【作者】 张宇鑫；

【导师】 宋玉普； 刘德富；

【作者基本信息】 大连理工大学 ， 结构工程， 2002， 博士

【摘要】 伴随着大体积混凝土结构在现代工程建设中的广泛应用，存在其中的大体积混凝土结构温度应力问题越来越引起人们的重视。而仿真分析计算是解决这一问题的有效手段。目前，对于较为重要的大体积混凝土结构，均需采用仿真分析来指导设计，如小湾、龙滩、溪洛渡、沙牌、三峡、普定、二滩等等著名工程均采用了仿真计算指导方法。它的重大现实意义使其成为当前科学研究的一个热门话题。 但是目前，大体积混凝土结构全过程多因素的仿真分析仍面临着许多困难，这给科研工作者提出了许多富于挑战性的课题。本文针对目前大体积混凝土结构仿真计算尚存在的问题，从仿真计算模型的精度及仿真计算的计算量问题及仿真计算前后处理的可视化技术及计算参数真实确定等几个方面展开了如下研究工作： 1．针对差分法进行不稳定温度场求解时，差分步长过大会造成绝热温升计算误差加大，差分步长过小又会引起计算量成倍增长的问题，根据差分法求解的基本特点，提出了一种误差修正方法，在计算量得到成倍提高的同时，保证了求解精度，较好的解决了这一问题。若不考虑中间变化过程，甚至可取2天、5天为步长，计算结果在精度允许范围内。并对三种常用混凝土绝热温升计算公式的修正规律及时间步长与精度的关系等问题进行了研究。 2．仓面保护是一些重要工程在混凝土夏季施工中必须采用的一种温控措施，仓面喷雾是较新采用的一种保护方式，降温效果受喷雾机俯视角度，离喷头距离，风向、风速、环境温度与入仓温度关系及实际喷雾效果等多种因素影响，因此计算模型复杂。本文根据仓面喷雾方式的物理作用原理，建立了相应的理论求解模型。利用拉氏变换方法及叠加原理，求解出保温板保温、仓面喷雾、流水养护这三种常用仓面保护方式降温效果理论解答；并基于此理论解答，对三种仓面保护方式的特点及规律进行了研究，从数值上分析了几个影响温度变化的主要因素：保温板厚度、内外温差梯度，距表面不同深度等对每种保护方式降温效果的影响。 3．在环境参数与材料参数一定的情况下，解决温度应力的主要工程措施是施工过程中的温度控制。本文利用数值仿真计算方法，以溪洛渡实际工程为依托，对大体积混凝土施工中常采用的温控措施对混凝土温度变化的影响规律进行了全面系统的研究，包括分缝分块方式、浇筑温度、混凝土间歇时间、一期冷却方式(包括不同进水温度、不同水管布置、不同通水时间)等。对影响大体积混凝土内部最高温度与断面平均温度的各种参数进行了敏感性仿真分析，其结论可为工程实际制定温控措施方案提供决策依据。 4．针对常规的混凝土应力计算方法不支持长浇筑块的通仓浇筑方案，而通仓浇筑方法却在工程实际得到越来越多的应用(如二滩，最长浇筑块为60m；溪洛渡，最长浇筑块为69m)的情况，通过数值仿真分析计算方法，在同等条件下计算了不同浇筑块长度(20m、40m、60m、80m、120m)的温度过程与应力发展过程。从各块体中部最高温度、最大水平约束应力、断面平均水平约束应力、典型点应力发展过程、正反向应力变幅等5个方面，比较系统地阐述了大体积混凝土通仓浇筑问题。其结果在一定程度上支持了混凝土超长浇筑块的施工。 摘 要 5．本文自主开发了模拟大体积混凝土结构跳仓浇筑施工全过程的温度场及应力场三维有限元仿真分析软件FZFX3D，以溪洛渡拱坝实际工程为依托，以较小时间步长（如0．5天，1天）为单位，逐步模拟大坝的浇筑过程，并全面考虑每个施工步对应的外界温度变化，自身水化热作用、冷却水管效果、新混凝上对老混凝土、蓄水、徐变、自生体积变形的影响等因素，实现了坝高270m以上拱坝的模拟跳仓浇筑的温度应力仿真，对跳仓浇筑高拱坝施工全过程温度及应力的特点及变化规律进行了研究，成果对设计单位选择最优的温控措施从而降低坝体温度应力具有重要参考价值。 6．基于Laplace积分变换法和遗传算法，本文提出了一种求解混凝土一维瞬态导热反问题的新方法。运用Laplace变换方法将温度的求解表示为只与空间坐标及浇筑时间有关的函数，从而避免了用隐式差分法、有限元法求解时需求解联立方程的因而对测点选择的依赖，也避免了显式差分法求解稳定性受时间步长，测点间距大小限制的缺点，因而具有测点布置灵活的特点。运用遗传算法寻求非线性反演问题全局最优解，只需要若干点温度实测值便可实现多个热学参数的同时反演，并通过算例对本文反演方法的反演精度及数值稳定性给出了满意的证明。 7在气温、水温、自身材料特性变化等复杂因素作用下，大体积混凝土结构内部温度变化非常复杂，沿各项均有热量传递，很多情况下一维、二维传热模型假定虽然节省了计算量，但却无法满足计算精度的要求，尤其对于施工期的混凝土温度场，需要建立三维传热模型进行分析。本文基于瞬态温度场有限元求解理论与反演算法，提出了一种反演混凝土三维瞬态温度场主要热学参数的通用方法。只需要若干点温度实测值便可实现多个热学参数如绝热温升、导温、导热系数及热交换系数等?更多还原

