This project aims to enhance relationships that quantify earthquake induced damage in reinforced concrete (RC) structures, in terms of Engineering Demand Parameters (EDPs) and/or Damage Indices DIs. In the seismic vulnerability assessment process structures are classified onto Damage Scales (DS) based upon their expected performance. The damage level is quantified by Damage Indices (DIs) as a function of Engineering Demand Parameters (EDPs). This research aims to enhance the relationships that quantify damage in Reinforced Concrete (RC) structures in terms of empirically derived EDPs equations as a function of material properties, geometrical properties of sections and detailing aspects. Current relationships found in literature are generally defined at yield and ultimate damage states, or at the occurrence of a particular failure mechanism in terms of chord rotation. Assessment procedures have however evolved from these two limit states onto multiple state assessment. Relationships referring to intermediate states of damage are therefore proposed. EDP relationships are derived from datasets of low cycle fatigue tests on columns found in literature. The number of elements with design and detailing aspects referring to old design practices are limited. Recent earthquakes have shown that such structures are very vulnerable. Hence, an experimental campaign consisting in RC elements with varying detailing aspects, material properties and geometric properties, designed to old design codes was conducted to enhance the dataset, act as a benchmark, and to investigate failure mechanisms. Low cycle fatigue tests generally refer to monotonic or cyclic loading patterns without any direct reference to earthquake loading or response. A procedure describing the determination of the loading history based on earthquake demands is therefore considered. The experiments also indicate that the loading pattern is a function of chord rotation capacity. This effect is taken into account in the development of the EDP relationships. Multivariable stepwise regression was used for the development of the EDP relationships. The selection of the explanatory variables was based on significant parameters used in existing EDP relationships, parameters found in existing relationships describing particular failure modes, and dimensional analysis. A comprehensive model of chord rotation and stiffness are provided at yielding, maximum force, 10% maximum force reduction, 20% maximum force reduction and 50% maximum force reduction. Relationships that relate residual stiffness, chord rotation and energy dissipation are derived. The testing campaign on columns not only highlights the behaviour of reinforced concrete designed without seismic detailing, but adds to the database in literature. The beam-column connection tests indicate that the behaviour at the nodes affects the behaviour of RC structures, and stress the importance of their inclusion in further investigations. Finally, proposing a method to determine lowcycle fatigue loading regimes based on seismic response is an attempt to address an anomaly where tools that are used to quantify seismic damage are not linked in any way with earthquakes.

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.

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.

The cylindrical shell is one of the most efficient structures for resisting axial compression. They are found in many weight-critical engineering applications due to their low mass and large internal volume. Their structural efficiency is derived from surface curvature which results in large buckling loads. Ultimate failure is generally due to local buckling (i.e. loss of stability of the shellwall) which is followed by global collapse. A consequence of this unstable non-linear behaviour is that the structures are sensitive to imperfections and buckle at loads that are a fraction of their linear buckling eigenvalues. In contrast, flat structures (such as plates and stiffened panels) display a relatively well-behaved post-buckling response. In this thesis an investigation into the post-buckling behaviour of variable-stiffness shell structures is presented. Its aim is to determine whether or not cylindrical shells can be designed to have stable post-buckling configurations by adopting non-uniform material properties. In order to create shells with new and novel responses, the design space must be expanded by removing the standard rules for laminate design. Therefore, the present work focuses on laminates in which the reinforcement fibres are not straight but follow curvilinear paths. Such structures are termed variable-stiffness composite structures, due to their smooth variations in anisotropy (i.e. their section stiffnesses and kinematic coupling). Cylinders, curved panels and flat plates are tailored for improved post-buckling performance using numerical methods. In the case of cylindrical shells, dynamic analyses are performed in order to capture the effects of instability, inertia and path switching. Here, tailoring was performed on cylinders with a circumferential fibre-angle variation in a parametric study. The results show that a wide range of responses can be achieved by varying the shell's geometry and fibre-angle distribution. New evidence is presented that cylinders with stable post-buckling responses are possible by using variable-stiffness laminates. Tailoring is also performed on curved panels through an optimisation process. Panels .are modelled using Koiter's asymptotic method and a quadrature-based discretisation of the domain. Optimisation is performed using a genetic algorithm with the objective of increasing the structure's tangent stiffness in the vicinity of the bifurcation. An optimised shell design is presented which is practically unaffected by the increase in radial displacements in terms of axial stiffness.

