A numerical study for assessing tunnelling-induced distortions of infilled structures

This study investigates the critical influence of masonry infill nonlinearity on tunnelling-induced responses of frame structures, employing a validated Two-Stage Analysis Method (TSAM). Departing from conventional elastic approaches, a refined elastoplastic constitutive model (CDP${}^{\ast }$) is implemented for the infills to accurately capture their role in structural damage evaluation. The analysis accounts for the full three-dimensional geometry of the infilled frames, including infill dimensions, column cross-sections, slab thicknesses, and the spans between adjacent columns and between floors. The research investigates the influence of building eccentricity ($e/B$), soil–structure interaction (${\mu }_{\text{soil}}$), and frame–infill interface conditions (${\mu }_{\text{infill}}$) on structural behaviour. For both the soil–foundation and frame–infill interfaces, contact conditions are varied from fully smooth to rough by adjusting the frictional coefficient based on a Coulomb friction law. For each parameter, two types of frames with different transverse widths are considered to assess the effect of building width on the response. Validation of the two-stage analysis method is conducted against centrifuge modelling tests and advanced geotechnical analyses of tunnelling beneath bare frames. Results reveal that elastic models underestimate shear distortion ($\beta$) and tensile strain (${\varepsilon }_{99}^t$), particularly in symmetric configurations ($e/B=0$) where infill plasticity dominates the response. This study proposes new guidelines to enhance current assessment frameworks for infilled frames, accounting for infill nonlinearity under different parameters of building eccentricity, soil–structure and frame-infill interfaces.