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Spherically voided biaxial slabs (SVBS) present structural advantages for static loading which can lead to economic solutions. There exist however lacunae, in the knowledge on the behaviour of SVBS diaphragm systems when subject to seismic induced ground motion which, if overlooked, would restrict their future advancement and proliferation into seismic regions. The assertion, of lower floor seismic accelerations due to the 25-30% SVBS mass reduction, should factor the response uncertainty due to the diaphragm stiffness, higher natural frequency and floor acceleration magnification. The present research presents an innovative structural modellisation approach to facilitate the nonlinear transient dynamic analysis (NLTDA) of SVBS diaphragms by the transmutation of their in-plane diaphragm bending behaviour into 3D Kirchhoff beam finite elements. The SVBS diaphragm in-plane flexural response is captured using a novel adaptation of the 2D static-nonlinear moment-curvature analysis (2D-SNLMCA) procedure on partially-perforated RC diaphragms. A method is proposed for the 2D-plane stress (2D-PS) models to directly emulate the 3D-SVBS diaphragm behaviour by converting their 3D morphology into a 2D-PS diaphragm configuration without the need of using 3D-solid-continuum nonlinear finite element analysis. The numerical tools adopted were validated using available experimental data and verified using the closed-form differential equation of motion for a dynamic system and RUAUMOKO dynamic finite element suite. The 3D-NLTDA model accurately captured the global diaphragm demands in terms of force, deformation, floor acceleration magnification and ductility levels which are compared to the diaphragm 2D-SNLMCA capacity levels. Diaphragm energy dissipation optimisation is possible through an iterative matching approach of the seismic demands using the 3D-NLTDA with the diaphragm designed moment-curvature response from the 2D-SNLMCA. This shows that the proposed methodology could be adopted in the design towards increasing energy absorption and therefore reducing structural damage. The 3D-NLTDA shows that the better performance of SVBS diaphragms during a seismic event, compared to a solid diaphragm, is not by default due to their lighter mass, as sometimes claimed in the literature, but is conditional on the diaphragm stiffness, floor acceleration magnification and reinforcement levels which can be assessed using the proposed methods.

Driven by increased urbanisation, construction of buildings and infrastructure continues to grow worldwide, further exacerbating the social and environmental impacts created by this sector. Large scale projects, requiring thousands of component parts and globally sourced materials, flow across supply networks to construct built assets. Embodied within these supply networks are minerals, energy, water, labour, waste, modern slavery and other human rights abuses. This thesis focuses on the UK construction industry and the ability of the main contractor, a key procurer of materials and manager of the build process, to affect the sustainability of the final asset. This research is case study based on unprecedented access to staff and key suppliers of a major UK main contractor, Carillion plc. The work is an holistic approach to sustainability, incorporating both social and environmental lifecycle thinking, sustainable supply chain theory, and the fields of stakeholder and collaborative working. Applying grounded theory methodology, four major themes emerge from this inductive research; fragmentation, the role of focal nodes, inter- and intra-company collaboration and knowledge of sustainability. Set within the context of a lifecycle perspective they define the ability of the main contractor to directly implement or influence sustainable build. The research develops theory uniting economic equity, network actor perspective and life stage impacts. The findings demonstrate that operating within current unsustainable business models the main contractor can only play a bit role. Additionally, it provides the basis for recommendations on business model, policy and process change.

Steel-concrete-steel (SCS) sandwich panels are an efficient means of achieving a strong and stable composite wall. Development in the 70's and 80's focussed on tunnelling, with other applications, particularly in the defence and offshore sectors, appearing later. Renewed focus has been placed on the system in recent years due to a proliferation of proposals for new nuclear power stations in Europe. Many new nuclear projects that have been completed in recent years have been significantly delayed by problems with reinforcement congestion. SCS construction offers a potential solution to this, since reinforcement is either significantly reduced or eliminated entirely in most designs. As a result of this renewed interest, industry has sought to develop improved design rules, both for economy and easier regulatory approval. As with any composite system, the strength of the system is derived from the ability of the materials to interface efficiently with each other where they are connected. Review of existing design guides and research showed a gap in understanding of the effects of shear connection on the overall behaviour of the system, particularly when resisting out-of-plane loads. This thesis aims to improve this understanding, leading to improved design provision and a wider range of applications for SCS panels in industry. An extensive literature search found a large body of test results. However, the majority of these tests are for designs where shear connection is over-provisioned, meaning shear connection is not critical. The tests that were conducted with lower degrees of shear connection were found to be insufficient to draw definitive conclusions about changes in behaviour. For this reason, numerical modelling using finite element analysis was used to supplement the test data. A validation and verification exercise was performed, which showed that the model accurately predicted the behaviour seen in testing, for all of the relevant failure modes. This thesis focusses on the three design checks that are required for panels subject to out-of-plane loads; bending resistance, shear resistance and deflection. The effect of reduced shear connection on each of these design checks is explored in turn. For bending resistance, design rules based on first principles cross-section equilibrium are found to accurately predict the point of failure for the majority of cases. However, the existing assumption of a smooth profile of shear connector force is found to be incorrect on the tension plate, with tensile cracking leading to discontinuities in the stud force profile. Further interpretation of this result shows that this can lead to an unconservative prediction of the failure load when a panel with a low degree of shear connection is subject to a uniformly-distributed load (UDL). A new design rule is presented for this situation. Design equations for shear resistance are found to vary considerably between design codes and countries. As with the bending check, the test database is found to be lacking in tests with low enough degrees of shear connection to draw definitive conclusions about any changes in behaviour. A parametric FE study is presented to investigate these effects. The study focusses on varying the degree of shear connection for groups of beams loaded at different shear-span to depth ratios. Different behaviour is observed in each group, with the influence of shear connection varying, depending on which shear transfer action is dominant. The study shows that unconservative predictions are made for a number of the design models, particularly for slender beams with low degrees of shear connection. A new adjustment is presented for the Eurocode shear resistance model that removes the unconservative predictions. The models from the fib Model Code are suggested as a better alternative, again with some adjustment to account for reduced degree of shear connection. Deflection of SCS panels is usually predicted using linear-elastic models. Debate has occurred about whether to base the stiffness used on the contribution of the steel plates only, or whether the concrete stiffness should be included. This work finds that a partial concrete contribution should be assumed. It is also found that simple bending prediction models, based on Euler-Bernoulli principles, tend to overestimate stiffness for beams with low shear-span to depth ratios. In these cases, models that include shear deformation (such as the model by Timoshenko) are found to produce more accurate predictions. Reduced shear connection is found to lead to non-linear load deflection response curves, which cannot be easily approximated with linear-elastic models. A new load-stiffness curve is proposed for simplified non-linear modelling, which could be easily implemented in most current software packages with non-linear solvers. Finally, partial resistance factors for the bending and shear design checks are calculated, using the procedure presented in Annex D of Eurocode 0. This method takes into account the precision and conservativeness of a particular design equation through a systematic comparison with available test data, and penalises studies that are based on limited test data. The procedure is found to be deficient when the design model includes contributions from multiple materials and large numbers of parameters. To overcome this, a novel extension to the existing procedure is proposed, termed the 'matrix method'. In general, it is concluded that lower degrees of shear connection are not immediately detrimental to the performance of the system. This thesis highlights the changes in behaviour that can occur, which designers should account for when calculating the resistance of panels. This thesis also presents new adjustments and design rules to allow resistance to be accurately calculated in such cases.

