The fatigue phenomenon is a common issue for steel bridges, affecting their safety and long-term performance. Estimating the fatigue lives of these structures is challenging for bridge managers and owners. This study presents a comprehensive methodology for evaluating fatigue performance of the cope hole detail with two butt weld configurations on the Southern Danube Railway Bridge in Budapest (SDRB). The long-term SHM strain gauge measurement, combined with multi-level finite element models verified and validated through dynamic and static load tests, was utilized for fatigue evaluation. More than 150 FE analyses are performed under various train loads, revealing three critical stress concentration points in the investigated detail. The regression analysis of FE results demonstrates a robust correlation between the measured and the effective stresses experienced at the critical welded detail, allowing for a direct conversion of the stress-time history measured by the SHM strain gauge to the equivalent effective stress-time histories at the relevant critical locations. The nominal stress method and the effective notch stress-based evaluation methods are used for fatigue damage estimation, and the accumulated fatigue damage is assessed to evaluate the fatigue performance over the entire monitoring period. Results indicate that the effective notch stress-based maximum principal stress predicts the shortest lifetime, and the proposed approach is effective for continuous fatigue assessment in steel railway bridges.

The application of design by finite element analysis (FEA) is becoming increasingly prevalent in engineering practice; however, codified provisions remain scarce. The vision of CEN/TC250/SC3 was to develop a new comprehensive document based on the existing provisions currently distributed throughout the different Eurocode 3 parts, and with extension where necessary to cover all fields of structural steel design. Within the development process, two documents were prepared: (i) the code, EN 1993‐1‐14 and (ii) a Technical Report, TR 1993‐1‐141. The new code provides rules on the use of finite element analysis and other numerical methods for verifying ultimate limit states, serviceability limit states and fatigue. In parallel, the Technical Report provides background information and explanations on all aspects of the code, as well as benchmark cases and design examples to support the correct application of the EN 1993‐1‐14 design rules and the necessary benchmarking required for model verification and validation. The assumed stakeholders are mainly designers who can find direct guidance for design by finite element analysis in daily engineering practice. The current paper gives an overview of the new code and accompanying Technical Report, as well as the development process and harmonisation within the current Eurocode 3 framework.

Demountable steel–concrete composite structures, utilised in sustainable building construction, incorporate demountable structural elements and shear connectors designed for reuse, aligning with the principles of the circular economy. This research and development project focuses on designing a demountable steel–concrete composite slab system for building applications, aiming to establish a design method based on Eurocode standards. The proposed structural solution comprises steel beams and precast reinforced concrete panels, featuring steel assemblies, mortar filling and embedded bolts as demountable shear connectors. A push-out experimental programme was conducted and extended by numerical studies. The results indicate that the shear connection demonstrates a suitable performance with adequate stiffness, resistance and ductility. The material properties of the concrete and mortar filling, particularly in the region surrounding the shear connector, significantly influence structural behaviour. The numerical model that is developed accurately represents real behaviour, facilitating a numerical parametric analysis of key parameters, including bolt grade, concrete grade, bolt position within the holes and panel thickness. Based on these results, a proposed structural solution has been developed and optimised, with mortar filling playing a crucial role in improving bolt hole clearance and force distribution. This updated solution has been used to design full-scale composite beam specimens for testing in the next research phase.

A ferdekábeles hidakon alkalmazott kábelek jellemzően érzékenyek a gyalogosok által keltett dinamikai hatásokra, aminek következtében sok esetben a kábelekre csillapítóelemek kerülnek beépítésre. A budapesti atlétikai stadion beruházása keretében megépült Osztószigeti ferdekábeles hídra – vagy elterjedt nevén Robinson hídra – a kivitelező (Hídépítő Zrt.) döntése és a tervező (Speciálterv Építőmérnöki Kft.) támogatása alapján nem kész termék, a piacon elérhető csillapítóelem, hanem egyedi gyártású, saját fejlesztésű csillapítóelem került megtervezésre a Speciálterv Építőmérnöki Kft. és a Budapesti Műszaki és Gazdaságtudományi Egyetem Hidak és Szerkezetek Tanszék együttműködésében. A cikkben a híd bemutatása után ezen csillapítók tervezésének és fejlesztésének folyamatát és specifikumait mutatjuk be.

