Water represents a major threat to human activities and infrastructures, a risk further exacerbated by climate change. Phenomena such as coastal flooding caused by storm surges or tsunamis (given Italy’s high seismicity), river floods due to intense rainfall, and corrosive effects from prolonged exposure to seawater or lake water endanger people, the economy, and strategic structures (dams, protective barriers, offshore wind platforms). The interaction between water and structures is at the core of this research project.

On one hand, the goal is to assess the impact of water on structures by quantifying the risks to which they are exposed. On the other, the project aims to monitor structures under extreme loading conditions—whether due to impulsive mechanical loads or corrosion effects resulting from prolonged contact with saltwater. Ultimately, the objective is to monitor structural behavior and predict the evolution and degradation of damage.

The tools used for this investigation are advanced applications of continuum mechanics, such as fluid–structure interaction, fracture mechanics, mechano‑diffusion, and related methods. When studying the structural performance of materials and structures in extreme environments, it is necessary to consider a wide range of phenomena, including the deterioration of elastic solids caused by microscale processes such as nucleation, growth, and coalescence of microcracks, promoted by mechanical loads and by the presence of a solute diffusing within the solid. These mechanisms are relevant to many real‑world applications, such as lithium‑ion batteries (where lithium ions diffuse into solid anodes), hydrogen embrittlement of metals (where hydrogen diffusion makes metals brittle), intercalation‑induced magnetism in non‑magnetic bulk materials, and water diffusion in dentin adhesive polymers, which leads to mechanical softening and hydrolytic degradation.

The interaction between seawater and civil structures is particularly relevant for strategic infrastructures primarily exposed to marine conditions, such as offshore platforms for energy production and transport. These structures are of strategic importance and require adequate protection systems against accidents and sabotage. From this perspective, targeted research efforts are needed to develop suitable structural monitoring systems, continuously assess safety, and control the nucleation and propagation of damage.

In this context, two complementary strategies must be implemented:

1. Studying damage evolution through advanced computational mechanics tools, developing a solid theoretical understanding of the involved phenomena via an in‑depth literature review, and designing more efficient computational strategies.

2. Investigating the feasibility of developing new materials using advanced manufacturing technologies. In this regard, 3D printing is a natural candidate, offering maximum flexibility in shape optimization, material savings, and—especially in recent years—the possibility of using highly efficient materials. The adoption of 3D printing, particularly when new materials are involved, must be supported by an adequate experimental testing campaign to evaluate material performance in terms of stiffness parameters, suitable constitutive models, and operational limits. This includes assessing responses to applied loads (static and, more importantly, impulsive loads), resistance to corrosion or other chemical hazards, and fatigue behavior (mechanical and thermo‑mechanical).

As highlighted above, the project integrates multiple topics and methodologies to achieve a unified objective: modeling potential risks to strategic structures, monitoring both immediate and long‑term damage effects, and identifying the most effective protection strategies.

Integrated Numerical Strategy

The project proposes an integrated approach for risk quantification in marine environments, combining ad hoc numerical tools to achieve accurate yet computationally sustainable simulations over large domains. To manage the complexity of the problem, two operational regions are distinguished:

• Far field, where the fluid evolves far from structures and can be described using simplified models.
• Near field, where direct interaction with structures, barriers, or platforms requires more sophisticated methods capable of capturing impacts, large deformations, and non‑hydrostatic pressure fields.

Far Field: Shallow Water Approximation

In the far field, the Shallow Water (SW) approximation is adopted, reducing the vertical dimension of the problem by assuming an essentially hydrostatic pressure distribution. This simplification allows the simulation of waves and currents over large areas with limited computational cost and good accuracy for large‑scale quantities of interest. SW simulations are ideal for preliminary risk assessments, multiple scenario analyses, and for providing fast and repeatable boundary conditions.

Near Field: Lagrangian Particle Methods

In the near field, where structures significantly alter the pressure field and free‑surface dynamics, Lagrangian particle methods (SPH, MPS, and related techniques) are employed. These methods are particularly effective for modeling impacts, free‑surface breaking, and large deformations, providing the time history of impact pressures and local stresses required for structural assessment. However, achieving reliable results requires high numerical resolution, with significant computational and memory demands.

Innovative Coupling Between Far Field and Near Field

The innovative element of the project is the coupling between far‑field and near‑field simulations through a dedicated data interface:

• SW simulations provide the local domain with incoming conditions (free‑surface elevation, horizontal velocities, turbulence parameters, and chemical concentration profiles).
• Lagrangian simulations return detailed information on impact pressures and their temporal evolution.

This scheme leverages the efficiency of reduced‑order models for large domains while concentrating high‑resolution computation only in critical areas, optimizing time and resources.

Damage, Diffusion, and Structural Degradation

To address the degradation of submerged structures, the project develops coupled diffusion–deformation–damage models. The diffusion of aggressive ions (e.g., chlorides or sulfates) is treated as a scalar field influencing the mechanical properties of concrete: the presence of such chemical species lowers damage thresholds and modifies mechanical response, while deformation can alter permeability and thus diffusion rates, generating a complex feedback loop.

To study these phenomena in a controlled manner, the project begins with a 1D beam model to calibrate parameters and verify physical consistency, with the goal of extending the approach to full 3D models.

Hemivariational Approach to Damage

From a mathematical standpoint, the project adopts a hemivariational approach to damage modeling: a variational formulation incorporating unilateral constraints on damage variables, ensuring irreversible (non‑decreasing) damage evolution and deriving evolution laws consistently from energetic principles. This overcomes limitations of many existing formulations, where damage evolution is often prescribed arbitrarily and not explicitly linked to the concentration of degrading agents.

Dynamic simulations will also include dissipative terms, such as those represented by a Rayleigh functional, to account for friction and energy dissipation during system evolution. The coupling between chemical diffusion, damage, and mechanical response will be treated in a fully coupled or semi‑coupled manner depending on the case, with particular attention to numerical stability and nonlinearities.

High‑Performance Computing and Structural Health Monitoring

High‑performance computing resources are essential: high‑resolution Lagrangian simulations and parametric studies require HPC infrastructures, efficient parallelization, and optimized I/O strategies. Collaboration with supercomputing centers such as CINECA and with national and international research groups will ensure access to resources and expertise for implementing and scaling the codes, preferably using open‑source software to promote reproducibility and collaboration.

Integration with Structural Health Monitoring (SHM) systems completes the operational framework: experimental data collected on site will be used to calibrate and validate the models, improve measurement interpretation, and reduce monitoring costs and redundancies. Numerical models, in turn, will provide useful indicators for diagnostics and for predicting the service life of structures, enabling the anticipation of damage evolution and the planning of targeted interventions.