Study on Initial Defects of Concrete Structures Generated during the Construction Process

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The study aims at in the first place estimating the amount of initial defects, specially the thermal residual stress or the width of crackings due to it and in the second place to estimate the effect of those defects on the ultimate strength of the structure. The experiment using a large scale mass concrete specimen was carried out and it is recognized that the thermal deformation occurs not only to the horizontal direction but to the vertical direction as well which are decomposed into the axial deformation and the bending deformation similarly to the ordinary beam deformation under the axial load and bending moment.The FEM programs to give the residual thermal stress are developed, i.e. 3-D and 2-D isoparametric FEM programs and finite prism element program. For the purpose of the simple design conveniency, the compensation line and plane methods, the accuracy of which are almost comparable to the FEM analysis are proposed.The effects of the initial defects on the ultimate strength of concrete structures were calculated using the elastic plastic analysis and it was recognized that the reduction of the ultimate strength sometimes exceeds the 20 percent of the initial strength.