Bistable Reeled Composite (BRC) booms have the potential to be used as lightweight structural elements for a number of space applications. This thesis details an approach for increasing the natural frequency and stiffness of extended BRCs. The motivation for this research is the desire to increase the scalability of a flexible “roll-up” solar array which, in its deployed state, consists of two cantilevered BRCs supporting a flexible Photo Voltaic (PV) cell-covered blanket betwee n them. A parametric study has been presented, which analysed the effects of design parameters on the vibration characteristics of a single boom using a Finite Element (FE) approach. A numerical model was combined with a nonlinear constrained optimisation to maximise the natural frequency of BRC booms with respect to the fibre orientation angles and ply discontinuity locations, under the constraints of the physically achievable braid angles and constant coiled diameters resulting from the deployment mechanism design. The results demonstrate that careful selection of the fibre orientation angles and introducing a step change in the number of plies at strategic positions along the boom length can significantly increase the natural frequency. For instance, the natural frequency of a four-carbon/epoxy-nominalbraid-ply boom (L = 5.1 m, R = 38 mm, and β = 345◦) has been improved by more than 50%. The agreement between the natural frequency values for the complete solar array and the corresponding individual BRC booms indicates that the optimised solutions for a single boom model are applicable to the complete model for the first (cantilever) mode. Experimental verification of the vibration characteristics of optimised BRC booms has also been conducted. Finally, a dynamic stability analysis of the optimised BRC booms under bending has been carried out using FE simulation, to quantify the maximum angular acceleration that they can withstand before failure. The optimised BRC booms exhibit a higher resistance to bending during a spacecraft manoeuvre.

This research is aim at investigating Climate Change effects on buckling strength of steel plate elements. Climate change is the consequence of global warming as a result of the increase of greenhouse gases in the atmosphere due to both natural and anthropogenic reasons. This can lead to changes in environmental and atmospheric pollution parameters which may affect the deterioration rate of engineering materials and infrastructural systems. A review of the state-of-the art dose-response function, which are capable of linking atmospheric pollutants concentrations and environmental variables with long-term deterioration, was carried out to quantify the potential impact of climate change on material corrosion loss of carbon steel. The corrosion loss was then linked with the long-term buckling strength of steel plate elements to produce long-term performance models. A full mapping of corrosion loss from 0%-90% section thickness loss under compressive and shear loads was undertaken using both linear and non-linear buckling finite element analyses through ABAQUS in order to find out the impact of the effect of section thickness loss on the buckling strength of steel plate elements used in plate girder bridges. A total of 522 three-dimensional finite elements models of realistic plate elements were analysed under different corrosion intensities and patterns, the latter including uniform and non-uniform corrosion as well as pitting corrosion. The dose-response functions were then utilised to predict long-term corrosion under different climate scenarios. The damage assessment by the well-known ISO model was compared to that of two other models, Klinesmith et al. (2007) and Kallias et al. (2016). From the damage assessment using the dose-response functions it was discovered that the ISO model tends to underestimate the corrosion loss while the Klinesmith and Kallias models were found to result in comparable predictions for corrosion loss over time. The buckling FE results were normalised and plotted in terms of reduction factor curves which can offer a quick way for estimating the buckling strength loss over time, for different corrosion scenarios. These curves can offer useful support to infrastructure owners and managers to assess the implications of corrosion on plate elements and plan effective maintenance strategies throughout the life cycle of assets in the face of challenging climate change uncertainties and financial constraints.

The application is based on works carried out in 5 distinct phases throughout a career at the University of Surrey spanning 36 years but with a 20 month gap in 1982 where I worked at Wimpey Laboratories undertaking research work on lightweight concretes. Initially, I was employed on an EPSRC NETCEM contract awarded to Prof Dave Hannant and Dr Jeff Keer where I developed and tested a replica of the Big 6 asbestos cement sheet. There was then a period where I was then employed on an advanced polymer composites contract awarded to Prof Len Hollaway. Although I had no specific technical knowledge of advanced polymer composites at this time I did have considerable expertise in conventional engineering materials and in experimental techniques. Within the period of this contract I gained sufficient knowledge and understanding to co-author a follow up contract. Additionally, I was able to contribute to the supervision of experimental techniques and the numerical modelling of structures undertaken by the PhD students in the research group at that time. Once taken on as a member of staff, albeit on a contractual basis, I undertook supervision and co-supervision of contracts that I had co-authored. I also applied for EPSRC starter funding available at the time. Whilst the application was not successful, Prof Len Hollaway and I were invited to take the principles of the application for reinforcing and strengthening conventional construction materials further and to expand them into a full application where we were subsequently awarded an EPSRC contract. Prof Len Hollaway and I were also requested by Prof Chris Clayton (then Head of Civil Engineering) to include other members of staff onto our contract applications. The first application included Prof Gerry Parke (then Reader in the Department of Civil Engineering) and the second application included a new member of staff Dr Toula Onoufriou (Reader in the Department of Civil Engineering). Both EPSRC applications were successful and resulted in fruitful contracts. We further included other new members of staff, albeit not successfully, on EPSRC applications for novel composite concrete beam configurations for which I took the principal investigator roll. I have since taken a proactive roll in investigating new areas of research, firstly with a PhD studentship in Electronic Engineering with Prof Graham Reed (then Reader in Silicon Wave Guide Applications in the Department of Electronic and Electrical Engineering) and then with the Composites Group in the Materials Department. This link with Prof Steve Ogin incorporated Graham’s expertise for our investigations into measurements in composite materials and then damage detection in composite materials. The major thrust in all of the work throughout this latter period of my career has been in the development and application of FRP composites through research into aspects of applied physics, optoelectronics, materials science and engineering and structural mechanics. It has been made possible through grants and contracts to which I have acted as co-investigator and co-supervisor of PhD students. This has been through both my own research effort and through my participation in an inter-disciplinary research group of staff in the Faculty of Engineering and Physical Sciences spanning across the underpinning engineering disciplines. For the first 16 years, I was the primary member of this group with specific expertise in numerical modelling and simulation of engineering structures under mechanical and environmental loading conditions. Whilst I have been the primary lead in these areas over this period it has always been necessary to choose the Principal Investigator carefully to suit the funds applied for. In this early stage of the development into the research area we have been investigating fundamental materials research based on the formative crack density work conducted by Prof Steve Ogin, Prof Paul Smith and Dr Lynne Boniface. It was thus necessary to install Steve as the Principal Investigator over either Graham or myself for the applications to be successful.

