Stress Analysis Of LNG Storage Tank Under Impact Loading

As a kind of top level power source, Liquified Natural Gas (LNG for short) has been meeting an increasing demand within the globe, accordingly, the demand for LNG storage tanks also rise. As important equipment in the gas source station, it is an indispensible part to guarantee the gas supplying for the significant gas sectors as well as their facilities safe operation. LNG in the tank is flammable and explosive,once damaged, tones of flammable liquid will leak and burn and destructive secondary disasters will happen. Therefore, the safety of the storage tank under the impact load during the tank construction is one of important issues.The paper generally introduces the development history of LNG storage tank; the basic principles of structural dynamics analysis;dynamic mechanical properties of reinforced concrete under impact loading; specify the elements type, material model and contact details problems aiming at analysis software ANSYS / LS-DYNA in solving the impact issue to select the suitable modeling method for storage tank under impact loading structure analysisThe research aims at the dynamic performance of the LNG storage tank under the impact load.A mass block is used to hit the wall and dome of the storage tank.,Selecting eleven load cases and comparing the analysis results.1. When the mass block with the fixed quality and velocity hits the different part of the wall of the LNG storage tank, its equivalent stress decreases with the height of the storage tanks;and when the quality is fixed but velocity is different ,when the LNG storage tank were impacted by the mass with 70m/s, the greatest impact has happened.2. When the mass block hits the dome with different speed, as time increasing the stress dispersion of dome increases gradually,when the diffusion range meets its maximum,it almost covers the whole dome.Stress exists between junction part of the dome and the tank wall, by then the impact for the mass block to hit the dome is the most obvious. Under the strike the stress of the storage tank expands from the impact point to the outward in a round shape. The largest stress of the storage tank occurs at the impact point.3. In the cases when the impact point exists on the wall of the tank, the largest storage tank stress occurs in case 7,and the most influence range occurs in condition 10 and 11. In condition 7, Only surface concrete fail, But internal concrete dosen't damage So we should strengthen the dome and tank wall depending on structural measures to avoid the severe damage occurred.And the impact of dome shows lasting for a long time, widely,and because of the gravity,make the weight hit dome repeatedly,influent the dome obviousely,so,we should strengthen the protection,avoid the weight dropping.4. Impact load will only affect the impact point at local stress,produce high stress, strain,and other parts won't be affected.The results show that:In the program that the impact point is on the tank wall, the impact on the upper tank wall is relatively greater than the others,but only surface concrete failure,the internal concrete won't damage. Therefore, to strengthen the junction of the dome and the tank wall is necessary to avoid serious damage in the future. And the impact of dome shows lasting for a long time, widely,and because of the gravity,make the weight hit dome repeatedly,influent the dome obviously.