Non-uniform Corrosion and Load Bearing Capacity Deterioration Tests of Reinforced Concrete Beams Under Load and Chloride Salt Environment
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摘要:
为考察持续荷载与氯盐干湿循环共同作用对钢筋混凝土梁抗弯性能的影响，先后进行19根钢筋混凝土梁的腐蚀试验和抗弯承载力试验，研究不同持续荷载等级和干湿循环天数对裂缝分布、钢筋质量锈蚀率以及受腐蚀构件受弯性能的影响，并分别总结纵筋最大和平均质量锈蚀率与承载力降低比的关系. 研究结果表明：纯弯段的钢筋锈蚀程度较高，纵筋锈蚀程度沿圆周分布不均匀；纵筋质量锈蚀率的极值点位置与初始横向裂缝的出现位置无必然关联性；纵筋最大质量锈蚀率随荷载等级和干湿循环天数的增加而增大，受干湿循环天数的影响更明显；腐蚀后梁峰值荷载呈下降趋势；当纵筋锈蚀率较小时（平均值<3%或最大值<6%），锈蚀率与承载力降低比的相关度较低，且最大质量锈蚀率的相关度小于平均质量锈蚀率；当纵筋锈蚀率较大时（平均值>3%或最大值>6%），质量锈蚀率与承载力降低比的相关度提高；在纵筋平均质量锈蚀率相同时，采用自然腐蚀试件的承载力降低程度高于采用外加电流腐蚀的试件.
Abstract:To explore how sustained loading and drying-wetting cycles of chloride salt affect the flexural behavior of reinforced concrete (RC) beams, the corrosion tests and flexural capacity tests of 19 RC beams were carried out at first. The effects of various sustained loading grades and drying-wetting cycle periods were studied on the crack distribution, the mass corrosion rate of longitudinal reinforcements, and the flexural behavior of corroded members. The relationship was summarized between the maximum and average mass corrosion rate of longitudinal reinforcements and the flexural bearing capacity reduction ratio. The study results show that the corrosion degree of longitudinal reinforcements was higher in the pure bending segment than in other areas, and distributed non-uniformly along the circumference of the longitudinal reinforcements. There was no noticeable correlation between the position of the extreme mass corrosion rate of longitudinal reinforcements and the occurrence position of initial transverse cracks. The maximum mass corrosion rate of longitudinal reinforcements increased with the loading grade and drying-wetting cycle period, and was more notably affected by the drying-wetting cycle period. The peak load of the beam decreased after corrosion. When the mass corrosion rate of the longitudinal reinforcements was low (average value below 3% or maximum value above 6%), the correlation between the mass corrosion rate and the reduction ratio of bearing capacity was low, and the maximum mass corrosion rate has less correlation with the reduction ratio of bearing capacity than the average mass corrosion rate. When the mass corrosion rate of longitudinal reinforcements increased (average value above 3% or maximum value above 6%), both the maximum and the average mass corrosion rates of longitudinal reinforcements had an increased correlation with the reduction ratio of bearing capacity. When the average mass corrosion rate of longitudinal reinforcements is the same, the reduction of bearing capacity of specimens with natural corrosion is higher than that of specimens with external current corrosion.
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图 3 试件在氯离子环境下的干湿循环过程
Figure 3. Drying-wetting process of specimens under chloride environment
图 4 锈蚀梁受拉面的锈蚀特征
Figure 4. Corrosion characteristics of tensile surface of corroded beam
图 8 A 组试件受拉纵筋最大质量锈蚀率
Figure 8. Maximum mass corrosion rate of tensile longitudinal reinforcements of group A specimens
图 10 腐蚀后梁跨中荷载-挠度关系曲线
注：O1/0d/0%表示试件O1的参数，干湿循环天数0天，承受荷载比0%.
Figure 10. Load-displacement relationship at mid-span of corroded beams
图 11 承载力降低比与纵筋质量锈蚀率关系
Figure 11. Relationship between reduction ratio of bearing capacity and mass corrosion rate of longitudinal reinforcements
图 12 承载力降低比与纵筋平均质量锈蚀率关系
Figure 12. Relationship between reduction ratio of bearing capacity and average mass corrosion rate of longitudinal reinforcements
表 1 试件参数
Table 1. Specimen parameters
试件 荷载比（P/Pu）/% 干湿循环天数/d 加载方式 O1 0 0 不加载 A1 0 182 不加载 A2 23.7 182 与 B2 互锚 A3 37.6 182 与 B3 互锚 A4 0 364 不加载 A5 23.7 364 与 B5 互锚 A6 37.6 364 与 B6 互锚 A7 0 546 不加载 A8 23.7 546 与 B8 互锚 A9 37.6 546 与 B9 互锚 B1 0 182 不加载 B2 23.7 182 与 A2 互锚 B3 37.6 182 与 A3 互锚 B4 0 364 不加载 B5 23.7 364 与 A5 互锚 B6 37.6 364 与 A6 互锚 B7 0 546 不加载 B8 23.7 546 与 A8 互锚 B9 37.6 546 与 A9 互锚 
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表 3 材料力学指标
Table 3. Material mechanical indexes
MPa 钢筋类型 屈服强度 极限强度 HPB300 308.2 484.9 HRB400 471.7 628.1
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表 4 抗弯承载力试验结果与纵筋锈蚀程度
Table 4. Test results of flexural bearing capacity and corrosion level of reinforcements
试件
编号峰值荷载/
kN峰值荷载时
跨中挠度/mm平均质量锈蚀率/% 最大质量锈蚀率/% O1 136.22 12.31 0 0 B1 133.83 11.56 0.34 0.62 B2 120.69 9.31 0.68 0.75 B3 112.61 8.50 0.78 1.05 B4 127.54 12.29 1.38 3.98 B5 132.96 12.61 1.06 4.77 B6 115.11 9.54 1.88 5.28 B7 99.24 9.45 3.47 9.84 B8 99.03 10.19 4.37 10.96 B9 98.91 N/A 4.15 10.57
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