Building works include construction and demolition activities, which are common in cities across the world. Building-related activities contribute a considerable amount of the construction and demolition waste material worldwide. These activities have the potential to produce particulate matter (PM), including PM10 (≤10 μm), PM2.5 (≤2.5 μm) and PM1 (≤1 μm), and airborne ultrafine particles (≤0.1 μm). Recent studies have indicated that the rate of building works undertaken each year is growing exponentially, to meet new urban design guidelines and respond to demand from the adoption of new building technologies, which highlights the importance of measuring the amounts of particle emissions from these sources. The principles of sustainable urban development are well established, but the extent of pollution due to construction and demolition activities is still unknown. Through laboratory and field studies, this thesis aims to comprehensively investigate the release of coarse (referred to as PM2.5–10 fraction), fine (PM2.5) and ultrafine particles from various building works, assess their physicochemical properties, and estimate the associated occupational exposure risk from them to on-site workers and individuals in the close vicinity. Experiments for this thesis were carried out to measure PM and airborne ultrafine particles in the size range of (0.005–10 µm) using a fast response differential mobility spectrometer (DMS50), a tapered element oscillating micro balance (TEOM 1400), a GRIMM particle spectrometer (1.107 E) and OSIRIS (2315). Measurements were made in various locations: a controlled laboratory environment (i.e. concrete mixing, drilling, cutting), indoor field sites (i.e. building refurbishment) and at outdoor field sites (i.e. construction and demolition). Moreover, dust samples were collected simultaneously for physiochemical analyses (e.g. SEM, EDS, XPS and IBA). Several important findings were then extrapolated during the analysis. These findings indicated that ultrafine particles dominated (74-97%) the total particle number concentrations (PNCs) while the coarse particles (PM2.5-10) contributed to the majority of the total particle mass concentrations (PMCs), during the laboratory, indoor and outdoor field experiments. The highest proportion of PNCs and PMCs was found during the concrete cutting, drilling and wall chasing activities. In addition, the highest proportion of PMCs was observed in the excavator cabin during a building demolition at an outdoor field measurement site. Moreover, combining the results of SEM, EDS, XPS and IBA analysis suggested the dominance of elements such as Si, Al and S in the collected samples. The data were also used to assess the horizontal decay of the PMC through a modified box model to determine the emission factors and the occupational exposure to on-site workers and nearby individuals. The results confirmed that building-related works produce significant levels of coarse, fine and ultrafine particles, and that there is a need to limit particle emissions and reduce the occupational exposure of individuals by enforcing effective engineering controls. These findings could also be useful for the building industry to develop mitigation strategies to limit exposure to particulate matter during building works, particularly for ultrafine particles, which are currently non-existent.

This study deals with the progressive collapse of full scale square-on-square double-layer space truss (DLST) systems. The failure of certain space structures in recent years, ranging from a lattice dome in Romania, Burcharest 1963 to the DLST in Hartford USA, 1978 and the recent collapse of the Sultan Zainal Abidin Stadium, a double-layer space frame constructed in Malaysia, 2009, gives an insight into how sensitive some space structures are to progressive collapse. These tragic incidents have provided very valuable lessons for designers of the importance of understanding progressive collapse in these structural configurations. By understanding what caused such failures engineers may avoid any reoccurrence and in addition help to develop safer structures. Hence, a study of this particular problem has been conducted and the results obtained are presented in the thesis. Evaluation on the consequences of progressive collapse leads to the determination of structural Vulnerability Index due to sudden loss of an individual member (Case 1) or losses of members progressively (Case 2). In order to trace the collapse behavior a nonlinear analysis subject to increasing applied load was used. However, it is difficult for engineers to perform this nonlinear analysis due to its complexity. Hence, a simple linear analysis as an alternative method was used whereby assessment of Vulnerability Index using linear analysis is carried out using two different approaches, i.e. Rate Factor and Probabilistic Approach. Since a DLST has large number of members which correspond to a large data set, hence, these two proposed approaches are suitable. A close statistical correlation between both approaches indicates that there is a high correlation between both approaches. To ensure reliability of the proposed approaches, their results are compared using nonlinear collapse analysis and the results are found to be in good agreement. The solution strategy used to analyse the full scale models was first tested using small scale models. The numerical results of the small scale models have been verified with pre-existing experimental results and good agreements between the results are obtained. Behavior of each DLST member and also the overall structural behavior can be obtained from the nonlinear analysis. There are three different boundary conditions of the DLSTs considered. Vulnerability of the DLSTs susceptible to progressive collapse are identified and then are compared for the identification of efficient structures. The Vulnerability Index of the DLST helps engineers to discover failures that may occur due to damage or loss of its members.

Concrete is the most used man made material worldwide with about 1.4 m3 being produced per person every year. As the service life of civil engineering structures is usually 50-100 years, the long-term durability of concrete is a significant issue. The content and mobility of water especially in the surface layers plays an important role in most durability aspects of concrete. Conventional tests of water transport in concrete are empirically derived and usually based on mass increase or visual observation. These tests give no information on the state of water or the saturation within the pore structure of concrete and are not linked to transport theories. Few, if any in-situ, non- destructive test method exists that provides spatial resolution of water content as a function of distance from the surface. A recently developed one-sided ‘H nuclear magnetic resonance (NMR) setup allows the investigation of samples larger than the equipment itself and gives spatial resolution of water profiles down to a depth of circa 25 mm. Moreover, in principle, NMR allows the classification of water in porous materials by pore type. The aim of this work was to use a one-sided NMR with a standard procedure for water content that can be readily applied and easily interpreted and understood. Both the test protocol and the instrument, which were developed under laboratory conditions, required refinement for application in an industrial setting. This required the calibration of the measurement and the optimisation of data acquisition and analysis for concrete and mortar. The practical limitations of the NMR method are discussed. To provide a scientific background for these tests the water profiles obtained by NMR were compared to conventional capillary absorption and permeability test results. Further investigations of water transport revealed that swelling of the calcium-silicate-hydrate gel is a probable cause for the sorptivity anomaly. The NMR results showed that visual observation is a poor indicator of water penetration depth as there is a significant amount of water present beyond the visual waterfront.

Engineered Cement Composite (ECC) materials have the potential to be used in civil engineering applications where a level of pseudo-ductility is required. Of particular interest is the possibility of eliminating the steel from reinforced cementitious structures ensuring that no long-term corrosion exists, which is especially relevant for hydraulic tunnels. Uncertainties remain, however, with regard to the mechanical performance, physical properties, durability and shrinkage of these materials, especially when they are used in thick sections for large scale engineering structures. The current work has studied ECCs in this light. The physical properties such as density, porosity and fibre dispersion and orientation are also of interest: this forms the classic materials engineering triangle of the links between material composition and manufacturing process, the microstructure and mechanical properties. A cementitious matrix, reinforced with polymeric fibres, has been manufactured using two different processes and fibre types. Specimens have been tested in tension and flexure, and multiple matrix cracking has been observed, which leads to a pseudo-ductile behaviour. Enhanced mechanical performance in tension is in line with a greater fibre alignment and higher levels of porosity do not necessarily lead to a loss of pseudo-ductility. Flexure testing shows a pseudo-ductile behaviour maintained for over three years. The fibre surface coating and the interfacial properties are relatively stable, which is in line with the maintaining of the pseudo-ductility. Theoretical models suggest that the results are in line with the ACK model, particularly for a fibre volume fraction which considers fibre orientation and fibre pull-out is likely to be responsible for the pseudo-ductile behaviour of the material. ECC materials tend to exhibit a high shrinkage on cure; this could result in cracking, which could compromise the longevity of structures. Methods for controlling shrinkage include the controlling of the environment and use of additives such as powder micro-silica.

