The behaviour of symmetrical single and double storey frameworks, constructed with cold-formed thin-walled plain channel members and semi-rigid connections, is investigated both analytically and experimentally in this thesis. A method of analysis, which is based on the matrix stiffness method, is developed and written into a computer programme. Generalized relationships between forces and displacements at the ends of an element with semi-rigid connections are derived and presented in a matrix form. The analysis takes account of local and torsional flexural buckling, connection strength and full moment-rotation behaviour, axial load effects, member plasticity, initial imperfection and shortening due to flexure. Using the theoretical analysis, the full loading history of the framework can be traced up to the final failure load. Results are finally presented graphically and in tabulated form. Details of an experimental investigation, which was undertaken to obtain the moment-rotation relationship of connections of various stiffnesses, are given. From the experimental data, a standardized theoretical model capable of representing the full moment-rotation behaviour of the connections is developed. Results from the model are compared with the experimental data and the agreement is generally very good. The theoretical model is incorporated in to the theoretical analysis to account for the change in stiffness of the connection during loading. For the frameworks, an extensive experimental investigation was undertaken to ascertain the accuracy of the theoretical analysis. Details of the fabrication of the specimens, construction of the frameworks, testing equipment and procedures are also presented. Results of the framework experimental investigation are compared with the theoretical predictions. The agreement between theory and experiment is shown to be very close in general. Some wholly theoretical numerical results are also presented and discussed. The findings of the investigation are summarized and the main conclusions are listed.

There is a current trend towards ever more slender concrete floor structures, which is resulting in more frequent problems with their vibration serviceability. Predictive methods for vibration serviceability must consider not only the structures themselves, but also the non-structural elements which are attached to them, as these may have a significant effect on the dynamic characteristics of the floor structural system. As there has been very little past research in this area, this thesis describes an investigation into the effects of raised access floors on the vibration serviceability of long-span concrete floors. The development of a new modal testing facility based on electrodynamic shaker excitation, which was capable of producing high quality estimates of the modal properties of full-scale floor structures, is described. This was subsequently utilised to determine the modal properties of three full-scale floor structures, before and after the installation of various configurations of raised access floors. The response of these structures to controlled pedestrian excitation was also measured. Realistic finite element models of all structures were developed and updated using the results from the experimental work. These were subsequently utilised for investigation of the experimentally measured effects of the raised access floors. It was found that raised access floors had only minor effects on the modal properties of the long-span concrete floors. Reductions in natural frequencies due to the increased mass were, to some extent, offset by the slight increases in stiffness following the installation of the access floors. Modal damping ratios increased for some modes of vibration, but these changes were rather unpredictable and hence they were too unreliable to be used in design. The response of the structures under controlled pedestrian excitation reduced following the installation of various configurations of raised access floors. The reduction appeared to be greater for relatively deep access floors (500 - 600 mm) than for relatively shallow access floors (150 - 200 mm). Therefore, it is recommended that the effects of access floors may be included in vibration serviceability analyses by applying a reduction factor to predicted responses calculated by assuming a bare floor. The proposed reduction factors are 0.9 for access floors where the finished floor height is less than 500 mm and 0.8 for access floors where the finished floor height is 500 mm or greater.

In this thesis a brief history of dynamic pile analysis methods and the associated background theory are presented. In addition an unpublished rigorous mathematic proof of the Case method and new general theoretical model for dynamic pile analysis, developed as the Aberdeen method, are given. The dynamic and static response of model concrete piles in dry sand to impact and static loads have also been investigated experimentally and the results are reported in this thesis. Pile response has been found to be crucially dependent on the damping in the system. The method of modal analysis has been found to be the best approach to determine the damping factor of both the onshore and the offshore piles and is discussed in detail. A theoretical relationship between the initial and the reflected stress waves and the dynamic point resistance is used to calculate the force-penetration relationship and nonlinear parameters for the special case of pile points on dry sand. The shock relation, equations of motion and compatibility of the dynamic measurement at pile top are given by the Aberdeen method. This method gives a mathematical description of the behaviour of impact response which has not been achieved in either the Case or the TNO method. At present, the Case and TNO methods are used to investigate the integrity of piled foundations by means of the impact concept. This thesis introduces a third method, the J-integral method in the study of piled foundation. In addition, the thesis also gives a theoretical explanation to the TNO method which have not been provided elsewhere.

