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Studies have shown that the connection details used for cable anchorage blocks on cable-stayed bridges have the potential for fatigue damage due to fluctuating stresses generated by the cyclic traffic loads passing over the bridge. To investigate the fatigue damage and determine the remaining fatigue life of a cable anchorage block used on a cable-stayed bridge, finite element (FE) analyses were undertaken by using the Fatigue Load Model 4 (FLM 4) proposed by the Eurocodes to identify the most fatigue-critical locations within the details. One of the main objectives of this research was to identify the critical area prone to fatigue in the anchorage block due to the response in traffic loads. Therefore, two types of numerical models of a typical cable anchorage block were analysed as a three dimensional sub-model which was driven by global cable forces obtained from the global analysis of a three-span cable-stayed bridge. These models are of the cable anchorage block without the longitudinal girder modelled and the cable anchorage block with the longitudinal girder modelled. The cable anchorage blocks without the longitudinal girder model were classified into three categories of model types namely; model types 0, A and B. Similarly, the cable anchorage blocks with the longitudinal girder model were classified as model types A-G, B-G and C-G. These model classifications are based on several boundary conditions simulated in the analyses. In addition to this, the fatigue behaviour of the cable anchorage block was analysed by using three different approaches namely; by using the nodal stresses at the location of the stress concentration (node stress concentration), by using a stress averaged over an area in the vicinity of the stress concentration (average elements) and by using the hot-spot method, in order to identify the stress ranges that adversely affect the remaining fatigue life of cable anchorages. Each approach was analysed with three different mesh sizes; 5mm by 5mm, 10mm by 10mm and 20mm by 20mm in order to carry out a mesh sensitivity analysis of the resulting stresses and associated stress ranges. The 10mm by 10mm mesh size was found to be most appropriate for this fatigue appraisal. This finding is supported because the 10mm by 10mm mesh size is specified in several code of practices such as the International Institute of Welding (IIW) and BS 7608 as guidance for use when determining hot-spot stress when using the hot-spot method for the fatigue analyses of a welded detail. The critical stresses from model type C-G were used in the fatigue appraisal as the behaviour of this model represented more accurately the actual cable anchorage block on the cable-stayed bridge compared to the other types of models used. Model type C-G were selected for further fatigue appraisal as this model include the correct boundary conditions and applied load that represented the actual condition of the anchorage behaviour on the cable-stayed bridge. This included the movement of the top anchorage block due to the displacement of the cable and in addition the deck movement. Also, non-uniform pressure was applied on the bearing plate which was included to model possible construction tolerances which was one of the important properties of the model type C-G. In evaluating the possible fatigue damage in the cable anchorage block, the cumulative model for fatigue failure expressed in terms of Miner’s rule was used. In addition to this, the condition of the structural detail due to fatigue with increasing traffic loading was determined by projecting traffic volume increases of up to 20%. Based on the results calculated, if the long distance traffic characteristic was used in fatigue appraisal, the cable anchorage block was justified to be not ‘safe’ as the damage accumulation for fatigue, Dd at the top gusset was recorded as 1.270, which exceeded the limiting value of 1.0 corresponding to a 120 year design life. However, if medium distance traffic characteristic was used in the fatigue appraisal, the cable anchorage block will remain ‘safe’ except when a 20% increase in traffic volume was included in the analysis, which resulted in Dd value of 1.016. Also, if a more conservative value of Dd = 0.5 as suggested by IIW (2008) was used, the cable anchorage block appraised by using both the long distance and medium distance traffics was found not safe from fatigue damage and would not survive its design working life without structural repair. For future fatigue appraisals of anchorage blocks (and other important structural details), it is strongly recommended that the numerical model of anchorage block is analysed together with the longitudinal girder using the hot-spot method. A 10mm by 10mm finite element mesh size is suggested and it is also necessary to specify the displacement at the top of the anchorage block to simulate the cable movement together with the girder movement both of which are obtained from the global analysis of the whole bridge structure.