The increasing demand for concrete in construction places pressure on its constituent materials including aggregate. Attention has turned to alternative aggregates, such as recycled concrete (RCA), recycled asphalt (RA), and manufactured Lytag (lightweight) aggregates, to reduce the impact of quarrying. The aims in this research were to investigate the very early age behaviour and properties of RCA, RA, and Lytag concretes in relation to normal (gravel) concrete using non-destructive testing (NDT). This would lead to the use of NDT in the assessment of early age strength and setting of concrete. Early age was taken as the period from immediately after concrete mixing and up to 28 days. It was also the aim to investigate the early age concrete creep properties using UPV measurements. Finally, possible improvements in RA concrete strength were also investigated. A computerised data acquisition system was set up for continuous early age measurement of UPV. Strengths, during the first 24 hours, are higher for Lytag than normal and RCA concretes, and all are higher than RA concrete. Beyond 24 hours, similar strengths are produced by Lytag and gravel concretes, which are higher than RCA concrete, and all higher than RA concrete. During early hours after concrete mixing, higher UPV values are obtained for concretes containing Lytag and RCA aggregates, which have higher acoustic absorption. This recedes with maturity, producing higher UPV for concrete containing gravel than RA, which is higher than RCA, and all significantly higher than Lytag. Rebound number deviates from strength in its behaviour with aggregate type, with higher surface hardness produced by the concrete with the higher pore content. Strength and UPV relationships obtained for the period up to 1 day and 28 days enables the estimation of strength from UPV. UPV can also be used to determine concrete setting. Early age specific creep is higher for RA than Lytag and RCA concretes, which are higher than gravel concrete. Measurements of UPV can reflect the presence of creep and the determination of its value. Concrete containing recycled asphalt, roughened for 3 hours, can produce similar strengths to gravel concrete.

Cementitious materials are characterised by low tensile strengths and low tensile strain capacities. They are brittle and, as such, benefit from reinforcement, which increases their ability to withstand tensile and shear stresses. The mechanical performance of cheap, lightweight, aggregated cement sheets can be improved significantly by incorporating fibre meshes just beneath either surface. Such "cement-boards" have potential for use in several load-bearing and non-load-bearing applications, in both interior and exterior construction environments. For this to be possible, it is necessary to develop an understanding of the manner in which these materials fail and to be able to predict the properties of the composite in terms of those of its constituents. In the present work, a commercially available cement board and several experimental boards have been examined using reflected light and scanning electron microscopy, enabling the main micro structural features to be characterised. A methodology for producing damage free specimens for mechanical characterisation has been developed. A bend rig suitable for the testing of specimens up to 0.5 m in length and 70 mm in width, in three or four point bending, has been designed and built. The properties of the boards have been measured in flexure and in tension and the relevant failure mechanisms have been identified. Also, the properties of the glass fibre crenette and the cement core from the boards have been measured individually and the effect of the accumulation of damage in reducing the Young's modulus of the commercially available board has been studied and modelled analytically. It was found that the stiffness of the cement board is dependent solely on the properties of the cement core, while the ultimate strength is dependent on the properties of the crenette. The geometry of the crenette has an influence on the manner in which the cement board fails.

Under certain conditions a sewer pipe may completely lose its structural integrity and 'collapse'; resulting in capital, social and environmental costs. A number of integrated methods have been used to identify and understand the factors associated with an increased likelihood of sewer collapse; namely, a series of sewer collapse site visits, the development of an Interaction Matrix (IM) based on expert knowledge, a statistical investigation and experimental work. The statistical investigation involved the integration of 6 previously disparate data sources into a single data set representing 636km of sewer. Analysis of the data using the logistic regression method allowed the formation of univariate and multivariate models to investigate the association of 18 independent variables with sewer condition. In addition, first order interactions of the independent variables were considered. Of the 18 explanatory terms investigated, 14 were found to be statistically significant in univariate analysis and 10 were retained by stepwise multivariate logistic regression. Further to this 7 first order interaction terms were found to be significant. The site visits, IM method and statistical investigation returned similar results in that all methods identified a wide range of parameters as being important in determining the likelihood of an existing rigid sewer pipe collapsing. The methods were not able to highlight a parameter, or small group of parameters, as being of particular importance. A laboratory based soil box test facility for the structural testing of small diameter sewer pipes was designed and constructed. Experimental work was conducted to investigate the performance of sewer pipes under repeated cyclical loading conditions when laid within beddings of varying compaction levels. Pipes within compacted material were found to perform significantly better, over both short and long time periods, than those in uncompacted material. Suggestions were made regarding the potential for UK water companies to develop predictive models for sewer structural condition as part of overall sewer rehabilitation strategies.

Over the last three decades there has been a growing awareness amongst civil and structural engineers of the importance of advanced polymer composites in the civil infrastructure. The application of fibre-reinforced polymer (FRP) plates and jackets for the strengthening and repair of RC beams and columns has now become commercially viable. Further developments of FRP composites have resulted in new constructions being conceived and developed, with considerable emphasis on bridges. The aim of the current study was to develop, manufacture and determine the structural properties of an advanced composite/concrete (duplex) beam. This beam comprised of a compressive concrete section and a tensile advanced composite box section. The webs consisted of a sandwich construction of +/-45° glass fibre reinforced polymer (GFRP) composite and rigid foam to enhance the buckling capacity. The tensile flange of the box section consisted of a hybrid uni-directional carbon fibre reinforced polymer (CFRP) and +/-45° GFRP composite. The webs were continued into the compressive section to provide permanent formwork for the concrete section. The structural properties of the beam system were determined by flexural tests on 1.5m span beams under static, creep and fatigue load regimes and long-term environmental exposure tests on 0.75m span beams. The short-term strength of the beam was designed and shown to be similar to that of an RC beam of similar dimensions with 2.5% of tensile steel reinforcement. The creep and fatigue properties (strength and stiffness) were shown to be superior to those of the equivalent RC beam due to the elimination of the tensile concrete and steel reinforcement. Exposure to freeze/thaw cycling and a warm, humid environment had no significant effect on the strength or stiffness of the duplex beam. The experimental tests were supplemented with linear and non-linear FE analyses that successfully modelled the short and long-term behaviour of the duplex beam. It was concluded that the duplex beam was particularly suitable in applications where a severe environment is present and provides a superior alternative to RC beams. This is of vital importance considering the large stock of deteriorated RC structures present world-wide. Therefore, the duplex beam forms an economic and durable structural solution for the global civil infrastructure.

This thesis presents an efficient method to predict the behaviour of some space structures, namely, single layer grids and domes. The approach is based on transforming a dense space structure into a similar space structure with lower density (fewer number of nodes and elements). This reduced structure is then analysed in the usual manner and the results are employed to obtain an approximation to the behaviour of the actual structure. In order to assess the accuracy and the limitations of the proposed method, a number of practical examples are analysed. The influence of irregularity of loading and support conditions have also been investigated. The comparison of the results obtained by the exact analysis has shown that the accuracy of the proposed method is satisfactory for the design of space structures. For generating data and organizing the graphical output of the examples studied, the concepts of formex algebra together with the programming language Formian have been utilised. The application of the proposed method is extended to the dynamic behaviour of grids and domes. The proposed method provides a simple means for designers to estimate the effects of changes in the density of the configuration on the behaviour of grids and domes. The method has the potential of being extended in many directions and, in particular, to the study of non-linear behaviour of space structures.