In this thesis, some nonlinear effects associated with the buckling behaviour of plated steel structures are examined using a modified finite strip method. To include the effects of plasticity over parts of the cross-section, a more general stress-strain relationship than previously included has been used. The method is also extended to account for the large deflection behaviour of perfect and imperfect plates in the elastic range. The only restriction on the method presented here is that the buckling mode varies sinusoidally in the .;, longitudinal direction, which implies either that the ends of the structure are simply supported or that the wavelength of the buckled mode is small in comparison with the overall length of the structure. The present study may be divided into three parts. In the first part the small deflection theory is used to determine the stiffness and stability matrices of ~ individual strip and these are assembled to form an overall stiffness matrix, representing a structure which may be under concentric load, eccentric load or pure bending. In some cases a structure with an overall initial imperfection is considered. The Wittrick-Williams Algorithm is used to obtain the smallest critical buckling load. The method is applicable to the analysis of various structures such as isolated plates, stiffened panels, rolled sections and stiffened box-girder bridges. To check the accuracy of the method a comparison with some published theoretical and experimental results is undertaken. Secondly, a parametric study for stiffened panels, columns, and beams is presented. For the stiffened panels, the effect of seven parameters (slenderness ratio, residual stress, dimensions and shape of the stiffener, mode of buckling, the longitudinal boundary conditions, and the yield stress) has been investigated. Approximate design curves for the optimum dimensions of panels stiffened by flat stiffeners are given. The capability of the method for the analysis of a stiffened box-girder in bending is also shown. The effect of seven parameters (dimensions and shape of the cross-section, the slenderness ratio, the material yield stress, the residual stress, the initial overall imperfection and the eccentricity of the applied load) on the inelastic buckling of columns and beams has been studied. All the results are given in nondimensional graphs or tables. Finally large deflection plate theory is applied to study the post-buckling behaviour of both perfect plates and those with initial imperfections. The work in this section is restricted to the elastic state. The longitudinal axial compression is assumed to act on the plate through two rigid bars at the ends, and various in-plane boundary conditions for the longitudinal unloaded edges have been considered. The Newton-Raphson method is used for the solution of the non-linear equations.

A number of reinforced concrete slabs have been exposed to blast and impact loading in order to access modes of slab behaviour under these extreme dynamic loadings. Two sizes of specimens were used; small scale slabs modelled the large slabs at 1: 2.5 scale. Impact loads were produced by a free falling hammer impacting coaxially onto a cylindrical bar of steel placed at rest in the centre of the slab. The steel bar was instrumented with electrical strain gauges which recorded the stress pulses produced by the impact. Blast loads were produced using explosive charges made of Plastic Explosive PE4. In most cases the charge used was hemispherical in shape and was placed centrally above the slab at close range standoffs, i.e. up to 10 times the radius of the charge. Additional blast tests were conducted in order to monitor the transient and spatial pressure distribution across the slab by using the pressure gauges placed in replica steel slab. Transient deflections of the slabs under both types of load were obtained using long stroke displacement transducers, whilst transient strains in the steel reinforcement of the slabs were obtained using electrical resistance strain gauges bonded to the steel bars at mid span point. A rotating prism high speed camera was used to film the damage on some of the small scale specimens at rates of up to 10,000 pictures per second. The Hopkinson pressure bar tests were used to obtain the dynamic characteristics of the concretes used at high rates of loading. Differeent concrete mixes were used for the 1:1 and 1:2.5 scale slabs. An analytical function of the spatial and transient blast pressure distribution based on the detonation pressure of PE4 was established. This is in close agreement to experimentally measured results. The nature of the local and overall failure are discussed, and the time sequence of the slab failure is established for the case of explosive loading. The crack pattern that occurs soon after the explosion in area of local failure has been established from the high speed films whilst the overall deflected shape was obtained from the displacement vs time records. After test scab sizes and slab perforations were used to establish a relation between the slab thickness, amount of explosive and the slab damage in respect to scabbing and perforation. The displacement records and the shape of after test damage provided the basis for comments on "gravity neglected - the ultimate strength" modelling law that was employed in this research.

The modelling of unbounded domains is an important consideration in many engineering problems, for example in fluid flow, electro-magnetics, acoustics and solid mechanics. This thesis focuses on the problem of modelling elastic solids to infinity, with the specific purpose of modelling dynamic soil-structure interaction (DSSI). However, the reader should be aware that the techniques presented may also be adapted to address those other physical phenomena. The need for techniques to model the soil domain to infinity and a qualitative introduction into the problems associated with dynamic soil-structure interaction are outlined in chapter 1. This is done to illustrate why such an abstract mathematical concept of modelling infinite domains has an important role to play within the design process of large, safety critical, civil engineering structures. A brief review of a number of alternative ways of addressing this problem is given in chapter 2. Their relative strengths and weaknesses along with the typical applicability of the techniques is discussed. A consequence of this review is the identification of a very promising rigorous approach [59] which is singled-out for further study. A detailed explanation of this (Consistent Infinitesimal Finite Element Cell Method, CIFECM) method is then given in chapter 3. Attention is restricted to the use of the technique for solving the 3-D vector wave equation in the time domain. The features of the non-linear dynamic finite element code, into which the CIFECM has been incorporated, is highlighted in chapter 4. The non-linear (microplane) material model for quasi-brittle materials is described along with the solution strategy employed. It should be mentioned that the soil is treated within this thesis as drained linear elastic medium. The method of coupling the CIFECM into the dynamic equation of force equilibrium for both directly applied and transmitted loading regimes is detailed. Application of the code follows in chapter 5; firstly by introducing the simplest test problem of one finite element coupled with one CIFECM element to model a surface foundation. Comparisons are made between the dynamic displacements resulting from the method and standard FE solutions obtained from the use of extended meshes and fixed boundary conditions, along with a study of the influence input variables. Following these examples a larger (more realistic) engineering problem is tacked involving the simulation of an aircraft impact on a reinforced concrete nuclear containment vessel. This represents the first use of the method in a 3-D nonlinear structural analysis problem. The results illustrate the practical implications of including DSSI in the analysis. III In chapter 6, a series of general observations on the method are made with an assessment of its value together with a discussion on its wider application to other engineering fields. Possible future developments to make the method more computationally efficient are finally suggested.

