Finite Element Analysis for Compressive Failure Mechanism of Plain and Confined Concrete Considering Defects inside Concrete

(1)基于Diana软件的三维有限元分析本文对混凝土内部的应力和损伤分布，包括应变软化程度进行了三个系列的三维有限元分析和讨论：1)素混凝土；2)圆形截面约束混凝土；3)方形截面约束混凝土。在一定程度上明确了不同类型侧筋约束混凝土的破坏机理。(2)含缺陷素混凝土的抗压破坏试验研究了混凝土的抗压强度和破坏形态。主要影响因素包括试件尺寸、试件内部宏观缺陷的数量和大小以及试件与载荷板之间的摩擦。通过试验，在一定程度上阐明了宏观缺陷对破坏行为的影响。(3)进一步研究了无宏观缺陷的素混凝土和约束混凝土的三维有限元分析。含宏观缺陷混凝土的破坏模式分析有待进一步研究。

There are two main stages in the present study.(1) 3-D FEM Analysis with DIANA CodeFollowing three series of 3-D FEM analyses and discussion has been conducted on stress and damage distribution inside concrete including strain softening level.1) Plain concrete2) Confined concrete with circular section3) Confined concrete with square sectionIn the discussion, following two parameters have been newly defined : Equivalent confining pressure, and Damage index. The discussion has made clear to some extent the failure mechanism of confined concrete with various types of lateral bars.(2) Experiment on Compressive Failure of Plain Concrete with DefectsA series of experiment has been carried out to investigate compressive strength and failure pattern of concrete. Main factors include size of specimen, number and size of macro-defect inside a specimen, and friction between a specimen and loading plates. >From the experiment, the effect of such macro-defects on the failure behavior has been clarified to some extent.(3)Further Study3-D FEM analysis for plain and confined concrete without macro-defects has been successfully conducted in the present study. The analyses for failure patterns of concretes with macro-defects need to be carried out as a further study.