Steel Railway Bridges Research Articles

Erratum to: Changes to the lambda model for fatigue loads on steel railway bridges in Europe

Erratum to: Changes to the lambda model for fatigue loads on steel railway bridges in Europe

Research on heavy-haul adaptive technology and strengthening measures for existing railway steel bridge

PurposeThis research addresses the diverse characteristics of existing railway steel bridges in China, including variations in construction age, design standards, structural types, manufacturing processes, materials and service conditions. It also focuses on prominent defects and challenges related to heavy transportation conditions, particularly low live haul reserves and severe fatigue problems.Design/methodology/approachThe study encompasses three key aspects: (1) Adaptability assessment: It begins with assessing the suitability of existing railway steel bridges for heavy-haul operations through comprehensive analyses, experiments and engineering applications. (2) Strengthening: To combat frequent crack defects in the vertical stiffener end structure of girder webs, fatigue performance tests and reinforcement scheme experiments were conducted. These experiments included the development of a hot-spot stress S-N curve for this structure, validating the effectiveness of methods like crack stop holes, ultrasonic hammering and flange angle steel. (3) Service life extension: Research on the cruciform welded joint structure (non-fusion transfer type) focused on fatigue performance over the long life cycle. This led to the establishment of a fatigue S-N curve, enhancing Chinese design codes.FindingsThe research achieved several significant outcomes: (1) Successful implementation of strengthening and retrofitting measures on a 64-m single-span double-track railway steel truss girder on an existing heavy-duty line. (2) Post-reinforcement, a substantial 26% to 32% reduction in live haul stress on bridge members was achieved. (3) The strengthening and retrofitting efforts met design expectations, enabling the bridge to accommodate vehicles with a 30-ton axle haul on the railway line.Originality/valueThis research systematically tackles challenges and defects associated with Chinese existing railway steel bridges, providing valuable insights into adaptability assessment, strengthening techniques and service life extension methods. Furthermore, the development of fatigue S-N curves and the successful implementation of bridge enhancements have practical implications for improving the resilience and operational capacity of railway steel bridges in China.

Study on manufacturing and mechanical properties of stainless-clad bimetallic steel

The stainless-clad bimetallic steel not only has strong corrosion resistance, but also has low production cost and high strength. Compared with a single stainless steel or ordinary carbon steel material, the strengths of stainless-clad bimetallic steel are obvious, such as a wider market prospect and better material properties. Presently, the stainless-clad bimetallic steel has been successfully applied in the maintenance system of railway steel bridge panels and high-rise building curtain wall. In order to promote the application of stainless-clad bimetallic steel in structural engineering, this paper systematically introduces the manufacturing process of the stainless-clad bimetallic steel, including production technology and welding technology. In addition, the mechanical properties such as corrosion resistance and composite interface properties are studied and analyzed. The research of the stainless-clad bimetallic steel has important economic significance, social significance and strategic value. It is hoped that results from this paper can provide reference for researches on the stainless-clad bimetallic steel in the further.

Remaining Fatigue Life Assessment of a Steel Railway Bridge Based on Fracture and Stress Life Approach

Remaining Fatigue Life Assessment of a Steel Railway Bridge Based on Fracture and Stress Life Approach

Fatigue resistance of rib-to-bimetallic steel deck welded joints in orthotropic steel bridge decks

The stainless-cladding techniques have been applied in the top plate of the orthotropic steel decks in the high-speed railway steel bridges to improve the corrosion and wear resistance. The rib-to-deck (RD) welded joint with the stainless-clad bimetallic steel deck plate becomes a new critical fatigue detail. This study firstly examines the fatigue performance of this full-scale new RD joint through six high-cycle constant-amplitude fatigue tests and two beach-mark tests under eccentric over-rib loading. The structural hot-spot stress at the weld toe on the deck plate is obtained by strain gauges and the linear extrapolation method for each RD specimen before the cyclic loading. Experimental results indicate that five RD specimens suffer from the toe-deck failure modes, while the rests encounter root-deck cracking. The fatigue strength of these new RD joints satisfies the FAT100 hot-spot stress S-N curve based on the IIW design recommendation. Numerical simulation is further conducted to investigate the effect of different cracking modes and welding technologies on the fatigue crack propagation behavior of this new RD joint. Root-deck cracking mode shows weakly higher fatigue resistance than the toe-deck failure case. Using the double-side welds between the U-rib and deck plate, and the thickened-edge U-rib technology can slightly enhance the fatigue life in terms of toe-deck cracking mode in contrast with the traditional single-side groove welds. Experimental and numerical validation quantify the excellent fatigue performance of this new RD joint in comparison with the other types of RD welded joints.

