A case study of the new breakwater of the Port of Genova

Abstract

Breakwaters used to protect harbours and coastal areas worldwide are one of the most common coastal structures. The complexity of the physical processes associated with the design has led to the development of many empirical formulas while a standardized method for the selection of breakwaters’ design parameters in the EU does not yet exist. The most common approach to design such a structure nowadays entails using information and recommendations from design manuals and guidelines such as PIANC and the Eurotop Manual. A new Eurocode 1 which includes specific considerations for coastal structures such as breakwaters is in the development process. This study aims to compare the PIANC method with the method to derive actions/loads included in the Eurocode proposal prEN1991-1-8. To do so the following research question has been formulated:
“What differences between the PIANC method and the method proposed by the new EUROCODE in the design of a vertical wall breakwater can be identified, using the new breakwater at the Port of Genoa as a case study?“
As mentioned in the question, a case study is used. The Port of Genoa, one of the biggest ports in Italy plans to construct a new vertical wall breakwater. An initial design is openly available along with wave and water level data. This design is assessed using both methods and is further optimized. The aim is to gain insights into the differences between the PIANC and the new method.
At first, the failure mechanisms of such a structure are defined along with the safety factors and parameters. The data required to perform such an assessment is also an important aspect of the exercise. Most of the data are openly available during the consulting phase for the new breakwater in Genoa. In cases where extra data were necessary, they were based on the literature or on reasonable assumptions.
Based on the failure mechanisms and the retrieved data, the initial breakwater cross-section was assessed. The assessment both with the PIANC method and the new Eurocode proved that this design is sufficient and can be further optimized to decrease its costs. A high-level optimization is also conducted as part of this study in order to better understand the differences between the two methods. It can be concluded that the differences lay more in the method than in the actual result. For example, the proposed Eurocode creates a stable theoretical framework of how to choose a return period. The actual number may be very similar to the one that one would have used either way, but the choice can be argued in a better way.
On the other hand, the use of the new Eurocode revealed some problems and inconsistencies in the document which is confusing in certain parts. In addition, the new Eurocode which among others aims at standardizing the design process. However, parts like the combination of wave and water level actions and the choice of return period for the two main limit state functions are relatively clearer providing a solid base.