This research is concerned with the measurement and interpretation of ground displacements around three NATM tunnels forming part of the Heathrow Express Terminal 4 underground station and the prediction of these displacements using the finite element method. Ground displacements, using precise levelling and multiple-rod extensometers, were measured as part of the construction process. In addition the displacement of the shotcrete tunnel lining was monitored using three dimensional displacement monitoring. This database of information was supplemented with ground displacements measured ahead of the advancing concourse tunnel using chain deflectometers and inclinometers. All the monitoring results were interpreted and typical ground displacement patterns around the tunnel heading were established. An unique set of ground displacement vectors in a longitudinal plane on the tunnel centreline was produced. Such a set of field measurements is extremely valuable for the benchmarking of 3D finite element analyses. Based on the results obtained from the monitoring it was possible to evaluate the performance of the various instrumentation systems used. It was the first time that chain deflectometers had been used to measure ground displacements ahead of an advancing tunnel and their performance was very encouraging. Chain deflectometers provide an alternative for measuring vertical displacements and in addition provide horizontal displacements, which is unusual for horizontally installed instrumentation. The performance of the inclinometer system was also judged to be highly satisfactory and the use of sacrificial inclinometers ahead of the tunnel may usefully be considered for future tunnel instrumentation. The performance of the precise levelling and multiple-rod extensometers was adequate, while the performance of the in-tunnel lining deformation monitoring proved to be disappointing. Both 2D and 3D finite element analyses were conducted to investigate the effect of the different categories of assumptions and simplifications inherent to the method. The finite element analyses showed that the initial stress conditions, material model used and the modelling of construction details all have a significant effect on the predictions. Although the prediction of displacements in the far-field was disappointing for all analyses, reasonable predictions of the ground displacements around the tunnel heading were obtained with a 3D analysis using a non-linear elastic perfectly plastic material model.

Groundborne vibration from construction works can cause significant impacts on the environment, through damage to structures or disturbance of the occupants of buildings. Reliable prediction of the extent of such impacts can be a benefit to the cost and public tolerance of the works and to the effects on the wider environment. This thesis addresses the prediction of vibration caused by four mechanised civil engineering activities: percussive and vibratory piling, and dynamic and vibratory compaction. New field data are presented and analysed. These data have been compared with predictors in the literature for vibration from piling and dynamic compaction. The dearth of information in the literature relating to groundborne vibration from vibratory compaction stimulated a particular emphasis on the study of vibrating rollers. For dynamic compaction, it was found that the existing empirical predictive equation provided a reliable estimate of groundborne vibration, provided that its use was restricted to within the ranges of the parameters from which it was determined. For vibration caused by percussive piling, a number of limitations were identified in the existing prediction formulae. A modified empirical predictor is proposed based on a combination of the literature and the new data. For vibratory piling, it is demonstrated that the magnitude of vibration is not related to the nominal energy per cycle of the vibrodriver, although this is the basis of the predictors in the literature. A new empirical prediction equation for groundborne vibration from vibratory piling is proposed. The vibration arising from vibrating rollers is shown to be dependent upon those factors reported in the literature to determine the efficiency of a vibrating roller to achieve compaction. A new prediction equation is proposed which relates the groundborne vibration to the nominal amplitude of the vibrating drum. For ease of application, all the predictors proposed are based on parameters which are provided by plant manufacturers in their data sheets and the distance from the source. The ranges for each parameter from which the predictors were developed is specified: it is recommended that the predictors are not used outside these ranges.

A numerical model has been made for the solution of phreatic surface seepage (single-phase fluid flow), assuming continuity of flow between unsaturated and saturated soil zones. It allows for continuous variation of the hydraulic properties as a function of the pressure head using real soil data taken from relevant literature. Soil anisotropy and layering, one-, two-, or three- dimensional problems, seepage faces and hysteresis can also be handled. The computer code based on this model has been validated in comparison with analytical, experimental, field and numerical results found in the literature. The impact of several factors on the accuracy of the results has been investigated. The various methods for the mathematical simulation of the hydraulic properties are shown not to influence significantly the numerical results. Conversely, not all hysteresis models performed equally well in all situations. Slight improvement was achieved using lumping of the time-dependent matrix. Extensive comparisons have been made between the writer’s model results and those derived by other methods, used for phreatic surface seepage solutions. Such methods usually ignore flow in the unsaturated zone, or make oversimplifying assumptions about the hydraulic property variation in this zone. The comparisons were based on dam, trench drainage and local or regional pumping problems. Case studies of pumping have also been made, and the writer’s model has been applied to the simulation of groundwater level changes in inner cities (with particular reference to London). It has been shown that the results derived using the various methods may differ significantly, especially in transient seepage analyses. Ignoring hysteresis may also lead to significant discrepancies with observations. Realistic modelling of the hydraulic property variation in the unsaturated zone was demonstrated to be of major importance. It is claimed that, overall, the writer’s model has been able to produce improved results compared with other methods investigated herein.

This thesis is concerned with the mass compressibility of fractured chalk and its influence on the settlement of shallow foundations. A review of the literature reveals nineteen case records of load-settlement behaviour from relatively small diameter « 1m) plate loading tests but only six welldocumented case records of the behaviour of shallow foundations on chalk. The plate loading tests indicate that highly fractured near-surface chalk undergoes yield at relatively low stresses (200 - 400kPa) resulting in a significant reduction in stiffness. This behaviour contrasts with that observed in other rock types with similar discontinuity patterns. For chalk it has only been observed in one case record for a full-scale foundation. Little is understood about the mechanisms causing yield. At the time of starting this research, based largely upon the experience ..gained from in-situ loading tests carried out at Mundford, Norfolk (Ward et aI., 1968), it was known that factors such as fracture spacing and aperture played an important role in controlling the load-settlement behaviour of shallow foundations. Little attention was paid to the large variation in intact properties displayed by the chalk. In this research nine 1.8m diameter plate loading tests have been carried out by the author on chalks with different intact mechanical properties and similar discontinuity patterns. These data are used to evaluate other in-situ tests (such as SPT, surface-wave geophysics and visual assessment) as means of providing parameters for the prediction of foundation settlement. The results of this research indicate that fractured near-surface chalk undergoes yield within the range of stresses likely to be imposed by shallow foundations and that the pre-yield stiffness of the rock mass is controlled to a large extent by the looseness of the fracture-block system, which in tum appears to be associated with the intact mechanical properties of the rock. The post yield-stiffness of the rock mass is generally about one tenth of the pre-yield stiffness and is relatively insensitive to the rock material properties.

