Impact of the Crossrail tunnelling project on masonry buildings with shallow foundations (original) (raw)
Related papers
Case Study of Damage on Masonry Buildings Produced by Tunneling Induced Settlements
International Journal of Architectural Heritage, 2014
This paper analyzes the structural response of a group of masonry buildings subjected to real ground movements experienced during the construction of the L9 Metro tunnel in Barcelona, bored by a Tunnel Boring Machine (TBM)-Earth Pressure Balance Machine (EPB). The studied one-storey small dwellings represent a common building typology frequently used in those days in Barcelona's outskirts (more than 1000 were erected). Real settlement profiles are compared with the ones provided by empirical methods, which estimate the shape and the area of the trough according to the ground properties and the volume loss (inherent to the tunneling construction method). The first aim of the paper is to evaluate the effectiveness of two techniques used to predict damages in buildings resulting from tunneling subsidence: 1) the 'equivalent beam' and its subsequent refinements, and 2) the appliance of a non-linear Finite Element macro-model. The real structural damage presented in the buildings is compared with the predictions given by this two methods. Main model parameters have been determined by means of characterization experiments developed on the site and in the laboratory, thus giving a much higher significance to the analysis. The obtained predictions present a high correspondence with the actual damage registered, particularly in crack pattern and in crack widths.
Assessment of the settlement vulnerability of masonry buildings
2000
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). In this approach the building is modelled
IEEE Transactions on Consumer Electronics - IEEE TRANS CONSUM ELECTRON, 2012
The assessment of settlement induced damage on buildings during the preliminary phase of tunnel excavation projects, is nowadays receiving greater attention. Analyses at different levels of detail are performed on the surface building in proximity to the tunnel, to evaluate the risk of structural damage and the need of mitigation measures. In this paper, the possibility to define a correlation between the main parameters that influence the structural response to settlement and the potential damage is investigated through numerical analysis. The adopted 3D finite element model allows to take into account important features that are neglected in more simplified approaches, like the soil-structure interaction, the nonlinear behaviour of the building, the three dimensional effect of the tunnelling induced settlement trough and the influence of openings in the structure. Aim of this approach is the development of an improved classification system taking into account the intrinsic vulnerability of the structure, which could have a relevant effect on the final damage assessment. Parametrical analyses are performed, focusing on the effect of the orientation and the position of the structure with respect to the tunnel. The obtained results in terms of damage are compared with the Building Risk Assessment (BRA) procedure. This method was developed by Geodata Engineering (GDE) on the basis of empirical observations and building monitoring and applied during the construction of different metro lines in urban environment. The comparison shows a substantial agreement between the two procedures on the influence of the analyzed parameters. The finite element analyses suggest a refinement of the BRA procedure for pure sagging conditions.
Géotechnique
Heritage masonry structures require detailed monitoring during nearby underground construction, to address the concerns of building owners and mitigate uncertainties relating to the soil–structure system. This paper discusses innovative displacement and strain monitoring of a listed masonry church undergoing ground movements due to nearby tunnelling in London Clay. In addition to conventional surveying and tilt monitoring, laser scan displacement monitoring and fibre optic strain sensing was conducted. Prior to construction, point clouds of the structure were used to map pre-existing geometric distortions in the structure. During construction, detailed monitoring of displacements and strains was conducted across the building facades and the tower. The same techniques were also used to monitor the painted dome of the church where conventional displacement monitoring was not feasible. With a focus on the new engineering insight provided by the innovative monitoring techniques, the imp...
Soils and Foundations, 2019
The analysis and prediction of damage to buildings resting on highly compressible fine-grained ''soft soils" containing (organic) clay and peat are key issues to be addressed for a proper management of subsidence-affected urban areas. Among the probabilistic approaches suggested in literature, those oriented to the generation of empirical fragility curves are particularly promising provided that a comprehensive dataset for both the subsidence-related intensity (SRI) parameters and the corresponding damage severity to buildings is available. Following this line of thought, in the present paper, a rich sample of more than seven hundred monitored (by remote sensing) and surveyed masonry buildings-mainly resting with their (shallow or piled) foundations on soft soils-is analysed in four urban areas of The Netherlands. Probabilistic functions in the form of fragility curves for building damage are retrieved for three different SRI parameters (i.e., differential settlement, rotation and deflection ratio) derived from the processing of Synthetic Aperture Radar (SAR) images by way of a differential interferometric (DInSAR) technique in combination with the severity levels of the damage recorded from the visual inspection of over 700 masonry buildings. As a novelty with respect to earlier similar studies, the work points out the methodological steps to be followed in order to identify the most appropriate SRI parameter among the selected ones. Thus, the objective of the paper is to improve the existing geotechnical forecasting tools for subsidence-affected urban areas, in order to target areas that require more detailed investigations/analyses and/or to select/prioritize foundation repairing/replacing measures.
Lecture notes in civil engineering, 2021
Underground construction activities, such as tunnelling, cause local ground movements to occur. Nearby surface structures interact with the moving ground, potentially leading to building damage. Although it is understood that the severity of building damage is influenced by the façade opening ratio (OpR) and the stiffness of the floors, experimental work in this area is lacking. This paper describes the specification and design of an experimental campaign on brick masonry buildings subjected to vertical base movements. The specimens are half-scale models of walls of two-storey buildings; models with different window arrangements and with/without floor slabs are examined. To design the experimental setup, 3D finite element analyses of the model walls were conducted. Key analysis results, presented in this paper, indicate how the examined structural properties (OpR, building weight, floor stiffness) are expected to influence the patterns of damage in the masonry. The finite element results are also used to design an instrumentation system comprising Fibre Bragg Grating (FBG) sensors and a digital image correlation (DIC) system. Data from the tests will support the formulation and validation of structural models for predicting tunnelling-induced damage in masonry buildings.
