Damage Modes And Failure Mechanism Of The Large-scale LNG Outer Concrete Tank Under Impact Loading

In recent years,the demand for clean energy has been increasing year by year because of the growing threat of global warming.Liquefied Natural Gas(LNG)has gradually become the most important energy in this century due to its green,economical,safe and reliable advantages.LNG storage tank structure also gets more application.In view of the importance and particularity of the structure of LNG storage tank,the impact failure of tank structure and its secondary explosion and fire disaster can lead to great loss of life and property.Therefore,the damage models and failure mechanism of the outer concrete tank of the liquefied natural gas(LNG)storage tank under impact loading are investigated based on ANSYS/LS-DYNA FE analysis software platform to ensure the safety of LNG tank in major disasters,the main contents of the dissertation are as follows:(1)Numerical simulation corresponding to an experiment about impact perforation of reinforced concrete slabs subjected to projectile with high speed is carried out using ANSYS/LS-DYNA.By comparing the macroscopic damage image of reinforced concrete slabs under impact effect and the residual velocity of the projectile,the accuracy of the FE simulation method is validated and CSCM model is determined to use for further simulation.The FE model of the outer concrete tank of the 160000m3 LNG storage tank is established based on ANSYS/LS-DYNA FE analysis software platform and the influence of prestressing on the impact process is studied.Considering the computational efficiency and the accuracy of the results,the favorable effect of prestressing is ignored in the following study.(2)Based on response rules and failure phenomena of the dome for LNG outer concrete storage tank subject to impact loading,three damage modes are defined,which includes no damage,local distortion,concrete spalling and penetration,and the dynamic responses corresponding to each mode are studied.Based on the variation of energy,the whole impact process can be divided into three steps: energy applying,energy transfer,energy conversion and consumption,and failure mechanism for each mode is revealed from the view point of energy.(3)Based on the analysis of parameters,the change rules of the damage modes of LNG outer concrete tank under impact loading with varying speed,angle,location and diameter of impactor are studied.And the distributions of three failure modes are obtained.And the differences of dynamic response under different impact parameters are analysed by typical examples.The damage coefficient is proposed as the evaluation criterion of failure modes by studying the various factors influencing the distribution of the failure modes,and the range of the damage coefficient corresponding to each damage mode is determined.(4)In order to investigate the dynamic responses and damage modes of the LNG outer concrete tank under aircraft impact,the FE models of Bombardier Challenger 850 aircraft and Boeing757 aircraft are established to impact the wall,the wall-supporting column,the ring beam and the dome of the LNG outer concrete tank.In addition,the FE model of the reticulated shell with steel plate inside the concrete dome is established to study its influence on the anti-shock capability of the concrete dome.