Abstract
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.
Highlights
In the event of earthquake, the fire-protection piping system, as an essential nonstructural component in critical facilities such as hospitals, emergency clinics, and high-tech factories, must remain secure and operational in order to prevent the damage from fire
Based on the outcomes of relevant previous investigations [7, 8, 11], the present study, in order to reduce seismic-induced fire risk and develop a probabilistic risk assessment protocol for sprinkler piping systems in hospitals, (1) incorporated an analytical and numerical nonlinear T-joint model specified by experimental-test-derived moment-rotation relationships, (2) considered various seismic ground-motion intensities and various fault mechanisms as a function of uncertainties, (3) conducted multiple nonlinear time-history analyses for a Monte Carlo simulation, and (4) estimated the system’s change of probabilistic failure and acceleration sensitivity according to various earthquake-fault mechanisms
In the present study, a nonlinear moment-rotation relationship obtained from University of Buffalo (UB) cyclic-experimental data [5, 6] was used to generate the nonlinear finite element (FE) model of a threaded T-joint in a 2-inch black iron branch piping system
Summary
In the event of earthquake, the fire-protection piping system (sprinkler piping system), as an essential nonstructural component in critical facilities such as hospitals, emergency clinics, and high-tech factories, must remain secure and operational in order to prevent the damage from fire. Many previous reports have attributed the most serious earthquake damage to the poor performance of nonstructural components such as HVAC, ceiling system, and fire-protection piping system [1] rather than to structural components. In order to prevent or minimize damage from fire, hospitals’ nonstructural components including automatic fire alarm systems, HVAC systems, and fire-protection piping systems (sprinkler piping systems) must remain operational and functional both during and after earthquakes. Significant research has been conducted to evaluate the seismic performance and vulnerability of fire-protection piping systems in hospitals according to earthquake engineering principles. The University of Buffalo [5, 6] conducted experimental tests on Location 2 y x z
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