Abstract

For large LNG storage tanks, the thermal load has a very important influence on the failure mode of the thin-walled spherical dome. However, the traditional calculation of thermal stress is very complicated for the spherical shell. To obtain an analytic solution with a simple expression, an approximate method was proposed in this paper. The mechanical behaviour caused by the temperature difference is divided into two parts, i.e. the thermal strain directly acting on the shell and the binding force exerted by the boundary. The thickness is ignored in the calculation of deflection caused by boundary constraints. Then, its accuracy was verified by a linear elastic numerical model. Furthermore, the crack pattern in a nonlinear plastic simulation was also well captured. The case study shows that the thermal-induced meridional cracks distribute uniformly along the circumferential direction; these cracks first appeared on the inner surface at the edge of the tank dome, and then rapidly expand to the centre and outer surface; increasing the amount of reinforcement cannot effectively limit the development of such cracks.

摘要

对于大型LNG储罐，热负荷对薄壁球顶的失效模式有非常重要的影响。然而，传统的球壳热应力计算非常复杂。为了得到表达式简单的解析解，本文提出了一种近似方法。由温差引起的力学行为分为两部分，即直接作用在壳体上的热应变和边界施加的结合力。在计算边界约束引起的挠度时忽略厚度。然后，通过线弹性数值模型验证了其准确性。此外，非线性塑性模拟中的裂纹模式也得到了很好的捕捉。案例研究表明，热致经向裂纹沿圆周方向分布均匀；这些裂缝首先出现在罐顶边缘的内表面，然后迅速扩大到中心和外表面；增加配筋量并不能有效限制此类裂缝的发展。