Journal of Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회논문집)

Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회)
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Reliability-Based Design Optimization for a Vertical-Type Breakwater with an Emphasis on Sliding, Overturn, and Collapse Failure

직립식 방파제 신뢰성 기반 최적 설계: 활동, 전도, 지반 훼손으로 인한 붕괴 파괴를 중심으로

  • Yong Jun Cho (Department of Civil Engineering, University of Seoul)
  • 조용준 (서울시립대학교 토목공학과)
  • Received : 2024.01.25
  • Accepted : 2024.04.01
  • Published : 2024.04.30
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Abstract

To promote the application of reliability-based design within the Korean coastal engineering community, the author conducted reliability analyses and optimized the design of a vertical-type breakwater, considering multiple limit states in the seas off of Pusan and Gunsan - two representative ports in Korea. In this process, rather than relying on design waves of a specific return period, the author intentionally avoided such constraints. Instead, the author characterized the uncertainties associated with wave force, lift force, and overturning moment - key factors significantly influencing the integrity of a vertical-type breakwater. This characterization was achieved by employing a probabilistic model derived from the frequency analysis results of long-term in-situ wave data. The limit state of the vertical-type breakwater encompassed sliding, overturning, and collapse failure, with the close interrelation between wave force, lift force, and moment described using the Nataf joint probability distribution. Simulation results indicate, as expected, that considering only sliding failure underestimates the failure probability. Furthermore, it was shown that the failure probability of vertical-type breakwaters cannot be consistently secured using design waves with a specific return period. In contrast, breakwaters optimally designed to meet the reliability index requirement of 𝛽-3.5 to 4 consistently achieve a consistent failure probability across all sea areas.

우리나라 해안공학계에서 신뢰성 기반설계가 빠르게 체화되는 계기를 제공하기 위해 다 수의 한계상태를 지닌 직립방파제 신뢰성 해석과 신뢰성 기반 최적 설계를 우리나라를 대표하는 항이 운영 중인 부산, 군산 전면해역을 대상으로 수행하였다. 이 과정에서 상당한 정도의 신뢰성 해석을 수행하기 위해, 특정 재현 빈도의 설계 파 사용은 지양하였으며, 직립방파제의 파괴 여부를 결정하는 확률변수인 파력, 양력, 전도 모멘트에 내재한 불확실성은 장기 파랑 관측자료를 빈도 해석하여 얻은 확률모형을 사용하여 기술하였다. 직립식 방파제의 한계상태는 활동, 전도, 지지력을 고려하여 세 개로 구성하였으며, 파력과 양력, 모멘트 사이의 밀접한 상관성은 Nataf 결합확률분포를 사용하여 기술하였다. 모의 결과, 쉽게 예상해볼 수 있듯 활동만을 고려하는 경우 파괴확률이 과소하게 산출되는것을 확인하였으며, 특정 재현 빈도에 근거한 설계 파랑으로는 방파제 파괴확률을 일정하게 담보할 수 없다는 것을 확인하였다. 이에 비해 신뢰 지수가 𝛽 = 3.5~4를 충족하도록 최적 설계된 방파제는 두 해역에서 모두 균질한 파괴확률을 확보하는 것으로 모의 되었다.

Keywords

Acknowledgement

본 연구는 해양수산부가 발주한 한국형 설계기준 확보를 위한 개정용역의 지원을 받아 수행되었으며 연구비 지원에 감사드립니다.

