Arch Barrel Research Articles

The 3d response of a large-scale masonry arch bridge - part I: Performance under low and medium loading levels

Masonry arch bridges are characterised by three-dimensional (3D) behaviour when subjected to external eccentric loading (e.g., vehicle loads). The arch ring, abutments, backfill and spandrel walls may interact with each other in a complex manner, leading to a 3D mode of response that can have a significant impact on the initiation and propagation of damage. However, there is a dearth of experimental data from tests designed to investigate the 3D behaviour of masonry arch bridges, particularly under loading levels below those required to cause failure. This paper presents results from tests on a large-scale brickwork masonry arch bridge subjected to low- and mid-level static loads under laboratory conditions. Point loads of increasing magnitude were applied at different locations on the top of the backfill in order to investigate 3D response and damage accumulation. Details of the experimental setup, material characterisation, and the results obtained from static and repeated load tests at low- and mid-level load magnitudes are presented herein. Results demonstrate that the bridge exhibited a 3D mode of response under eccentric point loads. Loading at the mid-span resulted in greater deformation of the arch barrel compared to loading at the quarter- and three-quarter-span points, due to the shallower backfill depth over the crown. Under the mid-level loading, stiffness degradation was observed during the testing regime, suggesting an accumulation of damage in the bridge. Moreover, when loading was applied close to a spandrel wall, measurable out-of-plane deformation of the spandrel wall was observed, with this deformation increasing significantly as the load was increased from 150 kN to 250 kN. This results from a combination of increased lateral soil pressure and decreased shear resistance at the arch-spandrel wall interface.

The 3D response of a large-scale masonry arch bridge – Part II: Performance at failure

Masonry arch bridges continue to form a pivotal part of the transport networks of the UK and many other countries worldwide. However, their three-dimensional response (3D) under loading has to date been relatively little investigated. Here, details of a large-scale masonry arch bridge load tested to failure under laboratory conditions are presented. The bridge consisted of a brickwork arch barrel, abutments, spandrel walls, and compacted limestone as backfill material. Patch loading was applied to the surface of the backfill at the quarter and three-quarter span points to assess the failure mechanism, load-carrying capacity, and residual strength of the bridge. A range of sensors were employed to capture the 3D bridge response and ground-penetrating radar surveys were performed on both the virgin and load-tested bridge to compare its internal structure. The observed evolution of cracks and post-test deformed geometry demonstrated the presence of both a localised 3D mode of response in the arch barrel in the vicinity of the applied load and a global four-hinge mechanism. Failure-level load tests carried out first at the quarter span and then at the three-quarter span points showed that the load-carrying capacity of the bridge had reduced by only 10 % in the second test, though the stiffness of the bridge had decreased by around 35 %. During the failure-level load tests, significant in-plane and out-of-plane deformations of the spandrel walls were also observed, adding to the much smaller residual deformations recorded in low- and mid-level load tests.

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.

A novel retrofitting strategy for restoring railway masonry arch bridge undergoing failure by settlement due to scouring

Arch is most possibly one of the oldest structural forms used for bridge superstructures, especially for masonry bridges. Masonry arch bridges are the longest serving structural systems among the railway bridge population most of which are still performing well. To preserve our heritage and to utilize these bridges to their maximum capacity, understanding the behavior and assessing the integrity of arch bridges is vital. Proper maintenance of these bridges will improve the service life of these structures instead of rebuilding with new structure. In this paper, failure investigations are carried out on an old railway stone masonry arch bridge which is severely damaged due to heavy floods during the monsoon. Due to excessive scouring of the soil, uneven settlement of the piers occurred leading to cracks in the arch barrel which made the train traffic to be stopped. Immediate measures are taken to prevent the failure of arch by erecting temporary supporting of full arch and cement grouting of the cracks in order to restore the traffic limiting to minimum speed. In order to assess the integrity and performance of the arch bridge span during the movement of train traffic, instrumentation and response measurements are carried out during the passage of trains with supports under arch and also during the removal of the temporary supports. Field measurements indicated that the load carrying capacity of the arch is inadequate without the temporary supports. Analytical studies are carried out to design a novel retrofitting system to maintain the integrity of the structure while performing the permanent strengthening of the arch. Responses are measured after novel retrofitting to assess the efficacy of the proposed system during the passage of train traffic. The proposed retrofitting system is found to be effective in providing adequate integrity to the arch with less intervention to stoppage of traffic and river flow which will also be integral part of the permanent strengthening scheme for the arch span.

