大型液化天然气储罐混凝土外罐施工期间温度裂缝预测

以160 000 m³大型预应力液化天然气(LNG)全容罐混凝土外罐为研究对象,在利用ANSYS软件建立精细化LNG储罐混凝土外罐有限元模型的基础上,按实际结构施工顺序与时间,模拟了LNG储罐混凝土外罐全部混凝土浇筑过程,获得了在变温条件下,由水化热作用产生的混凝土外罐早期温度场分布;在考虑混凝土收缩和徐变的条件下,采用增量法计算了混凝土外罐的早期温度应力,确定了随时间及配筋率变化的混凝土早期抗拉强度,进而对LNG储罐混凝土外罐施工阶段的裂缝发育特征及分布规律进行了预测。结果表明,混凝土收缩对温度应力影响显著,在150 d的模拟时间段内结构温度应力呈现持续增长状态;第1浇筑段的LNG外罐温度应力明显大于其他浇筑段的温度应力,且该浇筑段的罐壁在模拟期内将产生竖向裂缝,扶壁柱处将产生局部环向裂缝。该结论可为同类工程施工建造开展相应的抗裂措施提供依据。

Temperature crack prediction in the construction period of a concrete outer tank for LNG storage

A fine finite element model for a 160 000 m³ LNG concrete tank with reasonable element types and mesh dimension was established using the finite element software (ANSYS) to simulate the actual construction process of the concrete tank. The temperature field distribution under the load of hydration heat was determined in thermal variation conditions. Considering the influence of concrete shrinkage and creep, the early thermal stress under temperature load was figured out with an incremental method, and the early tensile strength of concrete along with the reinforcement ratio and time was determined. Moreover, concrete crack growth characters and distributional rules of the LNG concrete tank were predicted by comparing thermal stress with the early tensile strength. The results showed that the concrete shrinkage has a significant effect on thermal stress, and the thermal stress of structures continues increasing during a 150-days simulation period. The thermal stress of the LNG concrete tank in the first pouring section is obviously greater than that in other pouring sections, and there occur a large number of vertical cracks and local circumferential cracks on tank walls in the simulation period. These conclusions above can provide a basis for taking anti-cracking measures in similar practical engineering.