疲劳荷载后锈胀RC梁抗弯刚度计算模型

腐蚀和疲劳作用影响钢筋混凝土梁的服役性能,降低结构的剩余使用寿命。为研究疲劳后锈蚀钢筋混凝土梁的刚度退化规律,采用电化学快速锈蚀试验得到了6根不同锈胀程度的钢筋混凝土梁,研究了不同疲劳荷载次数后梁在分级荷载下的荷载—挠度关系、混凝土裂缝发展规律、失效模式,分析了锈蚀水平对钢筋混凝土梁疲劳寿命的影响。试验结果表明,钢筋混凝土梁的挠度发展分快速上升—稳定—失稳三个阶段,混凝土锈胀对梁疲劳寿命的影响较大。引入刚度修正系数,发展了疲劳荷载后锈胀钢筋混凝土梁抗弯刚度计算方法,该方法可考虑疲劳作用、锈胀、混凝土弹性模量退化等因素的影响,并通过本文试验及现有文献中的试验结果进行了验证,可用于日后老化钢筋混凝土桥梁在疲劳荷载作用下的挠度计算和寿命评估。

Flexural Stiffness Model of RC Beams with Corrosioninduced Cracking after Fatigue Loading

Corrosion and fatigue deteriorate the service performance of reinforced concrete beams and shorten the residual service life of structures. In order to study the flexural stiffness degradation of corroded reinforced concrete beams, six reinforced concrete beams with different corrosion-induced cracking levels were prepared by accelerated corrosion test. The load-deflection relationship, crack propagation in concrete and failure modes of reinforced concrete beams after various fatigue loading cycles were investigated. The effects of reinforcement corrosion on fatigue life of beams were also analyzed. The results show that the deflection experiences three stages with the increase of fatigue loading, which is initial fast increasing stage, stable stage and unstable stage. Corrosion-induced cracking has a significant effect on the fatigue life deterioration of reinforced concrete beams. A theoretical method for flexural stiffness deterioration of corroded reinforced concrete beam after fatigue was developed by incorporating a modified stiffness coefficient. The presented method considered the effects of fatigue, corrosion-induced cracking, fatigue modulus degradation of concrete and other influential factors. The proposed method was verified by the experimental results in this paper and other published literatures. The proposed method and research results can be used for the deflection calculation and life assessment of aging reinforced concrete bridges subjected to fatigue loading.