氯盐环境下混凝土中锈蚀钢筋力学性能研究

基于试验、仿真及理论分析,探讨了氯盐环境下混凝土中锈蚀钢筋力学性能的退化规律及其影响机理。采用干湿循环法对钢筋混凝土试件进行了长达两年的锈蚀试验,对214根锈蚀钢筋进行机械拉伸试验。结果表明:当锈蚀程度较轻时,钢筋名义强度随锈蚀率增加呈线性下降;当锈蚀率较大时,钢筋名义、等效强度及延性均随其增加而下降;钢筋力与变形关系曲线中的屈服平台随锈蚀不均匀性增大逐渐缩短甚至消失;钢筋断裂形态与局部锈蚀特征相关,可分为三种类型;同等条件下细直径钢筋的力学性能对锈蚀更敏感。就试验现象进行理论和仿真分析表明:钢筋的实际抗拉强度在锈蚀前后并不降低;名义强度的降低,主要是由于锈损引起钢筋横截面积减小导致抗力减小而造成的;锈蚀引起的截面积减小、缺口效应及附加偏心作用是导致钢筋伸长率减小的主要原因;附加弯矩作用是导致钢筋力与变形关系曲线中屈服平台缩短、消失的主要原因。

Research on mechanical properties of corroded steel bar in concrete under chloride environment

Based on the experiments, theoretical analysis and numerical simulation, the rule for the residual properties of corroded reinforcing bars in chloride environment is discussed, and the cause is analyzed. 214 corroded bars were taken from the RC specimens experienced wet-dry cycle test for two years. The tensile experiment results show that when the corrosion ratio is small, the nominal strength of the steel bar decrease almost linearly with the reduction of corrosion ratio; when the corrosion ratio is large, the nominal strength and the equivalent strength decrease with the increase of corrosion ratio, so it is ductility. As to the force-displacement curve, the yield is lowered, even disappears as the corrosion is more and more non-uniform. The fracture morphology changes with local corrosion characters is tics, which can be described as 3 types. Under the same condition, the mechanical properties of corroded small-diameter bars are degraded more than that of large ones. From the analysis of theory and simulation based on experiment, it may conclude that the actual tensile strength of reinforcing bars changes not remarkably pre and post the corrosion. The nominal tensile strength is decreased, chiefly because of the cross sectional area decreased after corrosion that lead to the decrease of resistance. The decrease of cross sectional area, notch effect and the additional eccentric force due to corrosion have a remarkable influence on the elongation of steel bars. It is mainly attributed to the additional moment for the local non-uniform corrosion that the yield platform on the force-displacement curve is shortened, even disappears.