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Masonry arch bridges, despite their age, are still fundamental structures in transport networks throughout Europe, especially for railways. Furthermore, these bridges are often found in seismic-prone areas, such as Italy. Developing of specific fragility models is of fundamental importance for large-scale seismic risk assessments of these structures and related transport networks. Unlike other types of bridges, for which significant progress has been made in assessing their seismic vulnerability and fragility, comparable results for masonry arch bridges are not fully available. Moreover, a realistic risk assessment of masonry bridges should account for deterioration and damage, which most of these bridges have developed being more than 100 years old and often in a poor state of maintenance. Therefore, this work intends to provide seismic fragility models for two generalised classes of single-span masonry arch bridges, i.e. segmental and semi-circular, taking into account their potential degradation through 2 D finite-element modelling and parametric nonlinear static analyses. Material loss from the intrados of the arch, material degradation, and longitudinal cracks on the arch barrel vault are investigated as typical defects. Overall, the seismic fragility of masonry bridges increases appreciably when the effects of degradation are considered, the loss of material being the most influential defect. [ABSTRACT FROM AUTHOR]

Today, there are a large number of masonry arch bridges in service within railway networks. These old infrastructures have been designed for service loads in the past 100 years. Owing to increased service loads, it is essential to investigate the behavior of masonry arch bridges. Several empirical, analytical and numerical studies have been conducted to estimate the residual capacities of masonry arch bridges. The present study aims to employ the extended finite element method (XFEM) to obtain the ultimate capacities of old arch bridges for the first time. By adopting a non-geometric approach in fracture mechanics and defining initial structural defects, XFEM can easily predict the failure and ultimate capacity of a structure by using the crack growth pattern. Thus, the present study made use of two ageing railway arch bridges that are known to be cracked structures to build a three-dimensional XFEM model. The ultimate capacities and safety factors of the bridges are studied by defining several initial defects in different conditions. Finally, using experimental outcomes, the nonlinear finite element method along with the concrete damaged plasticity model are exploited to validate the results. The results indicate that XFEM agrees very well with the other methods. Considering its unique flexibilities, XFEM can be employed effectively and efficiently to analyze ageing cracked masonry arch bridges. [ABSTRACT FROM AUTHOR]

Seismic structural assessment of masonry arch bridges is essential due to their cultural, economic and strategic importance and vulnerability. A realistic and rigorous structural assessment is necessary in order to protect the bridges and use resources carefully. At this time, there are no standardised or widely accepted assessment procedures, and the performance criteria for masonry arch bridges are not available. This study presents an overarching reliability-based seismic assessment methodology based on analytical modelling, laboratory testing and probabilistic assessment. It investigates the performance criteria concept and proposes performance limit states. The methodology is applied to a historical masonry arch bridge in Turkey. To consider rigorously the uncertainties in material properties and seismic input, probabilistic nonlinear analyses are conducted using a detailed 3D finite element model. The results are combined with the proposed limit state definitions to generate the capacity and demand distributions. Both distributions are used in Monte Carlo simulation and First-Order Reliability Method (FORM) to estimate the probability of exceedance and reliability indexes for each limit state. The proposed probabilistic assessment methodology will be a useful approach to obtaining more reliable information about masonry arch bridges' expected seismic performance and for better-informed decision-making, especially when designing intervention actions and post-earthquake scenarios. [ABSTRACT FROM AUTHOR]

A probabilistic analysis approach for reliability-based assessment of masonry arch bridges is presented in this work. The methodology is tested on a medieval in-service construction located in Galicia, northwest of Spain. To estimate its ultimate load-carrying capacity, two different numerical approaches are employed; a three-dimensional non-linear finite element model and a two-dimensional rigid blocks limit analysis model. Aiming to alleviate the computational burden associated with the probabilistic analysis procedure, a surrogate modelling strategy is adopted. A complete understanding of the influence of model input parameters on the limit load of the structure is attained through the employment of global variance-based sensitivity analysis. The reliability assessment procedure is subsequently carried out, allowing to estimate the bridge failure probability. A difference of approximately 33% is obtained between the reliability index values drawn from both structural modelling strategies, so revealing the key role played by transversal effects on the strength capacity of masonry arch bridges. The proposed probabilistic assessment framework might be deemed as a useful tool, from which more reliable and objective information about the actual safety condition of existing masonry arch bridges can be derived, taking advantage of readily available numerical tools, but still demanding an affordable computational effort. [ABSTRACT FROM AUTHOR]

