自然锈蚀钢筋的疲劳试验

Experimental Study on Fatigue of Naturally Corroded Steel Bars

为科学预测并适当延长既有服役混凝土桥梁的使用寿命,在考虑锈蚀率和应力幅值影响的基础上,对在服役老化混凝土构件中截取的25根锈蚀钢筋试件进行了轴向拉伸疲劳试验.经统计回归分析,建立了考虑锈蚀率影响的轻度、中度、重度自然锈蚀钢筋疲劳曲线方程,探讨了轻度、中度、重度自然锈蚀钢筋疲劳寿命的退化规律,给出了50%保证率不同预期疲劳寿命下轻度、中度、重度自然锈蚀钢筋容许应力幅值的建议值,并与轻度、中度加速锈蚀钢筋容许应力幅值的建议值进行了对比.结果表明:轻度、中度、重度自然锈蚀钢筋的应力幅值与疲劳寿命均呈对数线性关系,但疲劳寿命急剧下降,且应力幅值越大其降低幅度越大.

In order to predict scientifically and extend properly the useful service life of aged existing reinforced concrete bridges,considering the mass loss ratio and cyclical stress amplitude,axial tensile fatigue tests were conducted on 25 naturally corroded reinforcing steel bars in air.The fatigue curves of slight,medium and extensive corrosion steel bars were obtained by statistical regression analysis on the basis of taking into account the influence of corrosion on the fatigue properties.The deterioration rules in fatigue life of the slight,medium and extensive natural corrosion steel bars were investigated.Then,suggested values of the allowable stress amplitude corresponding to different target fatigue lives under the 50％ guarantee rate were proposed for slight,medium and extensive steel bars naturally corroded,and compared with accelerated corrosion steel bars with the same level of corrosion.Test results indicate that the relationship between stress amplitude and fatigue life on a logarithmic scale for the slight,medium and extensive steel bars naturally corroded shows linear relation.However,a significant reduction in fatigue life was observed,especially under higher stress amplitudes.