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The tunnel boring process introduces soil settlements. Damage to nearby building could occur if settlements become too large. A reliable damage prediction model is necessary too asses the risks of damage to tunnel induced settlements. A widely used method for damage prediction is the Limiting Tensile Strain Method (LTSM). The LTSM models a masonry building as a weightless, isotropic, linear-elastic, rectangular beam on 2 supports. Although the LTSM is an easy method to use, it has its limitations. For facades for instance the perforation of the wall, which introduces weak spots in the wall and reduces the stiffness, is neglected. In this project the applicability of the LTSM in the case of facades is studied to improve damage predictions in the case of facades. A case study is performed to examine the response of facades in the Daniel Stalpertstraat due to settlements caused by the tunnelling process of the North/Southline. This field data is used to find a calibrated 2D numerical model of the facades. The calibrated numerical model is then subjected to larger settlements to obtain the behaviour of the facades at large settlements. Using linear and nonlinear analyses of the numerical model it is evaluated how accurate and how conservative 4 damage prediction models are. The first two LTSM models were examined: the standard LTSM model with E/G=2.6 and one with E/G=12.5. Based on the findings in the linear analyses also two models based on conventional beam theory were examined for their applicability: portal frame model and Forget-Me-Not model. With linear analyses it is checked how reliable the methods are in terms of strains and deformation under the imposed settlements. With nonlinear analyses the conservativeness of each method in terms of damage is evaluated by comparing the crack with found I the numerical model to the crack width calculated with the damage prediction models. The LTSM with E/G=12.5 gives the best results according to linear numerical analyses results. The LTSM with E/G provided the same curvature and shear distortion as found din the numerical analyses, the strains were approximated with 90%. The Forget-Me-Not model shows the best results according to the nonlinear analyses results. At large settlements this model provides the same results as found in the nonlinear numerical analysis results.

The increased number of underground infrastructure projects asks for a reliable and efficient assessment of settlement damages to buildings. Currently a three-stage method is in use: the first stage looks into the greenfield deformations, the second stage is a linear elastic 2D method in which greenfield deformations are applied onto a building and the third stage uses finite element methods and 3D models. The goal of this thesis was to improve the second stage by incorporating a non-linear masonry model and a soil-structure interface. A 2D parametric analysis has been performed in which various material and geometrical parameters were varied. The soil model was simplified to a linear-elastic model. The results of the research are twofold. On the one hand there are the results of the parametric analysis showing the effect of incorporating the non-linear masonry model and the soil-structure interface. On the other hand incorporating these two aspects a number of issues came up: the influence of the crack model and convergence criterion, the influence of the building location, the influence of the initial stress and the influence of the participating soil width. For each issue an explanation was sought and the consequences were determined. The results of the parametric analysis showed that including a non-linear material model and a soil-structure interface leads to lower acceptable volume losses. In practice it is generally believed that the current models are already too conservative. The difference between reality and the models must be sought in components that are still missing in the current model.

Recent tunnelling projects have received a great amount of media attention due to settlement induced damage. Due to the simplified approach of existing risk assessment methods, a new assessment system is in development, which can account for three-dimensional structural aspects of buildings. The aim of this study is to investigate the influence of the position and geometry of masonry buildings on the development of damage, while undergoing tunnelling induced settlements. In line with previous research, three-dimensional finite element analyses are used as a tool to perform a parametric study. A parametric study consists of an evaluation of the parameters position, aspect-ratio, grouping and orientation. The position parameter is divided into three characteristics: the sagging zone, a combined settlement profile and the hogging zone. The aspect-ratio parameter is also divided into three characteristics: shallow buildings, square buildings and deep buildings. The grouping effect parameter also distinguishes three characteristics: small and large isolated buildings and grouped buildings. The orientation parameter includes seven different increasing angles of the building main axis with respect to the tunnelling axis. The maximum measured crack width in the buildings gives input for a classification of damage, according the system of Burland et al. (1977). An average trend in the damage classification indicates the sensitivity to tunnelling induced settlements of the parameters. Both during and after tunnelling, a position of the building in the combined settlement profile appears to be the most sensitive to differential settlements. Buildings far away from the tunnelling axis generally obtain no more than slight damage. Structures with a low aspect-ratio seem on average to obtain equal amounts of damage as buildings with an aspect-ratio of 1. Structures with a higher aspect-ratio are less affected, both during and after tunnelling. Grouping of the buildings seems to be an influential parameter. Small isolated buildings obtain far less damage than large or grouped buildings. In relation to the numerical analyses, the empirical Limiting Tensile Strain Method (LTSM) seems to overestimate the damage for an isolated small building, but underestimate the damage in large or grouped buildings. For buildings in the sagging zone, a building with a low orientation angle is the least sensitive to differential settlement, while the maximum measured crack width increases by increasing the angle. The difference in maximum crack width can grow to a factor 3. A building in the combined settlement profile or in the hogging zone displays opposite behaviour. Cases with low orientation angles are the most susceptible to damage, while increasing the angle to 90 degrees lowers the maximum measured crack width. The difference in results can grow up to a factor 2.

