Seismic Experimental Assessment of Remote Terminal Unit System with Friction Pendulum under Triaxial Shake Table Tests

In recent years, earthquakes have caused more damage to nonstructural components, such as mechanical and electrical equipment and piping systems, than to structural components. In particular, among the nonstructural components, the electrical cabinet is an essential piece of equipment used to maintain the functionality of critical facilities such as nuclear and non-nuclear power plants. Therefore, damage to the electrical cabinet associated with the safety of the facility can lead to severe accidents related to loss-of-life and property damage. Consequently, the electrical cabinet system must be protected against strong ground motion. This paper presents an exploratory study of dynamic characteristics of seismically isolated remote terminal unit (RTU) cabinet system subjected to tri-axial shaking table, and also the shaking table test of the non-seismically isolated cabinet system was conducted to compare the vibration characteristics with the cabinet system installed with friction pendulum isolator device. In addition, for the shaking table test, two recorded earthquakes obtained from Korea and artificial earthquakes based on the common application of building seismic-resistant design standards as an input ground motions were applied. The experimental assessment showed that the various damage modes such as door opening, the fall of the wire mold, and damage to door lock occurred in the RTU panel fixed on the concrete foundation by a set anchor, but the damage occurred only at the seismic isolator in the seismically isolated RTU panel system. Furthermore, it was considered that the application of the seismic isolator can effectively mitigate the impact and amplification of seismic force to the RTU panel system during and after strong ground motions in this study.

Evaluation of unbonded Strip-STRP bearing based on current design guidelines

<p>The scrap tire rubber pad (STRP) made of natural or synthetic rubber offers substantial vertical stiffness and lateral flexibility, which are suitable properties for seismic isolator application. If a stacked STRP is used as an unbonded seismic isolator, the in-service stress-strain and displacement demand when rollover deformation is allowed can be different from that without considering the rollover. Although design guidelines are currently available for bonded type bearings, there are no established criteria for the unbonded bearings. To investigate the performance and stress-strain demand of unbonded strip-STRP isolators, finite element analysis (FEA) is performed to compare the analytical result with the existing design guidelines. The stress-strain demand of the strip-STRP isolators is substantially influenced by the <i>l/w </i>ratio, and it is found that the in-plane stresses are the key parameters in the determination of the allowable displacement and the effective length. The analysis shows that an STRP isolator carrying a vertical load of 5.0 MPa can efficiently be utilized up to 230% shear deformation.</p>