LNG储罐外墙温度应力分析及预应力筋设计

Thermal stress analyses on external wall of LNG storage tank and the design of prestressed reinforcement

大型LNG储罐的外墙一般由预应力混凝土建造,其应力分布及变形比较复杂。在介绍预应力混凝土外墙温度应力计算方法的基础上,采用理论分析的方法,推导出了圆筒形外墙温度应力的计算公式、外墙在温差荷载及其他普通荷载作用下预应力筋的计算公式以及最大环向应力所在位置计算公式,进而给出了预应力筋结构调整的方案。研究结果表明,内罐的超低温液体会使预应力混凝土外墙产生很大的温度应力,环向温度应力最大可达混凝土抗拉强度的一半,使外墙在受内压时更加危险,因此在环向预应力筋设计时须考虑温差荷载影响。而后采用ADINA有限元软件建立多个钢筋混凝土分离式模型进行数值模拟,不仅验证了所推导公式的正确性,而且证明了该结构优化方案使外墙的变形及应力分布更加合理。

The external wall of large-scale LNG storage tank is mainly built by the prestressed concrete and it has complicated stress distribution and deformation.Based on the introduction to a computing method for the thermal stress of prestressed concrete wall,we deduced computing formulae of the cylindrical wall thermal stress,the prestressed reinforcement of external wall subjected to the temperature difference load and other common loads,and locations of the maximum hoop stress by means of theoretic analyses.Consequently,a optimized scheme for prestessed reinforcement was then given.The results show that the ultra-low temperature liquid in the inner tank will produce a huge thermal stress to the prestressed concrete external wall and the maximum hoop thermal stress can reach up to a half of the tensile strength of concrete,which makes the external wall more dangerous when it is subject to internal pressure.Therefore,the temperature difference load should be considered in the design of the loop prestressed reinforcement.Numerical simulations taken afterwards by applying the automatic dynamic incremental nonlinear analysis（ADINA） finite element software to set up various discrete models of prestessed concrete verified not only the correctness of formulae deduced but also the prestessed reinforcement optimized scheme that makes the stress distribution and deformation of external wall more sound.