An efficient automatic modal identification method based on free vibration response and enhanced Empirical Fourier Decomposition technique

This paper presents an efficient yet practical approach for the automatic modal identification of structures based on their free vibration response. The proposed approach relies on the Empirical Fourier Decomposition (EFD) technique. It implements a new procedure to recognize automatically the number of modal components to be extracted from noisy data in such a way to prevent both mode-mixing and mode-splitting effects. A suitable strategy is adopted to improve the segmentation of the frequency spectrum of the free vibration response, so as to identify accurately the bounds of the frequency spectrum partition corresponding to each modal component. The related modal damping ratios are estimated by means of a robust area-based approach in order to mitigate the noise-induced disturbances whereas a time-domain method based on the phase shift of the free vibration response peaks is employed to identify the mode shapes.The proposed approach is first validated through the analysis of synthetic signals that embed closely spaced components and a lowly excited vibration mode. Finally, the proposed approach is applied to two real bridges. The first case-study deals with the identification of modal frequencies and damping ratios of the cables of a stay-cabled bridge. The second case-study involves the modal identification of a steel railway bridge deck that exhibits two closely spaced vibration modes. The outcomes obtained using the proposed approach based on EFD technique are compared with the results obtained by means of the Variational Mode Decomposition (VMD) technique as well as with those computed through classical operational modal analysis techniques. The consistent estimates produced by means of the proposed approach demonstrate its accuracy and robustness.

Minimum variance unbiased Bayesian smoothing for input and state estimation of systems without direct Feedthrough: Mitigating Ill-Posedness of online load identification

In this paper, the problem of moving load identification using pure displacement measurements is addressed. It is known that when no assumptions are made on the statistics of the unknown loads and a minimum variance unbiased (MVU) estimation approach is adopted, the existing methods in the literature suffer from a very elevated load estimation uncertainty. This elevated uncertainty is due to ill-posedness of the problem. In this paper a new method is proposed that addresses this issue via an MVU smoothing approach. To alleviate this problem, a MVU smoothing algorithm is proposed in this study, via modification of a MVU smoothing Bayesian estimator proposed by some of the co-authors of this paper hence referred to as MSBE, which leads to substantial decrease in the moving load estimation uncertainties using pure displacement measurements. The efficacy of the MSBE is studied through a simulated experiment corresponding to a numerical model of an operating steel railway bridge with riveted connections and a multi-axle load. The selection of the hyperparameters of the smoothing and filtering techniques are discussed, and the optimal values are presented. The parametric studies show that the proposed method can yield highly accurate results, and substantially outperforms a celebrated MVU filter proposed by Gillijns and De Moor.

Service life extension of strategic bridges

This article reports the process that allowed to check the condition of a steel railway bridge having a strategic position within the network. The framework representing the actions needed for the service life extension of the bridge is first described, then the conducted inspections are illustrated, together with the developed numerical analyses and the conception of specific tests on site. The conclusion, downstream of all these analyses and with the comparison of the real-life experiments, was to allow a limited extension of the useful life of the bridge, even with some reductions in the safety factor, respecting a reduction in the speed of railway trains and prescribing continuous monitoring of the bridge. In this context, all the test evaluations, combined with the surveillance/monitoring, and joined with an important numerical modelling activity, lead to the concept of “structural augmentation” of the bridge for service life extension purposes. The specific case of the examined bridge is supposed to be an example of good practice useful for infrastructure authorities.

Monitoring displacement, strain, and acceleration of a steel railway bridge

An evaluation of the existing steel railway bridge is necessary to obtain information in supporting policymakers to decide further strategies of the railway bridge maintenance process. The reliability and durability of the existing steel railway bridge were monitored regularly by installing instrumentations on the bridge. The railway bridge characteristics were reviewed by implementing a structural health monitoring system (SHMS). The advantages of the SHMS include an early warning system for the railway bridge structure in order to avoid failures. The objective of this study is to evaluate and monitor conditions of the railway bridge structure. The results of the study explained the vertical deflection of the railway bridge, the stress distribution of the entire truss, and the frequency that happens during loadings. This paper discusses and provides a recommendation to solve problems for users and necessary action in practice. This paper may be used by practicing engineers and researchers.