Since the structural assessment of steel bridges relies on the data collected from structural health monitoring (SHM), measurement singularities should be mitigated for more precise assessment. The presence of noise in measured data may obscure significant details and resulting inaccurate structural conditions; therefore, the signal-denoising process is essential. This study focuses on the noise treatment of the measurements recorded by strain gauges implemented through the SHM system of the Southern Danube Railway Bridge (SDRB) in Budapest. In the study, a wavelet-based denoising approach is investigated by implementing five wavelet mother functions (Haar, Daubechies, Symlets, Coiflet, and Biorthogonal) conjugated by two universal (hard and soft) thresholding methods, which in turn use four threshold techniques (Sqtwolog, Rigrsure, Minimaxi, and Heursure) to eliminate the noise and preserving the critical signal details. Three evaluation metrics, signal-to-noise ratio (SNR), square root of the error (RMSE), and the correlation coefficient (CC), are used to estimate the denoising performance. Further smoothness refinement of the denoised signal is achieved by investigating two filtering techniques (lowpass and Savitzky-Golay). The performance of filters is examined by estimating the smoothness of the filtered signal. The study revealed that the wavelet mother functions have comparable results, and the hard thresholding method implementing the Rigrsure threshold technique and lowpass filter shows higher performance. Further validation of the proposed approach is achieved by comparing its performance with the contemporary denoising methods. To ensure the adaptability of the proposed strategy, it is applied to a measurement recorded from a different structural system.

Structural health monitoring system (SHM) has an essential role in the prediction of steel bridges behavior and damage detection. Due to site difficulties and economic reasons, it is not possible to instrumenting all sensitive details within the structure. Finite element modelling is an effective tool for analyzing fatigue-sensitive details, as it enables the extension and interpretation of measured data. This study investigates the structural health monitoring (SHM) system of Southern Railway Danube bridge located in Budapest from fatigue sensitive details point of view. The research applies load testing data for the validation of finite elements models (FEM) which are to be used for specifying the sensitive details. Based on a detailed stress analysis, three fatigue-sensitive areas were identified in the bridge, as follows: 1. the cutout holes of cross girder, 2. the cope-holes, and 3. the transvers welding of bottom flange. Artificial cracks are applied in these details separately to investigate the efficiency of SHM system for crack detection. Stress values at the location of strain gauge points of the SHM system are calculated continuously as cracks size increased, simulating the propagation. The results show that the SHM strain gauges in the current placements not highly efficient to detect the cracks of the investigated details. The study extended to propose strain gauge positions to recognize the crack initiation and propagation in these details.

In Budapest, several buildings of historic value have been renovated and refurbished in the last 10 years. Among them two buildings of high historical prestige are presented in the paper: the 159-year-old palace building of the Hungarian Academy of Sciences, which is under renovation, and the Eiffel-designed 152-year-old steel hall of the MÁV Vehicle Repair Plant, which has been refurbished into the Eiffel Art Studios of the Hungarian Opera House. Both buildings were originally designed and built without standards and regulations, using the technical and technological knowledge of the time, and each of them has interesting and unusual technical solutions. The load-bearing structures of the buildings had problems in verifying that they met current standards. The reconstruction works were designed by KÖZTI Architects Engineers. Scientific and technical support was provided by the Department of Structural Engineering of the BME by expertizing the buildings, adapting the standard loads to the current site and analysing the behaviour of the load-bearing structure by advanced models. The paper describes the buildings, the technologies and scientific methods used in their renovation/refurbishment, which finally ensured the safety of the structure to the current requirements.

Corrugated web girders are widely used in buildings and bridges. This paper presents an experimental research program focused on prefabricated steel-concrete composite bridge girders with corrugated steel web. Web is the corrugated steel plate, bottom flange fabricated from steel, and upper flange is a reinforced concrete. The transfer of shear flow between the CW (corrugated web) and the concrete flange is facilitated by two mechanisms: (i) the embedding of the steel corrugated web into the reinforced concrete flange and (ii) the use of transverse rebars that pass through the web openings in the embedded web sections. Prior push-out tests conducted by the authors [1] suggest that this shear connection is likely to ensure complete shear flow transfer. The aim of this research is to investigate the bending and shear behavior, as well as the interaction between bending and shear. The pure bending resistance is primarily influenced by the accordion effect, rendering the contribution of the CW negligible Consequently, the focus of the study is to examine the shear contribution of the upper reinforced concrete flange to the overall shear capacity of the section under varying bending moments. In addition to assessing (i) resistance measurements, the study evaluates (ii) initial stiffness, (iii) failure mechanisms, (iv) collapse modes, and (v) post-buckling strength. Available experimental tests in the literature are quite limited. This paper presents laboratory tests conducted on five specimens subjected to eight different load scenarios. Based on the experimental results, a preliminary design proposal is developed for the bending-shear interaction resistance.