【Abstract】 With mass concrete structures being widely used in engineer practice, their thermal stress problem continues to increasingly attract our attention. Numerical simulation method is a useful way to solve this problem. Presently, nearly all the important mass concrete structures were designed by the aid of simulation method, such as Xiao wan, Longtan, Xiluodu, Shapai, Three gorges and other famous projects. Its important practical significance has made it the popular topic of present scientific researches.However currently, the simulation analysis of mass concrete structures for the process incorporating multi factors still faces many difficulties, which introudced a lot of challenging research. Focusing on some problems still unresolved, in simulation analysis, some research works have been done as follows:1. When the difference method is used to solve temperature problem, the error of adiabatic temperature rise of concrete is often caused by a difference step that is too big, at the same time computation workload increases greatly because of a difference step that is too small. Based on the basic characteristics of the difference method, this paper introduced one kind of correcting method, which can assure solution precision but doesn’t increase the calculating workload. We can even adapt 2 days or 5 days as a difference step by use of this method if the detailed change in process is ignored. Also the correcting rules of three kinds of common adiabatic temperature rise of concrete were researched.2. Bin’s surface protecting is a necessary thermal control method for the construction of concrete during the summer. According to the Laplace transformation method and superimposition principle, theoretical solutions of the effect of three typical bin’s surface protecting methods of thermal insulation were given. Based on the solutions, the characteristics and rules of three insulation procedures were analyzed in numerical calculation. The research results of this paper are valuable for engineers to design economical and viable bin’s surface insulation way.3. Provided that the environmental factors and material factors are all fixed, the main practical measure of solving thermal stress problems is to control the temperature variation during the construction stage. By using the finite element numerical simulating method, and studies based on the practical project Xiluodu arch dam, this paper studies systematically the type of joints, placing temperature, protection methods on the surface of concrete dams, the first stage artificial cooling method including different cooling water temperatures, cooling lasting days and cooling pipes arrangement. The sensitivity of parameters related to the highest and the average temperature of concrete dam has also been studied. The results will facilitate the design department in stipulating thermal control methods of concrete dams.4. Traditional theories for restrained stress of mass concrete does not agree with the construction method of long block without longitudinal joints, but now more and more dams are being constructed this way. By numerical simulating, this paper studies the temperatureinand thermal stress developing process of column concrete blocks with different lengths(20m,40m,60m,80m,120m). Five aspects, such as the highest temperature in the middle of block, maximum horizontal stress, average stresses of any sections, stress changing process of typical points, and stress changing range between tension and compression, are discussed in detail. The result is beneficial for stipulating construction method with long block.5. In this paper, a 3D finite element analysis software(FZFX3D) was compiled to simulate the construction process of mass concrete structures constructed with sequence method. Based on the practical project Xiluodu arch dam, the dam’s construction process was simulated by a small time step size, 0.5 or 1 days. The environmental temperature change, hydration heat rise, artificial cooling, creep, volum更多还原