In the event of an earthquake, it is essential to accurately assess the seismic fragility of piping systems to ensure the continued safety of society. When evaluating the seismic fragility of a piping system, which is generally a secondary structural system, this should mainly be an integrated model that includes both the primary structural frames and the secondary ones, unlike the primary structural system of a building. Hence, the piping seismic fragility evaluation has an issue in that it takes considerable computational time because numerical analyses must be performed on a relatively complex model. Given this background, the purpose of this study is to propose an efficient piping seismic fragility analysis method by utilizing the existing seismic fragility analysis method and the Bayesian updating concept. In order to verify the validity of the proposed method, it was applied to a building–piping coupled structural system example, and its results were analyzed and compared with the results of the existing method in terms of accuracy and efficiency. As a result, the proposed method showed a similar accuracy compared with the existing method while significantly reducing the numerical cost of nonlinear seismic response analyses necessary for these results.

Most nuclear and nonnuclear power plants have been designed in the frequency range of 2 to 10 Hz, but now, the design guidelines for structural and nonstructural components such as electrical cabinets must be improved by including high frequency greater than 10 Hz for sustainable energy. The electrical cabinet is the essential piece of equipment for safety functions and the uncertainty of seismic capability in power plants. Consequently, the attention of this study focused on evaluating the seismic demands of the electrical cabinet under high frequency earthquakes and also, seismic qualification of the electrical cabinet using the identification of experimental tests and numerical models. An experimental test based on ICC-ES AC 156 and IEEE std.344 was conducted for seismic qualification of the cabinet and then, a high-fidelity finite element model to capture the significant deformation was developed in this study. It is observed that the fundamental frequencies were 16 and 24 Hz from the experimental tests, respectively. In order to verify the proposed high-fidelity simulation model, the target fundamental frequencies of the cabinet were evaluated in the ABAQUS platform. It was interesting to note that the reconciliation of experimental and analytical results was extremely identical. Furthermore, in order to evaluate seismic response characteristics of the cabinet subjected to high and low frequency earthquakes, time history analysis was conducted in this study, using the ABAQUS platform. As a result, the observation showed that the seismic response of the cabinet system under a high frequency earthquake was relatively higher than that of low frequency. It can be very important to note that the cabinet system was sensitive to high frequency vibration.

The purpose of this study is to investigate the soil‐structure interaction (SSI) effect on the overall risk of a PWR containment building structure with respect to two failure modes: strength and displacement. The precise quantification of the risk within the seismic probabilistic risk assessment framework depends considerably on an accurate treatment of the seismic response analysis. The SSI effect is one of the critical factors to consider when accurately predicting structural responses in the event of an earthquake. Previous studies have been conducted by focusing more on the positive side of the SSI effects and the effects mainly on the seismic fragility result. Therefore, this paper presents the results of a study of the SSI effect on the overall risk. Also, the study relies on an emphasis on revealing a beneficial and a detrimental effect of the SSI by utilizing an example of the containment structure in three soil conditions and two main failure modes. As a result, the consideration of SSI shows a complete conflicting effect on the seismic fragility and risk results depending on two failure modes considered in this study. This has a positive effect regarding the strength failure mode, but this brings a negative effect regarding the displacement failure mode. The risk fluctuation width is particularly noticeable in the site having a considerable change in seismic hazard information such as Los Angeles on the western site of the US. Such results can be expected to be utilized in a future study for investigating the pros and cons of the SSI effect associated with various failure modes in diverse conditions.

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.

A successful, advanced safety design method for building and piping structures is related to its functionality and sustainability in beyond-design-basis events such as extremely strong ground motions. This study develops analytical models of seismically isolated building-piping systems in which multi-story piping systems are installed in non-isolated and base-isolated, low-rise buildings. To achieve the sustainable design of a multi-story piping system subjected to strong ground motions, Triple Friction Pendulum (TFP) elements, specifically TFP bearings, were incorporated into the latter building structure. Then, a seismic fragility analysis was performed in consideration of the uncertainty of the seismic ground motions, and the piping fragilities for the seismically non-isolated and the base-isolated building models were quantified. Here, the failure probability of the piping system in the non-isolated building was greater than that in the seismically isolated building. The seismic isolation design of the building improved the sustainability and functionality of the piping system by significantly reducing the seismic energy of extreme ground motions which was input to the building structure itself.