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Diaphragm walls are being used increasingly in connection with building basements and road improvement schemes, particularly in urban areas. Many of these walls retain overconsolidated clay, and the magnitude of the lateral stresses which will act on the wall under service conditions is uncertain. One of the reasons for this is that, although the initial in situ lateral effective earth pressures in an overconsolidated clay deposit will be high, they will be affected to some extent by the process of installation of the wall. Stress relief which occurs during installation should be taken into account, since it will influence the starting point for analysis of the post-construction behaviour. Ground movements which occur during installation are important in their own right, and might for a diaphragmtype retaining wall be more significant than those which occur during and after excavation in front of the wall. The investigation of this problem using a centrifuge modelling technique is the principal aim of the current research. An extensive literature review has been carried out to collate field data concerning the stress history and in situ lateral stresses of overconsolidated clay deposits. These were used to confirm that the proposed centrifuge modelling technique would achieve realistic stress states and changes in stress. A series of centrifuge tests has been carried out at the London Geotechnical Centrifuge Centre (operated jointly by Queen Mary & Westfield College and City University), on samples of overconsolidated speswhite kaolin, simulating the effects of excavation under a slurry trench and concreting the diaphragm wall. The background to the tests, and the geometry and design of the model are discussed. The influence of the groundwater level and panel width on ground movements and changes in pore water pressures during diaphragm wall installation have been investigated, and the results are presented. The centrifuge test results are compared with field data from various sites. The development of a simplified analytical method is presented, which may be used to estimate the installation effects of diaphragm walls in clay. The results of this analysis are compared with the centrifuge test results and field data. Finally, some areas of continuing uncertainty are highlighted and some suggestions for further research are made.

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No description available.

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The research described in this thesis, relates mainly to the current method of design of steel portal frame structures. The study is divided into two major parts, first being the full-scale test on a 24 metre span frame and the second deals with the problems of lateral-torsional buckling in the haunch region of the frame. Detailed accounts of the full-scale testing on the 24 metre span frame and the experimental results are given. Supplementary tests on beams cut out from the tested frame in order to establish the strain-hardening factor are also presented. A literature survey on the published material pertinent to the lateral torsional-buckling of a tapered member was undertaken. Different methods of treatment for the elastic stability of tapered members and any evidence from previous research in this area were reviewed. Details of an appropriate finite element and the corresponding computer programme are given. This section describes the assumptions and the Finite Element formulations adopted in the computer programme. The earlier work on this analysis dealt only with prismatic members and this was extended to solve tapered sections. Therefore, a full calibration of the finite element formulation for a tapered member was carried out. The stability clauses in BS 5950 are introduced systematically. Theoretical work which leads to the formulation of the clauses in Appendix G is also described. These stability clauses were assessed by the analysis of selected prismatic and tapered members using the finite element formulation. From this assessment some modifications to the clauses are proposed. The results of the modified clauses are compared with those given by the finite element analysis and the original clauses. Lastly, the modified clauses are checked with the results of the portal frame tested, to confirm its validity. This study leads to the proposal for some amendments in the clauses in Appendix G and Clause 5.5.3.5. of BS 5950.

This thesis reports the results of an investigation into the behaviour of fibre reinforced composite beams of various sizes subjected to flexural loading. The distribution of stress and strain through the depth of glass fibre reinforced composite beams were investigated using three experimental techniques, namely: interlaminar strain gauging, photoelastic coating, and thermal emission (SPATE) . Experimental results indicated that the beam geometry and type of flexural loading influenced the through thickness strains. Comparisons between experimental results and theoretical predictions from classical lamination theory, higher order displacement theory, and finite element analysis were conducted and discussed. The influence of the material quality (voidage) of bi-directional stitched glass fibre reinforced composite beam on beam performance was studied. It became apparent from the tests, that the void content plays a significant part in the strength and the mechanisms leading to failure, especially in shear mode. The influence played by changing the dimensions of uni-directional carbon fibre reinforced composite beams on strength and mode of failure was also investigated. It was shown that, the beam geometry (size) effects both its strength and mode of failure. The gross material failure and the onset of beam failure was predicted using approaches based on both macro mechanical and micro mechanical criteria. These criteria were developed either from experimental observation or extensions of existing failure criteria.