The UK has a long history in the railway industry with a large number of railway assets. Railway bridges form one of the major asset groups with more than 35,000 bridges. The majority of the bridge population are old being constructed over 100 years ago. Many of the bridges were not designed to meet the current network demand. With an expected increasing rate of deterioration due to the increasing traffic loads and intensities, the management authorities are faced with the difficult task of keeping the bridge in an acceptable condition with the constraint budget and minimum service disruptions. Modelling tools with higher complexity are required to model the degradation of assets and the effects of different maintenance strategies, in order to support the management decision making process. This research aims to address the deficiencies of the current bridge condition systems and bridge models reported in the literature and to demonstrate a complete modelling approach to bridge asset management. The degradation process of a bridge element is studied using the historical maintenance data where previous maintenance actions were triggered by a certain type of defects. Two bridge models are then developed accounting for the degradation distributions, service and inspection frequency, repair delay time and different repair strategies. The models provide a mean of predicting the asset future condition as well as investigating the effects of different maintenance strategies will have on a particular asset. The first model is a continuous-time Markov bridge model and is considered more complex than other models in the literature, the model demonstrates the advantages of the Markov modelling technique as well as highlighting its limitations. The second bridge model presented a novel Petri-Net modelling approach to bridge asset modelling. This stochastic modelling technique allows much more detail modelling of bridge components, considering: non-constant deterioration rates; protective coating modelling; limits of the number of repairs can be carried out; and the flexibility of the model allows easily extension to the model or the number of components modelled. By applying the two models on the same asset, a comparison can be made and the results further confirm the validations and improvements of the presented Petri-Net approach. Finally, optimisation technique (Genetic Algorithm) is applied to the bridge models to find the optimum maintenance strategies in which the objectives are to minimise the whole life cycle cost whist maximising the asset average condition. A hybrid optimisation that takes advantage of both bridge models, resulting in a significant time saving, is also presented.

The buffeting response is a type of vibration caused by wind turbulence. As the bridge span and structural complexity increase, this kind of response is notable. Therefore more accurate analysis simulation methods are needed to investigate this aerodynamic phenomenon. The aim of this thesis is to review, discuss and compare the different bridge buffeting simulation approaches in the frequency domain and find the possibility of Computational Fluid Dynamic (CFD) method application in bridge buffeting prediction. In this thesis, the conventional bridge buffeting statistical analysis methods considering the influence of different parameters such as mode coupling, self-excited forces and aerodynamic admittance on the simulation results are firstly reviewed and compared. Since wind turbulence may not excite all structural vibration modes in some frequency ranges, an alternative approach based on the Proper Orthogonal Decomposition (POD) is proposed to study the effective turbulence contribution to the structural vibration. However due to the complexity of turbulence, quasi-steady theory is widely adopted and some semi-empirical functions such as aerodynamic admittance, joint acceptance are introduced to simplify the simulation. With the development of CFD method, CFD simulation of bridge aerodynamic phenomena has become possible. Since the bridge buffeting response is induced by wind turbulence, it is very important to capture the time varying characteristics of wind turbulence. In CFD technique, to close the Navier-Stokes equations and reflect unsteady characteristics, turbulence modelling is always adopted. At present Direct Numerical Simulation (DNS) is an accurate model to capture the time variation unsteady characteristic of the wind turbulence. However, the problems of civil engineering are always high Reynolds numbers, which make the simulation of aerodynamic phenomena of civil engineering impractical based on DNS method. Therefore an alternative model, known as Large Eddy Simulation (LES), becomes popular. In this thesis an unsteady inlet boundary generation technique based on an Autoregressive Moving Average (ARMA) model is proposed to simulate the unsteady inflow turbulence. 3D LES will be selected to validate the applicability of this model in the prediction of the unsteady characteristic of buffeting simulation by investigating the flow characteristic around a square cylinder under different mesh density and different LES model such as standard LES model, dynamic LES model and WALE model at Reynolds number 13,000. Before comparing the influence of inflow boundary condition with turbulence intensity (5%) on the flow around a square cylinder, an empty domain is selected to validate current inflow turbulence generation technique. Major steps of Fluid Structure Interaction (FSI), suitable for future simulation of bridge structural buffeting response, are proposed to predict the structural buffeting response induced by the inflow turbulence. To test the propose procedure of FSI, a square cylinder will be used, the across-flow oscillation of square cylinder with constant damping ratio will be considered to investigate the influence of steady inlet boundary condition and unsteady one on the response of structure. In addition different LES models are considered to compare their influence on the response of square cylinder.