Numerical study on the structural response of a masonry arch bridge subject to flood flow and debris impact

Extreme flood flows in rivers and the floating debris they carry have the potential to generate significant impact forces on bridges spanning the watercourse. Recent flood events have highlighted the vulnerability of masonry arch bridges in flood events. This paper explores the structural response of a typical masonry arch bridge subject to flood flow and impact from flood-borne debris using a validated numerical modelling approach. The meshless method smoothed particle hydrodynamics (SPH) is used to model the fluid behaviour giving the pressure distributions on a single-span arch bridge arising from both the fluid and debris impact. Taking the pressure-time histories derived from the SPH model, the response of the bridge structure is then simulated using a nonlinear finite element (FE) model via Abaqus/Explicit. The effects of submergence ratio of bridge components: abutment, arch barrel, spandrel wall, debris orientation and flow velocity are explored. Results indicate that the debris impact resulted in greatest increase in the stresses in the bridge with a fully submerged abutment and side-on (0-degree) debris orientation. The influence of the debris impact with end-on (90-degree) orientation on the structural response was relatively low despite its higher peak pressure values. Moreover, for the type of realistic flow scenarios considered, significant local tensile stresses can be generated in the spandrel wall and arch barrel leading to structural damage.

Fragility of single-span masonry arch bridges accounting for deterioration and damage effects

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.

Numerical methodologies for the analysis of stone arch bridges with damage under railway loading

This paper reports two nonlinear modelling strategies resorting to FE methodologies to simulate the damage state condition in masonry arch bridges under service loading. The first one consists of a nonlinear simulation of the bridge behaviour using an equivalent continuous homogeneous Drucker-Prager model for the whole structure. The second one combines the potentialities of FEM with discrete crack modelling, to simulate a longitudinal crack opening in the arch barrel. These strategies were applied to a single-arch stone masonry railway bridge and its numerical model were used under static and dynamic loading, adopting a freight train load model defined through a simplified methodology in which the train is represented by a set of moving loads travelling over the bridge. By merging the capabilities of a continuous homogeneous model with a discrete crack modelling, a better representation of a longitudinal crack is achieved, in particular the transversal movement of the arch and spandrel walls. These simplified calibrated numerical FE strategies proved very efficient in nonlinear dynamic analysis under service loading.

Shakedown and dynamic behaviour of masonry arch railway bridges

Masonry arch bridges form an integral part of our rail infrastructure network and their safety is important for the functioning of our society. Although, there have been several studies to understand the in-service condition of masonry arch bridges, these are mainly focusing on static analyses. However, it is well known that moving vehicles exert a dynamic force on bridges as they cross them. This paper investigates the shakedown and dynamic behaviour of railway masonry arch bridges under traffic load conditions. A nonlinear, mixed discrete-finite element numerical model was developed to investigate static and dynamic response on a masonry arch bridge. Each voussoir of the masonry arch was represented by a distinct block, while the mortar joints were modelled as zero thickness interfaces which can open and close depending on the magnitude and direction of the stresses applied to them. Both static and real dynamic analyses were carried out investigate the effects of moving traffic loads. In addition, investigations into the train to bridge interaction were undertaken and the dynamic amplification factors (DAFs) were estimated. From the evaluation of the results, it was shown that as the external load passes through the bridge, plastic deformations and residual stresses exist in the arch barrel. Also, the dynamic amplification depends on the magnitude of the external load. As the load increases, non-linearity in the structure is evident, which decreases the natural frequency of the bridge. Hence the critical speed is decreasing. Observations provided here reveal new insight into the residual and load carrying capacity of masonry arch bridges.

