Analysis On Thermal Stresses And Cracking For Induced Joints Of RCC Arch Dam

In recent years, the construction technique in dam engineering has been revolutionized due to the rapid development of RCC (Roller Compacted Concrete), which is widely utilized in hydraulic engineering. With the completion of ShaPai RCC arch dam, the target of RCC arch dam beyond 100m is eventually realized. Thermal stress is the most principal cause for the damage of RCC arch dam. However, at present, if the coupling of multi factors is considered, the full process simulation analysis for RCC arch dam still faces many difficulties, which introduces a lot of challenging research. With the support of National Natural Science Foundation of China-Study on equivalent strength of induced joints of RCC arch dam (50179002), this paper focuses on some questions still unresolved about simulation analysis on temperature field and stress field of RCC arch dam, accordingly, some research work (i.e. constitutive model of RCC, simulation analysis on temperature field and stress field, cost and accuracy of simulation analysis, damage-fracture criterion for induced joints) are performed as following:1. The constitutive laws and damage evolution equations of RCC are established in tensile strain space and in compressive strain space respectively according to the distinct difference in mechanical performance and damage between tension and compression. In tensile strain space, its constitutive laws present elasto-brittleness, where the coupling of elasticity and damage is considered, and the behaviors of stiffness degradation and strain softening are described by orthotropic damage theory. Whereas, in compressive strain space, its constitutive laws present elasto-plasticity, where the elasto-plasticity is described by endochronic theory, and the behaviors of stiffness degradation and strain softening due to micro-crack propagation are described by orthotropic damage theory. No yield surfaces are needed in endochronic theory, hence the number of parameters and equations in the model is reduced significantly and the nonlinear calculation is simplified. Good agreement is observed between the predicted values using the proposed model and the experimental results of RCC under uniaxial and multiaxial loading.2. The theoretical solutions for temperature field of multi-layer thin plate structure are deduced by Laplace transform and superposition principle, where the differences of pouring time and emitting time of hydration heat between rolling layers are considered. Based on the above analytic solutions, the equivalent model for temperature field is established by merging multiple rolling layers into one composite layer, and the approximate formulas for equivalent initial temperature and equivalent adiabatic temperature rise are put forward. By this method, construction processes of RCC dam may be simulated, and analysis on temperature field for RCC dam can be simplified.Moreover, among forward difference method, central difference method or backward difference method, no matter which one is applied into unsteady temperature field calculation of massive concrete, the error of temperature is inevitable. Based on Langrage mean-value theorem and the uncoupling assumption of temperature difference and temperature change rate among all nodal points, an iterative algorithm is put forward, which proves an effectivemethod for temperature field calculation of massive concrete. By this method, computation is decreased and at the same time solution precision can be controlled when the time step is properly increased. On the other hand, if time step is kept at conventional level, computation will be increased appreciably, while solution precision can be greatly increased, and the numerical calculated results will approach theoretical results furthermore.3. By means of analysis on thermal performance of concrete, the concept of thermal damage is introduced. The thermal damage and effect of temperature on creep are adopted to describe the coupling of thermal field and stress field. With the consideration of the influence of temperature,...