锈蚀钢筋混凝土梁正截面受弯破坏模式及承载力简化计算方法

Bending failure modes and simplified bending capacity calculation methods for normal cross-sections of corroded RC beams

为快速准确评估受拉纵筋锈蚀对钢筋混凝土梁正截面受弯承载力的影响,采用解析方法计算受弯破坏时锈蚀钢筋混凝土梁正截面应力和应变分布,识别并定义锈蚀钢筋混凝土梁的3个界限锈蚀率和6种正截面受弯破坏模式,提出预判破坏模式再计算承载力的锈蚀钢筋混凝土梁正截面受弯承载力简化计算方法。采用该简化方法,计算相关文献中235根锈蚀钢筋混凝土梁的正截面受弯承载力,并与试验结果对比,验证该简化方法的准确性。通过两个算例,分别研究初始超筋梁和初始适筋梁的正截面受弯破坏模式及承载力随受拉纵筋锈蚀率的变化规律。研究结果表明:随着受拉纵筋锈蚀率的增大,初始超筋钢筋混凝土梁的正截面受弯破坏模式按照从“类似超筋”、“类似适筋”、“类似超筋”到“类似少筋”依次转变;初始适筋钢筋混凝土梁的正截面受弯破坏模式按照从“类似适筋”、“类似超筋”到“类似少筋”依次转变;钢筋混凝土梁正截面受弯承载力近似呈多段线性降低,最终退化为素混凝土梁的开裂弯矩,转折点位置为界限及临界锈蚀率。

In order to rapidly and accurately evaluate the influence of corrosion of tensile reinforcement on the flexural behavior of reinforced concrete(RC) beams, the stress and strain distributions over the cross-section of corroded RC beams at flexural failure were calculated analytically. Three bound corrosion ratios and six bending failure modes for corroded RC beams were identified and defined. Subsequently, a simplified calculation method for the flexural capacity of corroded RC beams was proposed that enables to predetermine failure mode first and calculate capacity later. The flexural capacities of 235 corroded RC beams collected from the literature were calculated by the proposed simplified method and compared with the corresponding experimental results, which demonstrated the accuracy of the proposed simplified calculation method. Finally, two examples were designed to investigate the evolution of flexural failure mode and capacity of the normal cross-section of an initially over-reinforced or under-reinforced RC beam with the corrosion propagation of tensile steel reinforcements. The results showed that as the corrosion ratio of tensile longitudinal steel reinforcements increases: the flexural failure mode of the normal cross-section of an initially over-reinforced RC beam changes in the order of “over-reinforced similar mode”, “under-reinforced similar mode”, “over-reinforced similar mode” and “slightly-reinforced similar mode”;the flexural failure mode of the normal cross-section of an initially under-reinforced RC beam changes in the order of “under-reinforced similar mode”, “over-reinforced similar mode” and “slightly-reinforced similar mode”;the flexural capacity of the normal cross-section of an RC beam decreases in an approximately multi-linear way and finally reduces to the cracking moment of a plain concrete beam, in which the turning point positions locate at the bound corrosion ratio and critical corrosion ratio.