| Large-scale storage steel tank is one of the main structural types for oil and gas storage,and the safety of this structure type has a significant influence on the energy security of China.Due to the flammable and volatile nature of oil and gas products,flammable gas cloud explosion caused by oil and gas leakage often occurs.The thin-walled steel storage tank tends to have large plastic deformation or penetration damage when subjected to blast or impact loadings caused by the explosion of flammable gas cloud.The damage of the tank will lead to the leakage of internal combustible liquid,which can cause secondary explosion and even chain explosion,and then resulting in greater economic and personnel losses.However,the relevant codes and research results have not yet put forward an effective measure to improve the blast and impact resistance of steel storage tanks.Therefore,it is urgent to carry out the study on blast and impact mitigation technology of large-scale steel storage tanks,so as to provide reference for the blast and impact protection design of steel storage tanks,and therefore contributes to the stability of energy storage and the safety of relevant equipment and personnel.In the past two decades,polyurea has been widely used in the blast and impact protection of different structures due to its convenient construction method,good bonding strength and excellent mechanical properties.It has been reported that polyurea layer is effective in improving the blast and impact resistance of steel plate,masonry wall and composite plates.In this paper,polyurea is used in the blast and impact mitigation of large steel storage tank,and the application method and effe ct of polyurea coating in tank design and reinforcement stage are focused on,and the scientific problem of response characteristics of polyurea sprayed cylindrical shell structure is mainly studied.The main study content and results are as follows:(1)Low velocity impact tests of polyurea coated steel plates were performed,and the effect and mechanism of polyurea coating were analyzed.The numerical model of impact process was built using LS-DYNA software,and the reliability of the model was verified by comparing with the experimental results.Based on the experimental and simulation results,the relationship between the impact resistance of the specimen and the spray location,coating thickness was studied.The area density energy absorption value is introduced as the quantitative index of the energy absorption efficiency of the coated steel plate specimen,and the optimal spraying position and spraying thickness in terms of energy absorption efficiency are obtained.(2)The finite element model of large-scale steel tank is built according to its design data.The response characteristics of steel tank under the impact of spatter are simulated and analyzed using LS-DYNA software.On this basis,the effect of polyurea coating on the impact response of steel tank is studied.The parametric study results show that the best impact protection effect can be achieved by spraying polyurea layer locally on the outer surface of tank wall,and the maximum energy absorption value,surface density energy absorption value and other impact mitigation performance indexes can be continuously improved with the increase of coating thickness.The mechanism of polyurea is concluded as cushion and velocity reduction.Finally,based on the law of conservation of energy and momentum,a theoretical formula was established to predict the relationship between the impact resistance and the coating thickness of the tank,which provided a basis for the design of impact protection for polyurea coated large-scale steel storage tanks.(3)The TNT explosive and combustible gas explosion experiments of polyurea coated small-scale model tank were carried out,and the effect of polyurea coating on reducing tank displacement was clarified.On the basis of the experiment,a numerical model of the blast response of the model tank is established and verified by comparing with the experimental results.Based on the experimental and numerical simulation results,a modified beam-on-foundation model representing the energy absorption mechanism of the model tank is proposed,and an approximate theoretical formula for predicting the displacement of the tank wall is established based on the model.Finally,according to the simplified model and theoretical formula,the action mechanism and law of polyurea coating are revealed,and the specific suggestions on spraying position are given.The research content of this stage systematically analyzes the explosion response and energy absorption mechanism of polyurea coated cylindrical shell structure,and provides the basis of numerical simulation method and theoretical analysis method for the subsequent study on the explosion response of polyurea-coated large-scale steel tank.(4)Based on the simulation method and theoretical model established by experimental study,the response of polyurea-coated large-scale steel storage tank polyurea under the action of gas cloud explosion was studied.The results show that the polyurea coating with the same thickness as the main deformation area of the tank wall can significantly reduce the maximum displacement of the tank subjected to gas cloud explosion.In the further numerical simulation study,it is found that the effect of coating will not be significantly reduced due to the changes of overpressure duration,maximum displacement,tank material properties and tank geometry size.According to the further simplified modified beam-on-foundation model,the approximate theoretical formula for predicting the relationship between the maximum displacement of steel tank and the coating thickness is established,which provides a reference for the blast mitigation design of polyurea coated steel tanks.(5)Futher numerical simulations show that the effect of polyurea coating is better than that of increasing the thickness of tank wal l in the aspect of impact protection,and the pure steel tank with equal surface density is better than that of polyurea coated tank in explosion resistance.Based on this result,combined with the main conclusions of parameter analysis,the application an d design suggestions of polyurea spraying technology in blast and impact mitigation of large steel storage tank are put forward. |
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