Dottorato in INGEGNERIA STRUTTURALE E GEOTECNICA

Titolo della tesi: Tunnelling effects on masonry-infilled frames with separated footings: a hybrid and numerical study

In recent years, tunnel excavations in urban areas have increased substantially, prompting the construction industry to require more precise assessments of the tunnel-soil-structure interaction processes. The prevailing trend in the field is the utilisation of numerical modelling to predict the movements induced by tunnel excavations on the surrounding structures. Nevertheless, these numerical models necessitate a rigorous parameter calibration and validation phase prior to their effective application in real-world scenarios. Previous and contemporary research has enhanced our comprehension of the interaction mechanism between the construction of a new tunnel and existing above- and below-ground structures; however, more clarity is required regarding the impact of tunnel excavations on framed structures, particularly on frames incorporating infill walls. Indeed, masonry infills contribute significantly to the overall stiffness and mass of the building and influence the interaction mechanics. More generally, infilled frames exhibit a complex response given the composite nature of the masonry for the walls and the reinforced concrete for the frame. This thesis focuses on two principal areas to elucidate the tunnel-soil-frame structure interaction phenomenon: numerical modelling of masonry-infilled frames with diverse footing configurations and hybrid centrifuge testing of multiple frame layouts located on separate foundations. The numerical modelling builds on previous research to address aspects that were less explored, including damage initiation in the infill walls, potential separation of the infill walls from the frame, and embedded discontinuous and continuous foundation schemes along the tunnel axis direction. The experimental campaign was conducted utilising a hybrid coupled centrifuge-numerical modelling approach to acquire valuable data regarding the response and induced damage on masonry-infilled frames. The hybrid approach, developed at the Nottingham Centre for Geomechanics at the University of Nottingham, was applied to overcome the limitations associated with the scaling-down of detailed structural elements and connections in centrifuge environments, and to accurately characterise their influence, the associated constitutive law, and the potential detachment between the frame and panels. Indeed, the coupled centrifuge-numerical modelling technique has the ability of integrating the tunnel-soil-foundation system, modelled in the centrifuge, and the framed structure, simulated in the numerical model, by allowing displacements and loading data exchange at the structure-footing interface in “real-time”. In the present study, the hybrid approach was extended to a three-dimensional numerical space to accommodate for more realistic framed building configurations. Furthermore, the nonlinear behaviour of masonry infill walls was described by a constitutive law that combines the effects of plastic deformation and progressive damage evolution. Finally, the potential separation mechanism between the panels and frame was characterised by the presence of interface elements. By bridging the gap between numerical modelling and centrifuge testing, this thesis endeavours to highlight the significant role of masonry infill walls, their constitutive law, and the presence of frame-infill interfaces in delineating the complex interaction phenomena between tunnel excavation and masonry infilled-framed structures.