Now showing 1 - 6 of 6
  • Publication
    Steps toward a probabilistic framework for tunnelling damage
    Globally, the high rates of urbanization over the past century have spurred unprecedented levels of tunnel construction. With each tunnel installation, there is a large affiliated risk for damage to aboveground structures, especially those of unreinforced masonry. Such damage (and the subsequent costs and litigation) occur, despite huge sums committed to construction monitoring and pre-tunnel mitigation. Arguably, damage still happens because the wide range of parameters and the extent of their variability are not sufficiently considered in the risk assessment process. To address these uncertainties, a probabilistic framework for the large-scale risk assessment of existing, unreinforced masonry buildings subjected to bored tunnelling is proposed by the Urban Modelling Group (UMG) at the University College Dublin (UCD). This paper summarizes the initial steps needed to achieve such a framework.
      337
  • Publication
    Numerical modelling options for cracked masonry buildings
    In most numerical modelling of buildings, there is an assumption that the structure is undamaged. However, with historic buildings, defects often exist. Failing to incorporate such damage may cause an unconservative estimation of a building’s response. Nowhere is this more critical than in the case of urban tunnelling where hundreds of unreinforced masonry structures may be impacted by ground movements. This paper examines the effectiveness and limitations of four numerical approaches in the modelling of existing discontinuities, in the form of masonry cracking when compared to traditional finite element methods. The comparative methods include a micro-poly method, a distinct element method, a discontinuity deformation method, and a combined continuum-interface method. Particular attention is paid to the ease of model implementation, the availability of input data, applicability of crack modelling, and the ability to define the initial state of the structure as part of the model. The methods are compared to each other and finite element modelling. Relative qualitative assessments are provided as to their applicability for modelling damaged masonry.
      568
  • Publication
    The Effect of Uncertainty on the Prediction of Building Damage Due to Tunnelling-Induced Settlement
    Prediction of the response of buildings to tunnelling-induced settlement for the extent of a tunnel route is a complex task due to the heterogeneous nature of ground conditions, variable tunnelling operations, and unknown building parameters. Consequently, there are generally uncertainties associated with building damage predictions. This paper presents a probabilistic numerical methodology to investigate the effect of uncertainties for the damage prediction of masonry buildings due to tunnelling-induced settlement. The methodology is employed to provide a Class C1 prediction for a previously documented case history. The results demonstrate the uncertainties that have a significant influence in terms of the building response prediction and, furthermore, provide a quantitative risk assessment for masonry buildings due to nearby tunnelling.  
      389
  • Publication
    Uncertainty Analysis of the Effect of Grout Injection on the Deformation of Multi-Wythe Stone Masonry Walls
    The eighteenth century Prince of Wales Fort in Manitoba Canada has experienced extensive freezethaw damage and mortar washout within the escarp walls resulting in distress and failures at multiple locations. Injection of grout could counteract this degradation of structural stability. However existing literature provides little guidance as to the improvement level that could be expected, especially with respect to out-of-plane performance. As such, the proposed treatment was modelled to include a high level of uncertainty in the system through the application of a Random Field Finite Element Micromodelling technique. A Latin Hyper cube simulation method was used in conjunction with a parametric finite element model to randomize the material properties of each stone and relevant grouting layer. The numerical results predicted that the stone-grout bond was the most critical parameter in the proposed intervention, and that in the grouted wall sections, collapse would be avoided and lateral displacements stabilized with the proposed treatment.
    Scopus© Citations 16  233
  • Publication
    Considerations for a District-Level, Tunnel-Risk, Screening Tool
    (Society for Mining, Metallurgy, and Exploration (SME), 2016-04-28) ;
    To more rigorously address tunneling risks to above-ground structures, vulnerability evaluation of all structures along a tunnel route is required. This multi-block area along the route can be considered a district. To fully assess each structure within a tunnel’s zone of influence, a multi-block or district-level model may provide new insights as to risk evaluation and mitigation strategies. However populating such a model with the existing geometry of the built environment poses a major challenge as measured drawings are not readily available for all structures along a tunnel’s route. Cost-effective population of such a model could arguably involve remote sensing data in the form of laser scanning or photogrammetry. However even for unreinforced masonry structures, where external, above-ground geometries can be captured, without a prohibitively expensive building-by-building, in person survey many factors would remain unknown. To consider these uncertainties in an automatic way, a performance assessment framework is proposed. Such a framework allows a more rigorous, initial, risk quantification than is currently possible within the simple empirical models generally being used in industry when tunneling risk is initially assessed. This paper introduces (within the allowable space limits of this format) considerations for auto-population and application of a district-level, tunnel-risk screening tool.
      351
  • Publication
    A semi-random field finite element method to predict the maximum eccentric compressive load for masonry prisms
    An accurate prediction of the compressive strength of masonry is essential both for the analysis of existing structures and the construction of new masonry buildings. Since experimental material testing of individual masonry components (e.g., masonry unit and mortar joints) often produces highly variable results, this paper presents a numerical modelling based approach to address the associated uncertainty for the prediction of the maximum compressive load of masonry prisms. The method considers a numerical model to be semi-random for a masonry prism by adopting a Latin Hypercube simulation method used in conjunction with a parametric finite element model of the individual masonry prism. The proposed method is applied to two types of masonry prisms (hollow blocks and solid clay bricks), for which experimental testing was conducted as part of the 9th International Masonry Conference held at Guimarães in July 2014. A Class A prediction (presented before the tests were conducted) was generated for the two masonry prisms according to the proposed methodology, and the results were compared to the final experimental testing results. The root mean square deviation of the method for prediction of eccentric compressive strength of both types of prisms differed by only 2.2 KN, thereby demonstrating the potential for this probabilistic approach.
    Scopus© Citations 20  538