Abstract

In this paper, a new approach for measurement of the fracture toughness of concrete using the edge cracked semi-cylinder disk (ECSD) specimens has been rendered. The critical stress intensity factor (fracture toughness) of concretes was determined by using the edge cracked semi-cylinder disk (ECSCD) type specimens. The normalized Mode I stress intensity factor of concrete was measured and estimated through a new formula. The versatile finite element method (FEM) was used to derive this appropriate formula and the Mode I fracture toughness of the specimens determined with a reasonable accuracy. In the laboratory, the notched Brazilian disks (NBD) were tested to evaluate the accuracy of the ECSCD method. A discrete element analysis of the ECSCD tests was also carried out to numerically simulate these experiments and validate the accuracy of the fracture toughness values. Finally, very good agreements gained by comparing the crack extension patterns obtained from the experimental tests with the numerical simulations’ results. However, the toughness values obtained through ECSCD experiments were lower than those measured from the NBD tests. This is due to the smooth distribution of tensile stress around the notch in the ECSCD concrete specimens.

摘要

在本文中，提出了一种使用边缘开裂半圆柱圆盘 (ECSD) 试样测量混凝土断裂韧性的新方法。混凝土的临界应力强度因子（断裂韧性）是通过使用边缘开裂的半圆柱盘 (ECSCD) 型试样来确定的。通过一个新的公式测量和估计了混凝土的归一化模式 I 应力强度因子。通用有限元法 (FEM) 用于推导此适当的公式，并以合理的精度确定试样的模式 I 断裂韧性。在实验室中，对缺口巴西圆盘 (NBD) 进行了测试，以评估 ECSCD 方法的准确性。还对 ECSCD 测试进行了离散元分析，以对这些实验进行数值模拟，并验证断裂韧性值的准确性。最后，通过将实验测试获得的裂纹扩展模式与数值模拟结果进行比较，获得了非常好的一致性。然而，通过 ECSCD 实验获得的韧性值低于 NBD 试验测得的值。这是由于 ECSCD 混凝土试样中缺口周围拉伸应力的平滑分布。