Structural Strength Analysis of Crude Oil Storage Tanks under Seismic Design Codes

Seismic design of crude oil storage tanks should follow both GB/T 50761-2018 and API 650 standards, adopting the structural concept of "weak top - strong wall - flexible bottom". The tank top adopts a spherical crown dome design (curvature radius 1:0.8~1.2), allowing ±15° elastic displacement. The tank wall adopts a variable cross-section cylinder (wall thickness decreasing from 30mm to 8mm in a gradient), with a circumferential weld overlap rate of ≤25%. The foundation design introduces an anchoring coefficient (≥0.785) and a lift-off coefficient to resist axial compression instability and overall overturning under seismic action.

The strength analysis focuses on three aspects: 1) Seismic verification adopts multi-level fortification, and the axial compressive stress of the bottom ring tank wall must meet σ≤0.9fy (fy is the material yield strength); 2) The sloshing wave height calculation considers the tank shape and seismic spectrum characteristics to avoid floating roof failure caused by liquid surface impact; 3) Finite element simulation is used for key nodes to verify the buckling stability of wind girders (spacing ≤3m) and stiffening rings under rare earthquakes.

In actual engineering, a coastal tank farm successfully withstood a magnitude 7 earthquake by optimizing the seismic design, with the maximum tank displacement controlled within 0.15D (D is the tank diameter). Compared with the traditional scheme, the steel consumption is reduced by 12%, comprehensively meeting the seismic performance requirements of API 650 and GB 50341, and the service life is extended to 30 years.