The total of 40 RC slabs extracted from existing port structures was tested in order to evaluate the relationship between visually judged deterioration grades and load carrying capacities. Wide variations were observed in the relationship in each deterioration grade, however, the load carrying capacity tended to be smaller than the design expectations when the symptom of deterioration appeared on the surface of concrete members. Moreover, the relationship was greatly influenced by localized deterioration and its position in the member.
　Based on the statistical analysis on the relationship between deterioration grades and load carrying capacities, the probabilistic evaluation method of the load carrying capacities of RC slabs was proposed as quantitative evaluation method of residual structural performance of existing port RC structures.