The Reliability Analysis Of Large-scale LNG Storage Tank

LNG, a clean and efficient energy, had been paid more attention by allcountries of the world due to energy crisis and environmental pollution. LNG tanks,especially large-scale tanks, had been built in the coastal cities of our country.Because LNG was inflammable and explosive, a huge economic loss, even personnelbereavement, would be caused when a tank was broken. At present, safety factor,which didn’t reflect the influence caused by material and load’s randomness, was stillused in aseismic design of the tanks. So it’s necessary to consider the reliability of thetank under the earth using probabilistic method. At the same time, it providedtheoretical basis for aseismic design.At first, the paper introduced the basic concept of structural reliability, includestructural systematic simplification, failure paths’ research and the arithmetic ofsystem reliability. Then, the paper established the tank’s finite element model basedon the reliability analysis module of ANSYS, and analyzed the tank’s systemreliability under earthquake using response surface method. In the paper, thedestruction of wall of tanks, composed by the top of the tank wall and the bottom, wasconsidered the most primary modality. And the two main failure modes, whichconsisted of a few units in parallel, formed a series system. When we started toanalyze the structural reliability, failure functions of different units were needed tocreate using the response surface method. At the same time, reliability index andfailure probability of unit was also needed to work out based on the procedure ofMATLAB. The follow-up failure units were get through the birth and death ofelement technology. By this way, a failure path could be find and an equivalentreliability index of two elements would be work out by equivalent linearizationmethod. So, we could solve the reliability index of a failure mode. Finally, the mostpossible failure mode could be find and the range of system reliability of the tankwhich be shocked by earthquake would be calculated using boundary estimation.