静力及风荷载作用下LNG储罐混凝土外罐受力性能分析

发布时间：2018-06-03 00:44

本文选题：LNG储罐 + 低温泄露　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：随着近年来对能源需求的急剧增加，液化天然气（Liquefied Natural Gas，LNG）以其热值大、性能高、使用安全及方便运输和储存等特点，成为能源发展结构中的重要组成部分。发展天然气工业也成为了解决能源问题及可持续发展问题的极佳途径，从而受到了各国的大力推广。大型LNG储罐作以其储存量大，占地面积小等优点，使得其建造数量大幅增加。然而，国内对LNG储罐的研究尚处于初级阶段，一旦因储罐内低温液体发生泄露性破坏，，将造成巨大的经济损失甚至人员伤亡。因此，在我国大力发展建设LNG储罐的同时，对其进行内罐泄漏下的静力分析及风荷载作用下的响应分析，具有实际工程意义。针对上述问题，本文的主要研究内容及结论如下：以某实际工程160000m3LNG储罐混凝土外罐为研究对象，在有限元软件ANSYS中建立了考虑罐壁、穹顶、环梁、扶壁柱及罐底桩位约束的混凝土外罐精细化模型，对其进行了不同静力荷载（自重、罐顶压力、罐内气压、罐内液压）工况组合下的结构响应对比，并讨论了泄漏后液位对响应的影响规律。分析结果显示：罐顶压力对结构的影响很小；罐内气压的作用不可忽略；液压作用对结构内力及变形起主导作用。针对LNG储罐中低温液体由钢制内罐泄露至混凝土外罐这种情况，本文建立稳态对流换热边界条件，利用有限元模拟混凝土外罐的温度场分布并获得其温度场分布规律。将节点温度转化为温度应力并利用低温下混凝土的本构关系，进行了热-固耦合分析，结果表明：低温液体泄露产生的温度应力使得储罐外罐发生整体收缩趋势；通过温度应力与其他不同静力作用结果组合，获得了考虑低温泄露时结构的最不利响应包络图，并提出了预应力钢筋布置方案。对比国内、外风压分布的计算方法，采用偏于保守的中国《建筑结构荷载规范》给出的风压分布，对LNG储罐外罐进行静力风荷载作用下的响应分析及顺风向拟定常假定下的风振响应分析。对比结果表明：风向与扶壁柱夹角为15°时为最不利风向，静力风和脉动风荷载作用下的响应与静力荷载下的响应相比很小，仅为静力最不利荷载作用下的5.47%。通过FLUENT软件对LNG储罐外罐周围的风场进行CFD数值模拟，得到了平均风荷载作用下的风压分布，经与中国《建筑结构荷载规范》给出的风压分布进行对比，验证了采用《建筑结构荷载规范》给出旋转壳顶和圆截面构筑物的风压分布模拟LNG储罐外罐风压分布的合理性。最后，模拟平稳强风的风速时程，经由CFD瞬态分析，获得了非同步脉动风压时程，同时，对平稳强风作用下的外罐结构风振分析结果进行统计处理，得到了最不利风振系数与平稳强风下的结构动力响应，并修正了预应力钢筋的布置方案。
[Abstract]:With the rapid increase of energy demand in recent years, liquefied natural gas (LNG) has become an important part of energy development structure because of its high calorific value, high performance, safe use and convenient transportation and storage. The development of natural gas industry has become an excellent way to solve the problem of energy and sustainable development. The large LNG storage tank has the advantages of large storage capacity and small area. However, the research on LNG storage tank is still in the primary stage, once the leakage damage of the cryogenic liquid in the storage tank occurs, it will cause huge economic losses and even casualties. Therefore, while developing and constructing LNG tanks in China, it is of practical engineering significance to carry out static analysis under internal tank leakage and to analyze the response under wind load at the same time. In view of the above problems, the main contents and conclusions of this paper are as follows: Taking the concrete outer tank of 160000m3LNG storage tank for a practical project as the research object, a fine model of concrete external tank is established in the finite element software ANSYS, which takes into account the constraints of the tank wall, dome, ring beam, buttress column and bottom pile position. The structural responses under different static loads (deadweight, top pressure, air pressure and hydraulic pressure in the tank) were compared, and the effect of liquid level on the response was discussed. The results show that the roof pressure has little effect on the structure, the pressure in the tank can not be ignored, and the hydraulic pressure plays a leading role in the internal force and deformation of the structure. In view of the leakage of low temperature liquid from steel inner tank to concrete external tank in LNG storage tank, the steady state convection heat transfer boundary condition is established in this paper. The temperature field distribution of concrete outer tank is simulated by finite element method and the temperature field distribution law is obtained. Using the constitutive relation of concrete at low temperature to transform the temperature of the joint into the thermal stress, the thermal-solid coupling analysis is carried out. The results show that the temperature stress caused by the leakage of liquid at low temperature causes the whole shrinkage trend of the external tank. Through the combination of temperature stress and other static action results, the most unfavorable response envelope diagram of structure considering low temperature leakage is obtained, and the layout scheme of prestressed steel bar is put forward. Comparing with the calculation method of the external wind pressure distribution in China, the wind pressure distribution, which is more conservative than that given in the Building structure load Code of China, is adopted. The response analysis of LNG storage tank under static wind load and the wind vibration response under the usual assumption of downwind direction are carried out. The results show that the wind direction is the most unfavorable when the angle between wind direction and supporting column is 15 掳, and the response under static wind and pulsating wind is very small compared with the response under static load, which is only 5.47% of that under the most unfavorable static load. The wind field around the outer tank of LNG storage tank is simulated by FLUENT software, and the wind pressure distribution under the average wind load is obtained, which is compared with the wind pressure distribution given by the Code of Building structure load in China. It is proved that the wind pressure distribution of the structure with rotating shell roof and circular section is reasonable to simulate the wind pressure distribution of the outer LNG tank by using the Building structural load Code. Finally, the wind speed time history of stationary strong wind is simulated, and the non-synchronous pulsating wind pressure time history is obtained by CFD transient analysis. At the same time, the results of wind vibration analysis of external tank structure under the action of stationary strong wind are statistically processed. The most unfavorable wind vibration coefficient and the structural dynamic response under steady and strong wind are obtained, and the layout scheme of prestressed steel bar is modified.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU375

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