Numerical Simulation Analysis Of Large Vertical Storage Tank Under Near Fault Ground Motions

Under strong earthquake,it has a "blood of industry" said the large vertical floating roof tank damage is serious,especially the seismic response is more intense in the near-fault earthquake,it will bring incalculable losses to the economy,environment and life safety.Based on the work of storage tank isolation that domestic and foreign scholars have studied,and in support of the research programs of National Natural Science Foundation of China and large pulse near fault ground motions,finite element analysis software ADINA was used to establish the simulation model about 15×10~4m~3 storage tank.A study on the seismic control of near fault seismic excitation is carried out.The main content of this paper is as follows:1.Summarize the definition,characteristics and generation of near fault ground motion,and according to the characteristics of near fault ground motions are classified into three categories.There are forward directivity velocity pulse near fault ground motion,fling-step effects velocity pulse near fault ground motion and without velocity pulse near fault ground motion.2.Established the model of 15×10~4m~3 tank,then analyzed earthquake response and mean value under three types of near fault ground motion.The results show that: Under the near fault pulse-typed ground motions the sloshing height was significantly greater than the without velocity pulse of near fault ground motions because of its rich long-period components.Base shear and base moment are also slightly larger.Under the near fault ground motion,the dynamic response is larger,so it is necessary to adopt isolation measures for large vertical storage tanks.3.Using lead-rubber bearings and friction pendulum bearings as isolation measures,and using spring-damping system simulation of the isolation layer,input three types of near fault ground motions and damping effect analysis.The results show that: The base shear and base moment are obviously controlled by the isolation device.The seismic-reduction rate reached about 80% under without velocity pulse near fault ground motions.However,the seismic-reduction rate reached only about 50% under two types of near fault pulse-typed ground motions.Base isolation cannot effectively control the sloshing wave height,even cause amplification effect under some seismic excitations.Under near fault pulse-typed ground motions,the displacement of bearings is too large.It may result in the failure of the isolation bearing.So it is suggested that the limit measures should be considered in the seismic isolation.4.Seismic response analysis of 15×10~4m~3 storage tank with variable stiffness limit rolling isolation.In view of the phenomenon that the displacement of the bearing is too large under the excitation of the pulse near fault earthquake,a kind of Variable Stiffness Limit rolling isolation system is designed to adapt to the change of the ground motion characteristics.Using the nonlinear spring element to simulate the limit device,input two types of near fault pulse-typed ground motions and damping effect analysis.The results show that: The displacement of the bearings is obviously controlled.What's more,the displacement is larger,the control effect is more obvious.Base shear and base moment are larger than that of the non-limit displacement device isolation,but compared with the non-seismic isolation,it still has great damping effect.In the three cases of non-seismic isolation,without limit displacement device isolation,the peak of the sloshing wave height have little difference.It is shown that isolation cannot control the sloshing wave height.It is recommended to use the integrated damping to control the sloshing wave height.