Size effects in unreinforced and lightly reinforced concrete beams failing in flexure
Size effects in unreinforced and lightly reinforced concrete beams failing in flexure
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DOI：
10.1016/j.engfracmech.2021.107987
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发表时间：
2021-09
影响因子：
5.4
通讯作者：
L. Nelson;J. Lees;L. Weekes
中科院分区：
文献类型：
--
作者：
L. Nelson;J. Lees;L. Weekes
基于裂缝的模型通常使用特征长度作为确定混凝土梁中尺寸效应的基础。特征长度与混凝土断裂过程区有关，并根据混凝土断裂特性定义。半经验常数，然后开发，以适应任何身份不明（几何或裂纹桥接）的参数。然而，半经验因素的依赖可能会限制不同的系统，混凝土和加固材料的适用性。目前的工作的目的是制定一个分析的尺寸效应模型的基础上完全基本的材料和几何属性。特别关注的是无钢筋和轻度钢筋混凝土梁，由于不稳定的裂纹扩展而导致弯曲失效。建议的“广义”的特征长度的方法是基于模式-I的混凝土断裂行为，并包括由于纵向钢筋的存在下，裂缝桥接力。理论表达式表明，梁的几何形状，混凝土的断裂性能和裂纹桥接力（如果存在）显着影响的特征长度。几何相似的无筋和轻钢筋混凝土梁的实验研究进行了初步验证的手段。然后将验证扩展到文献中现有实验结果的更广泛数据集。广义特征长度法能够同时考虑混凝土强度的影响和纵向钢筋的尺寸效应。这证实了通用方法具有前景，并且可以扩展到其他准脆性材料和非常规增强材料。
Fracture-based models commonly use a characteristic length as the basis for determining size effects in concrete beams. The characteristic length is related to the concrete fracture process zone and defined in terms of the concrete fracture properties. Semi-empirical constants are then developed to accommodate any unidentified (geometric or crack bridging) parameters. However, a reliance on semi-empirical factors can limit the applicability to different systems, concretes and reinforcing materials. The aim of the current work is to formulate an analytical size effect model based solely on fundamental material and geometric properties. The particular focus is unreinforced and lightly reinforced concrete beams that fail in flexure due to unstable crack propagation. The proposed ’generalised’ characteristic length approach is based on the mode-I fracture behaviour of concrete and includes crack bridging forces due to the presence of longitudinal reinforcement. The theoretical expressions suggest that the geometric shape of a beam, the fracture properties of the concrete and the crack bridging forces (where present) significantly influence the characteristic length. Experimental investigations on geometrically similar unreinforced and lightly reinforced concrete beams are undertaken as a means for initial validation. The validation is then extended to a wider dataset of existing experimental results in the literature. The generalised characteristic length approach is able to capture both the influence of the concrete strength and the size effect mitigation due to the inclusion of longitudinal reinforcement. This confirms that the generalised approach holds promise and could be expanded to other quasi-brittle materials and non-conventional reinforcing materials.