Masonry Arch Bridges Research Articles

On the Structural Safety of Saddling Technique for Strengthening of Masonry Bridges: Design-Oriented Parametric Study and Practical Application

ABSTRACT An effective and versatile method for improving the load-bearing capacity of masonry arch bridge is the use of the saddling technique consisting in replacing the existing backfill with in-situ poured concrete. However, this technique is seldom utilized in practice because it can be considered dangerous for the overall stability of the bridge while executed. The primary objective of this research is to evaluate the structural safety of masonry arch bridges with various geometrical configurations during the execution of the saddling technique. To achieve this objective, the study uses a step-by-step simulation approach to analyse the structural safety of the bridge during each stage of the saddling process. The process is in-depth simulated for a reference bridge, and then extended to several configurations to investigate the effect of bridge geometrical parameters on structural safety. The research findings demonstrate that, for conventional masonry bridges, the saddling technique can be safely executed with a high degree of safety. The paper concludes with the practical application of the saddling technique to the Langa de Duero bridge in Spain. The results of this research would promote the wider adoption of the saddling technique as an effective, durable, and safe method for strengthening masonry bridges.

A study of stone arch bridge’s flood reliability through a surrogate model approach

Europe’s historic masonry arch bridges are culturally and economically significant, but their long-term safety must be ensured. Scour effects are the most common cause of collapse, so it is necessary to carry out structural assessments to mitigate the risk and prevent potential failures. In this study, a metamodel-based method was used to determine the probability of failure of an existing stone arch bridge in Portugal due to local and contraction scour on the abutments. Non-linear finite element analysis supported the calculation of the reliability index, which took into account the soil-structure interaction and the failure mechanism. The variables with the greatest influence on the load-carrying capacity of the structure were identified and a surrogate model was implemented. Fragility curves were then derived based on the surrogate model, using scour depth as a measure of intensity and load factor as an engineering requirement parameter. The results of the study indicate that the load capacity of the numerical model is compromised when the scour depth of 1.5 m reaches the base of the foundation. As a result, stability problems and settlements are observed in the model. At a depth of 2.5 m, the soil reaches its ultimate bearing capacity.

Enhancing the fiber-based modeling approach for flexure-shear behavior in seismic evaluation of long-span railway masonry arch bridges

Masonry arch bridges are considered a significant part of the rail and road transportation infrastructures in many countries, and seismic assessment of these structures is of great importance for increasing their resilience. Despite some shortcomings in comparison to more complicated modeling techniques, i.e. continuous and discrete techniques, one-dimensional continuous modeling approaches such as the fiber beam approach are more practical for engineering purposes. Although the fiber models can acceptably predict the axial and flexural behavior of structural members, shear or flexure-shear failure behavior, which could be one of the dominant failure modes in masonry structures, cannot be predicted appropriately in this approach. The purpose of this article is to enhance fiber-based modeling approach to consider these brittle failure modes for the seismic assessments of long-span masonry arch bridges. Using the existing analytical-empirical prediction equations reported on the results of stone masonry walls, an iterative approach is proposed to enhance fiber-based model to include flexure-shear interaction. the proposed method is verified with a series of arch samples with different geometric properties with results from discontinuous models of the sample arches. Following that, different models of a span of a case-study masonry arch bridge is created, verified with health monitoring field observation, and analyzed to compare from different aspects and validate the application of the fiber beam method along with its enhancements. The results of the proposed method for fiber models show promising conformity with the results of more precise numerical models, and it can be used for the seismic evaluation of long-span stone masonry bridges.

Vulnerability assessment and lifecycle analysis of an existing masonry arch bridge

This paper presents a comprehensive study on structural verification and proposed improvements for an ancient masonry arch bridge. The research encompasses multiple stages, starting with a detailed survey utilizing LiDAR and aerial techniques to collect precise data on the bridge’s condition. Mechanical inspections assess deterioration levels and identify critical areas requiring attention. Based on the gathered data, a structural model of the bridge is developed, considering geometric parameters and material properties. The model undergoes rigorous verification procedures to assess its seismic response and ensure compliance with safety standards. The analysis includes identifying potential collapse mechanisms, such as the formation of plastic hinges, which can lead to structural failure. The study proposes structural improvements to enhance the bridge’s performance and safety. These interventions specifically target vulnerabilities identified during the verification process. They include additional support elements, reinforcing critical areas, and utilizing advanced materials to improve tensile strength and durability. The feasibility of the proposed retrofitting solutions will be proved by performing a cost analysis, while environmental impacts are evaluated through an environmental assessment (Lifecycle Assessment — LCA) in which all the main bridge refurbishment phases have been included. Finally, some of the advantages of bridge refurbishment measures are shown by comparing the proposed intervention with a bridge reconstruction in terms of costs and environmental impacts. The outcomes of this study contribute to the existing knowledge on the rehabilitation of masonry arch bridges and serve as a valuable reference for engineers and practitioners involved in preserving architectural heritage.

