Life-cycle cost assessment of seismically base-isolated large tanks in LNG plants

A new methodology is being introduced to address the life-cycle cost (LCC) of base-isolated large liquefied natural gas (LNG) tanks. The relationship between LCC and seismic fortification intensity is established to evaluate how much reduction of earthquake force can minimize the LCC. Each composition of LCC is analyzed including the initial cost, the isolators cost and the excepted damage cost. The isolators cost consists of the cost of lead rubber bearings and dampers. The cost of lead rubber bearings is proposed proportional to its volume and the cost of dampers is not only related to its maximum displacement but also to its tonnage. The concept of seismic intensity is being used to estimate the expected damage cost, greatly simplifying the calculation. Moreover, a tank in a LNG receiving terminal in China is employed as an example to assess its LCC in isolated and non-isolated situation respectively. The results show that the proposed method is efficient and the expected damage cost is enormously reduced because of the application of isolators, which leads to the reduction of the LCC of the tank.