不同应力幅下锈蚀疲劳耦合钢筋混凝土梁性能退化试验

Performance Degradation Test of Corrosion-fatigue Coupled RC Beams under Different Stress Amplitudes

为了探究锈蚀与疲劳荷载的耦合作用对钢筋混凝土构件抗弯性能的影响,分别对3组钢筋混凝土梁试件开展了在不同应力幅下的单纯疲劳加载试验与锈蚀疲劳耦合加载试验。通过模型试验,对比分析了单纯疲劳试验梁与锈蚀疲劳耦合加载试验梁在3种不同应力幅下的裂缝发展规律、荷载-挠度变化趋势、疲劳寿命及最终破坏形态。试验结果表明:应力幅一定时,在相同荷载循环次数条件下,锈蚀疲劳耦合加载试验梁的裂缝数量及开展程度均明显大于单纯疲劳加载试验梁;整个加载过程中,锈蚀疲劳耦合试验梁的刚度退化速率大于单纯疲劳加载试验梁,锈蚀疲劳耦合作用加速了钢筋混凝土梁的裂缝开展和刚度退化;相同应力幅下,锈蚀疲劳耦合试验梁XP-2,XP-3相比单纯疲劳试验梁P-2,P-3,疲劳寿命分别下降27.5%,18.6%;锈蚀疲劳耦合作用下,钢筋混凝土梁的破坏形式为底部受拉钢筋发生疲劳脆性断裂,钢筋断口处锈蚀严重,断口表面凹凸不平,呈现出撕裂的斜截面形状,与单纯疲劳加载梁钢筋断裂处断口平滑的特征有明显区别;锈蚀疲劳耦合试验梁在最终破坏状态下破坏区域更大,混凝土脱落更严重,锈蚀疲劳耦合作用下钢筋混凝土梁的塑性明显降低。

In order to explore the coupling effect of corrosion and fatigue load on the flexural performance of reinforced concrete members,the simple fatigue loading test and the corrosion fatigue coupled loading test on 3 groups of reinforced concrete beam specimens under different stress amplitudes of are carried out.Through the model test,the crack development rules,load-deflection change trends,fatigue lives and final failure forms of the beams in simple fatigue test and the corrosion fatigue coupled loading test under 3 stress amplitudes are compared and analyzed.The test result shows that(1) when the stress amplitude is constant,under the condition of the same number of load cycles,the number of cracks and the propagation degree of the corrosion fatigue coupled test beam are significantly larger than those of the simple fatigue loading test beam;(2) during the whole loading process,the stiffness degradation rate of the corrosion fatigue coupled test beam is greater than that of the simple fatigue loading test beam,and the corrosion fatigue coupling effect accelerated the crack propagation and stiffness degradation of the reinforced concrete beam;(3) under the same stress amplitude,the fatigue lives of the corrosion fatigue coupled test beams XP-2 and XP-3 decreased by 27.5% and 18.6% respectively compared with those of the simple fatigue test beams P-2 and P-3;(4) under the coupling effect of corrosion and fatigue,the failure mode of reinforced concrete beam is fatigue brittle fracture of the tensile steel bars at the bottom,the fracture of the steel bar is severely corroded,and the fracture surface is uneven,showing a torn oblique section shape,which is obviously different from the characteristic of smooth fracture at the fracture of steel bars of the simple fatigue loaded beam;(5) in the final failure state of the corrosion fatigue coupled test beam,the damage area is larger,the concrete falls off more seriously,and the plasticity of the reinforced concrete beam is obviously reduced under the action of corrosion fatigue coupling.