping effects, which is caused by surface waves on the back water of dam, was theoretically analyzed, but the analysis was restricted to the case that the resultant of the hydraulic pressure exerted on the weir plate passes under the trunnion pin. It was concluded as follows : Tainter-gates fundamentally possess the property of a self-excited oscillation.