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在内罐泄漏等特殊工况下,预应力混凝土罐壁将直接暴露在-162℃的超低温环境中,由此产生的温度应力和变形可能会对储罐的结构安全带来威胁。因此,对LNG储罐混凝土外罐进行泄漏等低温条件下的力学验算和评估十分重要。本文利用有限元法(FEM)对内罐泄漏工况下的大型LNG预应力混凝土储罐进行热-结构耦合分析,结果表明:混凝土罐壁的降温过程较为缓慢,温度沿壁厚(0.8m)方向达到稳定需要大概一周的时间;热保护角范围以外的预应力钢绞线温度分别降低至-87℃(夏季)和-102℃(冬季);低温作用使混凝土罐壁产生较大的内力和变形,罐壁内外两侧温差越大,内力、变形越大,在设计中可通过设置热保护系统来防止其对储罐结构可能造成的破坏。研究成果对于评估超低温对混凝土外罐结构安全的影响、制定液化天然气储罐结构安全规范具有一定的指导意义。
Under special conditions such as internal tank leakage, the prestressed concrete tank wall will be directly exposed to the ultra-low temperature of -162 ℃. The resulting temperature stress and deformation may threaten the structural safety of the tank. Therefore, it is very important to check the mechanics and evaluate the cryogenic conditions of LNG tank concrete outer tank. In this paper, the finite element method (FEM) is used to analyze the thermal-structural coupling of large LNG prestressed concrete tanks with internal tank leakage. The results show that the cooling process of concrete tank wall is relatively slow, and the temperature along the wall thickness (0.8m) The direction of stability to achieve about a week; prestressed strand outside the scope of thermal protection angle were reduced to -87 ℃ (summer) and -102 ℃ (winter); low temperature makes the concrete tank wall have a greater internal force and Deformation, the larger the temperature difference between the inside and outside of the tank wall, the greater the internal force and deformation, the thermal protection system can be set in the design to prevent possible damage to the tank structure. The research results have certain guiding significance for the assessment of the influence of cryogenic temperature on the structural safety of concrete outer tank and the development of LNG tank structural safety code.