Author(s): Dimitra Malliouri; Nikolas Martzikos; Vasiliki Tsoukala

Linked Author(s): Vasiliki (Vicky) Tsoukala

Keywords: Coastal structures; Coastal storms; Failure probability; Reliability analysis; Cumulative damage

Abstract: Coastal zones and coastal structures are increasingly threatened by environmental forcing under a changing climate. Therefore, coastal structures, such as rubble mound breakwaters, should be properly designed to meet these requirements and ensure resilient coastlines. Reliability analysis of these structures aims to estimate the probability that the structures meet predefined safety and performance levels, by considering uncertainties related to actions, resistance, and design tools. This assessment requires evaluation of the structures’ response under a range of environmental actions. Furthermore, coastal structures are commonly subject to severe environmental forcing, e.g. extreme storms, during which no maintenance may be safe to undertake, and, consequently, such structures can be exposed to additional risk of damage, or even total failure. In this paper, the adopted methodology describes how to ensure coastal structures’ resilience to extreme wave conditions, i.e. their ability to withstand further wave actions without reaching their ultimate limit state, the total failure. To accomplish this, a fully probabilistic reliability analysis of a rubble mound breakwater is performed here, in combination with a prediction analysis of the expected time for the structure’ maintenance and repair. The methodology combines information on the joint probability density function of significant wave height, spectral peak wave period and storms’ duration and calculates the probability of occurrence of different levels of damage in the structure’s lifetime via a fully probabilistic method in order that the median mass of the breakwater’s armor units to be selected. In this step, the breakwater’s armor state is supposed to has a zero damage level, before it is exposed to each storm. Moreover, a resilience analysis is also described and applied by using the armor’s damage evolution model by Melby and Kobayashi (1999), estimating the expected year that maintenance of the breakwater should take place. Another output of the aforementioned methodology is the assessment of the failure probability of certain levels of cumulative damage of the armor’s layer of the structure, considering the random nature of independent storms’ sequence. Also, the methodology is applied to hindcast data at a location of the Mediterranean Sea close to the Barcelona coast in Spain, and detects and represents storm events in the coastal area of interest. Thereby, an insight is gained for the extreme forcing on coastal structures induced by coastal storms enabling the assessment of structures’ probability of failure and repair. In short, the necessity for performing a combination of a reliability and resilience analysis of rubble mound breakwaters is derived from the present paper, in order that those structures be properly designed and, also, timely repaired to be continuously in an admissible level of damage, defending thus aptly coastlines from extreme sea conditions.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221268

Year: 2022