This research is concerned with the application of distributed computer technology to the solution of non-linear structural dynamic problems, in particular the onset of aerodynamic instabilities in long span suspension bridge structures, such as flutter which is a catastrophic aeroelastic phenomena. The thesis is set out in two distinct parts:- Part I, presents the theoretical background of the main forms of aerodynamic instabilities, presenting in detail the main solution techniques used to solve the flutter problem. The previously written analysis package ANSUSP is presented which has been specifically developed to predict numerically the onset of flutter instability. The various solution techniques which were employed to predict the onset of flutter for the Severn Bridge are discussed. All the results presented in Part I were obtained using a 486DX2 66MHz serial personal computer. Part II, examines the main solution techniques in detail and goes on to apply them to a large distributed supercomputer, which allows the solution of the problem to be achieved considerably faster than is possible using the serial computer system. The solutions presented in Part II are represented as Performance Indices (PI) which quote the ratio of time to performing a specific calculation using a serial algorithm compared to a parallel algorithm running on the same computer system.

Pandrol Rail Fastenings Limited are a designer and manufacturer of railway rail-fastening systems. As an organisation they have the capability to reduce the noise impact of bridges using resilient track components. They also have a commercial interest in providing such technology. Knowledge of the processes behind bridge noise is important to Pandrol in two ways; to aid the engineers within the organisation in the design of fastening systems and to demonstrate a state-of-the-art understanding of the problem of railway bridge noise to customers, as this will aid in the sale of Pandrol products. The fitting of new rail components to an existing track form, or failure to meet noise regulations with a new track form, can be costly. It is important to be able to predict accurately the effectiveness of noise reduction techniques. Currently, Pandrol’s knowledge of the problem consists almost entirely of experience gained and data gathered while working on existing bridge projects. To expand their knowledge base, Pandrol perform noise and vibration measurements on railway bridges and viaducts and then use the measured data to predict the performance of their systems on other bridges. This completely empirical approach to predicting bridge noise is both costly and situation specific results cannot be provided before the installation of the fastening system. ii Another approach to predicting bridge noise is through the application of analytical models. Limited analytical modelling in the context of bridge noise is currently conducted within the organisation. For these reasons, Pandrol are sponsoring research into bridge noise in the form of this EngD project. Here an existing rapid calculation approach is identified that relies less on the exact geometry of the bridge and more on its general characteristics. In this approach an analytical model of the track is coupled to a statistical energy analysis (SEA) model of the bridge. This approach forms a suitable basis from which to develop a better model here by concentrating on its weaknesses. A mid-frequency calculation for the power input to the bridge via a resilient track system has been developed by modelling the track-bridge system as two finite Timoshenko beams continuously connected by a resilient layer. This has resulted in a power input calculation which includes the important effects of coupling between the rail and bridge and the resonance effects of the finite length of a bridge. In addition, a detailed study of the frequency characteristics of deep I-section beams has been performed using Finite Element, Boundary Element and Dynamic stiffness models. It is shown that, at high frequencies, the behaviour of the beam is characterised by in-plane motion of the beam web and bending motion in the flange. This knowledge has resulted in an improved calculation for the mobility of a bridge at high frequencies. The above improvements are included in an improved model for use by Pandrol in their general activities. Data from real bridges is compared to predictions from the improved model in order to validate different aspects of the model. The model is then used to study the effect on noise of varying many bridge design parameters. It is shown that the parameter that has most influence on the noise performance of a bridge is the dynamic stiffness of the resilient rail fastening system. Additionally it is demonstrated that for a given bridge and noise receiver location, an optimum fastener stiffness exists where the noise radiated by the bridge and track is at a minimum.

The noise level associated with a train travelling on a bridge is normally greater than that for a train travelling on plain track. It is sometimes the bridge noise that causes the highest levels of disturbance to people in the vicinity or triggers action under regulations such as the Environmental Noise Directive. Consequently, there is a need to study means of predicting noise levels from proposed bridges, noise control measures for existing structures and principles of low-noise bridge design. This thesis describes a programme of work in which an existing calculation model for bridge noise and vibration has been tested and alternative calculation methods have been developed where required. The existing model is based on analytical models for wheel-rail interaction and the calculation of the power input to the bridge. The response of the various component parts of the bridge for this power input is found using a simplified SEA scheme. In this work, the existing model has been tested against measurements made on railway bridges and the results of an advanced method of structural analysis, the Waveguide Finite Element (WFE) method. This method is well-suited to modelling some important types of railway bridge. Specifically, it allows a numerical modelling approach to be used up to higher frequency than conventional Finite Element methods. It has been found to offer some significant advantages over the existing bridge noise model, particularly for concrete-steel composite bridges and concrete box-section viaducts. The track support structure has an important influence on bridge noise and vibration, through its role in the transmission of vibration from the rail to the bridge. Laboratory measurements have been made in this work to characterise the vibration transmission properties of two important types of track support structure on bridges; ballasted track and two-stage resilient baseplate track. Improved methods of modelling the dynamic behaviour of these track forms have been developed from the measurements, which can be used in calculation models for both bridge noise and also for rolling noise.

