Study On Temperature And Stress Of Concrete Based On Degree Of Hydration

Temperature control and crack prevention of concrete is a quite complicated subject, there are many factors in the formation of concrete crack such as normal loads, temperature, autogenous deformation, dry shrinkage, restraint, and so on. In the present paper, the thermal and mechanical character, outogenous volumetric change character and some techniques in the calculation of temperature and stress of concrete were studied. Main research contents and innovative results are as follows.(1) The character of hydration and heat generation of concrete is studied in two aspects of theory and test, and new calculation models of adiabatic temperature rise and thermal conduction are established which base on the degree of hydration, the character of surface heat exchange of concrete is also tested. Then the nonlinear heat conduction equation basing on the degree of hydration is established, so that the distribution and development of temperature in concrete can be described more comprehensively and accurately.(2) The calculation models of concrete compression strength, Young's modulus, tensile strength are established which base on the equivalent age, and the change of concrete active energy is included in these models. The calculation models of concrete Poisson ration and expansion coefficient are established which base on the degree of hydration. So the development of mechanical character of concrete can be described more comprehensively and the stress state of concrete in structures can be reflected more accurately.(3) By the representation of mechanism and influencing factor of concrete autogenous shrinkage, the new calculation model of concrete autogenous shrinkage is established which base on the degree of hydration. And the difference of concrete autogenous shrinkage between the interior and surface of structures caused by the different temperature can be reflected, and the influence of this difference to stress can be described.(4) On the basis of normal models, new calculation model of autogenous expansion of MgO concrete is established which base on the degree of hydration. With this new model, the temperature compensation effect of MgO concrete in different regions of dam is analyzed.(5) The basic principle of genetic algorithms is represented, and the application of...