Finite Element Analysis Of Mechanical Behavior For Reinforced Concrete Structure Considering Crack Propagation

With weak tensile strength, reinforced concrete structures usually work with cracks. In order to get the crack width and height, significant indicator of evaluating safety performance of the structure, and the influence on mechanical behaviour from crack, crack propagation is a necessary part when finite element modeling of reinforced concrete structure.The discrete crack model which based on fiction crack theory is realized by introducing crack interface element. The interface element is composed of an array uncoupled springs, which characterizes the element boding-strength. The stiffness of the spring elements is changing as the bonding strength depending on the tension-softening curve of concrete. The program is realized by writing code and writing and reading files continiously and the results are got by the post processing.The major work which has been carried out on this thesis and the important conclusions are summarized as follows:1. The discrete cracks are modeled based on fiction crack theory in reinforced concrete beams. The analysis results are compared with those without crack. The comparative study shows that after crack extension, the tensile stress in pure bending segments is released effectively and the maximum tensile stress is shifted to the edge; the stress of the steel bar near the crack increases significantly; height of compressive region decreases and the average compression stress in compression zone rises.2. The crack width and deflection of the reinforced concrete beams under service loads are calculated in according to Code for design of concrete structures (GB 50010-2010) and EN1992-1. The calculations are compared with FE results. The comparative conclusions suggests that the results of the two codes differ a lot about crack width, but differ a little about deflection; the crack width and deflection simulated by FE rise slower in the early and quicker in the later compared with the two codes, but match well with EN1992-1 on the whole; the discrete crack model based on fiction theory is reliable.3. The discrete crack model based on fiction theory is applied to large-scale LNG tank. Mechanical properties are studied under 12 conditions under service loads. Mechanical properties of the tank at the most unfavorable condition in the most disadvantage position are studied while considering crack propagation. The result shows that the crack width, the height of compressive region and the average compression stress in compression zone are meet the requirements of EN14620-1. Therefore, the serviceability requirement and liquid-tightness can be satisfied.