**5. Conclusions**

In this study, a scour risk assessment procedure was proposed. Scour hazard was calculated by giving variability to the variables of the empirical formula and was expressed as the probability of the scouring depth. Scour fragility was calculated as the probability that the response of the structure to the environmental load would exceed the limit state. Scour risk was obtained by integrating the product of the scour probability and the fragility for all possible scour depths. The scour risk assessment procedure was applied to PSB supporting 5.5 MW OWT installed on the Gunsan coast in Korea. From the numerical analysis, the reliability index was 4.85 if SF of 1.25 is applied. This level of reliability can be accepted enough when some OWT design standards are used.

**Author Contributions:** Conceptualization, Y.-J.K. and D.-H.K.; methodology, Y.-J.K. and D.-H.K.; software, Y.-J.K.; validation, D.-H.K.; formal analysis, Y.-J.K.; data curation, Y.-J.K. and D.-V.N.; writing— original draft preparation, Y.-J.K. and D.-V.N.; writing—review and editing, D.-H.K.; supervision, J.-H.L. and D.-H.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2020R1F1A1076884).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
