Assets of the architectural heritage buildings are a unique fortune of the entire world belonging to everyone regardless of ethnicity and as such shall be safeguarded and preserved. This very complex topic is a part of a multidisciplinary field of activities to be undertaken by experts of architecture, engineering, history and so on. Absence of data on these assets and the large variety of typologies such as materials, constructive typologies, techniques and more, requires the inclusion of many intrusive measures on such intricate structures. Adding to it the vulnerability to natural hazards, particularly seismic activity as the most adverse, such structures under very low stresses are known to be susceptible to intensive damage or collapse. Hence the study of these assets is still an open challenge to the scientific community that holds essential the development of proper methodologies of assessment, including constitutive models of strongly nonlinear structural responses at low levels of loading. In addition, the great variety of typologies of ancient structures requires an individuated methodology of analysis, which are to be custom fitted by experienced researchers who can handle the matter in an interdisciplinary manner. Consequently, the number of unknowns is larger and confined to each asset with no possible way of generalization and the constraint of the low intrusiveness perplexes the problem. The closest and the most optimized approach, respecting non-intrusiveness and low number of input, to tackling such a problem is the limit analysis application considering no-tension and frictional joints approach.
This research focuses on the mechanical modelling using discrete approaches, the numerical implementation utilizing constitutive models and validation of the results via a tilting table that can simulate the earthquake action in a static manner. The results of the research are then further applied to selected studies with reference to seismic safety.
This research study is focused majorly on the themes that are communicated as objectives of the Work Programme for the Cultural Heritage to ensure the preservation and the increased awareness on the field. In respect to the latest provisions and guidelines given by the Charters with particular interest on Architectural Heritage for minor intrusiveness and individuated multidisciplinary studies on monuments and historical constructions, due to their complex and important nature, advanced computational tools are studied with additional involvement of digital tools that help this process of conservation, safeguarding and protection. The main research topics that this study covers are related to the material characterisation and mechanical modelling, the experimental validations with numerical implementation and the structural safety assessment as the fundamental outcome.
Architectural heritage constructions are characterized mainly by masonry structures with high anisotropy and nonlinear behaviour at low levels of loading. As such masonry as a construction material involves a very complex internal structures and presents a very diverse material in terms of size, shape, orientation and texture configuration. Standardization of all these characteristics is quite a demanding task. To avoid the many interpretations available and many various achievable and quite necessary parameters for a more representative behaviour, the focus of this study falls in localizing the nonlinearity to the joint interfaces. Historic constructions involve dry-joints or mortars of very poor quality in combination with high strength blocks, so the concentration of the nonlinearity on the joints and elastic assumption for the blocks is realistic and agrees with available literature resources. Furthermore, to be able to account for many types of real life structures and to implement the different damage causes or strengthening measures, additional parameters are introduced such as cohesion and settlements for the former and reinforcements for the latter.
To account for the aforementioned problem the limit analysis numerical implementation is chosen for this study as it is able to provide outstanding outcomes with few parameters input. In this way the numerous testing campaigns can be reduced and at the same time involve all the different levels of diversity and complex behaviour present. The experimental campaign also requires very light testing equipment of scaled models through the use of the tilting table that is able to represent the horizontal action as a percentage of the vertical gravity correlated through the angle of inclination. This method has shown exceptional results and exquisite correlation with the collapsing load and mechanism. The micro-modelling strategy that is involved in the limit analysis is considered at another level for non-standard materials and with the utilization of nonlinear and non-convex mathematical programming algorithms will be validated through the experimental campaign. Afterwards, the method is further compared with large models and other complex modelling strategies to ensure reliable results and assess the robustness, accuracy and the power of the technique in combination with non-intrusiveness.
Since the overall goal of the study is to ensure the proper safeguarding and conservation of the heritage structures, the safety evaluation is the key outcome. Besides many other political, social and natural risks that these buildings are subjected to, the one that falls under this discipline is the structural safety assessment from natural hazards (particularly earthquakes), rheological or even man-induced damage. The validation of all the above are effectively validated when employed in case studies with comparisons of modelling methodologies and in a multidisciplinary research context. The outcomes of this study are then included into monitoring and risk mitigation strategies by the research group by providing helpful data and rapid assessment without the need for additional testing or intrusion to the building.
In conclusion, modern challenges that are subjected to the safeguard and conservation of the architectural heritage buildings are intensively increasing with the modern demand increase for development. Traditional mechanical models are improved utilizing contemporary computational advancements in combination with theoretical backgrounds to achieve better assessments and decision-making strategies to these structures. Simplification of the inputs validated through campaigns of examination and investigation in combination with the powerful tools and enhanced levels of accuracy, are able to provide safety measures based on the actual requirements in terms of risks to natural hazards. Furthermore, avoid damages at small scales of these hazards or even collapse to larger scales.