Study on Seismic Behavior of Mechanical Snubbers

机械减振器是用于管道系统在高温、放射性等特殊环境下的抗震装置，由滚珠丝杠、飞轮、制动盘和制动蹄组成。它对管道的热膨胀等缓慢运动无阻力地移动，并抑制地震等快速运动引起的位移。由于机械减振器在负载和频率响应方面都具有非线性，因此对其阻力特性进行理论分析比较困难，本文推导了机械减振器的运动方程，并利用连续系统仿真语言（CSSL）对机械减振器的阻力特性进行了仿真。对缓冲器的各种物理特性进行了数字仿真，仿真范围较宽。利用CSSL软件对减震器支承的管道（简支梁）的地震反应进行了数值模拟。讨论了减震器在地震作用下的减震效果和最大阻尼力，并与油阻尼器进行了比较，利用试制的振动试验机测试了市场上一种减震器的阻尼力特性。实验结果与数字仿真结果吻合较好，验证了数字仿真的有效性。此外，还从理论和实验两方面探讨了由滚珠丝杠、飞轮和垂直摆动调速器组成的新型机械阻尼器的隔振效果。该阻尼器对于飞轮的惯性矩J的较大值起缓冲器的作用，并且对于J的较小值起一般吸收器的作用。

The mechanical snubber is an earthquakeproof device for piping systems under particular circumstances such as high temperature and radioactivity, and consists of a ball screw, a flywheel, a brake disk and brake shoe. It moves without any resitance in response to a slow movement such as thermal expansion of pipings and restrains displacement caused by a rapid movement such as earthquake. It has nonlinearities in both load and frequency response, so it will be very difficult to analyze the resisting force characteristics of the mechanical snubber theoretically.In this research, the equation of motion of the mechanical snubber was derived and the resisting force characteristics of the snubber were simulated using Continuous System Simulation Language (CSSL). The digital simulations were carried out for various kinds of physical properties of the snubber and over a wide range. The earthquake responses of piping (a simply supported beam) which is supported by the snubber were also simulated using CSSL. The restraint effect and the maximum resisting force of the snubber during earthquake were discussed and compared with the case of an oil damper.The resisting force characteristics of a snubber available in the market were measured using the vibration testing machine built as trial. The experimental results agreed fairly well with the results of the digital simulations, so that the validity of the digital simulations were substantiated.Moreover, the effects of vibration isolation of a new type of mechanical damer which is composed of a ball screw, a flywheel and a vertically oscillating governor were discussed theoretically and experimentally. This damper acts as a snubber for larger values of the moment of inertia J of the flywheel and acts as general absorber for smaller values of J.