As a the limit-cycle oscillation, vortex-induced vibration (VIV) does not cause catastrophic failure but it can lead to fatigue in long and slender structures and structural elements, especially for long span bridges. Assessing this behaviour during the design stage is therefore very important to ensure the safety and serviceability of a structure. Currently, this task requires very time-consuming wind tunnel or computational simulation since a reliable mathematical model is not available. Moreover, knowledge of the underlying physical mechanism of the VIV and, particularly, of the turbulence-induced effect on the VIV is insufficient. Turbulence is normally considered to produce suppressing effects on the VIV; however, this influence appears to depend on cross sections and a comprehensive explanation is yet to be found. This issue can be resulted from some limitation that most wind tunnel or computational studies have used sectional models. The flow field is therefore dominated by 2D flow features. In this research study, the 5:1 rectangular cylinder is selected as the case study since it is considered as the generic bride deck geometry. Using the wind tunnel at the University of Nottingham, a series of wind tunnel tests using a static and elastically supported sectional model is conducted in smooth flow. This wind tunnel study is complemented by a computational study of a static and dynamic sectional model; the computational simulations are carried out using the Computational Fluid Dynamics software OpenFOAM and the High Performance Computer system at the University of Nottingham. A Fluid-structure-interaction (FSI) solver is built to model the heaving VIV. By comparing the surface pressure measurement between these two studies, it uncovers the two separate flow mechanisms and associated flow features, which are both responsible for the VIV. The series of wind tunnel static and dynamic tests is also repeated in different turbulent flow regimes. By analysing the forces, moment, surface pressure and structural response, it reveals the mechanism of the turbulence-induced effect on the aerodynamic characteristics as well as on VIV. By improving the proposed FSI solver, a novel computational approach is introduced to simulate the VIV of a flexible 5:1 rectangular cylinder excited at the first bending mode shape. Employing the Proper Orthogonal Decomposition (POD) technique and comparing against results of the sectional model, some emerging span-wise flow features are revealed together with their influences on the mechanism of the bending VIV. The Hartlen and Currie mathematical model for the VIV is generalised so that it is able to simulate the VIV response of a 3D flexible structure. Such modifications and improvements are originated from and assessed by results of the computational simulation of the flexible model. A case study of the Great Belt East bridge is then carried out to verify this modified model.

Masonry arch bridges still play an important role in the transportation infrastructure today in the United Kingdom. Previous research has mainly focused on the load carrying capacity in the span direction. The three dimensional behaviour is often investigated by simplifying into two dimensions with modified arch parameters but these simplified analyses cannot represent all aspects of behaviour. Spandrel wall failure in some railway masonry arch bridges has raised concerns recently, and this is one aspect which cannot be modelled in two dimensions. This thesis presents a research which attempts to model the interaction behaviour between arch, backfill and spandrel wall with the aim of representing the three dimensional nature of real bridges. It mainly focuses on the spandrel wall defects under increasing load, including crack development across the wall and longitudinal cracks in the arch barrel underneath spandrel wall. Experimental results from the laboratory tests on engineering blue brick and a hydraulic premixed mortar as well as brickwork masonry specimens are presented. Numerical analysis was initially performed on these brickwork masonry specimens for validation. Three dimensional FE models were proposed for both small and large scale bridges. The general behaviour of the small scale bridge under rolling load and large scale bridge under increasing load were studied. Reasonable agreement between the FE analyses and experimental results from previous literature was obtained, indicating the model validated for small masonry specimens could be scaled up to full-scale bridges. A series of computer models were constructed to investigate the relationship between a range of geometric and material parameters and the lateral behaviour of arch bridges. The backfill depth and spandrel wall thickness have greatest impact on both bridge strength and lateral behaviour. The fill properties also have an importance influence on the load carrying capacity. This provides an indication of which bridge should be more closely monitored for spandrel wall defects. Separate FE models was constructed to simulate existing longitudinal cracks found in the arch barrel for old bridges and the influence of strengthening of spandrel wall with tie bars. The general behaviour under a concentrated load is studied and discussed. It has been demonstrated that it is possible to effectively model the three dimension behaviour of masonry arch bridges and in particular, spandrel wall failures.

Two novel demountable shear connectors for precast steel-concrete composite bridges are presented. The connectors use high-strength steel bolts, which are fastened to the steel beam with the aid of a special locking configuration that prevents slip of bolts within their holes. Moreover, the connectors promote accelerated construction and overcome typical construction tolerances issues of precast structures. Most importantly, the connectors allow bridge disassembly, and therefore, can address different bridge deterioration scenarios with minimum disturbance to traffic flow, i.e. (1) precast deck panels can be rapidly uplifted and replaced; (2) connectors can be rapidly removed and replaced; and (3) steel beams can be replaced, while precast decks and shear connectors can be reused. A series of push-out tests and a beam test were conducted to assess the behavior of the connectors and quantify the effect of important parameters. The experimental results showed that shear resistance and slip capacity can reach 2.5 and 2.7 times respectively of those of welded shear studs along with superior stiffness and strength against slab uplift. Additionally, shear stiffness of M16 mm LNSC was equal to that of M19 mm welded studs. Identical tests reveal negligible scatter in the shear load – slip displacement behavior. Design equations are proposed to predict the shear resistance with minimum deviations.