Risk assessment and rotation monitoring of a masonry arch bridge according to the Lombardia Regional Guidelines

Within a recent project between Politecnico di Milano and Regione Lombardia, a methodology was developed for the structural/hydraulic risk assessment and monitoring of bridges. In the paper, the methodology is applied to a historical masonry arch bridge called the Candia bridge. The bridge is known to be affected by riverbed erosion; consequently, the definition of a monitoring system to detect scour-induced effects is addressed. In the present study, measurements of the pier rotations are performed using tiltmeters; in addition, environmental parameters (such as temperature, water level and riverbed changes) are monitored to check possible correlation with the measured rotations. The results from the first two years of monitoring highlight anomalous changes in the rotation-temperature correlation of various piers.

Multi-hazard assessment of a masonry railway bridge in landslide areas

Earthquakes and landslides pose a high risk to road infrastructure due to unfavorable geological conditions in conjunction with extreme climate events. In particular masonry arch bridges are very often affected by natural events such as floods, landslides, and earthquakes, causing the partial or total collapse of the bridge. To determine the vulnerability to the multiple hazards related to a specific area, a multidisciplinary approach that allows to analyze the different issues is needed. Non-destructive survey strategy based on the study of geo-morphological area, in situ tests and accurate numerical modelling are required to perform a multi-hazard vulnerability assessment of a masonry bridge in a landslide area. In this paper, a multi-disciplinary multi-sensor methodology is proposed based on photogrammetric and thermographic surveys, for the definition of an accurate georeferenced three-dimensional geometrical models of the bridge for a reliable definition of a numerical model to be adopted for the structural assessment of the bridge consistent to a multi-hazard scenario. Namely, a discrete macro-element models (DMEM) based on the software HiStrA Bridge has been applied to determine the soil-structure interaction associated to landslides events. The masonry arch railway bridge chosen for this study is located in a complex geological and geomorphological context. In fact, earth landslides affecting the bridge and poor physical-mechanical characteristics create the conditions for a complex case study. The objective of this study is to assess the vulnerability of masonry bridges subject to the combined effects of landslides, and hydraulic hazard due to bridge occlusion by the modeling of these effects.

Post-tensioning system as a strengthening solution for masonry arch bridges: numerical and experimental results

One of the most common bridge typologies in roadway and railway networks in Italy is the masonry arch bridge, typically built more than a hundred years ago. To keep these structures operatives with increasing traffic load, strengthening interventions are required in some cases. The solution investigated in this work is the external post-tensioning system, which consists of applying external loads to the arch by means of tensioned cables, resulting in a better configuration of internal forces. An experimental campaign was conducted on pre-damaged single span masonry arches by anchoring the cables to the intrados of the arch. The results of cyclic eccentric vertical load tests show an increase in displacement and load-carrying capacity. Numerical tests were performed to validate the experimental results using the rigid-block analysis method. The comparison between the experimental and numerical results is reported in terms of limit load capacity.

Refined modelling methods of structural reinforcements in the analysis of masonry bridges