The field plate test has been used to derive elastic stiffness and undrained strength parameters of clay soils. Generally the interpretations are based on the measurements of the plate load and settlement, though occasionally additional measurements have been made in an attempt to improve the interpretation. The interpretations of soil parameters from the test rely on simplified assumptions of the soil behaviour. In particular the soil-is often assumed to be linear elastic perfectly-plastic. The complexity of the stress and strain paths induced within the soil by a field plate load test belies the simplicity of the interpretations. This Thesis examines the use of the field plate load test as a method of deriving in-situ parameters of clay soils, using the finite element method to conduct a parametric study of the test. The results of these studies have been used to assess the validity of the parameters determined from the test and also to examine how the interpretation may be improved. The Thesis concludes that the interpretation of the plate test can be improved to yield non-linear elastic parameters of soil at small strain. In addition the results from a plate test can, theoretically, be used to predict the elastic load settlement response of full scale foundations. The test can also be used to measure consolidation and undrained strength characteristics of a clay soil appropriate to the analysis/design of full scale foundations of similar geometry and load direction.

Stress relief techniques for measuring stresses have only been recently applied to concrete structures. The release of stresses due to either hole-drilling or slot-cutting are normally measured by surface strain gauging. A new technique is proposed in which an instrumented cylindrical inclusion is inserted inside a small hole in concrete to measure the stress relief due to overcoring. This thesis describes an experimental development of the proposed technique for in-situ stress measurement in concrete structures. The analysis, design and fabrication of the instrumented inclusion is described and a programme of calibration experiments is also described. Two types of instrumented inclusions of biaxial and triaxial configurations were used for bi-dimensional and tri-dimensional stress measurement respectively. Field trials using the inclusion technique were performed with limited success on three reinforced concrete bridges. Results of the field testing showed that the technique provides an extension of the existing stress relief methods for stress measurement by surface gauging. The potential use of the inclusion technique for in-situ stress measurement in existing structures is recognised but further refinement of the method and analysis is also recommended.

A review of experimental data on free embedded cantilever walls is presented. Normalization of limit equilibrium depths of embedment and maximum bending moment was successfully carried out, but it was found that very little data were in existence. In contrast, many methods of limit equilibrium design were found to be in use. Subsequently, new experiments have been performed, using a small-scale model of a free embedded cantilever wall. Further experimental data have been obtained on maximum bending moments, depths of embedment at failure, and also normal and shear stresses mobilized between soil and wall. New comparative analyses have been performed between these data and predictions by current design methods. The adequacy of these methods has been assessed in the light of the new data. A special model wall facility was built for these experiments. It comprised a test tank, a small-scale model wall, and instrumentation for measuring normal and shear stresses between soil and wall. New types of boundary normal stress and boundary shear stress transducers were developed, using the Hall effect principle. A re-assessment of the phenomenon of cell action factor has also been carried out. Previous design criteria for diaphragm-type boundary normal stress transducers did not predict accurately values of cell action factor measured in this thesis. Accurate predictions of cell action factor were obtained only by a design criterion considering the influence of soil modulus, which was determined in the triaxial test using local strain devices.

The objective of the work reported in this thesis is to study the behaviour of stiffened compression flanges of steel box girder bridges. Various collapse modes and many different parameters that effect the behaviour of the stiffened panels which make up the flanges have been considered. In order to achieve this, a series of three parametric studies have been carried out using a finite element package (LUSAS), which allows for both material and geometric non-linearities. The aim of the work was, in the main, to provide a datum for assessing design recommendations being prepared for the ECCS (European Convention for Constructional Steelwork), and to help in their development. The recommendations were developed as part of this research programme. The first parametric study looked at a range of isolated stiffened panels subjected to uniform uniaxial compression, representing the compression flange of a box girder subjected to pure moment. This validated the basic requirements within the recommendations for the strength of longitudinally stiffened flange panels. The second study was aimed at examining the effect of the shear flexibility of the flange of a girder loaded by vertical shear. In order to study the influence of this flexibility which results in a lag in stresses across the box width relative to the edges (shear lag), finite element results were generated for panels loaded along their longitudinal edges by in-plane uniform shear stress. A new model has been established from these results to predict the effect of shear lag. The model consists of two equations. The first is concerned with the prediction of the elastic shear lag effective breadth ratio while the second is concerned with the effect of shear lag at collapse. The latter is substantially different because of the ability for plastic redistribution of direct stress to occur across the flange prior to collapse. Finally, a third study looked at the forces on, and the behaviour of the cross-frames in orthogonally stiffened flanges. The results of the study showed that the flange applied a more complex lateral load distribution to these stiffeners than currently considered in design practice with, for some parameters, substantially higher load levels than required in the strength requirement of the British code for the design of bridges. A modification is proposed to the rules to provide transverse stiffeners which satisfy both stiffness and strength considerations.

A neai-coincident doubly-symmetric branching system is first considered in general terms. The form and stability of the equilibrium paths of the ideal system are studied. In the presence of two major imperfections the system exhibits a preferred mode of buckling corresponding to the least-stiff uncoupled path of the ideal system. A classification of the system is made based on the stability of the bifurcation point when imperfections purely in the form of the most-stiff buckled mode and solely in the form of the least-stiff buckled mode are applied. This general theory is then applied to three theoretical models and the imperfection sensitivity surfaces of their natural equilibrium paths are generated. The first model is a strut on a Winkler type foundation. An investigation of the effect of variations of energy coefficients, splitting parameter and imperfections leads to the four general forms of stability boundaries proposed. According to the form of the stability boundary a system will behave statically, partially dynamically or dynamically for all combinations of the two imperfections. The second is a modified Stein model which is analogous tothin rectangular plates under in-plane compression and the third is a simply-supported rectangular plate, laterally restrained, under uniaxial compression. Finally a series of experiments, conducted to verify qualitatively the simple theories proposed, are described. Rectangular steel plates were held in a semi-rigid test frame which provided simple support to all edges while restraining the unloaded edges from lateral movement. A number of out-of-plane point loads were used to represent the imperfections. Uniaxial compression was applied to the plates and Fourier analyses carried out on the out-of-plane displacements of the longitudinal centreline provided the interaction between the component modes of deflection, in particular the predicted coupling between the one- and two-halfwave deflected forms.

This investigation deals with the vibration problem of a rotating shrouded bladed disc and with the dynamic stresses of blades and packets of turbine blades. The wave propagation technique in periodic structures is introduced into the finite element method to reduce the overall number of degrees of freedom. The application of wave propagation technique to discs, disc-blades and shrouded bladed disc results in a small size eigenvalue problem which is easily solved to obtain the frequencies and mode shapes of these assemblies under the effects of rotation, disc thickness variations, disc flexibility and other design parameters. The numerical integration is used to evaluate the integrals of the stiffness and mass matrices of the variable thickness discs. The influence of rotational speeds and other design parameters such as; pretwist angles and stagger angles on the free vibration characteristics of blades, curved beams and packets of blades is studied using finite element method. The results of the natural frequencies are compared with the experimental results and with the results of other investigators. The dynamic stresses of blades and packets of blades are derived from the eigenvectors obtained in the vibration study of these components. The effects of rotational speeds, pretwist angles, stagger angles and shrouding on the dynamic stresses are studied.

Structural design is the process of determining the configuration and member dimensions of a structure, subject to specified performance requirement. Traditional optimum design techniques require a reanalysis after each modification in the design variables. The techniques developed for modification of structural analysis have to be selected for each type of structure and modification. This thesis presents an attempt to develop a practical technique for structural optimization, with particular reference to flat grid structures. The material of the thesis is arranged in the following manner: The preliminary definitions and relations and a review of some relevant aspects of structural optimization are given in Chapter one. The results of the analysis of a large number of flat grids, in a form suitable for minimum weight design, are presented in Chapter two. In Chapter three, the concepts of norm and limit of vectors and matrices are employed to develop an original technique which can be used to estimate the change in the internal forces and displacements of any type of structure due to variations in some features of the structure. Chapter four contains some applications of the proposed technique for various structural systems and an algorithm which can be used for analysis of large structural systems. Chapter five contains the conclusions.

