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Field monitoring research was performed by Imperial College London, as part of an Engineering and Physical Sciences Research Council (EPSRC) funded research project, in collaboration with Crossrail urban railway project, to investigate how tunnelling affects adjacent existing tunnels. This field research aims to establish a high-quality case history involving comprehensive instrumentation and monitoring around earth pressure balance tunnel boring machine (EPBM) tunnelling in London Clay. Surface and subsurface instruments were installed in Hyde Park and bordering Bayswater Road, beneath which the new Crossrail twin-bore tunnels were constructed by EPBMs in London Clay below the existing London Underground Central Line tunnels. Responses to tunnel construction of the 'greenfield' ground and the ground near the existing tunnels were measured. Sufficient resolution and accuracy of the monitoring systems were established through pre-construction measurements to ensure that reliable data were obtained. The Hyde Park monitoring data are analysed and interpreted to characterise the surface and subsurface ground displacements and stress changes which are compared with similar results from other case histories of tunnelling in cohesive soils. They are also studied together with the Crossrail contractor's measurements from instruments within the existing tunnels and in Hyde Park. It is demonstrated from the monitoring results during the construction of the first tunnel that the surface and subsurface settlement troughs were wider in the ground near the existing tunnels, compared with the troughs in the 'greenfield' ground, indicating the influence of the presence of the old tunnels. The form of the surface and subsurface settlement troughs induced by the second tunnel construction is found to be dictated by the more recent construction of the first tunnel, with larger settlements and wider trough widths on the side of the first tunnel, indicating the strain-softening effect of the ground by the tunnel construction. The measured ground displacement field in near vicinity of the EPBM tunnelling, determined from the subsurface vertical and horizontal displacement measurements, is found to be directed towards the tunnel construction (i.e. 'inward' displacement field), as opposed to the 'outward' displacement field observed in an instrumented site at Dagenham for a similar EPBM tunnelling for the Channel Tunnel Rail Link project (Standing and Selemetas, 2013). It is believed that the nature of the ground displacement field in close proximity of an EPBM tunnelling (i.e. 'inwards' or 'outwards') depends largely on the relative magnitudes of the machine face pressure and tail grout pressure compared with the in-situ overburden pressure. The mechanisms of ground displacements in the near vicinity of EPBM tunnelling are established by analysing key EPBM operation variables in conjunction with the measured surface and subsurface ground response.

Tensegrity structures are a type of structural systems that consist of a given set of cables connected to a configuration of rigid bodies and stabilized by internal forces of the cables in the absence of external forces. Such structures provide an important platform for exploring advanced active control technologies. This thesis is, thus, a research on tensegrity structures' related problems across a wide range of engineering disciplines and from a control system's viewpoint. It proposes a new algorithm for the form-finding of tensegrity structures. This is a process that involves using the mathematical properties of these structures to search and/or define a configuration that makes the structures to satisfy the conditions of static equilibrium while being pre-stressed. The dynamic model of tensegrity structures is derived using the Finite Element Method (FEM), and the static and dynamic analyses of tensegrity structures are carried-out. Furthermore, the effect of including additional structural members (than strictly necessary) on the dynamics of n-stage tensegrity structures is also investigated and how the resulting change in their geometric properties can be explored for self-diagnosis and self-repair in the event of structural failure is examined. Also, the procedures for model reduction and optimal placement of actuators and sensors for tensegrity structures to facilitate further analysis and design of control systems are described. A new design approach towards the physical realization of these structures using novel concepts that have not been hitherto investigated in the available literature on this subject is proposed. In particular, the proposed realization approach makes it possible to combine the control of the cable and bar lengths simultaneously, thereby combining together the advantages of both bar control and cable control techniques for the active control of tensegrity structural systems. The active control of tensegrity structures in a multivariable and centralized control context is presented for the design of collocated and non-collocated control systems. A new method is presented for the determination of the feedback gain for collocated controllers to reduce the control effort as much as possible while the closed-loop stability of the system is unconditionally guaranteed. In addition, the LQG (Linear system, Quadratic cost, Gaussian noise) controllers which are suitable for both collocated and non-collocated control systems is applied to actively control tensegrity structural systems for vibration suppression and precision control.

