Mechanical Behavioral Of LNG Concrete Containment Outer Tank Under Static And Wind Loads

As the demand for energy grows rapidly these years, Liquefied Natural Gas (LNG) has become one of the significant parts of the energy structure for its high calorific value and performances, as well as the ease of transport and storage. To develop Natural Gas industry is apparently a good way to solve the problem of energy and sustainable development. Thus, many countries spend a lot on it. The large LNG containment tank is becoming more and more popular as it has large capacity and little occupied area. However, in China, the research on LNG containment tanks has just begun recently. Once it is broken by cryogentic liquid, it will bring severe economic loss and even casualty. Therefore, it’s reasonable to discuss the response of LNG containment outer tank under wind loads and static loads especially under leakage occasion.The main content and important conclusions of this paper are as follow:Taking a160000m3LNG containment tank in real project as study object, an accurate model is established in ANSYS, tank shell, domed roof, ring beams, buttresses and the actual position of the piles have been taken into consideration. The response comparison of LNG concrete outer tank under different static loads (gravity, roof load, gas pressure and hydraulic pressure) has been made and the liquid level on the influence of the response under leakage occasion is discussed. The results show that the roof load has little influence while the inner gas pressure is non-ignorable. The hydraulic pressure is the dominating factor on the deformation and stress of the structure.When leakage occurs at the inner steel tank, the cryogenic liquid will flow to the outer concrete tank. Considering steady convection as the boundary condition, thermal analysis has been conducted to gain the temperature distribution of the outer concrete tank. The node temperature is transformed into thermal stress and the cryogentic constitutive relation is applied for thermal-structural coupling analysis. The results show that leakage thermal stress makes the LNG tank a shrinkage deformation. Through finite element analysis of load cases considerting thermal stress and different static loads, the most adverse envelope diagram is obtained and then the configuration of pre-stressed reinforcement is proposed.The comparison of the wind pressure distribution given by foreign scholars and Chinese load code proves that Chinese code load is conservative. Adopting the wind pressure distribution given by Chinese code load, the response analysis is carried out under static wind and along-wind fluctuating wind load based on quasi-steady assumption. The conclusion is that the most adverse wind direction is15°from the buttress, and compared with the response under static loads, the response under static wind and along- wind fluctuating wind load is little. The extreme response of max circumferential stress under fluctuating wind load is only5.47%of the result under the most unfavorable static loads.Through FLUENT software, the CFD numerical simulation of wind field around the LNG storage tank is conducted. The wind pressure distribution from CFD analysis proves the rationality for the adoption of the wind distribution of domed roof and circular-section structure given by Chinese code load on the wind distribution simulation. According to the synthetic wind speed time series of stationary strong wind, CFD transient analysis is carried out and wind pressure time series are obtained, which gets rid of the synchronous fluctuation. By statistical treatment on the results of wind-induced response of outer concrete tank under stationary strong wind, the most adverse wind vibration coefficient is proposed and the configuration of pre-stressed reinforcement is modified.