Objectives Based on thermal fluid-structure coupling, the stress and deformation of the inner tank structure of the LNG three-layer wall storage tank under the action of operational baseline earthquakes (OBE) was analysed.

Methods Firstly, the initial data of the LNG three-layer full-capacity tank and the thickness of the inner tank wall were designed. Secondly, the heat transfer problem of the storage tank was analyzed, and the cold insulation structure between the outer tank and the middle tank was arranged, and the temperature field simulation of the inner tank wall was carried out by ANSYS APDL. Thirdly, the tank dynamics and fluid-structure coupling problems were analyzed. A specific OBE response spectrum was designed based on the seismic response spectrum, and the storage tank model was constructed by simplified particle calculation and modal analysis. Fourthly, using ANASY software, the static load analysis, thermal analysis and response spectrum analysis for operation modes combination were analyzed with the square root sum of squares(SRSS) combination.

Results The maximum displacement of the inner tank caused by horizontal OBE seismic action is 7.83 mm, the maximum normal stress is 31.310 MPa, the maximum displacement of the inner tank caused by vertical OBE seismic action is 6.42 mm, and the maximum normal stress is 13.576 MPa.

Conclusions On the basis of considering the thermal fluid-structure coupling, the maximum seismic stress of horizontal OBE is located at the anchorage zone perpendicular to the seismic direction, and the lower part of the two sides of the main vessel is parallel to the two sides of the seismic direction. The maximum seismic stress of vertical OBE is located at the junction of the dome and the outer tank wall and the annular space at the bottom of the tank wall.