Research On Temperature And Deformation Self-adjustment Of Smart Concrete Structure

This dissertation was supported by the Key Project of National Science Foundation under grants No. 50238040.Concrete is one of popular engineering structural materials. Some momentous concrete structures must be used for decades even hundreds years. Regular concrete structures for water conservancy usually work in abominable climate and environment, such as concrete dams. Temperature is main load of these structures, and alternant between positive and negative temperature would cause asymmetric deformation, crack, freezing-thawing damage and fatigue damage of structures, affecting their normal work and even resulting in disasters. In addition, Cement structures such as bridges often come into being distortion or excessive temperature stresses due to the sun radiation, creep, or shrinkage. MAGLEV railway is a good example. The flatness of MAGLEV railway is one of the most important factors restricting speed of MAGLEV trains. Therefore, study of diagnostic and control method for momentous structures is important in construction engineering.Some research works were done to adjust temperature differential and deformation of carbon fiber mat concrete laminate beams which were possessed of multi-function, in addition to their structural performance. The study involved theoretical derivation, finite element simulation and experimental research.The following conclusions and innovation can be obtained:Firstly, carbon fiber mat concrete laminate beams possessed of sensing and acting functions and structural performance were designed and fabricated according to the sensing and acting functions of carbon fiber concrete and multiple and designable functions of laminate structures. Experimental researches were done for electro-thermal effects of the laminate beams. Laws of electro-thermal effects and response of the samples were obtained, which are the basis of self-adjustment.Secondly, the theoretical model was set up for electro-thermal-mechanical problem of smart concrete laminate beams, and then temperature stress and deformation responses driven by the electro-thermal effect of a type of carbon fiber mat cement beams were studied. The results shows that the temperature increment and deformation driven by electro-thermal effects of the carbon fiber mat laminate beams is proportional to input electrical power, and the deformation is mainly caused by the temperature differential between the top and bottom surface. Stable temperature differential determines stable deflection of the beam. The theoretical results are similar to the experimental results. The theoretical results are important basis of self-adjustment.Thirdly, infinite element plain and three-dimentional models were set up forelectro-thermal -mechanical problem. Numerical simulate analysis was done using MARC infinite element software. The results are similar to the experimental results and theoretical results, which could verify the correctness of the theoretical analysis and the vadility of the numerical simulate analysis. In this dissertation, some simulate researches were done to analyze the electro-thermal-mechanical effects of the steel reinforced concrete laminate beams. The results show that temperature field and deformation driven by the electro-thermal-mechanical effects of the steel reinforced concrete laminate beams are different from laminate beams without steel bars due to difference of their thermal and mechanical parameters. But steel bars have little influence on the electrical features of the samples.The forth, according to the temperature-sensing and Seebeck effects of carbon fiber reinforced concrete, some transducers were designed and disposed. The temperature-sensing and Seebeck effects of carbon fiber (mat) reinforced concrete were researched. In order to eliminate the interfere of input power, an insulated interface was used. Then temperature and temperature differential were detected on line. Temperature compensate method was proposed to detect the deformation in the course of the temperature adjustment.Fuzzy and neural netwo...