Risk-based assessment of breakwater armour units including effect of epistemic uncertainty on wave hazard

Abstract

A formulation to assess a breakwater damage probability and to select the optimal maintenance strategy is presented and illustrated with a case study in Mexico. The formulation includes the calculation of annual and lifetime exceedance damage probabilities, the cost of damage/failure consequences, epistemic uncertainty and information on port logistics. The limit-state corresponds to the stability of the breakwater core (armour) units and the cost of failure consequences includes the explicit consideration of costs of fatalities, loss of armour units, damage and loss of property to port facilities, and economic loss due to business interruption in the port. The Van der Meer approach is followed to describe the damage state and the number of waves is modelled as lognormal instead of normal. A curve of tetrapod’s weight versus wave height is proposed as an approximation to the tetrapod’s fragility. FOSM (First Order Second Moments) and MCS (Monte Carlo simulation) techniques are implemented. The wave height is identified, through the calculation of gradients, as the most sensitive parameter for epistemic uncertainty. The optimal maintenance is selected after assessing three maintenance alternatives by balancing costs and safety. A breakwater located in Mexico called Tampico Port is used as case study to illustrate the formulation.

Keywords:

• Breakwater armour elements
• costs of failure consequences
• epistemic uncertainty
• failure probability
• Monte Carlo simulation
• percentiles
• significant wave height

Acknowledgements

The authors acknowledge the breakwater data from Mexican Institutions (Dirección de Puertos, Secretaría de Comunicaciones y Transportes, SCT) (Dirección General de Puertos y Marina Mercante and México (DGPMM), 2001). This work was partially supported of CONACYT (Consejo Nacional de Ciencia y Tecnología), through a postdoctoral stay granted to Lourdes Loza Hernández in Engineering Faculty of Autonomous University the State of Mexico, in Mexico, in 2019.

Disclosure statement

No potential conflict of interest was provided by the author(s).