In a context of deteriorating civil infrastructure and limited funds available to ensure their functionality and safety, there is a need for accurate assessment methods leading to a better allocation of the available resources and a timely detection of abnormal behaviours. Nowadays, technological advances have enabled the acquisition of reliable monitoring data concerning environmental conditions, loadings and structural responses from civil infrastructure assets. With massive amounts of data generated by monitoring systems, the challenge lies on how to extract relevant information that can be used for an enhanced management of civil infrastructure. Motivated by this, the research presented herein is devoted to the development of data-based models and associated methodologies for monitoring data interpretation, assessment and probabilistic life prediction in the specific area of fatigue reliability of welded joints in orthotropic steel decks. Moreover, it contributes to the definition of temporal and spatial requirements for monitoring campaigns and to the assessment of their cost-effectiveness within the present work's application framework. The proposed data-based models, associated methodologies and analysis are illustrated using the monitoring data from the Great Belt Bridge (Denmark). Polynomial regression models are firstly developed to characterize the correlation patterns between environmental conditions (pavement temperatures), operational loads (heavy traffic counts) and a strain-based performance indicator proportional to S-N fatigue damage at monitored welded joints. Monitoring outcomes are also used to develop time series models for simulating the main actions contributing to the fatigue process under consideration, namely pavement temperatures and heavy traffic counts. A methodology for probabilistic fatigue life prediction is then developed by integrating the different data-based models within an S-N fatigue reliability framework. It is based on Monte Carlo Simulation to account for the uncertainty in random variables (e.g. material properties, fatigue model) and random processes (e.g. traffic, temperature) and estimate the remaining fatigue life of selected welded details. The developed method enables to quantify the effect of different scenarios in terms of changes in pavement temperatures and heavy traffic counts. Moreover, an algorithm based on statistical control charts defined by the prediction bands of the regression models is proposed for the interpretation of new monitoring data and the identification of abnormal behaviours, as part of an envisaged "real-time" assessment. Temporal and spatial requirements for monitoring campaigns are determined on the basis of the quantification of the epistemic uncertainty reduction provided by increasing monitoring datasets within the context given by the developed methodology for probabilistic life prediction. Finally, the benefit of monitoring techniques is assessed at different points in time through a posterior decision analysis. The work presented in this thesis provides a theoretical framework that could be adopted in assessing other structural components under different deterioration mechanisms, hence contributing to a wider and more effective use of monitoring-based techniques for enhanced infrastructure asset management.

The everyday passage of trains over railway bridges produces fatigue damage at critical bridge locations. The amount of fatigue damage accumulated is very sensitive to the stress ranges producing it. The passage of trains produces dynamic amplification of the internal stresses which depends on the train velocity. Therefore, it is imperative to have a reliable estimation of dynamic effects as these directly affect bridge member stresses. Although this topic is well treated in terms of plate girder bridges and dynamic effects considering the ultimate limit state, less literature is available on the case of tlUSS railway bridges and the fatigue limit state. This thesis addresses this gap of quantifying dynamic effects for everyday train passages and their interaction with the accumulation of fatigue damage in tlUSS railway bridges. Three-dimensional finite element (FE) analyses of a typical metallic tlUSS railway bridge are canied out under the passage of railway freight loading and the effect of different modelling parameters on the intemal forces is qhantified. Subsequently, dynamic amplification factors (DAFs) for all the bridge members are estimated from the FE analyses, under different load models and train velocities, and compared with their bridge code counterparts. Statistical analysis of the estimated DAFs is also employed to propose distributions that capture the variability of the DAF among the bridge members which can then be used for the purposes of probabilistic analysis. Lastly, the effect of dynamic amplification on fatigue damage is explicitly quantified by comparing the damage estimates obtained through the use of codespecific DAFs with the ones obtained in this study.

Masonry arch bridge building declined considerably in· the twentieth century due to the development of faster methods of construction, such as reinforced concrete. However, in recent years, the repair and maintenance of bridge structures has become a major concern. The lower maintenance costs and longer 'design life of arch bridges over alternative bridge designs were key reasons in the selection of several arch bridges built towards the end of the twentieth century and the beginning of the twenty first century. The FlexiArch design allows a masonry arch system to be cost competitive with other forms of bridge systems while offering superior durability and lower long term maintenance. The aim of this research was to extend the knowledge of the FlexiArch bridge system into the behaviour of FlexiArch bridge systems with skew and to address the shortfalls found in the literature review. The literature review demonstrated that skew arches are complex 3D structures, and that the assumptions used in current 2D analysis methods to define the effects in the transverse direction often incorrectly predict the behaviour of the skew arch. This research investigated the behaviour of the skew FlexiArch bridge system through a detailed experimental test programme. The experimental test programme involved the design, construction and testing of five third scale skew FlexiArch bridge systems with varying angles of skew. As the skew angle was increased, and the square span and square width were kept constant, the peak load decreased. The skew arch systems transferred the load along the shortest load path; namely the square span direction where possible, or the shortest distance in the highly skewed arch systems. The experimental test data was compared against an analytical model and a 3D NLFEA model, which were found to accurately predict the behaviour of the skew arch.

