Comparative Analysis of a Base-Isolated LNG Storage Tank Using Friction Pendulum Bearings and U-shaped Dampers

Base isolation is commonly employed to protect liquefied natural gas (LNG) storage tanks from earthquake damage. However, large deformation may occur to isolators under near-fault earthquakes, leading to risks of structural overturning, pipeline fracture and liquid leakage for LNG storage tanks. U-shaped dampers are highlighted as energy-dissipating devices used in combination with isolation bearings for high performance of base-isolated structures. This paper aims to investigate the effect of U-shaped dampers on a 160,000 m(3) LNG storage tank isolated by friction pendulum bearings (FPB). A finite element (FE) model of the FPB equipped with U-shaped dampers was first established, which was validated by comparison with existing experimental results. Parametric analysis was performed on the isolation devices, including variables of damper thickness (i.e., 16, 30, and 42 mm) and material properties of the damper (LY160 steel and Q345 steel). Afterward, a refined FE model of the 160,000 m3 LNG storage tank was developed, and the effect of the isolation devices on the LNG storage tank subjected to near-fault earthquakes was investigated. Seismic responses of the tank, including acceleration of both the outer and inner tanks, hydrodynamic pressure of the inner tank, base shear and isolator displacements were extracted and analyzed. Results showed that for the 160,000 m3 LNG storage tank (isolated by 285 FPBs with a sliding radius of 3.0 m), it was recommended to employ the U-shaped dampers manufactured by LY160 steel with a thickness of 42 mm or the U-shaped dampers manufactured by Q345 steel with a thickness of 30 mm.