Modal strain monitoring of the old Nieuwebrugstraat Bridge: Local damage versus temperature effects

Vibration-Based Monitoring (VBM) from modal strains is a promising alternative to traditional VBM methods, which are primarily based on exclusively monitoring natural frequencies. The advantages of modal strains are that they offer a lower sensitivity to temperature and a higher sensitivity to small-scale damage, when compared to natural frequencies, rendering them ideal for detecting damage at an early stage. Furthermore, modal strains can be obtained in a dense grid with a relatively low cost, when fiber-optic sensors, such as fiber-Bragg gratings (FBG) are employed, which enables the monitoring of several critical locations and increases the possibility of early damage detection and localization. Modal strains can be obtained with high accuracy and precision thanks to a recently developed methodology that makes use of FBG sensors and of a high resolution acquisition system. The temperature sensitivity of modal strains has been investigated in the field but their damage sensitivity has previously only been investigated through laboratory experiments and numerical simulations. In this study, a 110-years-old steel railway bridge is monitored with 80 FBGs. Its modal strains and natural frequencies are automatically identified with the use of hierarchical clustering from ambient and operational dynamic strains. Before the scheduled replacement of the bridge, artificial damage is introduced by means of local cuts, simulating fatigue cracks, in order to investigate the damage detection and localization capabilities of modal strains on a full-size civil structure for the first time. The influence of temperature and operational factors is also investigated and compared with that of damage.

Parametric Study of Additional Temperature Stresses in Continuously Welded Rails on Steel Truss Railway Bridges

Additional temperature stresses in continuously welded rails (CWRs) are caused by track/bridge interaction (TBI) due to thermal actions. Exceeding permissible stresses in CWRs on the bridge can lead to track buckling or rail cracking, compromising the safety of railway traffic. The main aim of the conducted study is to determine the effects of the key parameters such as rail cross-sectional area, track longitudinal resistance, bridge expansion length, and longitudinal stiffness of the fixed bridge support on the reduction of additional temperature stresses in CWRs on steel truss railway bridges. To quantify the effects of these parameters, two steel railway bridges with CWRs and the maximum expansion lengths according to UIC Code 774-3 were analyzed: (1) simply supported truss bridge with expansion length of 60 m and (2) continuous truss bridge with expansion lengths of 2 × 60 m. According to the obtained results, the track longitudinal resistance had the most significant impact on additional temperature stresses in CWRs, leading to their reduction of up to 72%. The bridge expansion length and the rail cross-sectional area led to reductions of up to 25% and up to 18%, respectively. Considering the deformation criteria of TBI, the longitudinal stiffness of the fixed bridge support had a minor effect on the reduction of additional temperature stresses in CWRs.

Changes to the lambda model for fatigue loads on steel railway bridges in Europe

AbstractFor the fatigue design of steel railway bridges in Europe, the European standards EN 1991‐2 and EN 1993‐2 provide a factored Load Model '71, called the lambda model. The stress range in the fatigue detail of study should be determined with this model. Engineers can easily verify their structural design for fatigue by comparing this stress range to the fatigue reference strength of the detail.This paper compares the load effect caused by the lambda model with the load effect of actual trains measured with ‘Weigh In Motion’ systems during 7 years at 81 locations in the rail network of The Netherlands. Locations with heavy loads are selected and their load effects in terms of stress ranges and fatigue damage are determined for various influence lines, including one, two and three span beams with spans ranging between 1 and 150 m. The design (i.e. elastic section modulus) is optimized such that the calculated fatigue damage using the damage accumulation rule of Palmgren Miner equals 1 for a 100 years design life for these locations. This elastic section modulus is compared to the elastic section modulus obtained by designing according to the lambda model.Improvements are proposed to the lambda model based on this comparison, such that the resulting design gives a reasonable agreement with the design based on measured loads, while maintaining the current ease of use of the lambda model. Uncertainties such as possible changes in axle loads and train speeds in future are taken into account.