The relatively few available practice-oriented proposals for performance-based seismic design of conventional and isolated bridges, aim primarily at a more consistent description of seismic demand and capacity of structures on the basis of simplified analysis, and to a lesser extent at the direct consideration of multi-level performance criteria using advanced analysis tools. In view of the type/device-specific existing methods, the present study presents a broad-scope methodology for the seismic design of bridges emphasising on (i) displacement-based principles, (ii) use of nonlinear dynamic analysis, and (iii) explicit consideration of multiple performance levels (PLs) and objectives (POs) in a practical design context, suitable for inclusion in design codes. The deformation-based design (Def-BD) procedure, initially developed for seismic design of conventional (non-isolated) buildings, is first tailored to concrete bridges with energy dissipation in the piers. The key issues in this respect are the proper consideration of the intended plastic mechanism under the considered PLs, and the design of the bearings. The efficiency of the proposed design methodology is demonstrated by applying it to an actual bridge selected with a view to enabling comparisons among Def-BD, the modal direct displacement-based design (MDDBD), and a force-based code-type (Code-BD) method. Refined analysis along with the consistent performance-based design format within Def-BD, result in superior seismic performance. Significant cost reductions are achieved compared to MDDBD, whereas potential cost reductions may generally be obtained compared to ‘standard’ code design. Considering the diversity of passive devices and their inherent weakness to optimise the bridge response under multiple PLs, a methodology is developed to enable the identification of the critical performance requirements and the comparative evaluation of different passive schemes at the early stages of design. Originating from an earlier study focusing on bilinear isolators, the method is extended with a view to developing generalised design equations (GDEs) capable of providing reliable estimates of peak response in linear/bilinear isolation systems with/without supplemental linear/nonlinear viscous damping under different PLs associated with code-based target spectra of different intensity. The Def-BD method is finally extended to address passive (isolation and energy dissipation) systems. Novel features are introduced, including (i) the use of GDEs for the preliminary ‘near-optimal’ selection of the basic system properties and the consideration of nonlinearity of viscous dampers, (ii) the enhancement of POs in line with the higher performance expected in the case of isolated bridges, (iii) specific conditions ensuring the effectiveness of the isolation system, and (iv) the proper consideration of the orthogonal component of seismic action under bidirectional excitation. The validity of the procedure is demonstrated by applying it to the bridge previously used to develop the Def-BD method for bridges with ‘ductile-pier’ behaviour. Alternative isolation schemes are investigated and compared with the design resulting from Eurocode 8 (Part 2), offering a useful insight into some pitfalls of modern code-based approaches. Assessment of the Def-BD designs reveals enhanced and controlled performance under multiple PLs, and significant cost reductions in the substructure design compared to the design for ‘ductile-pier’ response. On the other hand, further cost reduction observed in the case of the code-based design, results in reduced efficiency of the isolation system and improper performance of the piers. In view of the previous remarks, Def-BD emerges as a rigorous methodology, applicable to most of the common concrete bridge configurations, albeit at the expense of additional computational effort associated with the use of nonlinear dynamic analysis and the design for multiple PLs. Nevertheless, minimum iterative effort is ensured by providing design ‘routines’ that facilitate the implementation and address implications resulting from the use of nonlinear dynamic analysis. Considering the suitable formulation of Def-BD, a framework of performance-based control principles for the future extension towards the integration of advanced structural control techniques, is finally set forth.

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Data from existing research are linked together to produce an overview of the effects of chloride-induced corrosion on reinforced concrete structures. The effects of chloride-induced corrosion on the following mechanisms have been investigated: (i) Cracking. (ii) Bond strength. (iii) Flexural strength. (iv) Shear strength. (v) Column behaviour. Models have been developed to link material and structural aspects of deterioration. Despite the complexity of the behaviour, many of the models are modifications to existing procedures contained in UK codes. Material and structural models are integrated together in a spreadsheet for assessing the variation in load-carrying capacity with time. Time to cracking and residual load-carrying capacity are found to be sensitive to small variations in key parameters such as the cover and the surface chloride level. Predictions from a spreadsheet model indicate that structures designed and built to BS 8110 should achieve their design life without the need for significant repair. The predictions also indicate that the UK Highways Agency was justified in making BD 57 more onerous than BS 5400. With validation against further test data the procedures developed in this Thesis could form the basis for codes of practice for the assessment of corrosion-damaged concrete structures and the durability design of new concrete structures.