A Széchenyi lánchíd közel 175 éves történeti szerkezetünk, nemzeti szimbólumunk, amelynek legutóbbi felújítására 2021–2023 között került sor. A híd főtartója, a lánckötegek jelentős része több mint százéves, a láncelemeket összekötő csapok elfordulási képessége az előrehaladott korrózió és a jelentős súrlódás miatt kérdéses volt, ami jelentősen befolyásolja a láncelemek és a felfüggőrendszer statikai viselkedését. Ezért a felújítási folyamathoz kapcsolódva a Budapesti Műszaki és Gazdaságtudományi Egyetem Hidak és Szerkezetek Tanszék a tervezőkkel (Főmterv Zrt. és MSc Kft.) együttműködve megvizsgálta a láncelemek csapjai elfordulási képességének, a láncelemek korróziós állapotának a teherbírásra gyakorolt hatását. További tervezői és kutatói együttműködést igényelt a lehorgonyzó tömbön átvezetett nyomócsővezeték szerkezetre gyakorolt hatásának vizsgálata. A cikkben ezen két, a híd felújításához kötődő vizsgálat eredményét mutatjuk be.

Demountable steel‐concrete composite structures, applied in sustainable building construction, incorporate reusable structural elements and shear connectors, aligning with circular economy principles. This research and development project aims to design and develop a demountable steel‐concrete composite slab system for building applications. The proposed structural solution comprises steel beams and precast reinforced concrete panels connected by embedded bolts as demountable shear connectors. The shear connection was evaluated and optimized through push‐out laboratory experiments, complemented by numerical simulations and parametric studies. The findings indicate that the connection exhibits adequate stiffness, resistance, and ductility. Full‐scale beam tests were conducted to assess the global behaviour of the demountable composite beams. The results confirm that the proposed structural solution offers sufficient stiffness, resistance, and ductility, making it practical for industrial application. Numerical simulations were applied for the composite beams and validated by the test results which can follow the observed behaviour. This paper summarises the results and the general behaviour of the developed novel composite beam.

Demountable steel-concrete composite structures provide a sustainable solution for the construction industry by aligning circular economy principles, promoting reuse, adaptability, and reduced embodied carbon. This research focuses on developing a demountable steel-concrete composite system consisting of steel beams and precast reinforced concrete panels, with demountable shear connectors playing a key role in ensuring structural performance and reusability. An extensive push-out test program was conducted and supported by numerical simulations to evaluate and optimise the performance of these shear connectors. Based on these findings, full-scale beam tests with varying shear connection configurations were performed to investigate the global behaviour and structural performance of the composite beams. This paper presents the development and experimental evaluation of the proposed demountable steel-concrete composite system, with a focus on the effect of the demountable shear connectors and the precast slab arrangement on the global behaviour of the system under full-scale beam testing. The results confirm adequate stiffness, resistance, and ductility, demonstrating the feasibility of the system for industrial applications. The test specimens demonstrated ductile behaviour, characterised by a combination of elastic and plastic responses, with failure predominantly occurring through bolt shear and bending, accompanied by significant beam deflection and panel end slip. The composite beams exhibited elastic behaviour in the serviceability limit state load level, with no plastic deformation or visible damage, demonstrating their potential for dismantling and reassembly.

The Széchenyi Chain Bridge is an almost 170-years-old historical structure located in the downtown of Budapest. Its reconstruction was made between 2020 and 2022, when the deck system of the bridge is replaced by an orthotropic deck and the main girder is renewed. During the design the damages and the rotation of the pins between the eyebars in the chain system were questionable due to corrosion and friction. Therefore, the rotation capacity and the corrosion grade of the chain elements were investigated before and during the reconstruction process to clearly determine the structural health and further lifetime. Four on-site measurements were executed to analyse these issues: (i) loading test to measure the bending moments in the chains and checking the rotation of the pins, (ii) one-year-long monitoring system operating during the renewal process having the aim to check the bending moment distribution in the chain elements during the reconstruction process, (iii) chain element corrosion measurements and (iv) load test of the reconstructed bridge. The paper introduces the new design, the measurement results regarding the corrosion grade and the monitoring system data. The main conclusions of the measurements and accomplishing statistical evaluations are presented in the paper to evaluate the structural health to estimate the further lifetime of the bridge.

Two key research areas have recently gained increased attention: (i) Finite element Method (FEM)‐based design of steel structures and (ii) assessment of existing steel structures. This paper combines these fields by applying advanced FEM techniques, specifically the direct resistance check, to a critical detail of an existing highway bridge in Hungary. The bridge required strengthening after its structural bearings were replaced, introducing a new load path and altering stress distribution in the diaphragms at the supports. The BME Department of Structural Engineering conducted an extensive static analysis to compare the effects of the old and new bearings, with special focus on local load introduction, stress concentrations and design resistance of the diaphragms. After the installation of new structural bearings, on‐site measurements and a load test were carried out to validate the predicted stress distribution in the diaphragms. The study highlights the consideration of stress concentration within advanced numerical models and presents the application of direct resistance check in case of an existing steel bridge.