Tunnelling and Underground Space Technology, 2018
Current procedures for the assessment of buildings response to tunnelling take into account the effect of soilstructure interaction through the definition of the building stiffness relative to the soil stiffness. Limitations of these procedures are uncertainties in the evaluation of structural parameters and inconsistent results between different methods. In this paper, three existing formulations of the Relative Stiffness Method (RSM) were been critically evaluated by analysing the governing factors in the building stiffness calculation and their effect on the structural damage assessment. The results of a sensitivity study on building height, eccentricity, opening ratio, tunnel depth, soil and masonry stiffness, and trough width parameter quantified the effect of these factors on the considered RSMs. The application of different RSMs to a real masonry building adjacent to the Jubilee Line tunnel excavation highlighted the significant effect of window openings, façade stiffness and neutral axis position on the building stiffness calculation and deformation prediction. These results highlight the need for a consistent and robust damage assessment procedure.
DYNAMIC RESPONSE OF MASONRY BUILDINGS CONSIDERING THE TIME- DEPENDENT SOIL SATURATION CONDITIONS
The main aim of this work is to investigate the seismic vulnerability of traditional masonry buildings, taking into account the impact of dynamic soil-structure interaction (SSI). More specifically, the dynamic response of a typical unreinforced masonry (URM) building constructed over a silty sand layer is examined. The main novelty of the present study is that it considers time-varying soil mechanical properties, i.e., depending on the soil saturation level, which usually varies with time. In addition, a new structural assessment approach, which aims to accurately assess the performance levels (Limit States) of historic buildings and monuments after performing certain seismic rehabilitation measures has been applied. Under this perspective, a quite simple and efficient-in terms of time, cost and effectiveness-intervention was considered, in which blocks of expanded polystyrene (EPS) geofoam are placed at the perimeter of the foundation of theURM building in order to improve its dynamic response and reduce its seismic vulnerability under the examined circumstances. Subsequently, the calculation of building's nominal life is performed in a realistic manner by taking into account the annual changes in the soil saturation level. 1 INTRODUCTION Modern regulations for the evaluation of existing structures [1-3] are based on performance-based assessment, which aims to implement a number of limit states in relation to predetermined seismic actions scenarios [4]. On the other hand, the challenge of balancing safety versus maintenance of the architectural and artistic features of historic structures remains a crucial issue to address, usually on a case-by-case basis. Τhere is a lack of a unified approach for the assessment of seismic risk of monuments and historic structures. Ensuring the monumental buildings' integrity in long terms is an issue that needs further attention and improvements. The most important difficulty, in creating a holistic methodology for assessing the seismic hazard of cultural heritage structures, is the limitations that are imposed on structural interventions. The constraints on the implementation of interventions in cultural heritage buildings are arising from the internationally accepted guidelines and the conceptual differences compared to design of new structures [5]. The best retrofitting practice in monumental structures is considered the application of reversible interventions in order to limit their vulnerability in a less intrusive manner. Performance through Limited Duration Rehabilitation Interventions (LDRI) is a new methodology, which aims to assess the seismic risk of monumental structures [6, 7]. This methodology attempts to provide a framework that quantifies the " safe " duration (i.e., the nominal life) of an intervention that upgrades structural integrity in a specified manner. The nominal life of an intervention is defined as the period for which this action ensures that the structure fulfills selected performance level(s) for a certain seismic scenario (e.g., probability of exceedance 10% and 20% in 50 years, respectively for Significant Damage and Damage Limitation Levels). A typical two-storey URM building, recently presented by the authors [8], was selected as a case study to perform the LDRI methodology, introducing also a new retrofitting scheme as it will be presented in the sequence. In the previous work [8], the impact of silty sand soil saturation level on the dynamic response of a typical masonry building was presented. Additionally, a slight retrofitting scheme was also examined, in which reinforced concrete (RC) friezes were placed at the floor levels and wooden lintels were replaced with RC lintels. The results indicated that the examined building presented higher drifts when the structure was constructed on relatively dry soil, while the slight strengthening with RC elements substantially improved its
Effects of soil-structure interaction on performance-based assessment of masonry buildings
All the modern seismic codes are based on the Performance-Based Assessment (PBA). PBA generally uses pushover analyses and the verification by the non linear static procedures.Usually pushover analyses are performed assuming a fixed-base structure. However for heavy and rigid masonry structures, compliance and geometry of the foundation system, in combination with the non-linear behaviour of the foundation soil, may significantly modify the actual response in terms of both capacity and demand. Regarding the capacity, taking into account soil compliance modifies the pushover curve, leading to more flexible systems. Regarding seismic demand, spectra including soil-foundation-structure interaction differ from those traditionally obtained in case of free-field ground motion. In this paper, firstly, specific impedance functions for flexible masonry foundations are proposed and then parametric non linear analyses on 3D-complex masonry buildings (by using the Tremuri Program) are performed in order to gain insight into the influence of the foundation-soil system compliance on PBA.