Study On The Response Characteristics And Damage Assessment Method Of Large LNG Tank Dome Subjected To Accidental Impact Loading

As a clean and efficient high quality energy,LNG(Liquefied natural gas)has become a hot spot resources in the world with entering the "post oil period".In order to win the world's LNG supply,many countries build large LNG tank in coastal areas,in view of the convenience of maritime transportation.Large LNG storage tank is an important storage device in the LNG industry chain.Because of its storage energy is huge,and the storage medium has the characteristics of flammable,explosive and easy to diffuse.Its safety requirements are the same as nuclear power facilities.The ability to resist the accident type impact load is an important design indicator of the facility.But the response characteristics of large LNG storage tanks to accidental impact loading are not clear.There is not enough relevant theory,numerical simulation and experimental data support to establish the design standards.In order to realize the independent design and establish the anti impact design standard at an early date.In this paper,the most complex and weakest dome of large LNG tank system is selected as the research object,and the response characteristics and damage assessment methods of flying objects and explosion loads caused by accidents are explored.The main contents are as follows:(1)Experimental study on the dome to impact loading:The local shell of large LNG storage tank dome was selected as the test target,and according to the standard,the projectile was fabricated with reference to the impact energy and shape of flange which is common in LNG receiving station.By changing parameter,the impact tests under 15 conditions were carried out.Based on the analysis of the local failure shape and the key damage information of dome,the damage characteristics is different from conventional concrete structure,the response characteristics and damage mechanism of the large LNG storage tank under the impact load were studied.(2)Numerical simulation of the dome to impact loading:The dynamic analysis model of local shell impact test and the whole tank model of LNG tank dome were established by using AUTODYN nonlinear calculation program.The validity and correctness of the numerical simulation method are verified by comparing the numerical simulation and the test results.The damage development process and energy distribution information is difficult to obtain from test are revealed.The feasibility of only selecting partial shells to analyze the response characteristics of large LNG storage tank dome to impact loading was verified by comparing the local shell and whole model.(3)Numerical simulation of the dome to blast locading:Based on the proposed standard of design specification,the whole tank structure analysis model under near field explosion impact load was established using the AUTODYN nonlinear program,with the leakage accident occurred in the low pressure pipeline as the background.The response characteristics and the limit antiknock ability of the large LNG storage dome under the near field explosion impact load are analyzed.At the same time,the impact of the contact type explosion on the dome of the large LNG tank in terrorist attacks and military operations is taken as a background.The local shell and the whole tank structure analysis model under the contact blast impact were established.The local damage characteristics of the dome of large LNG storage tanks under different loading capacity were investigated,and the corresponding relationship between typical failure modes and explosion power(TNT equivalent)is analyzed.(4)Study on damage assessment method under impact loading:Based on the initial and final state data of local shell impact test,the formula for calculating the critical damage amount under accidental impact loading was obtained.By introducing the ballistic limit velocity of thin steel plate,the penetration degree of the dome under the impact load of the projectile was corrected,and a damage shape judgement method based on the ratio of penetration depth to dome thickness(dimensionless parameter)was established.By comparing and analyzing the results of numerical simulation and common empirical formulas,the calculation method of key detonation parameters of dome under explosive impact load was given.Based on the correspondence between the explosive power and the damage form,the damage assessment method of the large LNG tank dome under the impact of the explosion and impact load was established.