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混凝土桥梁在服役过程中经常同时承受疲劳荷载和氯离子侵蚀,但现有研究多未考虑疲劳和氯离子侵蚀的耦合作用。本文研究了疲劳荷载与氯盐侵蚀耦合作用下混凝土中氯离子的扩散行为,并运用超声检测表征混凝土的疲劳损伤,以建立疲劳损伤与氯离子扩散性能之间的关系。研究结果表明:随着疲劳压应力水平提高,超声参数表征的混凝土损伤值也逐渐增大;应力水平低于0.4时,不同疲劳应力水平对混凝土中氯离子浓度分布没有明显影响,氯离子扩散系数甚至略有减小,这应是应力水平较低时混凝土中微孔隙和裂缝被压缩而降低了氯离子的扩散能力;应力水平为0.5及0.6时,混凝土中氯离子浓度显著提高,扩散系数明显增大,并且与应力水平呈正相关;超声参数表征的混凝土损伤与氯离子渗透性的发展趋势不一致,表明由于混凝土内部缺陷分布的不均匀性使得超声技术难以定量表征荷载引起的混凝土损伤。
Concrete bridges often suffer fatigue loads and chloride ion erosion during service, but most of the existing studies do not consider the coupling between fatigue and chloride ion erosion. In this paper, the diffusion behavior of chloride ions in concrete under the coupling of fatigue load and chloride salt erosion was studied. The fatigue damage of concrete was characterized by ultrasonic testing to establish the relationship between fatigue damage and chloride diffusion. The results show that with the increase of fatigue compressive stress, the damage value of concrete characterized by ultrasonic parameters also gradually increases. When the stress level is lower than 0.4, the different fatigue stress levels have no obvious effect on the distribution of chloride ion concentration in concrete. The chloride ion diffusion coefficient Even a slight decrease, which is due to the compression of micro-pores and cracks in the concrete when the stress level is low, and the chloride ion diffusion ability is reduced. At the stress levels of 0.5 and 0.6, the chloride ion concentration in concrete is significantly increased and the diffusion coefficient is obvious Which is positively correlated with the stress level. The development tendency of concrete damage and chloride ion permeability characterized by ultrasonic parameters is inconsistent, which shows that it is difficult for ultrasonic technique to quantitatively characterize concrete damage caused by load due to the inhomogeneous distribution of internal defects in concrete.