基于遗传算法的大体积混凝土温度场反分析与反馈研究

发布时间：2018-06-04 07:20

本文选题：大体积混凝土 + 温度场　；参考：《长安大学》2015年硕士论文

【摘要】：随着国民经济的发展,悬索桥锚锭、大坝以及其它大体积混凝土结构的修建越来越多,因混凝土水化热反应、约束条件以及环境因素引起混凝土的开裂问题应受到人们的重视,本文基于此问题,介绍了大体积混凝土裂缝的类型、形成原因及危害,并提出了相应的裂缝控制措施。本文以云南普立特大桥的散索鞍支墩基础为依托进行了相关研究。大体积混凝土内部温度场和应力场异常复杂,仿真模拟时热学参数的选取是一个难点,为解决这一问题,本文先利用Midas/FEA建立温度场反分析模型,确定反演热学参数以及目标函数,然后利用Matlab编制遗传算法程序,最后根据现场实测的温度资料,反演得到混凝土的最大绝热温升、反应速度、表面放热系数以及导热系数。进一步对散索鞍支墩基础进行反馈研究,首先,对比分析了基础混凝土中具有代表性的测点的温度实测值和计算值,两者吻合较好,验证了程序的可靠性,证明反演所得参数能够准确反映混凝土的热学性能;深入研究了基础在浇筑过程中的温度场的分布情况和发展规律,并在此基础上提出了一些温控措施,对今后的同类工程具有理论借鉴意义。其次,选取具有代表性的9个特征点,对散索鞍支墩基础内部的徐变应力场进行了研究,得出应力的分布情况、发展规律、最大时段以及裂缝的产生区域,并以此为依据提出一些控制应力的措施。再次,对散索鞍支墩基础在浇筑后的变形机理进行研究,得到最大变形产生的区域以及约束条件对变形的影响。最后,改变参数浇筑温度、表面放热系数和冷却水流量,对比分析了不同影响因素对散索鞍支墩基础的温度场或应力场产生的影响,得出对温度场或应力场的影响机理,并提出一些降低浇筑温度和减小表面放热系数的措施。对散索鞍支墩基础混凝土的温度场、徐变应力场以及变形的研究表明,大体积混凝土最易开裂的时段是浇筑初期和上层混凝土浇筑时,因此,应降低浇筑温度,加强养护,控制上下层温差,并尽可能改善约束条件,避免混凝土开裂。
[Abstract]:With the development of national economy, the construction of suspension bridge anchor ingots, dams and other mass concrete structures is more and more. People should pay more attention to the cracking of concrete caused by hydration heat reaction of concrete, constraint conditions and environmental factors. Based on this problem, this paper introduces the types, causes and hazards of mass concrete cracks, and puts forward corresponding crack control measures. Based on the saddle pier foundation of Puli Bridge in Yunnan Province, this paper has carried on the related research. The internal temperature field and stress field of mass concrete are very complicated, so the selection of thermal parameters is a difficult point in simulation. In order to solve this problem, a back analysis model of temperature field is established by using Midas/FEA. The inverse thermal parameters and objective function are determined, and then genetic algorithm program is compiled by using Matlab. At last, the maximum adiabatic temperature rise, reaction velocity, surface exothermic coefficient and thermal conductivity of concrete are obtained according to the measured temperature data in the field. Further research on the feedback of the saddle pier foundation is carried out. Firstly, the temperature measured value and the calculated value of the representative measuring point in the foundation concrete are compared and analyzed. The two values are in good agreement with each other, and the reliability of the program is verified. It is proved that the inversion parameters can accurately reflect the thermal properties of concrete, and the distribution and development of the temperature field during the pouring process of the foundation are deeply studied, and some temperature control measures are put forward. It has theoretical reference significance for similar projects in the future. Secondly, 9 representative characteristic points are selected to study the creep stress field in the foundation of the saddle support pier, and the distribution of the stress, the law of development, the maximum period and the region of the crack are obtained. Based on this, some measures to control stress are put forward. Thirdly, the deformation mechanism of the saddle pier foundation after pouring is studied, and the maximum deformation region and the influence of constraint conditions on the deformation are obtained. Finally, by changing the pouring temperature, surface exothermic coefficient and cooling water flow rate, the influence of different factors on the temperature field or stress field of the saddle pier foundation is compared and analyzed, and the mechanism of the influence on the temperature field or stress field is obtained. Some measures to reduce the pouring temperature and the surface exothermic coefficient are put forward. The research on temperature field, creep stress field and deformation of concrete foundation of saddle abutment pier with loose cable shows that the most easily cracked period of mass concrete is at the initial stage of pouring and when the upper layer of concrete is poured. Therefore, the pouring temperature should be reduced and the maintenance should be strengthened. Control the temperature difference between the upper and lower floors, and improve the restraint conditions as much as possible to avoid concrete cracking.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441

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