Even at the same open-type wharf, deterioration of the underside of superstructure is known not to proceed homogeneously. We empirically know that members located on the sea or land side tend to deteriorate more progressive, but do not understand what factors affect the deterioration progress and to what extent such factors affect the deterioration progress.

Regarding facilities subject to technical standards, routine inspection and diagnosis has become mandatory, and are carried out at least once every 5 years. Routine inspections include visual inspections, so visual inspection data are expected to accumulate. Regarding visual inspection of the underside of superstructure of open-type wharves, to diagnose the degree of deterioration of all members, analysis of visual inspection data of the underside of superstructure of open-type wharves, which will be accumulated quantitatively, may allow identification of the characteristics that contribute to deterioration progress. Therefore, in this study, we used the method of survival analysis to analyze visual inspection data of the underside of superstructure of open-type wharves (from 19 open-type wharves) and investigated the factors contributing to deterioration progress.

After analyzing the visual inspection data, each member type appears to have different factors affecting deterioration progress. As an example, Figure 1 shows an estimated survival function for each member type depending on the location of members in perpendicular direction to the normal line of an open-type wharf. BH (Figure 1 (a)) shows that members located on the sea or land side tend to deteriorate more progressive; BV (Figure 1 (b)) shows no difference in deterioration progress depending on locations of members; S (Figure 1 (c)) shows that members located on the sea side tend to deteriorate more progressive.