Research and Development of Viscous Fluid Dampers for Improvement of Seismic Resistance of Thermal Power Plants: Part 2 — Evaluation of Lifetime

Abstract

In 2011, Great East Japan Earthquake that is the largest earthquake ever observed occurred. The earthquake had large energy, long duration time and many aftershocks. Huge tsunami caused nuclear accidents. At present, a large number of nuclear power plants in Japan have not been operated yet. Then the base load power in Japan was shifted from nuclear power to coal-fired thermal power. Therefore it is very important to improve aseismic performance of coal-fired thermal power plants. Boiler structures in coal-fired thermal power plants are generally high-rise structures. In addition its combustion temperature is very high, so boilers are simply suspended from the top of the support structures in order to allow thermal expansion. Therefore boilers easily vibrate. In order to suppress vibration of boilers during earthquakes, stoppers are set between boilers and support structures. The stoppers are made of steel, and dissipate vibration energy by plastic deformation. However aseismic requirements for thermal power plants against large earthquakes having large numbers of repeat counts have been increased. Then authors have developed a vibration control damper for coal-fired power plants. The damper is set instead of conventional stopper made of steel, and it is able to perform in earthquakes with relatively large numbers of repeat count. Construction of the damper is similar to oil dampers, but inner fluid is viscous fluid. In this paper, a seismic response analysis using an analysis model of a boiler structure is conducted. The analysis model has plural stoppers or plural dampers. The response analysis result is arranged to investigate lifetime of the stoppers or the dampers. The accumulated plastic displacement of each stopper or damper is used for the evaluation. As a result, it was confirmed that the proposed damper has high durability compared with conventional stopper made of steel.