地基沉降对石油储罐象足屈曲的影响

Effect of foundation settlement on elephant foot buckling of oil tank

为优化大型石油储罐的抗震设计,针对大型非锚固外浮顶储罐,综合考虑地基、非锚固罐底、变壁厚、抗风圈等几何结构和材料特性等因素,采用有限元分析(FEA)法构建储罐全模型,分析地基沉降对罐壁象足屈曲临界载荷的影响;基于Fourier变换,通过若干阶谐波组合的形式模拟储罐地基沉降,分析地基谐波沉降前后储罐的径向变形、屈曲模态与屈曲强度,探明储罐地基单次谐波沉降的谐波次数、谐波幅值、谐波的波峰与波谷对象足屈曲临界载荷的影响。结果表明:地基谐波沉降在不同程度上降低了油罐的象足屈曲临界载荷。储罐象足屈曲临界压应力随地基谐波沉降幅值的增大而减小;相同沉降量下,随着谐波次数的增大,储罐抗屈曲的能力越来越弱。

The FEA method was used to build a full size model of large oil storage tank.Influences of foundation setdement on elephant foot buckling critical load of a large-scale,unanchored and external floating roof tank were analyzed in order to optimize the seismic design.Various items of tanks geometry including tank foundation,unanchored bottom with slope,tapered shell thickness,wind girders,stiffening rings,other attachments and appurtenances were taken into account thoroughly in the non-symmetrical full finite element model.On the basis of Fourier transform,foundation settlement was simulated by several combinations of harmonic waves.The radial deformation,buckling deformation mode and buckling strength were researched before and after foundation settlement.The influences of different orders of harmonic waves,harmonic wave amplitudes,trough and crest on elephant foot buckling critical load of tank were proved up while single harmonic settlement happened.The results show that foundation harmonic settlement has a negative influence on elephant foot buckling critical load,that the critical compressive stress of elephant foot buckling of tank shell decrease with the increasing harmonic amplitude of foundation settlement,and that the resistance capacity reduces as the harmonic order number rises under the same settlement.