Abstract—A massive 87-ton Tainter gate installed at the Folsom Dam failed during operation on July 17, 1995. To avoid similar future failures all potential causes of the accident must be considered. For this purpose, experimental modal analyses were undertaken on one of the similarly designed remaining Tainter gates to identify its in-air natural vibration characteristics. The experimental mode shapes and frequencies are presented. Subsequently, a Finite-Element Method (FEM) model of the Folsom gate was constructed and validated by comparing the calculated natural vibration characteristics with the corresponding measured values. The validated FEM model was then used to calculate the static structural deformation of the Folsom gate and corresponding stresses. From the methodical investigation presented in this paper, the static loading due to increased trunnion friction on the Folsom Tainter gate was insufficient to produce failure. Finally, a conceptual model of a closed energy cycle for the self-excited vibration of the Folsom Dam Tainter gate is developed. This conceptual model was validated through tests on a twodimensional 1/31-scale model of the failed Folsom gate.

Index Terms—Folsom Dam gate, Tainter gate vibration, Radial gate, Failure investigation, Mode shape, Coupled-mode self-excited vibration

Cite: Noriaki Ishii, Keiko Anami, and Charles W Knisely, "Retrospective Consideration of a Plausible Vibration Mechanism for the Failure of the Folsom Dam Tainter Gate," International Journal of Mechanical Engineering and Robotics Research, Vol.3, No.4, pp. 314-345, October 2014.