Excavation works in urban areas require a preliminary risk damage assessment. In historical cities, the prediction of building response to settlements is necessary to reduce the risk of damage of the architectural heritage. The current method used to predict the building damage due to ground deformations is the Limiting Tensile Strain Method (LTSM) [3]. This method is based on an uncoupled soil-structure analysis, in which the building is modelled as an elastic beam subject to imposed greenfield settlements and the induced tensile strains are compared with a limit value for the material. This approach neglects many factors which play an important rule in the response of the structure to tunneling induced settlements. In this paper, the possibility to apply a settlement risk assessment derived from the seismic vulnerability approach [1] is considered. The parameters that influence the structural response to settlements can be defined through numerical coupled analyses which take into account the nonlinear behaviour of masonry and the soil-structure interaction.

This thesis focuses on the modelling of settlement induced damage to masonry buildings. In densely populated areas, the need for new space is nowadays producing a rapid increment of underground excavations. Due to the construction of new metro lines, tunnelling activity in urban areas is growing. One of the consequences is a greater attention to the risk of damage on existing structures. Thus, the assessment of potential damage of surface buildings has become an essential stage in the excavation projects in urban areas (Chapter 1). The current damage risk assessment procedure is based on strong simplifications, which not always lead to conservative results. Object of this thesis is the development of an improved damage classification system, which takes into account the parameters influencing the structural response to settlement, like the non-linear behaviour of masonry and the soil-structure interaction. The methodology used in this research is based on experimental and numerical modelling. The design and execution of an experimental benchmark test representative of the problem allows to identify the principal factors and mechanisms involved. The numerical simulations enable to generalize the results to a broader range of physical scenarios. The methodological choice is based on a critical review of the currently available procedures for the assessment of settlement-induced building damage (Chapter 2). A new experimental test on a 1/10th masonry façade with a rubber base interface is specifically designed to investigate the effect of soil-structure interaction on the tunnelling-induced damage (Chapter 3). The experimental results are used to validate a 2D semi-coupled finite element model for the simulation of the structural response (Chapter 4). The numerical approach, which includes a continuum cracking model for the masonry and a non-linear interface to simulate the soil-structure interaction, is then used to perform a sensitivity study on the effect of openings, material properties, initial damage, initial conditions, normal and shear behaviour of the base interface and applied settlement profile (Chapter 5). The results assess quantitatively the major role played by the normal stiffness of the soil-structure interaction and by the material parameters defining the quasi-brittle masonry behaviour. The limitation of the 2D modelling approach in simulating the progressive 3D displacement field induced by the excavation and the consequent torsional response of the building are overcome by the development of a 3D coupled model of building, foundation, soil and tunnel (Chapter 6). Following the same method applied to the 2D semi-coupled approach, the 3D model is validated through comparison with the monitoring data of a literature case study. The model is then used to carry out a series of parametric analyses on geometrical factors: the aspect ratio of horizontal building dimensions with respect to the tunnel axis direction, the presence of adjacent structures and the position and alignment of the building with respect to the excavation (Chapter 7). The results show the governing effect of the 3D building response, proving the relevance of 3D modelling. Finally, the results from the 2D and 3D parametric analyses are used to set the framework of an overall damage model which correlates the analysed structural features with the risk for the building of being damaged by a certain settlement (Chapter 8). This research therefore provides an increased experimental and numerical understanding of the building response to excavation-induced settlements, and sets the basis for an operational tool for the risk assessment of structural damage (Chapter 9).