Study Of RCC Gravity Dam Strengthen Measures For Seismic Resistance

There has been a great improvement in seismic analysis of gravity dam by damage in the last 20 years. It was discovered that there is plastic strain during cracking, however concrete is brittle materials. As the plastic strain can't been considered in stress-based damage model and strain-based damage model, the energy-based damage is adopted in this paper. It studies the seismic response of a high RCC gravity dam in China western by plastic-damage model. It reveals the evolution of damage index and stress in cross section.It studies the energy dissipation in the fracture process of concrete. Then the energy response of gravity dam in earthquake is presented. The hysteretic characters, energy dissipation ability, failure mechanism and characteristics are researched, it introduces the responses of input energy,damping energy,elastic energy,kinetic energy,plastic energy dissipation and damage energy dissipation. Though it is popular in seismic analysis by damage mechanics or fracture mechanics, there almost isn't a common criterion for dam safe evaluation using these mechanics. Some people have explored a global dam damage index, which is main formed by the length of crack in the dam cross section and the modifying coefficient, the crack environment (such as upstream,downstream,underwater and so on) determines the value of modifying coefficient. But this global dam damage index just considers the local damage influence, in order to improve degree of accuracy a new global dam damage index is proposed, in this index the damage energy dissipation is considered, using this factor we can get the information of the damage area rate of the whole dam section.People have paid attention to the strengthen measures of high gravity dam for high intensity seismic, study of the measures is the main work in this paper. It proposes two measures:optimizing the material assigning design. It has been found that the different material assigning designs can lead very different dam cracking, so though comparing the global dam damage indices we get the optimum design. Then the paper introduces the theory of reinforced concrete finite element and the reaction between rebar and concrete in big volume rare-reinforcement concrete structure, the crack characteristic is very different from brittle plain concrete, so it also studies the fracture energy of reinforced concrete. In ABAQUS it develops a new constitutive model of reinforced concrete. in this constitutive model the local effect of crack is considered, once a crack processes the crack opening displacement takes place rapidly, but the strain of other undamaged zone will decreases, it leads to form just one crack in characteristic length. It studies the damping characteristic in the constitutive model, the nonlinear Rayleigh damp is adopted. Then it studies the seismic crack of dam using this constitutive model. At last it introduces the methods of calculating the reinforcement percentage, it states the disadvantage of the method in hydraulic concrete structure design code by linear finite element, explores a new method by nonlinear finite element according to the damage degree, and finds the appropriate reinforcement percentage.