Evaluation on spatial variability of corrison of steel bar in marine concrete structure

混凝土内嵌钢筋的腐蚀对钢筋混凝土结构的结构性能和耐久性有很大的影响。然而，钢筋腐蚀程度与结构性能之间的关系还没有得到充分的明确，因为结构构件内的腐蚀和结构内的各向异性有很大的变化。在本研究中，通过测量取自实际结构的锈蚀钢筋的横截面积，定量地明确了钢筋锈蚀的变化。此外，通过模拟钢筋腐蚀的各种变化，实验研究了腐蚀变化对钢筋混凝土结构力学性能的影响。结果表明，腐蚀钢筋的强度是用最大截面损失来估计的。在结构性能方面，采用钢筋截面面积最大损失准确地评价了第一次屈服荷载，但受腐蚀空间变化的影响不大。首次屈服后，钢筋局部腐蚀对结构性能的影响随钢筋直径、钢筋数量和腐蚀位置的不同而不同。腐蚀部位钢筋与混凝土之间的粘结应力传递机制对钢筋混凝土构件的承载能力影响较大。因此，用钢筋横截面积最大损失来估计结构性能是不可能的。在此基础上，提出了退化钢筋混凝土构件和结构承载力的简化评估概念。考虑到钢筋混凝土结构中钢筋腐蚀的变化，开发了生命周期管理系统。

Corrosion of steel reinforcement embedded in concrete has a great influence on structural performance and durability of reinforced concrete(RC) structures. However, the relationship between the degree of steel reinforcement corrosion and structural performance has not been made clear adequately because of wide variations in corrosion within a structural member and anisotropy within a structure.In this study, through measurement of the cross-sectional areas of corroded steel bars taken from real structures, variations in corrosion of steel reinforcement were quantitatively made clear. Moreover, an influence of the variation of corrosion on mechanical properties of RC structures was experimentally investigated by reproducing various variations of steel reinforcement corrosion.As a result, it was made clear that strengths of corroded steel reinforcement are estimated by using the maximum cross-sectional loss. Regarding the structural performance, the first yield load was accurately evaluated by using the maximum loss in cross-sectional area of steel reinforcement, but it was not greatly influenced by the spatial variation of corrosion. After the first yield, an influence of localized corrosion of steel bars on structural performance was varied depending on the diameter and number of steel reinforcement and position of corrosion. In particular, the load-carrying capacity of RC member was influenced by the mechanism of bond stress transfer between corroded steel reinforcement and concrete at the corroded position. Therefore, it was not possible to estimate the structural performance by the maximum loss in cross-sectional area of steel bar.Based on these results obtained in this study, finally, the concept of simplified assessment was proposed regarding the structural capacity of deteriorated RC members and structures. The life-cycle management system was developed taking into account the variations in corrosion of steel bars in RC structures.