Abstract
Liquefied natural gas (LNG) terminals, one of the lifeline facilities, need to be protected by a proper seismic design against extreme earthquakes. An LNG terminal consists of a series of process facilities that are connected by pipelines of various sizes. Boil-off gas (BOG) compressor is one of the critical process facilities whose failure will cause the functional failure of the LNG terminal. Process facilities, including BOG compressor, other than LNG storage tanks and pipes, have not been a major concern in terms of the seismic performance evaluation. In this study, the seismic performance of a BOG compressor is evaluated and the seismic fragility functions are presented. An integrated system of a BOG compressor is modeled by a 3 dimensional finite element modeling scheme. A series of time history analyses are conducted to monitor the behavior of anchor bolts, one of the most critical elements in the BOG compressor. To develop fragility curves, a set of 20 ground motions are selected from a database of the historic earthquake accelerations. Fragility curves are developed based on the maximum likelihood estimation approach with respect to the strength limit states. When an earthquake load is applied to the BOG compressor, the main motor is likely to overturn and the flywheel is likely to slide, and, consequently, anchor bolts will be subjected to tension and shear force, respectively. It is concluded that the BOG compressor is safe against the design level earthquake
Highlights
A liquefied natural gas (LNG) receiving terminal is a facility where LNG is unloaded from shipment, stored, regasified, and exported to distribution terminals
The purpose of this paper is to evaluate the seismic performance of a boil-off gas (BOG) compressor in terms of its fragility functions
Seismic fragility functions are developed based on the maximum likelihood estimation (MLE) approach with respect to various limit states of the anchor bolt failure
Summary
A liquefied natural gas (LNG) receiving terminal (or just LNG terminal for short) is a facility where LNG is unloaded from shipment, stored, regasified, and exported to distribution terminals. In addition to a direct hazard, its societal and economic impacts would be considerable to nearby urban regions when an LNG terminal is damaged and gas is leaked. Even if a facility is seismically designed, it is still vulnerable to earthquakes stronger than the design earthquake. An earthquake smaller than the design earthquake may damage the facility if the ductile design concept is applied. It is important to understand the seismic capacity of the facility over a wide range of earthquake intensities. The purpose of this paper is to evaluate the seismic performance of a boil-off gas (BOG) compressor in terms of its fragility functions. One of the typical BOG compressors in operation in a Korean LNG terminal is selected and its 3dimensional finite element model is built using a commercial program. Fragility curves for specific limit states are developed using the maximum likelihood estimation method
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