Bridge monitoring studies indicate that the quasi-static response of a bridge, while dependent on various input forces, is affected predominantly by variations in temperature. In many structures, the quasi-static response can even be approximated as equal to its thermal response. Consequently, interpretation of measurements from quasi-static monitoring requires accounting for the thermal response in measurements. Developing solutions to this challenge, which is critical to relate measurements to decision-making and thereby realize the full potential of SHM for bridge management, is the main focus of this research. This research proposes a data-driven approach referred to as temperature-based measurement interpretation (TB-MI) approach for structural performance evaluation of bridges based on continuous bridge monitoring. The approach characterizes and predicts thermal response of structures by exploiting the relationship between temperature distributions across a bridge and measured bridge response. The TB-MI approach has two components - (i) a regression-based thermal response prediction (RBTRP) methodology and (ii) an anomaly detection methodology. The RBTRP methodology generates models to predict real-time structural response from distributed temperature measurements. The anomaly detection methodology analyses prediction error signals, which are the differences between predicted and real-time response to detect the onset of anomaly events. In order to generate realistic data-sets for evaluating the proposed TB-MI approach, this research has built a small-scale truss structure in the laboratory as a test-bed. The truss is subject to accelerated diurnal temperature cycles using a system of heating lamps. Various damage scenarios are also simulated on this structure. This research further investigates if the underlying concept of using distributed temperature measurements to predict thermal response can be implemented using physics-based models. The case study of Cleddau Bridge is considered. This research also extends the general concept of predicting bridge response from knowledge of input loads to predict structural response due to traffic loads. Starting from the TB-MI approach, it creates an integrated approach for analyzing measured response due to both thermal and vehicular loads. The proposed approaches are evaluated on measurement time-histories from a number of case studies including numerical models, laboratory-scale truss and full-scale bridges. Results illustrate that the approaches accurately predicts thermal response, and that anomaly events are detectable using signal processing techniques such as signal subtraction method and cointegration. The study demonstrates that the proposed TB-MI approach is applicable for interpreting measurements from full-scale bridges, and can be integrated within a measurement interpretation platform for continuous bridge monitoring.

Masonry arch bridges have played a significant role in the road and rail transportation network in the world for centuries. They are exposed to damage due to overloading and deterioration caused by environmental actions. In order to reestablish their performance and to prevent their collapse in various hazardous conditions, many of them require strengthening. Fibre reinforced polymer (FRP) systems are increasingly used for repair and strengthening of structures, with particularly widespread application to concrete structures. However, the application of FRP composites to masonry structures is less well established due to the complexity of masonry caused by the material discontinuity. FRP strengthening masonry arch bridges has been even less studied due to the additional complexity arising from the co-existence of the normal interfacial stress and the shear interfacial stress at the curved FRP-to-masonry bondline. This thesis presents an extensive study investigating the behaviour of FRP strengthened masonry bridges. The study started with a laboratory test of a two span masonry arch bridge with sand backfill. A single ring arch bridge was first tested to near failure, and then repaired by bonding FRP into their intrados and tested to failure. It was found that the FRP strengthening not only improved the loading capacity and stiffness of bridge, but also significantly restrained the opening of cracks in the masonry. Shear and peeling debonding of FRP was observed. There have been two common strategies in finite element (FE) modelling of FRP strengthened structures in meso-scale: direct model and interface model. The former is necessary when investigating the detailed bond behaviour but challenges remain due to the difficulties in concrete modelling. A new concrete damage model based on the plastic degradation theory has been developed in this study to study the bond behaviour of FRP strengthened concrete structure. This robust model can successfully capture this bond behaviour and simulate the entire debonding process. A numerical study of masonry arch bridges including the backfill was conducted to study the behaviour of masonry arch bridge. A total of four modelling strategies were examined and compared. Although they all can successfully predict the behaviour of arch, a detailed solid model newly developed in this study is more suitable for modelling both plain masonry and FRP strengthened structures. Finally, a numerical study of bond behaviour and structural response of FRP strengthened masonry arch structures with sand backfill was conducted. In addition to the masonry and backfill, the mixed mode interfacial behaviour was modelled by the aforementioned interface model strategy and investigated in detail to achieve a deeper understanding of the behaviour of FRP strengthened masonry arch structures. The results are in close agreement with test results, and highlight the influence of the key parameters in the structural response to failure and revealed the mechanisms on how the load is transmitted through this complex multi-component structural system.