The response up to collapse of masonry arch bridges is very complex and affected by many uncertainties. In general, accurate response predictions can be achieved using sophisticated numerical descriptions, requiring a significant number of parameters that need to be properly characterised. This study focuses on the sensitivity of the behaviour of masonry arch bridges with respect to a wide range of mechanical parameters considered within a detailed modelling approach. The aim is to investigate the effect of constitutive parameters variations on the stiffness and ultimate load capacity under vertical loading. First, advanced numerical models of masonry arches and of a masonry arch bridge are developed, where a mesoscale approach describes the actual texture of masonry. Subsequently, a surrogate kriging metamodel is constructed to replace the accurate but computationally expensive numerical descriptions, and global sensitivity analysis is performed to identify the mechanical parameters affecting the most the stiffness and load capacity. Uncertainty propagation is then performed on the surrogate models to estimate the probabilistic distribution of the response parameters of interest. The results provide useful information for risk assessment and management purposes, and shed light on the parameters that control the bridge behaviour and require an accurate characterisation in terms of uncertainty. [ABSTRACT FROM AUTHOR]

The development of a condition-based deterioration modelling methodology at bridge group level using Bayesian belief network (BBN) is presented in this paper. BBN is an efficient tool to handle complex interdependencies within elements of engineering systems, by means of conditional probabilities specified on a fixed model structure. The advantages and limitations of the BBN for such applications are reviewed by analysing a sample group of masonry bridges on the UK railway infrastructure network. The proposed methodology is then extended to develop a time dependent deterioration model using a dynamic Bayesian network. The condition of elements within the selected sample of bridges and a set of conditional probabilities for static and time dependent variables, based on inspection experience, are used as input to the models to yield, in probabilistic terms, overall condition-based deterioration profiles for bridge groups. Sensitivity towards various input parameters, as well as underlying assumptions, on the point-in-time performance and the deterioration profile of the group are investigated. Together with results from ‘what if’ scenarios, the potential of the developed methodology is demonstrated in relation to the specification of structural health monitoring requirements and the prioritisation of maintenance intervention activities. [ABSTRACT FROM PUBLISHER]

This article presents the characterization of a mediaeval bridge located in Fillaboa, Galicia (northern Spain). The study of this bridge involves data acquisition about the structure (geometry, visual inspection of damages, and nondestructive testing), the evaluation of the possible damage mechanisms compatible with the observed cracks and fissures, and the dynamic evaluation of the structure. This bridge is a masonry four-lancet arches bridge, with damage on the piers and abutments. Two non-invasive methodologies are applied to obtain information about the bridge: ground-penetrating radar (GPR) survey and ambient vibration noise measurements. The drawings of the structure were created using close-range photogrammetry (CRP). A finite elements model of the structure was obtained prior to the vibration field measurements, as a preliminary evaluation. Data obtained from GPR and the geometry determined with CRP were the information used in this preliminary model of the bridge. This model was improved using the dynamic field test to compare model behavior and to validate the numerical results. A second and more accurate model was then obtained by using finite elements according to the experimentally measured modal frequencies (the possible first three transversal vibration modes of the bridge). [ABSTRACT FROM AUTHOR]

Notwithstanding its potentially high level, the seismic vulnerability of masonry arch bridges has yet to be completely perceived, possibly due to the relatively scarce damage evidence collected after recent earthquakes. The dearth of research studies on this topic is thus one of the main motivations behind the current endeavour, which aims at a better understanding of the dynamic interaction between the arch walls and the filling material of typical masonry arch bridges, and the consequent susceptibility of the latter to out-of-plane collapse mechanisms. Within this framework, a numerical model for the evaluation of the seismic out-of-plane capacity of bridge walls, including the effects of the infill material, is proposed. This methodology can be subdivided into three main components; computation of static earth pressure, evaluation of dynamic soil thrust, assessment of out-of-plane capacity of a masonry wall. In addition, a congruent and relatively simple procedure for the estimation of the seismic demand on the arch wall is described. Finally, a parametric study is carried out with a view to appraise the seismic vulnerability associated to typical masonry arch bridge typologies. [ABSTRACT FROM AUTHOR]