Paolo Nevone Blasi

Flood and flash flood events can generate severe hydraulic actions on civil structures, requiring modeling strategies able to link flow features to structural damage. This paper proposes a two-scale numerical framework based on advanced finite element modeling to assess the vulnerability of structures subjected to inundation and flood-driven impact. At the macroscale, the flood propagation and the interaction with the built environment are simulated through the depth-averaged Shallow Water Equations, adopting a time-explicit interface treatment to capture the evolution of the free surface. The macroscale model provides time-dependent water depth and flow velocity along the external surfaces of the structure, which are then used to derive hydrostatic and hydrodynamic actions, also in comparison with code-based formulations. At the mesoscale, these actions are transferred to a detailed structural model to investigate the nonlinear mechanical response of the building. Structural components are described through a coupled damage–plasticity constitutive law, enabling the prediction of stiffness degradation, cracking-driven damage patterns, and the identification of the most critical structural zones under flood loading. The proposed workflow is finally applied to a real structure located in the municipality of Cosenza (Italy), demonstrating the capability of the approach to combine hydraulic intensity measures with physics-based structural damage assessment, supporting scenario analyses and risk mitigation evaluations.

In this work, the structural behavior of masonry buildings under flash flood actions is analyzed by using a novel 3D multilevel fluid/structure model. The proposed numerical framework consists of a macro-scale model based on the computational fluid dynamic, able to simulate the dynamic free-stream flow of a fluid impacting rigid solids and a meso-scale structural model that employs a coupled damage-plasticity approach to describe the nonlinear behavior of the masonry buildings, subjected to the fluid dynamic pressure extracted by the macro-scale fluid analysis. The integrated model was employed to assess the fluid-structure interaction effects on the global structural response, in terms of load-carrying capacity and damage patterns, of a real-scale masonry structure subjected to flood-induced loading conditions. Finally, a parametric analysis is performed in order to understand the influence of the fluid inlet velocity and water depth on the failure mechanisms of the structure. The results highlight the good numerical capabilities of the proposed multilevel model, establishing it as a valuable numerical tool for the structural vulnerability assessments under flood actions.

A multiscale model is proposed to assess the impact of wave loading on coastal or inland bridges. The formulation integrates various scales to examine the effects of flooding actions on fluid and structural systems, transitioning from global to local representation scales. The fluid flow was modeled using a turbulent two-phase level set formulation, while the structural system employed the 3D solid mechanics theory. Coupling between subsystems was addressed through an FSI formulation using the ALE moving mesh methodology. The proposed model’s validity was confirmed through comparisons with numerical and experimental data from the literature. A parametric study was conducted on wave load characteristics associated with typical flood or tsunami scenarios. This included verifying the wave load formulas from existing codes or refined formulations found in the literature, along with assessing the dynamic amplification’s effects on key bridge design variables and the worst loading cases involving bridge uplift and horizontal forces comparable to those typically used in seismic actions. Furthermore, a parametric study was undertaken to examine fluid flow and bridge characteristics, such as bridge elevation, speed, inundation ratio, and bearing system typology. The proposed study aims to identify the worst-case scenarios for bridge deck vulnerability.

This paper presents a refined Finite Element (FE) modeling strategy for analyzing the failure behavior of regular masonry structures reinforced with timber-based retrofit solutions. The proposed model schematizes the masonry as brick units, modeled using two-dimensional linear elastic plane stress elements, mutually joined through zero-thickness cohesive interface elements. These interface elements serve to reproduce the nonlinear behavior of masonry because of the occurrence of failure mechanisms of the mortar joints. Reinforced timber frame elements are modeled using truss elements that exhibit elastic brittle fracture behavior. The interaction between the masonry sub-structure and the reinforced timber frame system is accounted for using special constraint conditions that simulate the mechanical behavior of anchorage connections. The reliability of the proposed model in reproducing the failure behavior of masonry is assessed through comparisons with experimental and numerical data available in the literature. Additionally, the efficacy of the retrofit technique based on timber frame structures is investigated in detail through pushover analyses on a two-story masonry wall representative of real-life masonry buildings. The results indicate that the proposed retrofitting strategy is an effective and eco-friendly retrofit solution to enhance the in-plane bearing capacity of masonry structures subjected to horizontal forces.

Recent studies have shown that the mechanical properties of bioinspired periodic composite materials can be strongly influenced by finite deformation effects, leading to highly nonlinear static and dynamic behaviors at multiple length scales. For instance, in porous periodic nacre-like microstructures, microscopic and macroscopic instabilities may occur for a given uniaxial loading process and, as a consequence, wave attenuation properties may evolve as a function of the microstructural evolution, designating it as metamaterials. The numerical outcomes provide new opportunities to design bioinspired, soft composite metamaterials characterized by high deformability and enhanced elastic wave attenuation capabilities given by the insertion of voids and lead cores.

Recent studies have shown that the mechanical properties of bioinspired periodic composite materials can be strongly influenced by finite deformation effects, leading to highly nonlinear static and dynamic behaviors at multiple length scales. For instance, in porous periodic nacre-like microstructures, microscopic and macroscopic instabilities may occur for a given uniaxial loading process and, as a consequence, wave attenuation properties may evolve as a function of the microstructural evolution, giving it the designation of metamaterials. The numerical outcomes provide new opportunities to design bioinspired soft composite metamaterials characterized by high deformability and enhanced elastic wave attenuation capabilities given by the insertion of voids and lead cores.

The ability to manipulate concrete-based and composite materials at the nanoscale represents an innovative approach to improving their mechanical properties and designing high-performance building structures. In this context, a numerical investigation of the reinforcing effect of nano-modified epoxy resin on the structural response of fiber-reinforced polymer (FRP)-plated reinforced concrete (RC) components has been proposed. In detail, an integrated model, based on a cohesive crack approach, is employed in combination with a bond–slip model to perform a failure analysis of strengthened structures. In particular, the proposed model consists of cohesive elements located on the physical interface between concrete and FRP systems equipped with an appropriate bond–slip law able to describe the reinforcing effect induced by the incorporation of nanomaterials in the bonding epoxy resin. Preliminary analyses, performed on reinforced concrete prisms, highlight an increment of 28% in the bond strength between concrete and the FRP system, offered by the nanomaterials embedded in the adhesive layer with respect to the standard one. Moreover, the numerically predicted structural response of a nano-modified FRP-plated beam shows an increment of around 5.5% in the failure load and a reduction in the slip between concrete and the FRP plate of around 76%, with respect to the reinforced beam without nanomaterial incorporation. Finally, the good agreement with experimental results, taken from the literature, highlights the excellent capability of the proposed model to simulate the mechanical behavior of such types of reinforced structures, emphasizing the beneficial effects of the nano-enhanced epoxy resin on the bond strength between concrete and FRP systems.

Multiscale failure analysis of fiber-reinforced composite structures via a hybrid cohesive/volumetric nonlinear homogenization strategy Daniele Gaetano, Fab