Modern society is challenged by economic and environmental issues, requiring engineers to develop more efficient structures. Using cold-formed steel (CFS) frame in construction industry can lead to more sustainable design, since it requires less material to carry the same load compared with other materials. However, the application of CFS structural systems is limited to low story buildings due to the inherent weaknesses of premature buckling behaviour of members and the low ductility of connections. Consequently, current design guidelines of CFS systems are very conservative especially in the case of seismic design. Furthermore, there is no generic optimisation framework for the CFS elements, capable of taking into account both manufacturing/construction constraints and post-buckling behaviour. This study aims to better understand, to predict, and to optimise CFS elements based on their strength and post-buckling behaviour. The optimised elements can be then included in full-structure modelling to develop more efficient CFS structural connections with high ductility and energy dissipation capacity, suitable for multi-story buildings in seismic regions. The geometrical dimensions of manufacturable CFS cross-sections were optimised regarding their maximum compressive and bending strength. All the sections were considered to have a fix coil width and thickness while the optimisation was performed based on effective width method suggested in EC3. The optimised solutions were achieved using Particle Swarm Optimisation (PSO) algorithm. The accuracy of the optimisation procedure was assessed using experimentally validated nonlinear Finite Element (FE) analyses accounting for the effect of imperfections To allow for the development of a new ‘folded-flange’ beam cross-section, the effective width method in EC3 was extended to deal with the presence of multiple distortional buckling modes. Improved strength were achieved for CFS elements by using the proposed optimisation framework. A non-linear shape optimisation method was presented for the optimum design of CFS beam sections based on their post-buckling behaviour. A developed PSO algorithm was linked to the ABAQUS finite element programme for inelastic post-buckling analysis and optimisation. The results also demonstrate that the optimised sections develop larger plastic area, which is particularly important in seismic design of moment-resisting frames. An experimental programme was carried out at the University of Sheffield to investigate the design and optimisation, considering interactive buckling in cold-formed steel channels under compression and bending. Both standard and optimised sections were tested. The specimen imperfections were measured using a specially designed set-up with laser displacement. Material tests were also carried out to determine the tensile properties of the flat plate and of the cold-worked corners. A total of 36 columns with three lengths and 6 back-to-back beams were completed. The column specimens were tested under a concentrically applied load and with pin-ended boundary conditions while the beams were tested in a four-point bending configuration. Based on the tests, numerical models were proposed and calibrated and the proposed optimisation framework was verified. A numerical study on the structural behaviour of CFS bolted beam-to-column connections under cyclic loading was presented. An innovative two node element which can take into account the slippage-bearing effects was proposed and implemented using an ABAQUS user defined subroutine. The connection performance in terms of strength, ductility, energy dissipation capacity and damping coefficient were investigated. The effects of bolt configuration, cross-sectional shapes and thicknesses on the connection performance were therefore examined. It is indicated that the proposed numerical model is robust and computationally efficient to simulate the failure modes and moment-rotation response of CFS bolted moment resisting connections.

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.

At the present time, the global business environment in all industries is characterised by organizational dependence based on information, knowledge and communication technology. This reliance on information technology raised concerns about how to gain the targeted benefit of IT investment. This research study aims to address the issues affecting information technology implementation. The study focuses more on investigating the context of IT implementation processes, in particular within the construction industry in Saudi Arabia. Furthermore, this study will provide an exploratory look at the possible gaps and problems that relate to IT implementation in construction companies. More specifically, this study examines several important issues that play a role in the implementation of IT: issues related to planning for the implementation such as the availability and allocation of resources, change management and organizational issues, alignment of IT with business, the need for an IT implementation strategy and the specific problems for a construction company's executives with regard to IT implementation. Investigating each of these issues is essential in developing a comprehensive understanding of the problems associated with the planning, adoption, and implementation of IT in construction companies. These issues set the foundations for the future development of an IT implementation framework for construction companies. To achieve the research aim and objectives, different methodologies have been applied in order to develop a framework for the successful implementation of IT. In addition to the in-depth review of the related literature, quantitative and qualitative research methods were used to answer the research questions. Quantitative research methods were applied to develop an exploratory study, investigating the factors and gaps that may affect business executives' thinking towards IT and its role in organizational performance. The exploratory study was conducted in 38 private organizations that have experience of implementing information technology. In addition, qualitative research methods were used to develop four detailed case studies to investigate Saudi construction organizations' experiences of implementing and applying IT and the possible factors viiiand difficulties that affected the achievement of its expected benefits. Individual and cross-case analyses were used to analyze the collected data in order to develop the research framework and to address the research questions. More than forty factors and difficulties were identified as critical issues that affected construction organizations' implementation of IT. These identified factors and difficulties have been placed into five different categories that reflect the main elements of the developed framework: organization readiness, resources, change management, IT alignment with business, and IT implementation strategy. In addition, the research has also identified difficulties and issues related to the company's policies toward changes, financial capabilities and the company's visions toward IT implementation. Moreover, issues related to the Saudi business environment and cultures were found to be critical to the implementation of IT. The analysis of these factors demonstrated the importance of the five elements and their role in achieving the successful implementation of IT in Saudi construction industry, and the analysis of the five elements was the main contributor to the development of the framework. However, it is argued that understanding these elements is essential when making IT decisions.

A recent innovation for the shear strengthening of reinforced concrete (RC) beams is to externally bond Carbon Fibre Reinforced Polymer (CFRP) composite plates or strips. This technique has become popular because of the many advantages of CFRP composites such as: high strength-to-weight ratio, good corrosion resistance, and versatility in coping with different sectional shapes and corners. This study focuses on shear strengthening of structural members using CFRP. The understanding of concrete structures designed for strengthening in shear is still an area where uniform design rules do not exist or are treated very briefly. The research programme to study the shear contribution of externally bonded CFRP sheets/strips of RC beams includes laboratory tests of more than twenty-nine beam samples (of an original conceptual model incorporating a shear plane) with beams of different materials: nine aluminium beams, twenty concrete beams, and some timber beams for initial studies. There are twenty-six pure tensile laboratory tests to study bond behaviour between the parent material and CFRP. In addition, there are six pure shear specimens and tests to determine other material properties. The numerical analyses employ the finite element method and many numerical models are developed for simulation of the contribution of the CFRP for shear strengthening and bond strength. On completion of the experimental programme and FE analyses, the resulting information is used to formulate a new proposal for shear strengthening of concrete beams using CFRP. The bond strengths predicted using existing methods and new proposals from this study are compared with experimental data of this study and previous studies, demonstrating that the new proposals are valid and offer improvement over existing methods.