LNG储罐球形混凝土穹顶的热应力及裂缝分布

Thermal stress and crack distribution of concrete dome of spherical LNG storage tank

对于大型LNG储罐,其穹顶因水泥水化热产生较大的热应力,引起混凝土开裂,严重影响储罐的耐久性。以某大型LNG储罐穹顶为研究对象,采用ADINA有限元软件建立精细化的有限元模型,模拟LNG储罐穹顶分段浇筑过程中的早期温度场分布,并将数值计算结果与现场测试结果进行对比;数值分析时考虑了混凝土徐变及龄期效应,对混凝土穹顶的温度场和应力场进行耦合计算,得到穹顶的热应力分布及裂缝开展情况,对穹顶混凝土开裂风险进行评估,进而对参数的敏感性进行分析。结果表明:穹顶内外在混凝土浇筑过程中产生温差较大,导致巨大热应力;第一浇筑带的热应力明显比其他浇筑带大,环向热应力大于经络向热应力,将使穹顶边缘产生沿环向分布的经络向温度裂缝;水泥种类对穹顶热力分析结果有很大的影响。

During the construction process of large-scale LNG storage tanks, the hydration heat of cement causes a great ther-mal stress to LNG storage tank dome, which leads to concrete cracking and seriously affects the durability of the dome. An improved finite element model for a large-scale LNG storage tank was established using the finite element program ADINA, and the temperature field in tank dome was determined in the process of segmented pouring of concrete, the numerical simu-lation results were compared with the field test results. The temperature field and the structure were coupled by considering concrete creep and age effects, the distributions of thermal stress and crack were determined, and the risks of concrete crack-ing were estimated. Furthermore, the sensitivity of the parameter was analyzed. The results show that a great temperature difference between the inside and the outside of the dome is generated in the process of concrete pouring, which will cause a great thermal stress. The thermal stress of the first pouring is greater than others, the hoop stress is greater than the meridian stress, and it will make the edge of dome produce meridian cracks along the circumferential direction. Types of cement have an important effects on the results of thermal stress.