1,721,106 research outputs found
Three-dimensional modelling of the interaction between buildings and tunnelling operations
Full text linkAn extensive programme of research has been carried out at Oxford University on finite elementanalysis of the interaction between masonry buildings and ground movements induced by tunnelling. The focushas been on the development of a predictive tool for assessing the probable damage to buildings. This paperpresents a brief summary of the work, with reference to other more detailed papers. The method is illustratedwith reference to the case of the Ramsgate harbour approach tunnel, in which a large diameter tunnel in chalkwas excavated at very low cover directly beneath a row of cottages. Both field measurements and analyses revealthat in this case the building responds flexibly, following rather closely the greenfield settlements, which weresmall. The slight damage to the buildings was also correctly modelled
Transferring a non-linear finite element code to the Oxford Supercomputer, Oscar
No full textA complex three-dimensional finite element model has been developed to study the effects of tunnel construction on adjacent structures. The model uses an in-house finite element code in which complex simulations and non-linear material models have been developed. This paper describes the transfer of this code to a large parallel computer, and the improvements in performance that resulted from the move. The examination of the code, which was necessary for the transfer, also led to improvements in the serial version
Numerical models in soft ground tunnelling
No full textNumerical modelling has been used for a number of years for problems relating to soft-ground tunnelling (i.e. where the ground being excavated is not rock). Three problems require solutions in soft ground tunnelling. Firstly the effects tunnelling will have on the surroundings are determined. Secondly, the stability of the works during and after construction must be assessed. The third problem is the design of the tunnel permanent lining. This chapter will cover aspects of the first two problems only. The first problem, that of determining the effects of tunnelling, is a major area of interest in the UK and elsewhere. The motivation is the increasing number of new tunnels proposed for urban areas. Installation of a tunnel in soft ground inevitably leads to movement of the surface above, particularly if the tunnel is shallow (i.e. having a depth of cover up to 30m). Semi-empirical techniques have been developed in the past to predict these movements. However, these methods have the drawback that they cannot adequately deal with the presence of structures on the surface which themselves change the movement pattern due to their stiffness and weight. Recent research has led to the development of models that include more accurate modelling of soil behaviour, particularly for clays, and simulation of modern tunnelling techniques such as sprayed concrete lining. Some of this recent modelling is reviewed here. Assessing stability is commonly approached using analytical approaches, which have been developed from empirical rules, or through the use of plasticity approaches. Of more interest to computational researchers are quasi-finite element techniques also based on classical plasticity. The use of these methods on collapse problems in tunnelling by the author is demonstrated in this chapter
On preconditioning strategies for geotechnics
No full textIterative solvers are of increasing interest in geomechanics with the move towards 3D finite element modelling. Potentially, these methods can lead to reduced computational complexity as, unlike direct methods, they do not require the full system matrix to be assembled. In general, however, iterative solvers have not been widely adopted in geomechanics due to problems with convergence. This paper reviews the background to iterative methods for elastic and elasto-plastic material models. In some cases, existing numerical methods can be taken from research in the mathematics community. For other systems, further work is needed. The paper provides demonstrations of the capabilities of some strategies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Generation of shape functions for rectangular plate elements
No full textThis paper describes a procedure for the generation of shape functions for a family of rectangular plate elements from Lagrangian polynomials. A novel generation procedure is developed from previous work for straight beam elements, where level one Hermitian polynomials were derived from simpler Lagrangian polynomials. A number of examples are provided to illustrate the technique
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