A study of the response of submerged mast-like structures to shock loads has been carried out. An analytical model has been developed which uses a lumped parameter system whose equations of motion are solved by the use of finite difference time integration techniques. The effects of the stiffness and damping inherent in the supporting restraints are successfully included into the analysis by assuming that they provide linear rotational stiffness and a viscous type of damping. An analysis of hydrodynamic interaction effects has been developed in order to investigate how the frequency response of the structure is affected by submergence. Changes in both the frequency and the damping characteristics are predicted as a function of the depth of submergence. Methods of incorporation of these hydrodynamic forces into the time domain solution of the lumped mass system are investigated and are found to be most accurate for slender structures. In order to develop a fuller understanding of the hydrodynamic response, two experimental investigations have been carried out. The first is laboratory based and uses carefully controlled free vibration tests to excite a number of modal frequencies of a rigidly clamped vertical mast in both submerged and partially submerged conditions. Results show that the frequency changes are closely predicted by the hydrodynamic analysis developed in this thesis and also show that hydrodynamic damping is a linear function of amplitude of deflection for the first natural response mode over the mast's elastic range of response. To investigate the shock response of submerged structures, a second test rig is used to subject a slender mast to a shock load radiating from an underwater explosion. The structural significance of the higher modal frequencies is evaluated through the use of Fourier Analysis and digital filtering techniques. The instrumentation performance including both damped and undamped transducers is assessed in order to make recommendations for future shock trials. The experimental investigation has shown that both the direct pressure loading and the movement of the supports are important factors in the mast response and that their combination produces important high frequency response modes.

The use of multi-component light-weight structures has increased considerably during recent years. Collapse of such structures may be propagated by progressive failures of their components and the load-deflection curves of these structures may be characterised by a number of limit points. The fundamental mechanics of sequential collapse behaviour of these structures is presented herein. Expressions relating the loads and deflections are derived for a general structural system. The family of curves obtained describes the essential characteristics of the sequential instability behaviour of large redundant structures. Simple structural systems displaying the complete set of characteristics are presented and investigated in detail. Large-deflection elastic buckling models and a plastic buckling model are considered. It is found that member behaviour and connectivity between the members have extremely important effects on the structure behaviour. The theoretical work is supported by experimental evidence. Tests are performed on a model structure subjected to large elastic deformations. High strength steel is used to construct the model to ensure elastic behaviour throughout. An extensive and thorough experimental investigation is carried out to obtain the complete set of equilibrium characteristics. The experimental results are in complete agreement with the general and detail theoretical work. The theoretical critical behaviour of the models investigated in this thesis is shown be governed by Thom's Swallowtail Catastrophe and this is verified by the experiments. These structures exhibiting a series of limit points in their load-deflection curves are prone to demonstrate dynamic snap under dead loading. As a consequence, the concept of dynamic snap is examined. The occurrence of premature global failure due to dynamic snapthrough is deduced from a study of the form of the potential surface. An investigation is also made of the important effect of initial imperfections on the sequential buckling process. It is shown that the presence of imperfections may markedly change the form of a collapse sequence for particular structural systems. The use of "Force Limiting Devices" to improve the collapse characteristics of structures liable to sequential instability is also investigated.

The non-linear analysis of stiffened plate structure is of growing importance in structural engineering, where design methods are frequently based on a knowledge of ultimate strength behaviour. This thesis describes a finite element method for analysing nonlinear response of three dimensional stiffened plate assemblages. Both material and geometric non-linearities are considered in the formulation. Plasticity in the plate is assumed to be governed by a full section yield criterion, while a multilayer approach is adopted for the stiffeners. Procedures which trace the history of thermal loading curing plated fabrication are incorporated to account for the effect of welding stresses and geometric imperfections. Elastic beam element with multipoint contraint nodes is formulated to represent portions of the structure which are assumed to behave in a linear elastic manner. The modified Newton-Raphson nonlinear technique is improved by adopting a robust automatic incremental procedure. Further introduction of Riks' fixing length approach improves the overall efficiency, especially in the post-buckling range of the analysis. Published numerical examples and experimental results are used to verify the accuracy and to illustrate the capability of the computer prof gram. The proposed method is applied to an unstiffened box column to study the effect of geometric imperfections with the presence of residual welding stresses. A study is made on the strength of box girders, focusing on web panels and their interaction with other components under combined moment and shear force loading. Results are used to compare and justify the safe loads calculated using the recently published British Standard of Designing Steel Bridges (BS5400). Finally results from analysing a complete stiffened box girder are presented and compared to experimental data.

The lateral pressures induced by the compaction of clay against rigid structures and the subsequent behaviour of the compacted clayey backfill with time (dissipation of the pressures), and when wetting takes place (swelling pressures), have been investigated. The use of compacted clays behind bridge abutments and other retaining structures could lead to significant savings in arease where granular fill is either unavailable or expensive. Preliminary laboratory work was undertaken in order to assess the basic relationships between the main variables involved in the process of compaction (such as energy, soil parameters, and the stresses induced). A subsequent laboratory investigation was carried out to study the change (dissipation) of the compaction pressures with time, as well as the lateral pressures induced when swelling occurs. Compaction and swelling apparatusses were developed for these laboratory tests which incorporated a new small size total earth pressure gauge. The final part of this investigation involved a pilot scale experiment jointly undertaken by the Geotechnical Engineering Division of the Department of Civil Engineering, University of Surrey, with the Ground Engineering section of the Transport and Road Research Laboratory of the Department of Transport. The results from this experiment indicated that large compaction lateral pressures (more than double the earth pressure obtained from an "at rest" classical analysis) can be induced in well compacted stiff clayey backfills. Existing compaction theory developed for granular soils cannot be used to predict either the magnitude or the distribution of these pressures. Following the latest draft for a revised edition of the "Specification for Road and Bridge Works" the air voids content of the fill was used to control the effectiveness of the compaction process instead of the method specification which is current practice. Therefore a rapid and reliable method for determining the dry density in-situ was needed. The performance of the TROXLER 3411-b in direct measurement mode was investigated in order to establish an experimental correspondance between the nuclear density tests and the other standard methods (i.e., sand replacement and core cutter) . For the second stage of this experiment, water was supplied to the fill and after a period of swelling of approximately four months, the lateral swelling pressures have reached magnitudes of around four times the predicted "at rest" values, and are in excess of the theoretical passive pressures. Considering that the mechanisms involved in the compaction and swelling behaviour of clayey backfills have not yet been clearly established and that there is still no theory able to predict with the accuracy and detail required the magnitude and distribution of the earth pressures investigated, it is suggested that very stiff clays of high plasticity should be carefully studied before being chosen as backfill material.

