Study on the optimal calculation method of bearing capacity of high pile of LNG storage tank under the influence of pile top isolation bearing

Liquefied natural gas (LNG), as a globally recognized clean energy source, is typically stored in large LNG storage tanks as cryogenic liquid LNG. To enhance the seismic performance of elevated tank pile foundations in coastal soft soil, isolation bearings are typically installed between the slab and pile heads. However, current pile foundation codes, which rely on the mechanical response at the pile head as the design basis, do not explicitly provide calculation methods for the bearing capacity of piles under the influence of isolation bearings. To solve this problem, this article takes a 220,000 3 LNG storage tank in Shanghai as an example and uses a nonlinear spring model to establish a finite element analysis model of pile-soil interaction, studying the mechanical response of elevated pile foundations equipped with seismic isolation bearings. The research shows that under displacement-controlled criteria, shifting the horizontal displacement loading point reduced the horizontal bearing capacity of the pile by 19.5%. Considering the second-order effects of vertical forces, the horizontal bearing capacity decreased by 26.3% after installing isolation bearings. Additionally, the analysis results for horizontal bearing capacity under serviceability limit states consistently fell below the design values for single-pile horizontal bearing capacity, which is of great significance for the design of subsequent large LNG storage tanks.