Refurbishing the historic Old Tweed Bridge, Scotland – the challenges and innovations

The historic Old Tweed Bridge is a three-span listed masonry arch crossing the River Tweed. Structural integrity concerns resulted in the bridge being temporarily closed to the public and propped. This paper discusses the challenges associated with the construction works necessary to refurbish the bridge permanently. The works involved installing a temporary propping and encapsulation structure, excavating the bridge infill, taking down and rebuilding the walls, casting a concrete saddle above the arches, waterproofing and resurfacing. Other innovative works involved closing the gap between the voussoirs and arch barrel using a bespoke arch pulling system and repairing voussoir stones in situ with a lime-based material. There were significant environmental challenges on the project as the bridge is located in an ecologically sensitive area. The River Tweed is one of the UK's great salmon rivers, which restricted working in the river and required strict pollution controls. Alternative roosts for bats were provided and netting was required around the bridge as part of an advanced works contract to mitigate the risk of birds nesting in the bridge.

Serviceability Assessment of Masonry Arch Bridges Using Digital Image Correlation

Serviceability deflections and strains at the crown, support, and quarter point of two aged masonry arch bridges under operating passenger and freight trains were assessed using a digital image correlation method. Three lasers recorded the passage of the wheels; these data were used to ascertain the wheel positions, which corresponded well with the peaks of the deflections measured. The measured maximum deflection and strain were 0.5 mm and 110 microstrain, respectively; these data were validated through a three-dimensional (3D) finite-element model incorporating saturated soil fill, masonry arch, and their interface. The predicted strains matched well with the field measurements. The variation of the strains with the wheel positions over the arch barrel was also simulated. The magnitudes of the deflection and strain were too small to cause serviceability limit-state exceedance alarms for the masonry arches.

Dynamic response of a damaged masonry rail viaduct: Measurement and interpretation

Despite recent advances in modelling and testing techniques, assessing the serviceability of ageing masonry rail bridges remains a significant challenge. Most assessment methods are based on ultimate strength, while reliable measurement-based assessment criteria are lacking. This paper aims to improve the understanding of serviceability behaviour through detailed dynamic monitoring of the bridge locally (e.g. in locations of damage) and globally (e.g. interaction of different components). Quasi distributed sensing techniques (Fibre Bragg Grating cables and Digital Image Correlation) were used to quantify the bridge dynamic response through extensive measurement of strains and displacements. Specifically, these techniques were applied to two damaged spans of the Marsh Lane viaduct in Leeds, UK. A detailed investigation of the dynamic pier and arch barrel movements reveal how the response mechanisms relate to, and likely propagate, the existing damage. For instance, rotation of piers in the bridge longitudinal plane causes significant span opening and closing, which in turn causes the skewbacks and backing to rock on the piers. This is accompanied by flexural deformation of the arch, which forces the existing transverse cracks to experience high compressive strains. Similarly, the transverse rotation of piers due to the presence of the relieving arches causes spreading of the relieving arches and opening of the longitudinal crack above. These observations provide new insight into behaviour and lead to suggestions for improving assessment techniques for masonry viaducts.

