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

研究的目的首先是估计初始缺陷的数量，特别是热残余应力或裂纹宽度，其次是估计这些缺陷对结构的最终强度的影响。采用大体积混凝土试件进行了试验，发现热变形不仅发生在水平方向上，而且也发生在垂直方向上，与普通梁在轴向荷载和弯矩作用下的变形类似，热变形分解为轴向变形和弯曲变形。开发了计算残余热应力的有限元程序，即三维和二维等参数有限元程序和有限棱镜单元程序。为了简化设计方便，提出了精度与有限元分析基本相当的直线补偿法和面补偿法。采用弹塑性分析方法计算了初始缺陷对混凝土结构极限强度的影响，发现初始缺陷对混凝土结构极限强度的影响有时超过初始强度的20%。

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.