This thesis presents the dynamic behaviour of a rotor consisting of multidiscs on a solid or hollow shaft, of the type used in gas or steam turbines. The effect of shaft flexibility on the dynamic characteristics of discs and the coupling effects between the discs and shaft modes are investigated. The influence of the disc flexibility on the hehaviour of single span and multispan shaft system is also investigated. A new, thick, three-dimensinnal, Isoparametric, cylindrical element is developed to determine the axial, bending and torsional modes and their coupling effects on the vibrating shaft-discs systems. The element is chosen to have eight nodes at its corners with twelve degrees of freedom at each node giving ninety-six degrees of freedom for a complete element. The triple integration over the element of stiffness and mass matrices are evaluated algebraically and numerically by Gaussian Quadrature using a 4 x 4 x 4 mesh. The main objective of the research reported in this thesis is to fulfil the requirement for a theoretical solution capable of accurate analysis, and the development of finite element program using a double precision arithmetic to obtain the dynamic characteristics of a multirotor system. The effect of disc flexibility on the dynamic characteristics of a system where the discs are carried in the interior of thin-walled cylindrical hollow shafts or "drums" are also studied. This type of disc-drum assemblies are used in aeroengines. Advantage of the rotational periodicity and linear periodicity of the wave propagation technique is fully utilised in the analysis. A new technique of combination of the two methodsis developed to investigate the dynamic behaviour of multidiscs - multi span systems. The present investigation is divided in two parts. The first part deals with several applications of the study of vibration characteristics of circular and annular discs, sector plates, cylindrical shells, hollow cylinders and shafts for various boundary conditions. The results for such applications are obtained separately by using the thick , three-dimensional element, and are compared with those of existing results given by classical plate and shell theory,by exact and other numerical methods of analysis. They also show very good agreement with the experimental results. The objective of this part is to present the accuracy of the thick, three-dimensional element solution including the effects of rotary inertia and shear deformation on the vibration characteristics in the case of axisymmetric and non-symmetric modes of vibration. The effect of the radii ratio b/a and thickness variation of uniform and variable thickness disc on the frequencies of vibration is discussed. The effect of sectorial angle 0 of the sector plate, the ratio of L/R[m], R[1]./R[o] and R[m]/t of the shaft on the dynamic behaviour are also studied. A thin, two-dimensional annular sector element with twelve degrees of freedom is also developed to find the mass and stiffness matrices and to obtain the frequencies of a uniform and variable thickness disc. A comparison between the results of vibrating disc obtained by the thick three-dimensional element and by this element is made to show the superiority of the thick, three-dimensional element to the thin, two-dimensional element for the dynamic analysis and also to find the influence of shear deformation and rotary inertia on the dynamic behaviour which is not allowed for in the thin plate theory. The large size of the stiffness and mass matrices obtained in the case of a three-dimensional cylindrical element analysis are reduced by using the eigenvalue economizer technique. The second part of this investigation is to present the coupling influence and interaction between the discs and the shaft by using the thick, three-dimensional element. Results presented for various cases with differing flexibility and geometry show clearly the coupling effects in a multi disc-shaft system. An inference diagram is developed from which the dynamic behaviour of a system can be predicted for differing flexibility relationships between the solid or hollow shafts and the discs. The effect of various fixing conditions and boundary conditions on the coupling characteristics are also presented. The effectiveness, simplicitiy of use and significance of the element applied and its superiority over other elements in the dynamic analysis is studied. The theoretical results show very close agreement with the experimental results.

The effect of a minor disturbing force on the stability of a structure which already is subjected to a major load near the critical state has been studied and is reported here. The approach taken is to develop physical insight to the problem by analysing representative models. The analysis is further developed on a continuum basis and tests are carried out on a small scale structural model. Two types of disturbing force are considered, that is a step pulse or a rectangular pulse. The dynamic response of a structure subjected to such a disturbing force is obtained by numerical integration using the Runge-Kutta method. The analysis neglects the possibilities of changing mode shape during the transient response. The theory developed was compared with a complementary experimental approach. The transient response of a thin wall column was experimentally studied. Special equipment was developed to permit the monitoring of the dynamic effect during the experimental programme. The results of critical disturbance force predictions are in good agreement with the experimental results.

This work presents a practical approximate technique for the analysis of dense space structures, with particular reference to single layer space structures. The technique is exemplified in terms of barrel vaults and flat grids. Following a general introduction in Chapter 1, Chapter 2 provides a general survey of the methods employed in the analysis of space structures, highlighting improvements to the methods of analysis which have been made to reduce the cost of analysis and storage requirements. The concept of formex algebra is described in Chapter 3, together with its application to data generation for structural analysis. A technique for frontwidth minimisation for frontal solution technique is also presented, with a number of illustrative examples. In Chapter 4, the concept of structural factoring is proposed as a basis for approximate analysis of very dense space structures. The Chapter gives the procedure by which the concept of structural factoring is used to estimate the structural behaviour of a dense space structure from the result of analysis of a similar structure with fewer number of nodes and members. Chapter 5 gives the details of all the barrel vaults analysed and the parameters varied to assess the accuracy of the proposed method. In Chapter 6, the results of the analysis are discussed. The results obtained by the method are compared with those obtained by the 'exact' analysis of barrel vaults and flat grids. The conclusions are given in Chapter 7, together with the suggested extensions.

New technologies for the manufacturing of glass reinforced plastics (G.R.P.) with possible outlets into the construction industry have broadened the capabilities of this material as well as the structural efficiency in design and construction. The pultrusion technique, although not a new production process, has not been used greatly in the structural field in spite of its enhanced strength and stiffness values, over the hand-lay production method, due to the unidirectional arrangement of the fibres. However, if a folded plate continuum G.R.P. structure of low modulus material requires to be stiffened by a compatible material, pultruded sections could be used to form a skeletal/continuum system with a much improved performance, the present work has investigated G.R.P. skeletal/continuum systems which are connected only at nodal points. In the present work the pultruded sections have a glass/polyester ratio of 65-35% by weight whilst the continuum component is manufactured by the hand lay-up method using chopped strand mat glass laminates with polyester resin with a glass/polyester ratio of 30-70% by weight. The theoretical analysis was undertaken by the finite element technique which provided a linear and a stability analyses of the skeletal/continuum G.R.P. space structures. The analytical procedure involved the combination of the stiffnesses of two types of elements in one overall stiffness matrix, these elements are the line element representing a two ended skeletal member in space of six degrees of freedom per node; three translational and three rotational (deltax, deltay, deltaz, thetax, thetay, thetaz) given by Livesley (9) and a rectangular plate element of four nodes and compatible degrees of freedom per node with the line element developed by Scordelis (15). The stability analysis was based on small displacements and the distinct bifurcation point related non-linearly only with the level of axial stresses in the skeletal members and the continuum. Small scale models were manufactured from perspex materials and tested; these were undertaken mainly to verify the theoretical analysis. The analytical solutions were then used to undertake parameter studies. Applications to G. R. P. composites included flat plates stiffened by pultruded members and a prototype vee sectioned composite roof system. All G. R. P. models were tested to failure to investigate experimentally the buckling characteristics of the composite systems; the results were compared with the buckling loads predicted theoretically. It was concluded that the theoretical method satisfactorily predicted the linear behaviour of skeletal/continuum systems as well as the stability behaviour of such systems in predicting the buckling loads of these composites.