In Shimane nuclear power plant of Chugoku Electric Power Co., a number of safety improvements are planned to be implemented aiming for the highest level of safety in the world to be achieved. One of the new safety measures is the application of viscoelastic dampers for seismic protection of safety related piping system and components.
High performance of viscoelastic dampers has been confirmed by direct testing of the piping natural scale model at the shaking table subjected to severe seismic accelerations up to 20 m/s2.
However, viscoelastic dampers as a dynamic protection device have frequency-dependent dynamic characteristics, which are difficult to reproduce in the frame of conventional seismic analysis based typically on the use of response spectrum method.
For example, the dynamic properties of viscoelastic dampers exhibit nonlinear dependence on dissipation energy, shear rate of viscous fluid, and temperature.
Method for Seismic analysis of systems with viscoelastic dampers (SAVD-Method) is one of the analytical approaches capable of considering the dynamic properties and nonlinear behavior of viscoelastic dampers.
The SAVD-Method is a comparatively simple but reliable approach for dynamic analysis of a piping system and components with viscoelastic dampers.
Frequency-dependent dynamic characteristics of the viscoelastic dampers are able to be modeled by a four-parameter Maxwell model.
To consider the nonlinearity of the dynamic properties of viscoelastic dampers, the Maxwell model parameters were determined for different usage conditions in conjunction with the adjustment dependent on the energy dissipation criteria.
Direct comparison of the shaking table measurements and analysis according to SAVD-method shows good matching of results for all controlled parameters and levels of seismic excitation.
