Preliminary Screening of Resonance-Prone Frequency Bands in Piping Systems Using Representative Korean Earthquake Records

Piping systems in critical facilities, such as power plants, hospitals, and industrial sites, are essential nonstructural components determining operational continuity during seismic events. Past earthquake events, including those at Northridge, Kobe, and Chile, have repeatedly demonstrated the vulnerability of sprinklers and utility piping, wherein leakage and connection failures led to severe secondary hazards. However, existing conventional seismic evaluations based on equivalent static loading are limited in capturing the frequency-dependent dynamic characteristics and resonance potential of inherently multi-degree-of-freedom piping structures. This study proposes a modal-based dynamic screening approach to pre-emptively identify resonance-prone frequency bands by incorporating the frequency characteristics of representative earthquakes recorded in South Korea. Water supply, sprinkler, and cooling water piping systems were analyzed using three key indicators: effective modal mass participation, cumulative effective modal mass ratios, and directional translational components of mode shapes. The results demonstrate that the proposed dynamic screening approach effectively identifies resonance vulnerabilities across different piping configurations, proving its utility as a more precise seismic screening tool compared to conventional methods. This study underscores the practical necessity of modal analysis as a preliminary step for advanced dynamic evaluations and provides a rational framework for enhancing the seismic safety of nonstructural components in critical facilities.