超大型LNG储罐顶梁框架及衬板结构体系的设计算法

A design algorithm used for the roof frame and liner system of extra-large LNG storage tanks

顶梁框架设计是LNG储罐设计中最重要的部分之一,但目前我国对于超大型LNG储罐顶梁框架系统的计算还存在着屈曲特征值衡量标准不统一、计算假定条件多、与国内规范规定不一致等诸多问题。为此,在引入材料非线性、结构非线性和考虑初始缺陷的基础上,应用大型非线性有限元计算软件ABAQUS开展了超大型LNG储罐顶梁框架及衬板系统的建模及其受力与稳定性的计算分析,进而建立了一套完整的超大型LNG储罐顶梁框架及衬板结构体系的设计算法,并应用于国内某20×10~4 m^3 LNG储罐的设计工作当中。应用结果表明:(1)该设计算法的结构体系由壳单元和梁单元组成,连接方式为共节点,能够准确模拟实际情况;(2)受力计算分为10个工况,屈曲计算分为7个工况,包含LNG储罐顶梁框架及衬板结构体系在施工过程中的所有工况;(3)顶梁框架最大应力为125.7 MPa、衬板最大应力为101.4 MPa、屈曲计算最小安全系数为2.57,LNG储罐顶梁框架在该体系下的受力及稳定性均能满足要求。该研究成果可为相关设计计算提供参考。

The design of roof frame is one of the most important parts of LNG tank design. In China, however, the calculation of roof frame system of extra-large LNG tanks is currently faced with a series of problems. For example, there is no united yardstick on buckling characteristic value, the calculation is based on many assumptions, and the calculation is inconsistent with domestic specifications and stipulations. In view of these problems, the material non-linearity and structural non-linearity were introduced and the initial defect was taken into consideration. Then, the large non-linear finite element calculation software ABAQUS was adopted to carry out modeling on the roof frame and liner system of extra-large LNG tanks and calculate and analyze the force applied on them and their stability. Finally, a complete set of design algorithm for the roof frame and liner system of extra-large LNG tanks was established and applied to the design of a certain LNG tank （20~ 104 In3） in China. It is indicated that this design algorithm can simulate the actual situations accurately. This de- sign algorithm is structurally composed of shell units and beam units, and it is connected in the pattern of common node. Besides, force calculation is conducted in 10 operational modes and the buckling calculation in 7 operational modes, including all operational modes in the construction process of roof frame and liner system of LNG tanks. It is also revealed that the maximum stress on the roof frame is 125.7 MPa, that on the liner is 101.4 MPa and the minimum safety coefficient used for buckling calculation is 2.57. Under this system, the force and stability of the roof frame of LNG tanks are satisfactory. The research results can be used as reference for relevant design and calculation.