Study Of Damage For Concrete Under Temperature

When mass concrete forms, defects will produce such as some micro crack resulting from the different temperature between the surface and the inside. How this micro crack forms and develops is a very important subject hi Materials. Focusing on the micro construction of concrete materials, some research has been done. Based on the former accomplishment and two theories: Fraction Mechanics and Damage Mechanics, the thermal damage model is established. The temperature damage developing equation is presented, as well as the calculation of arch construction. The main contents are as follows:1. Influence of the temperature field and stress field is ignored but some other factors are considered such as temperature difference between the surface and inside of the concrete, circumstance temperature, work sequence, shaping period, elasticity modulus, the volume etc. And the emulation technology is applied to calculating the construction of the concrete. The deficiency in emulation calculation is also mentioned.2. How to estimate roughly in lamination temperature field and temperature stress field of mass concrete of base-plate are presented. Physical and mathematical model of calculation in lamination is established. Calculation formula is given and so is the result.3. The ways to study damage under mechanical strain are systematically discussed. The character of damage development under mechanical strain is explained. The deficiency of the damage model is pointed out too.4. The temperature damage experiment about mixture of cements, stones and concrete is carried out for the first time. Principle that the damage changed with the temperature is analyzed. The results indicate the inner interface is the weakest one. First, the damage accumulates at the boundary, then it spreads toward the cements. The damage occurred at temperature increasing. However, both of them are not beneficial, for they will reduce the material's mechanics ability. So the temperature difference is the main factor.5.The damage principle of the concrete is analyzed according to the experiments, and the damage temperature model is put forward. In the view of the concrete's micro construction, it can conclude that the boundary is the weakest. Minute crack occurs firstly at the boundary, and then it spread toward the cements, which are produced by thermal stress. But thermal stress can't be calculated without damage. And then it provided in this article the equation of the elementary damage, material intensity, elasticity modulus and temperature evolvement of rupture energy.6. Damage finite element, which can be calculated by rupture-damage finite element program, is applied to arch construction to calculate damage field and stress field with damage character considered, hi the program temperature damage developing equation is presented.