Building heritage of the world, and especially in the Italian territory, is characterized by a large number of ancient structures of historical and archeological interest. Preservation and restoration of these structures is a complex matter, which involves a deep understanding in different fields such as history, architecture, structural analysis. Generally, these buildings appears as agglomeration of different constructive typologies with the presence of portions composed of masonry (walls, vaults, etc.), concrete and steel. It is well-known that these structures have an high level of seismic vulnerability, with poor resistance to horizontal actions such as the seismic ones. The study of historical structures is currently an open challenge both for monitoring their health status and for developing suitable methodologies to correctly simulate their response, including realistic constitutive assumptions, focusing on the strong non-linear behavior. Moreover, the great variety of typologies of ancient structures requires case-by-case methodologies of analysis, which have to be tailored, for any case studies, by experienced researchers who can tackle the matter in an interdisciplinary way.
A research team, expert in the area of structural mechanics, will drive the main Work Packages (WPs) of the project: (i) MECHANICAL MODELLING, focusing on constituent materials and related constitutive aspects, treated using discrete or non-standard continuous multiscale approaches; (ii) NUMERICAL IMPLEMENTATION and SIMULATIONS, using advanced computational tools; (iii) NON DESTRUCTIVE TESTS and APPLICATIONS for material and geometrical characterization, with next-generation materials and devices for monitoring and control of vibrations, dissipation and damage; (iv) CASE STUDIES and REAL LIFE APPLICATIONS for investigating the mechanical behavior of buildings aiming at risk mitigation and structural reliability assessment, with particular reference to seismic safety.
The proposed research focuses attention on the investigation of the structural behavior of heritage structures with particular regard to issues of material characterizations, computational mechanical modelling, health monitoring aiming at the safety assessment and conservation. These key topics are also addressed by Horizons Europe 2021-27 Work Programmed objectives (Pillar II, Cluster 2, Cultural Heritage) and aimed at preserving and enhancing the building heritage with advanced computational tools as well as strengthen the use of digital technologies to protect, preserve, restore and safeguard. Here below the main innovations proposed are synthetically described in detail.
MATERIAL CHARACTERISATION/MULTI-SCALE MODELLING. Complex materials, such as masonry or concrete, have internal (micro) structure (size, shape, orientation, texture of elements) and complex (non-linear) material behavior. Determination of material properties, structure and performance based on the development of new models for better understanding/discovery of complex functional material behavior, is essential both for traditional and innovative materials to use in restoration. Within this frame, mechanics plays a central role, although highly coupled with other concurrent phenomena. A basic problem is the identification of appropriate constitutive laws suitable for taking into account of the microscopic characteristics at the macroscopic level. To this aim, we plan to develop or enhance approaches based on non-classical and non-local continuum constitutive models and advanced strategies, known in the literature as multiscale techniques, to connect different scales of descriptions for capturing the evolutionary behavior (fracture, damage, fatigue, etc.) by exploiting the dialogue among different descriptive levels.
COMPUTATIONAL MULTI-TECHNIQUE MODELLING/EXPERIMENTAL VALIDATION Due to the growth in computational power, predictive modelling of materials can now be used to properly describe, traditional and innovative, complex material phenomenology, to assess reliability or even design materials and structures for restoration, significantly reducing the need for massive experimental testing, promoting innovation and reducing costs of manufacturing. Within the framework of High-Performance Computing (HPC), different approaches are proposed with related testing equipment: i) modelling at the microlevel (micromodelling), able to finely reproduce the organization of the material microstructure; ii) macromodelling through multiscale techniques. The fine approach (i) provides reliable results, but, due to high computational costs, its applicability is limited to small portions of structures; coarse scale desciptions (ii) aim at reducing the typically high computational cost exhibited by fully microscopic numerical analyses and provide high computational efficiency while keeping memory of the fine organization of the material. All the approaches are suitable to effectively represent the material non-linear behaviour with an appropriate descriptive power and numerical accuracy.
STRUCTURAL SAFETY ASSESSMENT/HEALTH MONITORING/RISK MITIGATION. Structural safety assessment periodically evaluates the state of health of and provides recommendations for possible maintenance actions. It exploits Structural Health Monitoring (SHM) approaches, in constant evolution for decades thanks to advances in sensing technology and computational capabilities. To prevent collapse of structures, particularly those having strategic importance or historic value located in highly seismic areas, efficient monitoring systems, combined with optimized vibration-based identification approaches, allows one tracking the dynamic response of the structure and offering the possibility to check the integrity level continuously over time.
The vulnerability of structures is taken into account in terms of innovative design or renovation strategies and, several vibration control techniques will be introduced in old buildings, like vibration control systems (e.g., Tuned Mass Dampers, Tuned Mass Damper Inerter, Vibro-Impact Control systems, etc.).
Finally, challenges for the contemporary society call for significant technological improvements to be achieved in the fields of risk mitigation of Cultural Heritage, including the design of next generation materials and methodologies for vibration mitigation and damage reduction of existing structure. Analysis and design of breakthrough products, such as fibre-reinforced composites, also made of natural/recycled inclusions for concrete/masonry strengthening, as well as the development of advanced computational identification strategies for model calibration, for realistic assessment of existing masonry and concrete structures are proposed for assessing strengthening, based on current safety requirements, and for preventing critical failure, especially in the presence of extreme loading (e.g. earthquakes).