Mesoscale partitioned modelling of masonry bridges allowing for arch-backfill interaction

Masonry arch bridges exhibit a complex three-dimensional behaviour which is determined by the interaction between different structural and non-structural components, including the arch barrel, the backfill and the lateral walls. This paper presents an advanced finite-element modelling strategy for studying the behaviour of masonry arch bridges under vertical loading which combines a mesoscale description of the arch barrel with a plasticity-based continuum approach for the fill and the spandrel-walls. The proposed modelling strategy is validated against available experimental laboratory test results on masonry arch bridges. Firstly, a bridge specimen with a detached spandrel wall is analysed considering a simplified strip model. Subsequently, the influence on the bridge response of backfill and arch characteristics, loading position, arch shape and abutment movements are investigated through a comprehensive parametric study. In the final part of the paper, the results of full 3D mesoscale simulations of an arch bridge with attached spandrel walls are presented and discussed. The analysis results provide significant information on the complex interaction between the different bridge components along the longitudinal and transverse direction, and can be used to validate and calibrate simplified approaches for practical assessment of masonry arch bridge.

Progressive cracking of masonry arch bridges

Numerous methods are available for the assessment of masonry arch bridges at the ultimate limit state. However, there is a lack of suitable methods for assessing behaviour at service levels of loading. To address this, non-linear three-dimensional finite element (FE) models that consider constitutive material models enabling progressive cracking and failure of the complete structural system were used to investigate the development of damage for three masonry arch bridges at both service levels and at the ultimate capacity. All of the elements contributing to the strength of the structure were represented in the models, including the arch barrel, spandrel, abutments, fill and surrounding soil. This allowed for consideration of the longitudinal and transverse capacities, the stiffening effects of the spandrel walls, the restraint and load distribution provided by the fill, the frictional behaviour between the masonry and fill, movement at the abutments and multiple causes of failure. While complex non-linear FE models are able to identify the ultimate load capacity there are alternative simpler approaches available for this, and it is the investigation of damage and crack propagation at service level loads where their use is of greatest benefit.

Influence of stiffening ballasted track bed overlying a masonry arch bridge using a polyurethane polymer material

A finite element analysis of a masonry arch railway bridge has been conducted to study the stabilizing effects on the bridge using polyurethane polymer reinforcement of part of the ballast. Ballast is a highly non-linear granular material and its behaviour is influenced by the formation and subgrade structure. The track support and its deterioration with time is dependent on a number of parameters. Arch structures were designed for lower vehicle loads than they are currently subjected to so this work is focused on finding an innovative way of extending the scope of a proven ballast strengthening technique (XiTRACK) to encompass arch bridges, allowing a better distribution of the loads from the trains and hence to reduce the pressure on the arch. This work will provide a technique for the stabilization of masonry bridges using polyurethanes in order to address specific problems associated with the bridge structure. This involves numerical modelling of the ballast structure, the arch fill and the response of an arch barrel to achieve the optimum use of the material. The work is still under development as the current analysis uses a linear elastic model of the bridge, due to calibration of the data readings taking from the actual bridge, however further work using non linear plasticity is underway.

Precast concrete voussoir geometry in a skewed arch bridge

The replacement of Midmill Bridge, a reinforced concrete arch bridge crossing Cruden Water in north-east Scotland, was accomplished by the construction of an arch comprising discrete interlocking precast concrete voussoirs. By eliminating reinforcement entirely from the arch structure, durability was improved. The re-aligned road crosses the river obliquely and to maintain the spandrels parallel to the road the arch has an end skew of 35°. Skewed arches pose a design challenge as the geometry of the coursing of the voussoirs is surprisingly complex. Three-dimensional computer-aided design modelling was deployed to obtain a single precast voussoir block that could be set out and placed on the barrel falsework requiring no more than conventional site skills and resources. In total 479 copies of this single voussoir were cast to construct the majority of the arch barrel. The voussoirs are placed in the English or helicoidal arrangement with special precast blocks to form the arch springings.