References

  1. Ang, H.S. and Tang W.H. (1984). Probability concepts in engineering planning and design. Decision, risk, and reliability, Vol. 2. John Wiley, New York. 
  2. Au, S.K. and Beck, J.L. (2001). Estimation of small failure probabilities in high dimension by subsets simulations. Probabilistic Engineering Mechanics, 16(4), 263-277.  https://doi.org/10.1016/S0266-8920(01)00019-4
  3. Burcharth, H.F., Sorensen, J.D. and Christiani, E. (1994). On the Evaluation of Failure Probability of Monolithic Vertical Wall Breakwaters. Proc. Wave Barriers in Deepwater, Port and Harbour Research Institute, Yokosuka, Japan, 458-46. 
  4. Castillo, C., Minguez, R., Castillo, E. and Losada, M.A. (2006). An optimal engineering design method with failure rate constraints and sensitivity analysis. Application to composite breakwaters. Coastal Engineering, 53, 1-25.  https://doi.org/10.1016/j.coastaleng.2005.09.016
  5. Cho, Y.J. (2024). Development of probabilistic models optimized for Korean marine environment varying from sea to sea based on the Three-parameter Weibull distribution. Journal of Korean Society of Coastal and Ocean Engineers, 36(1), 20-36 (in Korean).  https://doi.org/10.9765/KSCOE.2024.36.1.20
  6. Cho, Y.J. (2021a). Numerical analysis of modified bed-profiles due to the presence of a rubble mound breakwater using physics-based morphology model [SeoulFoam]. Journal of Coastal Disater Prevention, 8(3), 151-163 (in Korean).  https://doi.org/10.20481/kscdp.2021.8.3.151
  7. Cho, Y.J. (2021b). Development of physics-based morphology model with an emphasis on the interaction of incoming waves with transient bed profile due to scouring and accretion using dynamic mesh. Journal of Coastal Disaster Prevention, 8(4), 211-219 (in Korean).  https://doi.org/10.20481/kscdp.2021.8.4.211
  8. Cho, Y.J. (2021c). On the effects of non-gaussian wave-slope distribution on the failure probability of an armour block of rubble mound breakwater. Journal of Coastal Disaster Prevention, 8(3), 165-179 (in Korean).  https://doi.org/10.20481/kscdp.2021.8.3.165
  9. Cho, Y.J. (2021d). Proposal on hybrid design method of outer port facilities using failure probability. Journal of Coastal Disaster Prevention, 8(4), 237-253 (in Korean).  https://doi.org/10.20481/kscdp.2021.8.4.237
  10. Cho, Y.J. (2021e). Numerical analysis of modified seabed topography due to the presence of breakwaters of varying reflection characteristics using physics-based morphology model [SeoulFoam]. Journal of Korean Society of Coastal and Ocean Engineers, 33(4), 168-178 (in Korean).  https://doi.org/10.9765/KSCOE.2021.33.4.168
  11. Cho, Y.J. (2021f). Level III reliability design of an armor block of rubble mound breakwater using probabilistic model of wave height optimized for the Korean sea wave conditions and non-Gaussian wave slope distribution, Journal of marine science and engineering, 9, 223. 
  12. Cho, Y.J. (2021g). Development of physics-based morphology model with an emphasis on the interaction of incoming waves with transient bed profile due to scouring and accretion using dynamic mesh. Journal of Coastal Disaster Prevention, 8(4), 211-219 (in Korean).  https://doi.org/10.20481/kscdp.2021.8.4.211
  13. Cho, Y.J. (2021h). On the effects of non-Gaussian wave-slope distribution on the failure probability of an armour block of rubble mound breakwater. Journal of Coastal Disaster Prevention, 8(3), 165-179 (in Korean).  https://doi.org/10.20481/kscdp.2021.8.3.165
  14. Cho, Y.J. and Cho, S.H. (2022). Preliminary study on an amendment to the design guideline of outer port facilities against harsh wave conditions due to climate change based on design fidelity index. Journal of Coastal Disaster Prevention, 9(1), 75-89 (in Korean).  https://doi.org/10.20481/kscdp.2022.9.1.75
  15. Goda, Y. (2000). Random seas and design of maritime structures. Univ. of Tokyo Press, Tokyo. 
  16. Goda, Y. and Fukumori, T. (1972). Laboratory investigation of wave pressures exerted upon vertical and composite walls. Coastal Engineering in Japan, 15. 81-90.  https://doi.org/10.1080/05785634.1972.11924148
  17. Goda, Y. (1974). A new method of wave pressure calculation for the design of composite breakwater. Proc. 14th Int. Conf. Coastal Eng., Copenhagen, Denmark. 
  18. Goda, Y. (1975). Irregular wave deformation in the surf zone. Coastal Engineering in Japan, 18, 13-16.  https://doi.org/10.1080/05785634.1975.11924196
  19. JPHA (2007). Japan Port and Harbor Association, Technical Standards and Commentaries of Port and Harbor Facilities in Japan (in Japanese). 
  20. Jeong, W.M., Oh, S.H., Ryu, K.H., Back, J.D. and Choi, I.H. (2018). Establishment of wave information network of Korea (WINK). J. Korean Soc. Coast. Ocean Eng., 30(6), 26-336.  https://doi.org/10.9765/KSCOE.2018.30.6.326
  21. Nataf, A. (1962). Determination des distribution dont les marges sont donnees. Comptes Rendus de PAcademie des Sciences, Paris, 225, 42-43. 
  22. Takayama, T. (1992). Estimation of sliding failure probability of present breakwaters for probabilistic design. Report of Port and Harbour Research Inst., 31(5)