Theory of Critical Distances and static/dynamic fracture behaviour of un-reinforced concrete: length scale parameters vs. material meso-structural features
Theory of Critical Distances and static/dynamic fracture behaviour of un-reinforced concrete: length scale parameters vs. material meso-structural features
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DOI：
10.1016/j.engfracmech.2021.108220
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发表时间：
2022-01
影响因子：
5.4
通讯作者：
N. Alanazi;L. Susmel
中科院分区：
文献类型：
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作者：
N. Alanazi;L. Susmel
临界距离理论（TCD）将一些方法组合在一起，这些方法利用特定的长度尺度参数来建模和估计裂纹/缺口工程材料的强度。在TCD框架中，临界距离被认为是一种固有属性，并且该长度与材料的微观/中观/宏观结构特征有关。近年来，许多综合的理论/实验研究已经证明，TCD在评估包含各种几何特征的非钢筋混凝土的静态/动态I型/混合I- ii型强度方面也是成功的。然而，对于最明显的基础研究问题，即“TCD临界距离的物理意义是什么”，科学界尚未就一个普遍接受的答案达成一致意见。为了回答这一问题，通过对非钢筋混凝土试件进行静、动I型弯曲试验，得出了大量的试验结果。根据RILEM推荐的素混凝土断裂参数测定方法，本次综合试验工作不仅涉及素试件，还涉及含有裂纹样锯切缺口的试件。被测试的样品是通过使用不同的定制混合物来制造的，这样被测试的混凝土材料的主题结构特征就可以被控制，然后以一种非常精确的方式建模。系统的实验/理论研究结果表明，TCD临界长度接近于类裂纹锯齿形缺口尖端线与第一聚集体之间的平均距离，这些聚集体起到阻碍/影响裂纹扩展过程的作用。
The Theory of Critical Distances (TCD) groups together a number of approaches that make use of specific length scale parameters to model and estimate the strength of cracked/notched engineering materials. In the TCD framework, the critical distance is assumed to be an intrinsic property and this length is somehow related to the material micro-/meso-/macro-structural features. In recent years, a number of comprehensive theoretical/experimental investigations have proven that the TCD is successful also in assessing the static/dynamic Mode I/Mixed-Mode I-II strength of unreinforced concrete containing geometrical features of all kinds. However, the scientific community has not yet agreed on a commonly accepted answer to the most obvious fundamental research question, i.e.“what is the physical meaning of the TCD critical distance?”In order to answer this question, a number of experimental results were generated by testing specimens of unreinforced concrete under static and dynamic Mode I bending. According to what is recommended by RILEM for the determination of fracture parameters of plain concrete, this comprehensive experimental work involved not only plain samples, but also specimens containing crack-like saw-cut notches. The specimens being tested were manufactured by using different bespoke mixes so that themeso-structural features of the concrete materials being tested could be controlled and then modelled in a very accurate way. The results from this systematic experimental/theoretical study led to the conclusion that the TCD critical length approaches the average distance between the crack-like saw-cut notch tip line and the first aggregates, with these aggregates acting as barriers slowing down/affecting the crack propagation process.