大型LNG储罐混凝土外罐及穹顶施工期间全过程受力分析

发布时间：2018-05-15 08:45

本文选题：LNG储罐 + 温度应力　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：由于能源结构的转变及能源供应、储备的需要，大型预应力混凝土液化天然气(LNG)储罐在我国的建造日益兴起。目前，国内对于此类型储罐的设计、建造技术还未完全掌握，且LNG项目的投资金额巨大，如果能实现国内自主设计及建造施工，将会带来极大的经济效益。在已有的国内储罐建造工程中，混凝土外罐在施工期间极易出现裂缝，且储罐的混凝土穹顶施工安全问题引起建造、设计者的重点关注，为此，本文以一座160000m3大型LNG预应力全容罐为研究对象，以大型有限元分析软件ANSYS为平台，建立了精细化的有限元模型，精确地模拟了LNG储罐混凝土外罐罐壁及穹顶的实际施工过程，具体研究工作如下： 1.按实际结构施工顺序与时间，模拟了LNG储罐混凝土外罐罐壁全部混凝土浇筑过程；考虑随时间变化的环境温度，获得了由水化热作用产生的混凝土外罐早期温度场分布；在考虑混凝土收缩和徐变的条件下，采用增量法计算了混凝土外罐的早期温度应力；确定了随时间及配筋率变化的混凝土早期抗拉强度，通过与温度应力进行对比，对LNG储罐混凝土外罐施工阶段的裂缝分布规律进行了预测。研究结果表明：混凝土收缩对温度应力影响显著，在150天的模拟时间段内，结构温度应力呈现持续增长状态；LNG外罐第1浇筑段的温度应力明显大于其他浇筑段的温度应力，且该浇筑段的罐壁在模拟期内将产生竖向裂缝、扶壁柱处将产生局部环向裂缝； 2.分别探讨了施工模板材料、施工质量、施工季节及入模温度对混凝土外罐温度应力的影响及其规律，结果显示：模板对温度应力的影响作用较小，，施工质量及施工季节对温度应力的影响较大。在此基础上，将温度应力结果按各影响因素的作用进行拆解，视温度应力结果为水化热、混凝土收缩、外界气温及入模温度各自单一影响作用下温度应力的叠加，进而总结出了以调节施工季节为主，提高施工质量为辅的结构抗裂措施建议； 3.针对穹顶混凝土施工的支承模板结构－带钢板肋环型钢网壳，提出合理的稳定性分析方案，并对其进行非线性全过程稳定性研究；探讨了蒙皮钢板厚度、网壳杆件截面尺寸、矢跨比、初始几何缺陷形式及大小对带钢板网壳稳定性能的影响规律； 4.根据储罐穹顶混凝土浇筑的各个施工过程，分别建立相应的有限元分析模型，确定各施工段的施工气压，获得在相应施工气压及初始缺陷下的网壳结构安全系数，并对带钢板肋环型网壳结构进行优化设计。
[Abstract]:Due to the transformation of energy structure and the need of energy supply and reserve, the construction of large prestressed concrete liquefied natural gas (LNG) storage tank is rising in our country. At present, the design and construction technology of this type of storage tank have not been fully grased at home, and the investment amount of the LNG project is huge, if the domestic design and construction can be realized, It will bring great economic benefit. In the existing domestic storage tank construction project, the concrete outer tank is very easy to crack during the construction period, and the construction safety problem of the concrete dome of the storage tank causes construction. The designer pays attention to it. For this reason, this paper takes a large 160000m3 large LNG prestressed full tank as the research object, with large finite element. The analysis software ANSYS is used as a platform to establish a finite-element model, which accurately simulates the actual construction process of the wall and dome of the LNG tank concrete tank. The specific research work is as follows:
1. according to the construction sequence and time of the actual structure, the concrete pouring process of the concrete outer tank wall of the LNG storage tank is simulated. Considering the time changing environment temperature, the early temperature field distribution of the concrete outer tank produced by the hydration heat is obtained, and the concrete is calculated by incremental method under the conditions of concrete shrinkage and change. The early temperature stress of the external tank is determined, and the early tensile strength of concrete with the change of time and reinforcement ratio is determined. Through the comparison with the temperature stress, the crack distribution in the construction stage of the LNG tank concrete tank is predicted. The results show that the concrete shrinkage has a significant influence on the temperature stress and in the 150 day simulation time period. The temperature stress of the structure of the structure in the LNG tank first is obviously greater than that of the other casting sections, and the wall of the casting section will produce a vertical crack during the simulation period, and the local circumferential crack will be produced at the buttress column.
2. the influence and regularity of construction template material, construction quality, construction season and mold temperature on the temperature stress of concrete tank are discussed. The results show that the effect of template on temperature stress is small, construction quality and construction season have great influence on temperature stress. On this basis, the results of temperature stress are affected by various factors. The effect is dismantled, and the result of temperature stress is hydration heat, concrete shrinkage, the superposition of temperature stress under the single influence of external temperature and mold temperature, and then the suggestion of structural anti cracking measures is summed up by adjusting the construction season and improving the construction quality.
3. in view of the support template structure of the dome concrete construction - steel ribbed steel reticulated reticulated shell with steel plate, a reasonable stability analysis scheme is put forward, and the stability of the nonlinear whole process is studied. The thickness of the skin plate, the section size of the reticulated shell, the vector span ratio, the initial geometric defect form and the size of the steel reticulated shell with steel plate are discussed. The law of influence;
4. according to the construction process of concrete pouring in the storage tank dome, the corresponding finite element analysis model is established respectively, the construction pressure of each construction section is determined, the safety coefficient of the reticulated shell structure under the corresponding construction pressure and initial defects is obtained, and the structure of the ribbed ring reticulated shell with steel plate is optimized.

【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

【参考文献】