Field Vibration Tests and Proposition of Safety Measures for Dynamic Instabillity of Folsom-Dam Tainter-Gate

斜闸门（径向闸门）常被用作大坝泄洪的顶闸。1995年7月17日清晨，安装在加州福尔索姆大坝上的一个巨大的泰恩特门引起了振动，并发生了故障。从事故发生后不久就指出了振动参与其失效的可能性，并进行了一些失效分析研究。本文通过对45吨级泰恩特闸门和三维1-13尺度模型闸门进行振动试验，对泰恩特闸门可能存在耦合模态流致振动的理论分析进行了验证研究。此外，还对福尔索姆大坝泰恩特尔闸门进行了破坏分析，并对动力稳定提出了建议。研究结果总结如下：1。由于美国对恐怖主义的严重警告，本研究项目开始时计划进行的福尔索姆大坝堰式闸门现场振动试验未能进行。因此，在他的研究中，对日本实际使用的45吨全尺寸闸门进行了现场振动试验，以确定其在空气和水中的固有振动特性，其中首次采用了钢筋断裂试验来激发巨型闸门振动。对响应振动加速度进行了详细的测量，以确定固有振动的频率和模式。在水中振动试验中，也测量了水动压力，直接通过蒙皮板打一个小的压力孔。将实测数据与理论分析相结合，计算了水轮机在水中的振动频率和动力失稳曲线。结果，理论分析的有效性得到了很好的验证。建立了福尔索姆坝1/13比例的三维模型，并对其振动模态和水内振动频率进行了精心设计，使其与失效福尔索姆坝的振动模态和水内振动频率完全一致。将三维模型闸门安装在水循环型大型水槽中。因此，三维模型闸门确实再现了导致福尔松闸门破坏的剧烈耦合模态自激振动。通过三维模型闸门试验验证了理论分析的有效性。应用所建立的理论分析方法对Folsom闸门进行了破坏分析，从理论上分析了箱式闸门的动力失稳特征，并结合结构的有限元分析表明，在蒙皮的中心和底端，最大不超过11.9mm的小振动幅值引起了约为静载荷1.6倍的过大动水压力载荷；从而导致连接对角构件到主支柱的4个螺栓的早期失效。少

Tainter gates (radial gates) are frequently used as a crest gate of dam for a flood release. A huge Tainter gate installed on Folsom dam in California, induced vibrations and failed, early in the morning of July 17,1995. A possibility that vibration participated in its failure was pointed out from just after the accident, and some failure analysis studies have been performed by applicants.In this study, verification studies of theoretical analyses developed for a possible coupled-mode flow-induced vibration of Tainter gates were made by conducting vibration tests for 45-ton Tainter gate and 3-D 1-13-sclaed model gate. In addition, failure analyses of Folsom dam Tainter gate were made and suggestions for dynamic stability were presented. Research results are summarized as follows :1.Field vibration tests of Folsom-dam Tainter-gate which was being planned to conduct at the beginning of this research project was not able to be conducted because of severe cautions to terrorism in USA. In t … More his study, thereupon, field vibration tests were conducted for a 45-ton full-scale gate under practical uses in Japan, to determine its in-air and in-water natural vibration characteristics, where steel bar breaking tests were first adopted to excite the huge gate to vibrate. Detailed measurements of responding vibration acceleration were made to identify the frequencies and modes of natural vibrations. In in-water vibration tests, hydrodynamic pressure also was measures, where a small pressure hole was made directly through the skinplate. The measured data were incorporated into the theoretical analyses to calculate the in-water vibration frequency and the dynamic instability curve. As a result, the theoretical analyses were well verified for its validity.2.Three-dimensional 1/13-scaled model of Folsom dam Tainter-gate was made, where the vibration modes and its in-water vibration frequencies were carefully designed to be exactly same as those of failed Folsom Tainter-gate. The 3-D model gate was installed in a large flume of water circulation type. As a result, the 3-D model gate definitely re-realized the same type of violent coupled-mode self-excited vibration that must have caused the Folsom gate failure. The theoretical analyses were well verified for its validity by the 3-D model gate tests also.3.Folsom gate Failure was made by applying the developed theoretical analyses, where the dynamic instability of the Tainter-gate is theoretically examined and the major characteristics of this instability were presented, and an FEM analysis of the structure was incorporated to reveals that the small vibration amplitude of at most 11.9mm at the spanwise center and bottom end of the skinplate induced the excessive hydrodynamic pressure load of about 1.6 times the static load, thus causing incipient failure of 4 bolts connecting a diagonal member to the main struts. Less