This research examines the effect of plan irregularities on the progressive collapse of steel structures. Firstly, 2, 3 and 5-storey steel structures, regular and irregular, located in regions with different seismic activity designed in accordance with AISC (20 I 0) and ASCE7 (20 I 0). Secondly, the effect of the four plan irregularities on the progressive collapse of braced and unbraced steel structures located in regions with different seismic activity assessed. The collapse patterns of the I4 buildings is analysed and compared under seven loading scenarios using nonlinear dynamic and static analyses. In the nonlinear dynamic analyses, node displacements above the removed columns and the additional force on the columns adjacent to them are discussed. Furthermore, the capacity of the columns is compared to determine their susceptibility to collapse. ln the nonlinear static analyses, the pushdown curve and yield load factor of the structures are obtained after column removal. The results indicate that an irregular structure designed in site class C seismic zone collapses in most of the column removal scenarios. Moreover, when comparing regular and irregular structures designed in site class E seismic zone, the demand force to capacity ratio (D/C) of the columns in the irregular structures is on average between I.5 and 2 times that of the regular ones has been discussed by Homaioon Ebrahimi et.al (20 I7). The lack of 2-storey building bearing capacity to withstand the removal of the column is lower than that of the 5-storey structure, which is due to the level of redundancy that characterises in the 5-storey structure.

Railroad bridges are the most important connection parts of railroad networks. These bridges are exposed to heavier train loads compared to highway bridges as well as various detrimental ambient conditions during their life span. The railroad bridges in Turkey are mostly constructed during the late Ottoman and first periods of the Turkish Republic / therefore, they are generally close to about 100 years of age / their inspection and maintenance works are essential. Structural health monitoring (SHM) techniques are widely used around the world in order to increase the effectiveness of the inspection and maintenance works and also evaluate structural reliability. Application of SHM methods on railway bridges by static and dynamic measurements over short and long durations give important structural information about bridge members&rsquo / load level and overall bridge structure in terms of vibration frequencies, deflections, etc. Structural Reliability analysis provides further information about the safety of a structural system and becomes even more efficient when combined with the SHM studies. In this study, computer modeling and SHM techniques are used for identifying structural condition of a steel truss railroad bridge in Usak, Turkey, which is composed of six spans with 30 m length each. The first two spans of the bridge were rebuilt about 50 years ago, which had construction plans and are selected as pilot case for SHM and evaluation studies in this thesis. Natural frequencies are obtained by using 4 accelerometers and a dynamic data acquisition system (DAS). Furthermore, mid span vertical deflection member strains and bridge accelerations are obtained using a DAS permanently left on site and then compared with the computer model analyses results. SHM system is programmed for triggering by the rail load sensors developed at METU and an LVDT to collect mid span deflection high speed data from all sensors during train passage. The DAS is also programmed to collect slow speed data (once at every 15 minutes) for determination of average ambient conditions such as temperature and humidity and all bridge sensors during long term monitoring. Structural capacity and reliability indices for stress levels of bridge members are determined for the measured and simulated train loads to determine structural condition of bridge members and connections. Earthquake analyses and design checks for bridge members are also conducted within the scope of this study.

In Turkey, big investments are made to improve the existing train lines for use of new high speed trains. Most of the bridges on the existing train lines are typical and in this thesis one of the standard types, the classic steel truss bridge is investigated. This thesis presents the dynamic investigation of standard type existing truss bridge for passenger comfort criteria under the high speed train loadings. Two different computational analysis models have been developed to idealize the vehicle-bridge modeling to evaluate the passenger comfort that were influenced by dynamic vibrations on bridges induced by trains. Field tests of this bridge have been conducted by two separate institutes, Middle East Technical University and Turkish State Railways, to determine the state of the bridge under existing low-speed train loadings. Eigenvalue and Time history analysis of the LARSA 4D structural analysis program has been used to investigate the vehicle bridge interactions. The solutions obtained from the analysis have been evaluated with the experimental results. Different rehabilitation options are analytically studied to improve the serviceability of standard steel truss bridges per Eurocode 1990:2002, Eurocode 1991-2:2003, UIC 774-3 and UIC 776-1. The focus of this research is to define a relationship between span weight per meter and passenger comfort as well as the stiffness of this type of bridge.

Recent devastating earthquakes revealed that bridges are one of the most vulnerable components of the transportation systems. These seismic events have emphasized the need to mitigate the risk resulting from the failure of the bridges. Depending on the seismicity of the bridge local site, seismic vulnerability assessment of the bridges can be done based on the fragility curves. These curves are conditional probability functions which give the probability of a bridge attaining or exceeding a particular damage level for an earthquake of a given intensity level. In this dissertation, analytical fragility curves are developed for the ordinary highway bridges in Turkey constructed after the 1990s to be used in the assessment of their seismic vulnerability. Bridges are first grouped into certain major bridge classes based on their structural attributes and sample bridges are generated to account for the structural variability. Nonlinear response history analyses are conducted for each bridge sample with their detailed 3-D analytical models under different earthquake ground motions having varying seismic intensities. Several engineering demand parameters are employed in the determination of seismic response of the bridge components as well as defining damage limit states in terms of member capacities. Fragility curves are obtained from the probability of exceeding each specified damage limit state for each major bridge class. Skew and single-column bent bridges are found to be the most vulnerable ones in comparison with the other bridge classes. Developed fragility curves can be implemented in the seismic risk assessment packages for mitigation purposes.