ASSESSMENT OF THE FAILURE PROBABILITY OF UPGRADED RUBBLE-MOUND BREAKWATERS

Abstract

Nowadays, the existence of a huge number of aging harbor defense structures and climate change-induced forcing variability highlight the need for a methodology able to deal with uncertainties which arise during the design of new and above all upgraded structures. In the present work, a probabilistic design methodology based on the Monte Carlo simulation technique for the assessment of the failure probability due to independent failure modes and on the factor of change method for the inclusion of the effects of climate change is described, together with its application to the emblematic case study of the Catania harbor breakwater (Italy). The performances of the rubble-mound breakwater under present and future climate scenarios are assessed considering the existing structure and different upgrading options, which include both the raising of the wave wall and the addition of extra armor blocks. Three novel indexes describing the acceptability level of the structure performances as well as the rate of growth and the coefficient of variation of the failure probability along lifetime are employed to quantitatively asses the performances of the existing and upgraded breakwater under present and future climate, considering the ultimate limit state due to the collapse of the outer armor layer and the serviceability limit state due to excessive mean wave overtopping discharge. The obtained results demonstrate that such indexes may give useful indication to designers and decision makers who deal with the upgrade of existing harbor defense structures under the effects of climate change.