Nonstructural Components and Systems
The functioning of key nonstructural components such as electrical equipment during seismic events can be compromised even when there is no mechanistic damage. This is because most electrical equipment are acceleration sensitive; subsequently, they are vulnerable to high frequency ground motions. Following the accident during the Great Tohoku Earthquake in 2011, the nuclear regulatory commission (NRC) has examined the seismic safety of NPPs in the US and recently has stated that a risk-informed performance-based ground motion response spectrum (GMRS) can exceed the safe-shutdown earthquake (SSE) in high frequency ranges. The technical report by Electric Power Research Institute (EPRI) provides modified amplification factors for nonstructural components depending on the level of the floor where these components are installed. However, this guidance has been developed based on limited studies that had limited scope on the impacts of high frequency contents of ground motions. In addition, ASCE 7 has limited provisions for the performance of nonstructural components in high frequency ranges considering the potential for their operational failures.
This study evaluates the seismic performance of nonstructural components subjected to strong high frequency ground motions and suggests reliable amplification factors for electrical components attached to structures with various characteristics. For this purpose, a set of ground motion histories are modified to match the GMRS of an arbitrary building located in central eastern U.S. (CEUS). The seismic performance of nonstructural components in various types of buildings is evaluated using nonlinear time history analysis considering their nonlinear restraint conditions. Using this procedure, acceleration and displacement responses are evaluated, and the amplification factors are estimated considering involved uncertainties.
The result of this study enhances the understanding of the seismic performance of nonstructural components under strong high frequency ground motions, and helps in characterizing the impacts on both physical and operational failures. It also informs design provisions of ASCE 7 regarding the seismic design of nonstructural components in various types of buildings.