Reinforced concrete structures are often damaged by corrosion, which affects the interaction between reinforcement bars and concrete. Earlier studies mostly applied artificial corrosion to test the bond between deformed bars and concrete. However, there is a lack of knowledge on the effects of natural corrosion on plain bars. In this paper, 20 beams with naturally corroded plain bars and varying amount of damage were taken from an 80-year-old bridge and tested in three-point bending. All but three of the specimens anchored the yield force of the bars after the opening of one or two major bending cracks. At large deflections, the load-carrying mechanism changed from beam to arch action. Eventually, end-slip of the reinforcement bars was observed. The bars were extracted, cleaned, three-dimensionally scanned, and tested in tension. The average bond strength in the unyielded zone was found to be equal to 7.39 MPa, with a standard deviation of 3.33 MPa. The casting position was identified as an important factor: when uncorroded, bottom-cast bars had a higher bond strength than that of top-cast bars. However, they were more prone to splitting cracks and, consequently, loss of bond strength for small corrosion levels. Top-cast bars had increasing bond strength with increasing corrosion levels, owing to the absence of external cracks. These differences were likely related to a denser concrete surrounding the bottom-cast bars. The remaining bond capacity in the yielded zones was evaluated to be approximately 1.0 MPa.

中文翻译：

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受弯构件中自然腐蚀的普通钢筋的锚固

钢筋混凝土结构经常因腐蚀而损坏，这会影响钢筋与混凝土之间的相互作用。早期的研究大多采用人工腐蚀来测试变形钢筋和混凝土之间的结合。然而，缺乏关于自然腐蚀对普通钢筋的影响的知识。在本文中，从一座 80 年历史的桥梁中取出 20 根带有自然腐蚀的普通钢筋和不同程度损坏的梁，并进行了三点弯曲试验。在打开一两个主要弯曲裂纹后，除了三个试样外，所有试样都锚定了钢筋的屈服力。在大挠度时，承载机制从梁变为拱形作用。最后，观察到钢筋的端部滑移。将钢筋提取、清洁、三维扫描并进行拉伸测试。发现未屈服区的平均结合强度等于 7.39 MPa，标准偏差为 3.33 MPa。铸造位置被认为是一个重要因素：未腐蚀时，底部铸造的钢筋比顶部铸造的钢筋具有更高的结合强度。然而，它们更容易裂开，因此在小腐蚀水平下会失去粘合强度。由于没有外部裂纹，顶铸棒的结合强度随着腐蚀程度的增加而增加。这些差异可能与底部浇筑钢筋周围的混凝土密度较大有关。屈服区的剩余结合容量经评估约为 1.0 MPa。在未腐蚀的情况下，底部铸造的钢筋比顶部铸造的钢筋具有更高的粘合强度。然而，它们更容易裂开，因此在小腐蚀水平下会失去粘合强度。由于没有外部裂纹，顶铸棒的结合强度随着腐蚀程度的增加而增加。这些差异可能与底部浇筑钢筋周围的混凝土密度较大有关。屈服区的剩余结合容量经评估约为 1.0 MPa。在未腐蚀的情况下，底部铸造的钢筋比顶部铸造的钢筋具有更高的粘合强度。然而，它们更容易裂开，因此在小腐蚀水平下会失去粘合强度。由于没有外部裂纹，顶铸棒的结合强度随着腐蚀程度的增加而增加。这些差异可能与底部浇筑钢筋周围的混凝土密度较大有关。屈服区的剩余结合容量经评估约为 1.0 MPa。这些差异可能与底部浇筑钢筋周围的混凝土密度较大有关。屈服区的剩余结合容量经评估约为 1.0 MPa。这些差异可能与底部浇筑钢筋周围的混凝土密度较大有关。屈服区的剩余结合容量经评估约为 1.0 MPa。