The thesis is concerned with investigating the role of mathematical programming in expressing the general theory of and facilitating effective computation for elasto-plastic skeletal structures subjected to deterministic sources of dynamic excitations, Static-kinematic duality, a common feature in the static analysis of structures, is extended to dynamic systems through the adoption of d'Alembert's principle. This allows the full use of graph theoretic methods for describing the fundamental structural relations in both mesh and nodal forms. For structures whose dynamic characteristics can be effectively described by a rigid-plastic constitutive law, mathematical programming formulations are presented. They are compared and contrasted with existing formulations, especially those associated with impact loading. Elasto-plastic structures are studied and their dynamic response is shown to be given by the solution of a differential linear complementarity problem. Four equivalent formulations are presented and are solved numerically through the use of direct integration methods. The effects of change of geometry may also be important in the dynamic analysis of structures. Firstly, for relatively small displacements, the method of fictitious forces is shown to lead to alternative mesh and nodal formulations. For large displacements, only the nodal method proves to be effective. An incremental differential linear complementarity problem is obtained and a suitable numerical solution procedure is proposed. Finally, a perturbation technique is established for solving the resulting differential equations and differential linear complementarity problems. It is proved that this technique is more general and flexible than the direct integration methods.

Concrete is still the most widely used construction material of modern times. In very recent years attempts have been made by using steel fibre reinforcement to improve the inherent weaknesses that concrete possesses such as its low tensile strength and the tendency to shrink on drying and to creep under stress. In this context, the use of steel fibre reinforcement together with high strength concrete corbel joints has been investigated. This study came after fibre reinforced concrete had received wide recognition for its crack and deformation control, ductility and energy absorption characteristics. In the present study, the fracture behaviour and deformation characteristics of plain conventionally reinforced concrete corbels with and without steel fibre reinforcement has been investigated. The different types of steel fibres used and other experimental materials are described in chapter 3, whereas chapter 2 gives a review of the old and current design approaches used for concrete corbel design. In chapter 4 the deformation, cracking and ultimate strength of plain high strength concrete corbels has been studied with different cube strength ranged between 25 to 90 N/mm². In chapter 5 a proposed theory to predict the ultimate strength of high and normal strength concrete corbels, conventionally reinforced, has been derived. The influence of steel fibre reinforcement on the performance of conventionally reinforced concrete corbels has been studied in chapter 6. Melt extract steel fibres were used in the majority of the corbels together with other types such as crimped, hooked and plastic fibres (polypropylene). In the same chapter 6, the theory has been extended to account for the strength gained by fibre addition. The effect of steel fibre reinforcement on the shear transfer strength has been studied in chapter 7. The theory proposed in chapter 5 has been further extended to predict the shear strength of 'push-off' type of specimens of plain and fibre reinforced concrete, with conventional steel reinforcement.

No description available.

A literature survey on rock anchor design revealed that current rock anchor design methods are empirical and conservative in nature. The stability of a rock anchor depends on the assumed yield surface which has been found to be difficult to predict. A simple conical yield surface is currently adopted in practice. In this approach important rock parameters such as shear stress on the surface of the cone are usually ignored. Although both theoretical and experimental evidence are available to indicate that bond distribution along the fixed anchor length is highly non-linear at the tendon/grout/rock interfaces, current design still assumed the bond to be uniformly distributed along the whole fixed anchor length. Anchor interactions group effects, debonding at the proximal end of the anchor, the effect of tendon spacing and spacers, the effect of lateral pressure on the fixed anchor are not considered in current rock anchor design. To provide a more fundamental understanding of rock anchor behaviour a simple isoparametric finite element program has been written and thoroughly tested. The initial stress method with associated flow rules was used to simulate rock anchor behaviour. The plastic potentials used for simulating the tendon and, the grout and the rock, were respectively the Von-Mises and the octahedral shear stress yield criteria. Double nodes at interfaces provided a method of simulating a perfectly smooth interface without having to resort to special interface elements. The stress strain distribution pattern in the fixed anchor zone has been obtained for a modular ratio of 2.1, The results produced have indicated, that, in addition to physical material parameters, anchor behaviour is also dependent on the applied load, the slenderness ratio and the fixed anchor diameter. The most severe position of shearing has been found to be at the grout/rock interface. Analyses show that partial debonding is not a serious problem. Surcharge tends to reduce the shear stress at the grout/rock interface however the effect is negligible. A design curve is proposed for consideration.