Mechanical and damage mechanisms of reinforced ultra high performance concrete under tensile loading
Mechanical and damage mechanisms of reinforced ultra high performance concrete under tensile loading
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拉伸荷载作用下钢筋超高性能混凝土的力学及损伤机制
DOI：
10.1016/j.conbuildmat.2019.07.162
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发表时间：
2019-11-30
影响因子：
7.4
通讯作者：
Wang, Jun-Yan
中科院分区：
文献类型：
--
作者：
Bian, Chen;Wang, Jun-Yan
了解钢筋超高性能混凝土（RUHPC）的受拉机理对超高性能混凝土（UHPC）的结构设计和应用具有重要意义。对纵筋率分别为0%、2.3%和4.6%的RUHPC试件进行了直接拉伸试验，并进行了裂缝宽度检测和声发射源定位。研究了两种类型的RUHPC：高应变硬化型RUHPC（HSH-RUHPC）和应变软化型RUHPC（SS-RUHPC）。实验结果包括拉伸应力（载荷）-应变曲线、裂纹宽度-应变曲线和拉伸载荷下声发射源分布图。从两个方面阐述了其拉伸机理。从力学机制上看，第一阶段（弹性阶段）和第二阶段弹塑性阶段：（1）HSH-RUHPC的应力分布是均匀的，而SS-RUHPC中的钢筋从完全弹性状态到部分屈服状态再到部分应变硬化状态;（2）UHPC的抗拉强度在RUHPC中有所降低，且随配筋率的增加而降低的趋势更加明显。从细观损伤演化机理来看：（1）HSH-RUHPC在屈服前具有多个细观开裂模式，损伤分布较为均匀;（2）SS-RUHPC在软化后具有多个宏观开裂模式，损伤在裂纹位置呈现多个损伤集中。同时，Gini指数是评价RUHPC内部损伤分布不均匀性的有效参数。(C)2019爱思唯尔有限公司版权所有。
Understanding the tensile mechanism of reinforced ultra high performance concrete (RUHPC) is important for structural design and application of ultra high performance concrete (UHPC). In this study, the direct tensile test accompanied with crack width detection and acoustic emission (AE) source locating were conducted on RUHPC specimens with the longitudinal reinforcement ratios of 0%, 2.3% and 4.6%. Two types of RUHPCs were studied: high strain hardening RUHPC (HSH-RUHPC) and strain softening RUHPC (SS-RUHPC). Experimental results included the tensile stress (load)-strain curves, the crack width-strain curves and the AE source distribution maps under tensile loading. The tensile mechanisms were elaborated from two aspects. From the view of mechanical mechanism, during Stage I (the elastic stage) and Stage II (the elastic-plastic stage): (1) HSH-RUHPC had a globally uniform stress distribution while the steel rebar in SS-RUHPC changed from total elastic state to partial yielding and finally to partial strain hardening; (2) the reduction of the tensile strength of UHPC was observed in RUHPC, which was more obvious with the higher reinforcement ratio. From the view of damage evolution mechanism based on AE analysis method at the micro level: (1) HSH-RUHPC exhibited a homogeneous damage distribution owing to its multiple-micro-cracking mode before steel yielding; (2) SS-RUHPC showed several damage concentrations at crack positions after UHPC softening due to its several-macro-cracking mode. Meanwhile, Gini index was proved to be an effective parameter to evaluate the distribution non-uniformity of the internal damages of RUHPC. (C) 2019 Elsevier Ltd. All rights reserved.