No description available.

Sustainable development is a key policy objective in many countries. Its aim is to promote systems/practices that provide a good balance between the often conflicting demands of modern society namely economic growth, protection of the environment and social progress for all. Highway bridges play a crucial role on our ability to maintain a sustainable economy by means of improving transport links, shortening journey times and thereby reducing energy consumption by vehicles. However, their construction and maintenance could cause considerable impact on our environment and communities. Many of those who are involved in bridge design, construction and maintenance are cautious of sustainability issues either spontaneously or under pressure from various instruments introduced by the government. However, there is a frustration at a noticeable lack of relevant sustainability appraisal metrics and data on design alternatives for effective project level decision making. An overview of the existing sustainability appraisal tools demonstrates that most of them are solely applicable to the building structures, predominantly focus on environmental issues and fail to aggregate the various dimensions of sustainability which makes it difficult to identify the most sustainable solution where several options exist. In order to address the above need, a new model for sustainability appraisal of bridge structures has been produced. The tool termed System for Appraising the Sustainability of Structures (SASS) is a pseudo-quantitative methodology which has primarily been developed to appraise bridge structures but it is sufficiently general that it could easily be adapted for use with other types of civil infrastructures. SASS allows for the separate life cycle assessment of relevant sustainability issues in a straightforward, transparent, rigorous and repeatable manner. It also includes a means of combining the impacts to provide an overall assessment of sustainability. A case study on three alternative designs of bridges is presented to demonstrate its use.

Integral bridges are monolithic and are known to possess good earthquake resistance when founded on a stable soil. One important consideration is the relative displacements which can occur at the support points on structures where there is significant spacing between, i.e. bridges. Factors such as soil, foundation types etc. can all influence the dynamic response, and the stiffness of the bridge can influence how relative displacements affect the internal force actions within the structure. In this study, the effect of earthquakes on integral bridges built on several different soil types is examined, through computer simulation of an integral abutment bridge. The study is made based on Eurocode 8 recommendations, which provides data for different types of soil to be used for earthquake analysis. A symmetrical medium length integral bridge obtained from an existing structure is used for the analysis. Artificial EC8 spectrum compatible time histories (with a 0.35 g peak ground acceleration) are applied to the structure for a range of soil stiffnesses. In conjunction with this, both static and dynamic relative displacement studies are carried out to develop insight as to the significance or dominance of either dynamic or relative displacement effects. The final aim of this study is to propose a simplified approach for design/appraisal which can allow predictions of dynamic response based on the results of static relative displacement studies coupled with simple computer models, without having to resort to full nonlinear integration time-history analysis. Synthetic time histories for 5 different types of soil were created using Mathcad. The synthetic acceleration time history was validated using Seismospect (by Seismosoft). The time histories were then used to carry our full integration time history analyses in ANSYS (engineering simulation software) to simulate the dynamic response of the bridge. The results show that relative displacements play an important role in overall structural response of the integral bridge, compared to the pure dynamic response. The results also confirm that lower stiffness soils suffer a more detrimental effect of the earthquake compared to a soil of higher stiffness.

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No description available.

No description available.

About 40% of bridges in European transport network are masonry arch bridges (most built over 100 years ago) and are being subjected to increasing loading regimes. Assessment of the long-term fatigue capacity of masonry bridges is necessary to ensure that increased traffic loading does not result in premature deterioration and/or reduce their life expectancy. The study investigates the influence of compressive fatigue loading on the behaviour and mechanical properties of soft brick masonry, relevant to the structural loadbearing elements, for example the arch ring in canal masonry bridges. Masonry prisms were tested (n=70) under quasi-static and long-term fatigue loading to collect information on the number of loading cycles under a range of stress levels, changes in the stress-strain curves, evolution of strain and Young’s modulus during fatigue deterioration. Laboratory tests were performed under maximum stress levels between 55–80% of the compressive strength, at 2Hz frequency for a maximum of 107 loading cycles. Test data were analysed to develop analytical expressions to predict the response of masonry under fatigue loading. Test results reveal that fatigue deterioration is characterised by three distinct stages in strain evolution and stress-strain curves. The Young’s modulus decreased by 25%, while the maximum recorded strain increased up to 5.25 times. An expression for the stress - number of cycles - probability (S-N-P) curves was proposed based on probabilistic analysis to predict the fatigue life of masonry at any desired probability. A set of three formulas were developed to predict strain evolution at different stages of fatigue life and a linear equation was derived for the evolution of the Young’s modulus. The proposed S-N-P model can provide numerical data for fatigue analysis of masonry arch bridges, e.g. for the SMART method to evaluate the remaining service under any traffic loading level. The rate of change in strain can provide useful reference data for long-term monitoring to identify the stage of the fatigue life the structure is experiencing. A reduction factor for the Young’s modulus between 0.9–0.75, depending on the stress level, can be used for assessing masonry arch bridges under fatigue loading. As consequence, it is recommended that the evolution laws of the mechanical properties of masonry can be used for finite element software packages to develop time-dependent models for the analysis of masonry under fatigue.