局部减薄储罐拱顶非线性稳定性分析

STABILITY ANALYSIS OF LOCAL THINNED SHALLOW SPHERICAL ROOF OF STORAGE TANK

首先应用非线性有限元法进行局部均匀减薄拱顶的稳定性分析,计算结果表明,罐壁及罐壁油压对罐顶失稳的临界载荷影响很小。随后针对拱顶局部均匀减薄问题,提出一种近似的解析分析法,解析法将减薄部分分离出来,处理为受剩余部分弹性支撑的扁球壳,并导出相应的等效弹性支撑刚度计算公式,最后利用修正迭代法获得近似的失稳临界载荷计算公式。解析方法的计算结果与有限元法计算结果对比表明,文中提出的局部失稳临界载荷计算公式具有与有限元方法相一致的计算精度,可用于局部减薄拱顶储罐的局部稳定性评估,计算结果表明腐蚀区几何参数为9.5时最易出现局部失稳。

The nonlinear finite element method is adopted to calculate the global critical load of spherical roof of oil storage tank with axial symmetrical local corrosion region, and the local corrosion region is equivalent to a circular corrosion pit with uniform depth. The numerical calculation results show that the tank wall and irmer pressure of the stored oil have slight effects on the stability of the roof. To build the formula of local critical load of the tank roof, the circular corrosion pit is separated from the whole roof and treated as a shal-low spherical shell which is elastically supported on the rest part of the roof. The equivalent support stiffness is obtained by the deformation compatibility at the edge of the corrosion pit. And the nonlinear stability equation is solved with a modified iteration method to deter-mine the local critical load. This proposed method is then applied to evaluate the local critical load of an in-service corroded oil tank roof, the results agree well with those obtained by conventional nonlinear finite element method. The results also show that the geomet-rical parameter of the corrosion region corresponding to the minimal critical load is 9.5.