Study On Dynamic Behavior Of LNG Tank Farm Under Impact And Explosion

Liquefied natural gas(LNG),as a kind of clean energy,has a spurt in demand in recent years.The LNG terminal is a key node for storing as well as delivering LNG.As an important part of the LNG terminal,ensuring the safety of the LNG tank farm(LNG storage tank and surrounding RC structure plant)under various types of intensive loadings,e.g.,earthquake,external explosion,aircraft and wind-borne projectile impact,is of great importance to maintain the energy supply and social stability in China.However,there are few studies on LNG tank farms under long duration explosion and aircraft impact,and the relevant safety assessment cannot be effectively carried out.To address these limitations,this paper focuses on dynamic behavior of the LNG tank farm under impact and explosion,including dynamic bond-slip behavior of rebar-concrete under impact and blast loadings,dynamic behavior of typical plant components under long-duration explosion,dynamic behavior of storage tanks under commercial aircraft impact,and application of high performance materials to resist aircraft impact.The main work and conclusions are as follows:(1)The bond-slip behavior of the interface between concrete and rebars is usually ignored and assumed as perfect bond in most existing numerical studies for dynamic behaviors of RC structures under impact/blast loadings,leading to an inaccurate even unreliable numerical results.Thus,the influences of the bond-slip behavior between concrete and rebars for dynamic responses of RC members under low-and highvelocity impacts,short-and long-duration explosions were comprehensively examined,and the recommended simulation implementation methods as well as related parameters for the bond-slip behavior were further given for various scenarios.(2)The LNG tank farm usually locates in a large chemical industry farm,and its internal RC structure plant may be threatened by long-duration explosion from several kilometers away.To study the dynamic behavior of RC beams/slabs under longduration explosions,a near-planar blast wave generation apparatus was designed and nine test scenarios were conducted(peak overpressure: 0.1-0.7 MPa,duration: 85-135ms).Then,the applicability of the numerical structured arbitrary Lagrangian-Eulerian approach and theoretical single degree of freedom(SDOF)method was verified.The dynamic increase factors(DIFs)for concrete and steel rebars in SDOF method were suggested as 1.05 and 1.02,respectively.This work provides test data,numerical and theoretical analysis methods for the safety assessment of RC structures subjected to long-duration explosion.(3)The existing specifications only underline the aircraft impact but not gives detailed analytical and assessment approaches.To study the dynamic behavior of LNG storage tanks subjected to the commercial aircraft impact,the refined finite element models of Airbus A380 and A320 aircraft,and the base-fixed and base-isolated LNG storage tanks were preliminarily established and validated.Then,the impact resistance of the LNG storage tanks with different boundaries against aircraft collisions was numerically evaluated by the effective plastic strain of the inner tank.It was found that the integrity of inner steel tank under the A320 aircraft impact was maintained,whereas the safety under the A380 aircraft impact cannot be guaranteed.Besides,the influences of isolation bearing sizes and tank boundary conditions on the damage distribution and degree were limited.(4)Ultra-high performance concrete(UHPC)with high strength and ductility has been gradually adopted in protective structures against impacts,while the current studies are limited to the specific fibers and corresponding volume fraction.To assess the impact resistance of arbitrary configured(matrix strength,fiber type,fiber volume fraction,etc.)UHPC members,a mesoscale analysis method was proposed to establish the UHPC matrix and fibers separately considering the fiber-matrix bond-slip behavior.Furthermore,the macroscopic model parameters for UHPC assumed as a homogeneous material were obtained based on the validated mesoscale analysis method.Finally,the aircraft impact resistance of UHPC tanks with different fiber volumn fractions was analyzed.It was concluded that,compared with the normal concrete,the UHPC material can significantly reduce the structural deformation and damage distribution.The recommended volume fraction of UHPC with micro-straight steel fibers was 1.5%.This work provides a new insight into the UHPC application in the LNG storage tanks against the aircraft impact.