Load‐carrying capacity of Vierendeel bridges in Mechelen

AbstractFrom 1930 to 1960, in Belgium, steel railway bridges were regularly designed using the vierendeel system. Three railway lines cross the Mechelen‐Leuven canal in the town of Mechelen, providing a unique example of this type of application. Two of these bridges, which were constructed in 1953 were renovated in 2021–2022, including the installation of a new rail fastening. It was discovered that the 1936‐built third and oldest bridge had multiple cracks, mostly in the vertical members of the Vierendeel structure. Furthermore, secondary components like longitudinal beams and cross beams are severely harmed by corrosion. As a result, uncertainty grew over this bridge's ability to support loads. The monuments organization promotes the preservation of these old structures. The material properties, as well as the load‐bearing capacity and the fatigue strength, were evaluated by a thorough experimental and numerical investigation. The results of the examinations suggest that the significant strength variation of the steel components may be the cause of the cracking. It is more likely that cracks developed during the bridge's construction and subsequent repairs than that fatigue is to blame. In conclusion, the arrangement of the three bridges is too special to be destroyed and replaced, and the third bridge may also be sufficiently repaired and rebuilt for long‐term further use.

Structural assessment of an historical steel railway bridge in the north of Spain

AbstractAt the beginning of the 20th century, some railway lines were built in the north of Spain to support industrialization in this area. In the region there were coal and iron mines, as well as ports to market the products, reason why it was one of the first Spanish regions to develop. Due to the rugged relief, it was necessary to adapt the layout of the lines to the terrain, so many bridges were built for that purpose. At the same time, steelmaking was transitioning from manual to industrial metallurgical furnaces and processes. These processes determined the structural and durability characteristics of the metallic material used for those bridges. Nowadays, the maintenance of this type of bridges is conditioned by the difficulty of access to inspect, the structural typology of the details, and the mechanical characteristics of the material; and also the insufficient training of the technicians who inspect this type of structures. The case study is an old steel bridge that served the trade of an important regional factory. Routine inspections found no major structural defects; however, thanks to a complete historical and structural study that was being developed, significant damage was detected that made it necessary to immediately stop traffic on the bridge.

Review of the damage equivalence factors for steel railway bridges in the Eurocodes

AbstractProper fatigue design is essential for the sustainable operation of bridge structures. The fatigue design concept in the Eurocodes follows the damage equivalent concept allowing to conduct this relatively extensive design check as efficiently as possible. However, those factors cover a rather complex phenomenon and the code provides them in a standardized format. The actually required values are typically lower, but the parameter calibration and the included reserves are non‐transparent from the design standards.The objective of this paper is to recall the methodology for calibration of the damage equivalence factors and to review the damage equivalence factors given for steel railway bridges in EN 1993‐2. After a discussion on the assumptions in the Eurocode in context with the damage equivalent concept, the presented methodology is applied to recalculate the damage equivalence factors for the railway traffic spectrums in Eurocode 3. The obtained results verify the damage equivalence factors in the Eurocode 3 and figure out the span‐dependent safety margins in those factors. To investigate the influence of the traffic spectrum, the damage equivalence factors were also determined for a traffic spectrum provided by the Swiss national railway authorities for comparative purpose.

A combined iterative complex eigenvalue method and finite element-boundary element method for acoustic analysis of the railway steel bridge deck damped with constrained layer damping

This paper presents a combined method to predict structure-borne noise from the railway steel bridge deck damped with constrained layer damping (CLD), in which the frequency-dependent properties of the viscoelastic material are accurately considered through the iterative complex eigenvalue method (ICEM). Then, a 1:4 steel bridge deck model is designed and manufactured, and a series of hammer tests of the CLD-damped steel bridge deck are carried out in a semi-anechoic chamber to verify the proposed method. Then, the noise reduction effect of CLD is discussed in detail. It shows that the overall SPLs at the near field point S-3 and the far field point S-8 are reduced by 7.5 dB and 11.1 dB, respectively, and the noise attenuation rate along with distance is also improved significantly after damped with CLD. Finally, the influences of the key design parameters of CLD on noise reduction are quantitatively analyzed, so as to provide reference for the research and application of CLD in railway bridge engineering.