New and existing superstructures (such as bridges and buildings) supported on pile foundations and located in sites susceptible to liquefaction and lateral spreading are required to be assessed or designed to withstand the actions of extreme loads. As a result, the performance of the piles, foundations, and also superstructures must be estimated/predicted by sufficient accuracy using dynamic analysis. Usually a large number of analyses are required for assessing the performance of a dynamic system and obtaining the analytical fragility functions, as an example. Simplified-conventional solutions may not be accurate enough to address the complex dynamic phenomena involved in soil-pile interaction in liquefiable soil. In order to achieve this, it is necessary to simulate soil-pile system using a reliable method supported by realistic soil constitutive relations surrounding the pile. Therefore, a hypo-elastic bounding surface model has been developed in the framework of the macro-element to underpin and facilitate the concerns of 'performance-based design' and 'risk assessments'. In this case, it is expected that the macro-element approach is able to feedback quick response with high accuracy comparable to sophisticated and complex Finite Element (FE) models. Following the concept of hypo-elasticity, elastic stiffness of the macro-element should be estimated accurately. In this case, an elasto-dynamic solution has been developed for analyzing the soil-pile system under the pile-head and the kinematic earthquake loading. This method is also generalized for different types of pile foundations ranging from the short piles/caissons to long/flexible piles. Validations and verifications of the macro-element approach show its high accuracy on simulating the field test and dynamic centrifuge. It is concluded to move step forward by utilizing the macro-element for soil-pile system in liquefiable ground in order to produce precise results. Finally, a simple method for calculating the dynamic bending moment in pre-liquefaction phase (cyclic mobility phase) is proposed for the geotechnical desk study using the elastic continuum solution.

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Compared to normally vibrated concrete (NVC), self-compacting concrete (SCC) possesses enhanced qualities and improves productivity and working conditions due to the elimination of compaction. SCC generally has a higher powder content than NVC and thus it is necessary to replace some of the cement by additions to achieve an economical and durable concrete. The established benefits of using low volumes of fly ash in SCC, high volumes of fly ash in NVC and the search for uses of waste glass led to the research on the possibilities of use higher fly ash contents than hitherto and ground glass as an addition in SCC whilst maintaining satisfactory properties. Mix design methods, tests, target properties and constituent materials were selected. This was followed by investigating the influence of fly ash and ground glass on the mortar fraction of the SCC and then using these results to produce concrete mixes with the target fresh properties. Hardened concrete of these mixes were measured and the relationships between these investigated. The results show that for constant filling ability of the SCC, replacement of cement with fly ash or ground glass requires an increase in water/powder ratio and a reduction in superplasticiser dosage. Both additions degraded the passing ability, consistence retention and hardened properties but not to a prohibitive extent. SCC with up 80% cement replaced by fly ash or glass volume ratio of 6.4% is possible and the material properties of SCC are similar to those of NVC. Also the UCL method of mix design was extended to higher coarse aggregate contents and different additions. The project can lead to the use of higher volume fly ash and ground glass in SCC, thus widening the types of additions available for SCC, saving landfill and reduce CO2 emissions by the use of less cement.

Corrosion of reinforcing steel arising from contamination by chlorides from de-icing salt is the major cause of deterioration of concrete bridges in the UK and many parts of the world. Those elements of structures exposed to cyclic wetting and drying (BS 8500-1, XD3) have proven to be the most vulnerable to corrosion damage. Penetration of chloride in concrete exposed to wet/dry environments occurs by diffusion and absorption. Diffusion is a relatively slow and quite well understood process. However, absorption is a relatively rapid transport mechanism and there is a lack of understanding of the role of this mechanism on chloride ingress as studies on chloride penetration in concrete exposed to wet/dry cycles ignore the effect of this mechanism on chloride ingress. In addition, chloride penetration prediction models are mostly based on Fick’s laws of diffusion, ignoring the effect of absorption on chloride ingress. The aims of this work are: to develop a more detailed understanding of chloride penetration in concrete subjected to wet/dry cycles and identify the effect of absorption on chloride ingress; to produce reliable numerical model for chloride penetration due to this transport process; to recommend values of the minimum thickness of concrete cover to steel reinforcement relevant to this service environment or identify exposure conditions which require alternative methods of protection. The absorption test method used in this work is a cyclic regime as developed by TRL [Emerson and Butler, 1997] to represent site conditions. Concrete cubes, 100 mm³, were subjected to wet/dry cycles with the suction surface in contact with NaCl solution. Drying temperature was found to be the most critical factor influencing sorptivity and depth of chloride penetration. The salt solution concentration also had a significant effect on chloride penetration via the apparent surface chloride content. Moreover, the depth of chloride penetration was found to be proportional to the square root of exposure time. Two approaches to predict chloride penetration in concrete exposed to wet/dry cycling are proposed. The first is based on the relationship obtained in the present study between equilibrium sorptivity of concrete, Se, depth of chloride penetration, d, and time, t, which leads to the following general expression, where A, B and C are constants for a given cement type and salt solution concentration d = A×√t + B×Se + C The second method is simply based on the well known solution of Fick’s second law but utilises values of apparent diffusion coefficient appropriate to this transport process. The first model suggests that, initially, absorption has a significant effect on chloride ingress but that diffusion dominates long-term behaviour. The outputs from these models suggest that the thicknesses of concrete cover in structures exposed to class XD3 should be higher than those currently recommended in BS 8500-1 (2006). However, there are practical limits as to what can be specified for thickness of concrete cover and therefore alternative methods of protection such as coatings or cathodic protection should be adopted when the concrete cover does not provide sufficient protection.