| 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... |
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