EVALUATION OF RESIDUAL CAPACITY OF CONCRETE STRUCTURES DEMAGED BY SALT ATTACK

本研究分三个阶段进行，（1）通过腐蚀试验，研究累积电流、钢筋锈蚀量和混凝土表面裂缝宽度之间的关系;（2）在静态荷载作用下，研究钢筋锈蚀对梁抗弯承载力的影响;（3）钢筋锈蚀梁的疲劳强度试验，对于一期工程，累积电流与钢筋锈蚀量的关系符合法拉第定律，混凝土表面裂缝宽度随腐蚀量的增加而线性增加。钢筋锈蚀对钢筋混凝土梁静载性能的影响不大，除非混凝土表面裂缝宽度超过0.3mm，否则钢筋锈蚀不会降低钢筋混凝土梁静载性能。即使在跨中设置搭接接头，适当布置的箍筋也能使梁保持原样。当钢筋锚固充分时，纵向裂缝引起的承载力降低可小于30%，钢筋锈蚀对梁的疲劳性能影响很大。特别是锈蚀钢筋对应力集中敏感，容易降低疲劳抗力。在反复荷载作用下，钢筋锈蚀梁均发生钢筋断裂破坏，与锈蚀量无关。然而，疲劳寿命取决于腐蚀量。

The research project consisted of three phases, such as (1) to examine the relationships among the cumulative electric current, the amount of corrosion of steel bar and the crack width on the surface of concrete using an erosion test, (2) to examine the deterioration of flexural capacity of beams by corrosion of steel bars under static loading, and (3) to examine the fatigue strength of beams with corrosion of steel bars.As for the first phase of project, the Faraday's law was acknowledged for the relationship between the cumulative electric current and the amout of corrosion of steel bar, and the crack width on the surface of concrete was observed linearly increased with the amout of corrosion. Stirrups did not influence the relationships so much.Unless the crack width on the surface of concrete exceeded 0.3mm, the mechanical behavior of RC beams under static loading was not reduced by corrosion of steel bars. Even if lapped splices were provided at the mid span, the properly arranged stirrups made the behavior of beams as they were. When the anchorage of steel bars is sufficiently proved, the reduction of capacity due to longitudinal cracks may be less than 30 %.The fatigue behavior of beams was greatly influenced by corrosion of steel bars. In particular, corroded steel bars are sensitive to stress concentration, and are easy to reduce the fatigue resistance. Under repeated loading, all beams with corrosion of steel bars failed by the rupture of steel bars irrespecitive to the amount of corrosion. The fatigue life, however, depended upon the amount of corrosion.