Masonry arch bridges constitute a large part of today’s Italian architectural heritage. Italy has the highest percentage in Europe of masonry railway bridges with respect to the total. Due to the processes of degradation and to the increased levels of the loads and of the safety requirements, rehabilitation and retrofitting of these bridges is required. Among the available reinforcement techniques, the use of reinforcements with mortar/cement matrix fiber nets has gained great popularity due to the advantages shown over traditional techniques in terms of strength and durability. The FRCM, acronym of “Fiber Reinforced Cementitious Matrix” is a valid reinforcement alternative to the use of polymeric matrix reinforcements, due to its greater compatibility with the masonry support. The Italian technical standards suggest a simplified method for the design of the reinforcement based on empirical coefficients that increase the mechanical properties of the masonry materials, disregarding the consideration of the complex crisis mechanisms occurring, especially in more complex systems like the multi-arch bridges.The object of this work is the definition of a more refined and efficient method for the numerical modeling of FRCM reinforcement in the structural analysis of multi-span masonry arch bridge. Specifically, an equivalent reduced nets embedded in a mortar continuum determined with the area equivalence principle.The model is calibrated based on experimental characterization tests carried out on PBO-Mesh, and on the constituents. A validation test of the model is performed with reference to arch models reinforced with PBO-Mesh experimentally tested.The effectiveness of the proposed approaches is verified analyzing the seismic behavior of a masonry multi-span bridge, also considering the soil-structure interaction.

Dynamical features and FE modelling of a multi-span historical masonry arch bridge

The Italian road infrastructural asset includes a large number of historical masonry arch bridges. Many of these structures are today still in service, despite their ancientness and the frequent lack of maintenance and upgrading interventions. Given the strategic role they often play in the road network, their protection and conservation are an urgent priority to avoid connection issues, as well as losses of human lives. The structural assessment of these structures may be far from trivial since original design documents are generally missing. Thus, they must be subjected to articulate knowledge processes, which include geometrical surveys (both externally and internally), tests on material and, if possible, characterization of the overall dynamic behavior. Based on this premise, in the present paper the case study of a five-span masonry arch bridge in Mignano Monte Lungo (Caserta province, Italy) is addressed. A preliminary historical reconnaissance was performed together with a survey of the external geometry of the bridge. The collected data were enriched by means of a dynamical characterization of the entire structure, which allowed for realizing a preliminary finite element model in Abaqus software.

Structural Assessment of a Masonry Arch Bridge before and after a traditional inner arch retrofitting technique

To assess the structural behaviour of masonry arch bridge and identify the occurrence of damage reliable numerical models to perform accurate nonlinear structural analyses are needed. The innovative strategy known as Discrete Macro-Element Model (DMEM) is here employed to simulate the performance of a masonry arch bridge before and after a traditional structural retrofitting. The adopted numerical strategy assures a geometrically consistent model characterized by a very low computational burden and reliable results. As case study, a masonry arch bridge located in Maletto (Italy), belonging to the rail network, around Etna volcano, called Ferrovia CircumEtnea (FCE). The bridge has been built in 19th century and was subjected to a structural retrofitting in 1984, because of a light settlement of the central pier due to landslide. The bridge was reinforced with the introduction of a supplemental thin inner reinforced concrete arch, at the intrados of the existing stone arches, externally confined by an external steel corrugated thick plate also used as formworks. In this paper the HiStrA bridge software, where the DMEM is implemented, is used for providing a structural assessment of the bridge in its original configuration and after the structural retrofitting. Both push-down and push-over analyses are performed clearly showing the efficacy of the adopted traditional retrofitting strategy.

Modelling a reinforced concrete arch bridge by means of the Discrete Macro-Element Model: the case of Giovanni XXIII bridge in Ragusa

Numerical modelling of reinforced concrete structures in the nonlinear field requires the adoption of sophisticated although robust models. When it comes to bridges, to obtain an accurate numerical model uniaxial elements should not be employed due to geometrical inconsistency. Two- or three-dimensional elements are more appropriate even though the explicit modelling of concrete and steel bars can make the simulations too cumbersome for many practical applications. In this study, the Discrete Macro-Element Model (DMEM), implemented in the software HiStrA, initially introduced for the nonlinear modelling of existing masonry structures and also applied in the case of masonry arch bridges, is extended for modelling reinforced concrete structures. The presence of rebars is explicitly accounted for by introducing their contribution in the interface elements. The original modelling strategy is here applied to the Giovanni XXIII bridge in Ragusa (Italy), a road reinforced concrete supported deck arch bridge located in the city centre. The structure is currently a case study identified within an accurate survey and permanent health monitoring installation designed within the MonVia Project funded by the Italian Ministry of Economic Development. The results reported in this paper are relative to numerical simulations where the mechanical parameters of the linear elastic model are calibrated to match the experimental dynamic properties of the structure while the nonlinear parameters are consistent with those reported in the original design of the bridge. Nonlinear static analyses are performed considering both operational and seismic load configurations. The results could be used to define the threshold levels to be considered for the health monitoring of the bridge.

