Gagliardo, Raffaele (2021) Performance-based damage assessment of masonry structures subjected to settlement using rigid block models. [Tesi di dottorato]

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The issue of built Cultural Heritage (CH) exposed to natural hazards is a challenging topic in both research and engineering practice. In the last decades, many efforts were addressed to the protection of CH against seismic hazard, which is the main threat for the integrity and stability of structures. On the other hand, settlements induced by hydrogeological phenomena such as subsidence and landslides also represent a severe risk for existing buildings. Nevertheless, the investigation of damage induced by settlements on structures is a still open challenge. Empirical approaches were proposed, commonly based on the assessment of damage in terms of local parameters, e.g. crack widths. However, the severity of crack width can be affected by different factors such as structural configuration, masonry texture and material properties. Thus, models for the quantitative assessment of damage in terms of global safety levels of structures subjected to foundation movements are demanded. In this framework, this dissertation thesis aims at the development and application of a numerical approach based on rigid block modelling for the performance-based damage assessment of masonry structures subjected to settlement. Two in-house numerical models are proposed, namely a rigid block model with rigid contacts for the linear kinematic analysis and a rigid block model with no-tension elastic contacts for the non-linear kinematic analysis. The first tool aims at the prediction of the failure shape for settled structures as well as the value of the base reaction at the onset of mechanism. It is worth noting that masonry buildings usually exhibit a resilient safety behaviour with respect to settlements. Conversely, appropriate considerations of serviceability limit state are demanded to control damage on the structure and preserve the aesthetics. To this end, the non-linear kinematic model aims to predict the response of masonry structures under settlements also in the early damage states. The output is mainly represented by specific capacity curves, named "push-down curves", where the loss of base reaction is plotted as a function of the displacement of a control point at the settling support. Thus, the numerical formulation allows the damage propagation monitoring, from crack opening until incipient collapse. The dissertation thesis explores the possibility to use such a capacity curve to propose criteria for the displacement-based damage assessment and quantification. A comparison of the proposed approach with empirical damage classification methods is performed.

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