A combined method of autoregressive model and matrix factorization for recovery and forecasting of cyclic structural health monitoring data

Structures such as bridges, offshore platforms, wind power facilities, and drilling rigs generate a corresponding periodic structural response under cyclic loads such as solar radiation, tides and sea-land breeze. Data recovery and forecasting are major parts of the work to ensure structural safety using periodic structural health monitoring data. In this context, a combined method of autoregressive (AR) model and matrix factorization (MF) method is presented to reaching the tasks of data imputation and prediction. The combined method with a graph-based temporal regularizer can well capture the cyclic characteristics and random character. The verification of the method is conducted using an in-situ temperature monitoring dataset of a high-speed railway steel bridge. The application of the method for both data recovery and forecasting with structured missing entries is carried out, which indicates the combined method owns outstanding performance in accurately recover missing entries and making predictions. In the last part, the analysis of rank order and length of time lag is made to show its influence on imputation accuracy.

Probabilistic Assessment of the Equilibrium of a Steel Railway Bridge Based on Wind Tunnel and Traffic Records

The European railway network includes many steel truss girder bridges, often dating back to the end of the nineteenth century. Assessment by the partial factor method according to Eurocodes often reveals insufficient reliability of these bridges. In particular, they fail to satisfy the equilibrium limit state when a strong wind occurs simultaneously with an unloaded train crossing the bridge. To avoid unnecessary structural interventions and expensive traffic restrictions, representative types of these bridges are tested in a wind tunnel to refine the force coefficients of wind pressure for the specific shape of the bridge and selected types of lightweight train. The values of force coefficients based on wind tunnel tests correspond to 70–80% of those provided in EN 1991–1–4. Traffic flow records for the railway line under consideration are then utilised to obtain distributions of weights and heights of lightweight trains. Detailed probabilistic analysis focused on a long-span truss bridge with an intermediate bridge deck demonstrates that the reliability of this bridge is close to the target reliability level when wind tunnel force coefficients are considered along with site-specific free-field wind and railway traffic records.

Performing Fatigue State Characterization in Railway Steel Bridges Using Digital Twin Models

Railway infrastructures play a pivotal role in developing the national transportation system. Recently, the strategy of the railway engineer has been significantly shifted; along with the development of new assets, they tend to pay increasing attention to the operation and management of existing railway assets. In this regard, this paper proposes a Digital Twin (DT) model to improve fatigue assessment efficiency in the operational processes of railway steel bridges (RSBs). The DT concept mainly lies in the federation and interaction of a Fatigue Analysis System (FAS), which is based on Eurocodes principles, and a model in Building Information Modeling (BIM). Along with the proposed DT concept, a prototyping system for a real bridge is initiated and curated. The FAS is validated in good-agreement results with the ambient vibration test of the bridge (about 1.6% variation between numerical and experimental values), and close values were found between numerical and experimental stresses, the latter obtained by installing strain gauges on the bridge. The BIM model provides access to the numerical values of fatigue state results in a given bridge connection detail but also automatically represents that information in a 3D environment using a color-scale-based visualization process. Furthermore, a simulation model with the main input variables being the traffic and geometric conditions of the bridge is continuously updated for timely re-evaluation of the damage state, which shows promise for the lifecycle management of the bridge.

Mean stress effect in high‐frequency mechanical impact (HFMI)‐treated welded steel railway bridges

AbstractThe need for new railway bridges is driven by the growing volume of transportation demands for both passenger and freight traffic on railway networks. In the design of these bridges, the fatigue limit state is a criterion that usually limits the allowable applied load level and thus also the utilization of the high strength of the steel material. Therefore, improving the fatigue performance of welded details by high‐frequency mechanical impact (HFMI) treatment leads to a more efficient design. However, the fatigue performance of HFMI‐treated welds is known to be affected by the mean stress and this needs to be considered in the design of treated welded details in steel bridges. This is rather straightforward if the bridge is subjected to cycles from one type of train but becomes cumbersome when several different sets of trains (e. g. axle loads, axle distances) cross the bridge. In this article, a factor to take the mean stress effect (including self‐weight and traffic load variations) into account is derived from traffic data measured in Sweden. Moreover, the mean stress effect is also predicted using the different fatigue load models in the Eurocode. These models either consist of one‐load patterns such as LM71, SW/0, and SW/2 or are composed of different trains with different combinations. It was found that the mean stress effect is underestimated by the first group of models. On the other hand, the mean stress predicted by the light traffic mix is found to be close to that calculated using real traffic data, while other mixes (standard and heavy) underestimate the mean stress effect. Therefore, a correction factor to account for the mean stress effects in real traffic is derived (called here λHFMI). This factor can be used to correct the design stress range for fatigue verification of HFMI‐treated welded details in railway bridges.