Numerical Analysis Of Damage And Fracture For Early-age Concrete

With the development of material science and structure science of concrete, more and more large projects have been constructed, at the same time, high strength concrete and high performance concrete are extensively used. But this also leads to some problems, such as structure and durability failure in massive concrete structures, which were caused by the crack at early ages. It's very necessary to study the microstructure and macro-mechanical property of early-age concrete. Only by knowing the properties of early-age concrete well and taking some steps, we can guarantee the long-term quality of concrete structures.Based on the basic mechanics performance and fracture characteristic experimentations of early-age concrete, the characteristics of damage and fracture for early-age concrete were numerically analyzed in this thesis by way of the general finite element code ABAQUS. The study includes three parts as followings:1. the fracture experiment of three-point bending beams for early-age concrete was simulated and comparisons of LOAD-CMOD curves and LOAD-Displacement curves at different ages were brought into effect. Meanwhile, By applying the LEFM method, the critical stress intensity factor and critical crack tip opening displacement of concrete are calculated, all of which give a helpful reference to the study of I type fracture for early-age concrete.2. based on the classical beam mode of Arrea 和 Ingraffea, the mixed-mode fracture of early-age concrete beams were simulated, which characterized that the four point bending beam under complicate stresses undergoes a change from initially mixed cracking to dominantly separate cracking.3. based on the uniaxial tension tests of the early-age concrete, and by combining the concrete damaged plasticity mode with the smeared cracking mode, the whole process of concrete damage and crack was numerically simulated.