Seismic Fragility Study On The Vertical Storage Tanks Based On Reliability Theory

With the modern industrialization and urbanization development, oil consumption has been the world's highest proportion of energy in all types of energy, Vertical cylindrical steel storage tanks are the liquid storage container which are widely used in the oil field and petrochemical enterprises and so on. So,it is the basic infrastructure at oil and natural gas resources development and the essential facilities in energy use, reproduction and supply. Once the storage tanks are damaged by earthquake, often result in serious secondary disaster such as fire, explosion, environmental pollution, shortage of fuel and social instability. Therefore, the tank safety issues become a major research question. At present, research on seismic fragility of storage tanks is based on the extent of damage in past earthquake disaster statistics, give the extent of the damage tanks to seismic intensity for the ground motion parameters, However,regarded the ground peak acceleration as the parameters of ground motion, based on reliability theory and probability and statistics method , given the research of storage tank failure probability at a ground peak acceleration has not yet reported.Based on reliability theory and numerical simulation analysis method,the seismic fragility of vertical storage tanks are investigated in this paper. The main research work as followings:(1) The overviews of the seismic tank computing model development process and reliability theory and the theory of fragility research development are provided. The main contents of this paper are put forward;(2) Based on the two-particle system mechanical mode considering sloshing convective mass and rigid base rotation which put forward by Haroun, the three-particle system mechanical mode is established. The computing formula of the simplified particles mass and mass center relatively height to different vibration mode is fitted;(3) The dynamic equation of tank simplified mechanical mode is established according to structure dynamic theory; the seismic response of tanks under different sites and under different liquid storage level and different ratio of height to radius is calculated by adopting time-history analysis method and its mean and variance are given out;(4) The main failure mode of the tank is confirmed according to tank damage statistics and the damage characteristics of storage tank, the main damage type of the tank is given out in the light of damage classification principle of the structural building, so it can seismic provides a frame of reference for fragility analysis of the storage tank; the random variable probability model which affect the storage tank failure probability is counted and its statistical characteristics were discussed, based on reliability theory and probability estimation method, the research method of tank seismic fragility is proposed. Taking into account the relevance of failure mode, a computing method of storage tank system is worked out;(5) A storage tank seismic fragility prediction calculation procedures were adopted. Taken tanks'seismic damage prediction parctice in a reservoir area of Daqing city an example, a comprehensive analysis with regard to tank seismic fragility of the reservoir area, the seismic fragility analysis method effectiveness is verified. The impact of liquid-height ratio and height-radius ratio to the seismic fragility of tank is studied;(6) Conclusions: the results of research in this paper are systematic summarized and the further research in depth content closely related to the work this paper is proposed...