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Mathematical Problems in Engineering
Volume 2015, Article ID 525921, 8 pages
Research Article

Probabilistic Risk Assessment: Piping Fragility due to Earthquake Fault Mechanisms

1Department of Civil Engineering, North Carolina State University, Raleigh, NC 27695, USA
2Department of Civil Engineering, Gangneung-WonJu National University, Gangneung 210-702, Republic of Korea
3Steel Solution Center, POSCO, 100 Songdo Gwahak-ro, Yeonsu-gu, Incheon 406-840, Republic of Korea

Received 28 July 2014; Accepted 15 September 2014

Academic Editor: Sang-Youl Lee

Copyright © 2015 Bu Seog Ju et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A lifeline system, serving as an energy-supply system, is an essential component of urban infrastructure. In a hospital, for example, the piping system supplies elements essential for hospital operations, such as water and fire-suppression foam. Such nonstructural components, especially piping systems and their subcomponents, must remain operational and functional during earthquake-induced fires. But the behavior of piping systems as subjected to seismic ground motions is very complex, owing particularly to the nonlinearity affected by the existence of many connections such as T-joints and elbows. The present study carried out a probabilistic risk assessment on a hospital fire-protection piping system’s acceleration-sensitive 2-inch T-joint sprinkler components under seismic ground motions. Specifically, the system’s seismic capacity, using an experimental-test-based nonlinear finite element (FE) model, was evaluated for the probability of failure under different earthquake-fault mechanisms including normal fault, reverse fault, strike-slip fault, and near-source ground motions. It was observed that the probabilistic failure of the T-joint of the fire-protection piping system varied significantly according to the fault mechanisms. The normal-fault mechanism led to a higher probability of system failure at locations 1 and 2. The strike-slip fault mechanism, contrastingly, affected the lowest fragility of the piping system at a higher PGA.