Influence of backfill on the capacity of masonry arch bridges

The influence of the presence of backfill on the load-carrying capacity of a masonry arch bridge can be considerable. The backfill is responsible for transmitting and distributing live loads from the road or rail surface through to the arch barrel and also for laterally stabilising the arch barrel as it sways under load. However, it can be difficult to separate these two distinct effects, and hence also difficult to ascertain whether existing assessment code recommendations are realistic. To address this, a series of experiments designed to separate these two effects have been performed. A total of 27 small-scale bridge tests were undertaken and the experimentally obtained peak loads then compared with results from limit analysis software of varying complexity. It was confirmed that passive restraint and live load distribution both contribute significantly to bridge-carrying capacity, and that, when failure involves a four-hinge failure mechanism, even comparatively simple limit analysis software can model the various effects remarkably well.

Multi-tool inspection and numerical analysis of an old masonry arch bridge

Complex special inspection of an old masonry arch bridge according to the Guideline on Inspection and Condition Assessment of Railway Bridges and numerical analysis of the structure are presented. The guideline summarises recommendations for the step-by-step investigation of railway bridges applying enhanced methods developed during the EU-funded project Sustainable Bridges. For the investigation of the arch barrel, the ballast parameters and the inner structure of the backfill behind the arch barrel a number of various advanced non-destructive and minor-destructive testing methods were applied. Deformation of the structure during load tests was measured using three independent measuring systems: laser vibrometer, LVDT and microwave radar. Results of calculations performed with 2D and 3D models based on FEM are compared with the field load tests. Sensitivity of the ultimate load of the structure to investigated parameters is studied in FE model. Some general conclusions according to methods of testing and modelling of masonry arch bridges are presented and discussed.

Weetwood Bridge stabilisation, UK

This paper describes the design and construction processes involved in the stabilisation of Weetwood Bridge, Wooler, Northumberland. The bridge is a scheduled ancient monument and is located in a setting of high landscape value, especially when seen from the adjacent B6348 road with a back-drop of the Cheviot Hills. The bridge had severe structural problems apparent in the cracking of the arch barrel and tilting of the approach walls. The parameters that affected the design and construction of the stabilisation works are presented together with the issues encountered when working on an ancient monument in a site of special scientific interest with roosting bats present. The expertise of the in-house design team and specialist bridge workers delivered an innovative solution that resulted in the structure being repaired, conserved and subsequently removed from the ‘at risk’ register of English Heritage. The external appearance of the bridge remained unaltered but importantly the scheme took account of the principles of historic conservation in disturbing as little as possible of the historic fabric.

Condition Monitoring of Masonry Arch Bridges using Acoustic Emission Techniques

40% of European railway bridges are masonry, 60% of which are over 100 years old and are still carrying traffic loading. The weight and density of traffic has increased substantially over the last century and bridge owners have the continuous responsibility to ensure safe working condition of their bridges. The condition assessment of masonry bridges generally relies on visual observation and there are limited number of techniques that provide insight into the actual condition of the masonry structure. There is an increasing need for techniques to help determine the bridge condition and predict their life expectancy.The acoustic emission technique has been applied to a series of masonry arch bridges in laboratory and in field to investigate its applicability for routine bridge assessment. The technique has shown to be able to identify damaged regions in the arch barrel, detect crack propagation and warn of residual damage occurring to the arch. It is also able, for the first time, to record the period of damage propagation which can allow sufficient time to remove critical loading and avoid crucial damage. The acoustic emission technique is simple and easy to use and has shown great potentials for assessment and monitoring of masonry arch bridges in the traffic network.

Modified four-hinge mechanism analysis for masonry arches strengthened with near-surface reinforcement

A modified mechanism approach to estimate the load capacity of masonry arches strengthened with near-surface reinforcement is presented. This method is developed for reinforced masonry arches failing with a four-hinge mechanism in which measures have been taken to prevent premature failure by ring separation. The analysis takes into account crushing failure of the masonry and yielding of the steel reinforcement. Hinge positions are varied along the arch barrel and their optimum positions are identified when the minimum collapse load is achieved, in accordance with the upper-bound theorem of plasticity. Validation of the proposed method of analysis is carried out by comparing predictions of the load capacity and failure mode with those obtained from large-scale laboratory tests.