Understanding the response of masonry arch bridges under different scour scenarios

In the last decades, several flood-induced bridge collapses have been registered all over the world, in particular related to local scour phenomenon. Masonry bridges, which constitute the most of the existing infrastructure heritage worldwide, are significantly sensitive to this problem because of their high stiffness and typically shallow foundations. With the aim of helping to understand the response of masonry arch bridges under scour actions, this paper proposes a numerical study on a real case study. A 3D finite element model of the bridge is developed in Abaqus accounting for both mechanical and geometrical nonlinearities, then two possible scour scenarios are simulated by following a consolidated procedure proposed in previous works and the damage mechanisms activated at different scour levels are analyzed and discussed.

Nutcracker Deformation Of Arch Bridge In Consequence Of Slow Gravitational Slope Deformations

Italy is a geologically young territory and still subject to tectonic actions and orogenic thrusts, originating a significant and continuous geomorphological evolution. This is expressed both by landslides and by phenomena of slow deformation of the slopes. These are sometimes seemingly imperceptible deformations, which however can potentially lead to long-term damage to infrastructure, as for the case of the famous Lagonegro bridge. Very small deformations that modern technologies allow us to objectively document and monitor by satellite images. These images, when appropriately analyzed and elaborated, contribute to the understanding of the dynamics of territory.This work presents a set of cases related to arch bridges deformed by slow but continuous thrusts linked to gravitational phenomena which give rise to compressive deformations of the abutments which can give rise to deformations of the bridges which can be defined as "nutcracker". In this work, a roundup of Italian examples of how slow gravitational slope deformations can lead to the collapse of bridges is reported. It is also presented a preliminary investigation on bridge deformation based on satellite techniques. It is briefly presented the case of Albiano-Magra bridge in Tuscany, which collapsed in April 2020, and the case of the Lagonegro bridge which was dismissed since 1952. Other cases presented are the former FFSS 12-arch bridge of the old Paola Cosenza railway line, cases of masonry arch bridges in Basilicata along provincial roads 154 and 103 in the province of Matera and the case of the former FAL bridge of Cassano to the Ionian Sea in the province of Cosenza. These are all examples of how slow deformations can affect arch bridges creating the condition for the failure or for the final compromission of the bridge.

In-situ testing and modeling of a masonry bridge in Surrey (UK): Waverley Mill bridge

Many historic masonry arch bridges on road and railway systems across Europe and the United Kingdom remain operational despite exhibiting structural loss of performance. In the United Kingdom alone, there are more than 70,000 masonry arch spans, with many having undergone design modifications and load adjustments over the years. These modifications typically entail incorporating new materials and bearing elements, with compliance to modern standards being unsuitable and rare. Such circumstances lead to limited understanding of these structures, impacting the accuracy of the bridge capacity assessments. This study is dedicated to the examination of a composite bridge composed of two spans with limited accessibility, located in Waverley Abbey, Surrey. The research (reviews/investigates) two primary aspects: firstly, the diagnostic phase involving in-situ non- destructive methods such as Ground Penetrating Radar (GPR) and more intrusive techniques like coring. The second phase entails a numerical assessment using a limit analysis numerical model which considers several modelling assumptions including flooded conditions, ring separation and accounting for defects. In the future, discontinuity layout optimization (DLO) and structural health monitoring (SHM) techniques can be used to extend the scope of the traditional rigid block limit analysis method and useful for calibrating numerical models and performing direct checks of performance goal compliance. As the Waverley bridge serves as a representative example of the numerous structures predominantly found in the Surrey region, this investigation can be extended to include bridges sharing similar material, geometry and shapes.

Structural health monitoring of a masonry arch bridge: modal identification and model updating

Structural health monitoring of a masonry arch bridge: modal identification and model updating

Application of Digital Image Correlation to Field Monitoring of Masonry Arch Bridges

Many masonry bridges constructed in Europe during the Industrial Revolution are still in service. For over a century, continuous operation and weathering effects have contributed to material degradation in the main bridge components. To ensure that old masonry bridges remain safe even under increasing traffic loading, it is crucial to identify potential deterioration in bridge performance before the onset of critical irreversible damage. This task can be accomplished via periodic monitoring of the bridge response under traffic loading. Digital Image Correlation (DIC) is an effective non-contact method to measure displacements and strains. Most DIC applications have been in laboratory settings, and DIC techniques have yet to be extensively applied in the field. This paper showcases the potential of DIC monitoring for serviceability assessment of masonry bridges. Some results of an extensive monitoring program on railway viaducts in the UK are presented. Structures with different geometrical characteristics, including pier heights, span lengths, and span-to-rise ratios, have been investigated. The results obtained using specific targets attached to the monitored structures or using the actual masonry texture as natural targets have been compared; consideration is also given to the influence of camera characteristics and settings. A significant impact of the camera depth of field has been established, especially when measuring deflections at different locations on the intrados of the arch barrel.

