Research On Failure Mechanism Of Large-scale Steel Oil Storage Tanks Under Combustible Gas Blast

With the development of the global economy and the requirement of the natureresource, the competition for oil resources among the whole world increasesgradually, especially for the huge demand of the oil. The super-scale oil storagetanks which have larger capacity become the tendency of future development. Atpresent, the largest steel oil storage tank’s capacity has reached200,000m3, whilethe150,000m3steel oil storage tank has been built and put into use in China, and the200,000m3one is now under preparation.However, with the expanding scopes of the petroleum products storage andapplication, some accidents caused by the petroleum gas explosion have happenedoccasionally. The survey shows most of the explosion cases were triggered by thedetonation of the vapour cloud, which was generated by the petroleum products. Theshock wave of the explosion plays a significant role in the destruction of the oilstorage tank structure. Once a gas explosion occurs in a large oil depot or in astrategic petroleum reserve base, it would spread to more oil storage tanks anddestroy them, which would induce leaking, burning and even a series of explosions.Recently, it has limit research on the dynamic study about the large oil storage tankstructures resistance to the explosion at home and abroad, and yet some of them areimmature. Thus, it is important to carry out the research of the failure mechanism ofthe large oil storage tanks under the gas explosion, and the research of tank structureanti-blast protection will have a great scientific value and social significance.In this thesis, both small-scale tests and FE numerical calculations have beenused together to study the issue. Also, the failure modes and failure mechanism ofthe large tank also have been studied by an in-depth theoretical analysis. Thefollowing items are included in the whole thesis.1. Based on the structure’s mechanical characteristics, the oil storage tankcould be simplified to the cylindrical shells with different thickness tank walls.According to the theories of explosive dynamics, elastic-plastic mechanics andplastic dynamics, the differential equations of motion for the failure of thedeformation process of the micro units on the tank wall were set up. Meanwhile,according to the von Mises yield condition and strength theory, the generalized yieldfunction and failure criterion of tank wall under blast loading were established, andthe failure mechanism of oil storage tank structures under blast loading wereanalysed theoretically.2. With the acetylene/air mixture explosion source, the tests of blast wave impacting on the surface of rigid wall have been studied by GBS (short for GasBlast System) experimental facility. According to the feature of histories ofoverpressure and vibration acceleration, the combustible gas blast effect werestudied.Further more, small-scaled experimental models, which were madeaccording to two types of steel oil storage tank, the floating-roof one and thefixed-roof one, under combustible gas explosion were conducted in the GBSexperimental facility. The ultimate damage statements of the models under blastloading were obtained, and the history curves from experiments results wereconstrasted. Then, this thesis analysed the variety properties of different historycurves, and summarized the dynamic characteristics of oil-storage tank modelsunder blast impact induced by the combustible gaseous mixture.3. According to the results of small-scaled model experiments and theoreticalanalysis, the finite element numerical models of the experiments were set up andcalculated by explicit package ANSYS/LS-DYNA. The comparison betweennumerical analysis and experimental results were analysed, and a good agreementhas been achieved of the two methods, which proved the validity and reliability ofthe numerical method.4. According to the characteristic of the large steel oil-storage tank structures,finite element models of floating-roof and fixed-roof tanks have been established byANSYS/LS-DYNA. The dynamic responding processes of the structures under blastloading have been simulated. Through results analysis, the nonlinear dynamicresponse of the large steel oil-storage tanks and the failure criteria of the structuresunder combustible gas blast have been summarized.All of those above should lay the foundation for the resistance and protectionof large oil-storage tank structures under blast loading.