基于隔震后的LNG储罐桩顶约束系数计算新方法  

A new method for calculating the pile head restraint coefficient of an LNG tank with seismic isolation

作　　者：陈团海[1] 彭延建[1] 肖立[1] 扬帆[1] 刘洋[1] 陈严飞[2] CHEN Tuanhai;PENG Yanjian;XIAO Li;YANG Fan;LIU Yang;CHEN Yanfei(CNOOC Gas and Power Group,Beijing 100028,China;National Engineering Laboratory for Pipeline Safety,China UniversityPetroleum,Beijing 102249,China)

机构地区：[1]中海石油气电集团有限责任公司 [2]“油气管道输送安全”国家工程实验室·中国石油大学(北京)

出　　处：《天然气工业》2022年第12期125-132,共8页Natural Gas Industry

基　　金：国家自然科学基金项目“位移控制下耦合缺陷深海双层管道局部屈曲失效机理和应变评价研究”(编号:52171285)。

摘　　要：由于大型LNG储罐为典型的大跨度及超高剪力墙结构,地震荷载为储罐设计的控制荷载,为了满足设计要求,包含桩基础的超大型LNG储罐均需采取减隔震措施降低地震荷载的作用,但针对柔性约束条件下桩顶约束系数的计算方法缺失。为此,在提出了考虑桩—土交互作用的有限元分析模型的基础上,研究了隔震支座非线性参数获取方法及非线性特征模拟方法,最终确定了隔震后桩顶约束系数数值计算方法。研究结果表明:①LNG储罐隔震后采用位移控制和强度控制的方法计算桩顶约束系数结果基本一致,其值在1.05~1.50之间;②顶约束系数随土体刚度的增加线性增大,随桩径的增加以幂函数形式减小,而隔震支座刚度及桩顶水平力对桩顶约束系数没有影响;③震支座的力学性能及外部荷载对桩顶约束系数没有影响。结论认为,明确影响桩顶约束系数的因素及影响规律,可以为工程设计提供技术参考,并能为LNG储罐减隔震设计提供有效指导。Large LNG tanks are a typical large-span ultrahigh shear wall structure, so seismic load is the control load in tank design.To meet the design requirements, an ultra-large LNG tank containing pile foundation should be configured with seismic reduction and isolation measures to reduce the effect of seismic load. Currently, however, there is no method available for calculating the pile head restraint coefficient under flexible constraints. Based on the finite element analysis model considering the pile-soil interaction, the methods for obtaining the nonlinear parameters and simulating the nonlinear characteristics of isolator were investigated. Finally, a new method for calculating the pile head restraint coefficient of an LNG tank with seismic isolation was determined. The results show that the pile head restraint coefficients of an LNG tank with seismic isolation calculated by using displacement control and strength control are basically the same – between 1.05 and 1.5. The pile head restraint coefficient increases linearly with the increase of soil stiffness and decreases in the form of power function with the increase of pile diameter, while the isolator stiffness and the horizontal force at pile head have no effect on the pile head restraint coefficient. The mechanical properties and external load of the isolator have no effect on the pile head restraint coefficient. It is concluded that the identification of factors and patterns influencing the pile head restraint coefficient can provide a technical reference for engineering design and an effective guidance to the seismic reduction and isolation design of an LNG tank.

关 键 词：大型LNG储罐 减隔震 桩顶约束系数 群桩系数 柔性约束 桩基承载力 支座刚度 桩顶荷载 

分 类 号：TE972[石油与天然气工程—石油机械设备]