Post-Peak Analysis of Reinforced Concrete Structural Members with Internal Defects

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In the present research, the post-peak behaviors of two types of concrete structural members with the internal defects have been investigated.The one is on the uniaxial compressive behavior of prismatic concrete specimen with internal defects, such as rock-pocket and breeding. The experiments were carried out for the several sizes of concrete specimens with the different sizes of rock-pockets. In the case of experiment on the specimen without the end friction, the reduction in maximum compressive strength is found to be proportional to the projected area of defect to the section of concrete specimen. The 3-D finite element analysis (FEM) with DIANA has given almost the same results as those of experiments. On the other hand, in the case of experiment on the specimen with the end friction, the reduction in maximum compressive strength is found to be more rapid, compared with the case without the end friction. This phenomenon could not be represented numerically even with 3-D FEM analyse … More s, which lead to the same results as those of analysis without the end friction. It has been understood from this analysis that a sever failure pattern may be occurred in the case that the surrounding area of defect portion is constrained to some extent. Therefore, a unified numerical method and modeling are required to give a rise in moderate results for any kinds of boundary conditions.The other is on the flexural behavior of RC beam with internal defects, such as rock-pocket and breaking of hoop ties, The on-point loading experiment have been done for the RC beam (120×180×1,400 mm) with defects at its center. It has been found from experimental work that the existence of rock-pocket affects much on the post-peak behavior as well as the maximum strength, compared with the existence of broken hoop tie. The finite element program FEAP has been used to simulate the experiment, by applying the strain-softening type of constitutive model under the different confining pressures. From the analytical study it has been concluded that the existence of bigger size of rock-pocket, i.e., 0.3 times the beam width, cancels the confining effect from hoop tie and core-concrete becomes almost in a plain condition.Summarizing the present research, it can be said that the reduction in maximum strength as well as the post-peak behavior of concrete structural member should be more carefully considered if the defects exist in an expected failure zone or area of concrete member. Less