The Effects of River Torrents and Debris on Historic Masonry Vaulted Arch Bridges

The carrying capacity for vertical loads of well-maintained masonry arch bridges is reasonably high. This might not be the case for horizontal loads, the effects of which have not been the subject of extensive research aside from seismic occurrences. Arch bridges crossing rivers are subjected to sudden horizontal loads, due to river torrents, carrying debris from higher grounds. The magnitude of these horizontal loads is similar to those of coastal waves and debris; however, their effect on these structures has yet to be explored in detail. The narrow and high Devil’s Bridge across the Arda River (BG) and the wide, low Candia Viaduct across the Sesia River (I) were chosen as examples. Both are strongly exposed to fast-washing flow in the river during spring. FE simulations show that the impact of the rapidly rising river water influences the general stability, while the effect of debris mainly causes local damage. The results exhibit that tall, slender masonry arch structures fail due to the brittle fracture of the material, followed by the shear failure of a pier body. In contrast, lower and wider viaducts fail due to exaggerated tensile cracking in the upstream parts of a pier and the associated increasing pressure at its downstream parts.

Evaluation of strengthening efficiency based on combined global and sectional response of masonry arch bridges

The paper is focused on the numerical analysis of the efficiency of strengthening solutions dedicated to masonry arch bridges. An overview of common strengthening methods is described covering the most frequent techniques and their influence on the bridge’s structural behaviour. The numerical study concentrates on the longitudinal behaviour of the arch of single-span bridges. The applied methods are related to the addition of specific structural components on both sides of the arch – extrados and intrados. Two basic solutions are studied based on a rigid or flexible layer corresponding to the most common techniques being applied to these bridges around the world. A comparison of the selected strengthening techniques is given considering their impact on the bridge’s structural behaviour under incremental static loadings. Structural details of the solutions are given as well as their efficiency is evaluated through analytical and numerical analyses. Advanced nonlinear Finite Element models using a meso-modelling technique are presented and selected results showing the mechanical performance of the structure before and after strengthening are provided. The interpretation of the bridge model response parameters, representing the increment of resistance given by the addition of each reinforcement solution, is based on the analysis of the evolution of the structural failure modes up to the maximum load capacity of the bridges, namely in terms of the interaction of internal resistant forces M-N in representative arch cross-sections determined also analytically. Conclusions are formulated to identify optimal reinforcement solutions through the ratios of the maximum load capacity of strengthened and unstrengthened bridge cases, and the ratios between the areas of the M-N interaction diagrams of strengthened and unstrengthened solutions.

Long-term monitoring of a masonry arch bridge to evaluate scour effects

Evaluating the scour effects on masonry arch bridges is of utmost importance to ensure the continued operational safety of those infrastructures. Even if numerical and laboratory studies have demonstrated the possibility of detecting scour-induced effects by measuring the structural response of masonry bridges, there is a lack of long-term monitoring applications on real structures. Within this context, the paper presents selected results obtained during two years of continuous monitoring of a historical masonry arch bridge to evaluate scour-induced effects. Firstly, on-site inspections of the bridge revealed severe foundation erosion and extensive documentary research was carried out to identify the depth of the foundation level. Subsequently, a monitoring system was installed in the bridge, including several MEMS-based tiltmeters, 1 echosounder, 1 hydrometer and 1 weather station. The correlation between measured rotations and environmental parameters is investigated and a linear regression model is used to minimize/remove temperature-induced effects. The residual errors between measured and predicted rotations highlighted the occurrence of various anomalies.

Structural Modal Calibration of Historical Masonry Arch Bridge by Using a Novel Deep Neural Network Approach

Structural Modal Calibration of Historical Masonry Arch Bridge by Using a Novel Deep Neural Network Approach