In steel bridges with orthotropic decks, a common and important engineering structure, fatigue cracks can appear under long-term operation. Existing artificial detection is the main approach to detecting fatigue cracks in steel bridges, in addition to some non-destructive testing or image processing methods, and unmanned aerial vehicle are applied to improve accuracy and efficiency. However, the detection of fatigue cracks in steel bridges based on the variation of dynamic responses or dynamic parameters is another attractive idea, which is still rarely mentioned and investigated in the international literature. The reason is that local cracks usually have negligible effect on the global dynamic characteristics of steel bridges, resulting in the insensitivity to dynamic indexes to fatigue cracks. On this occasion, this study numerically explores and establishes two sensitive damage features to local damage, i.e., the crack in the vertical rib, based on the fatigue cracks found on the Türr Istvan bridge over the Danube River in Hungary. The local vibrations of the bridge are excited through the local impact on the structural details, i.e., the vertical rib, and then the high-order frequencies of the entire bridge are examined. The obtained high-order frequencies are proved to be more sensitive to the fatigue cracks on vertical ribs and increased with the crack depths. On the other hand, the correlation of the stress curves on opposite sides of the crack is sensitive to the depth of the crack. If fatigue cracks are found, the development degree of the fatigue cracks can be monitored more accurately by focusing on the correlation of local stresses near the crack. These two damage features are numerically proven to have feasibility and are expected to break through the insensitivity of the existing dynamic detection methods.

The influencing mechanism of the spatial variability in concrete materials on the seismic damage of concrete gravity dams is still unclear, and existing methods for evaluating the seismic damage are insufficient. In this work, the effects of concrete’s spatial variability on the seismic damage distribution, energy dissipation, and deformation in concrete gravity dams are performed based on the damaged plastic model of concrete. Prior to the seismic damage analysis, the method for seismic inputting and the correlation function for realizing random fields of concrete materials are carefully determined. Based on the seismic damage analysis of the Koyna gravity dam, the tensile strength has the greatest influence on the seismic damage, followed by the elastic modulus and fracture energy. Aiming at the parameter of tensile strength, the decrease of correlation distance and the increase of the coefficient of variation increase the damage degree and complicate the damage distribution. A convenient and comprehensive damage profiling indicator is proposed to avoid the one-sidedness and evaluation error caused by using a single scalar damage value. The triangular area enclosed by the three individual damage indexes represents the comprehensive damage degree, and the shape change of the damage triangle indicates the change in the damage pattern of the dam. This damage profiling indicator is specifically designed to quantitatively distinguish and evaluate the damage degrees between a series of damage cases.

The application of stochastic subspace identification (SSI) on identifying structural time-varying modal parameters suffers from the shortcomings of poor computational efficiency and susceptibility to spurious modes. This work overcomes the shortcomings by the following procedures based on existing covariance-driven SSI. First, the covariance-driven SSI is embedded with techniques of randomized singular value decomposition and subspace iteration for reducing computation cost and avoiding accuracy loss, forming the lightweight SSI (lwSSI). Then, the lwSSI is combined with the technique of sliding window for eliminating spurious modes and continuously identifying time-varying modal parameters. The proposed lwSSI-based identification method is applied on the simulation of a gravity dam, and the identified time-varying modal parameters show the same trend as the assumed time-varying elastic modules. Furthermore, the characteristics of the lwSSI-based identification method, including noise resistance, computational efficiency, and identification accuracy, are investigated. Finally, the identification of a steel cantilever beam with the time-varying modal parameters caused by the mass distribution experimentally validates the effectiveness of the proposed lwSSI-based identification method.

Sustainable composite structures in building construction are assembled using demountable structural elements that can be reused in the circular economy. The current research and development project, in cooperation with Budapest University of Technology and Economics and KÉSZ Group, bim.GROUP Ltd., Hungary, aims to design a novel demountable steel-concrete composite slab and frame system for buildings. The key component of this construction is the demountable shear connector. In the current research, novel bolted shear connectors with embedded bolts and threaded rods are developed and studied that can fit the applied technology of the industrial partner. One of the leading aspects of this connection is the consideration of bolt hole clearance, since it occurs initial slip and stiffness reduction of the composite beam. In the first phase of the research program, demountable and economical structural details were developed, which can reduce the stiffness reduction with the proper resistance and ductility features. To study the behavior of these shear connections, a push-out experimental program was designed and completed in March and April 2023. It is observed that novel shear connectors have a proper behavior with sufficient resistance and ductility, which is applicable according to the Eurocode 4 standard and fits the objectives of the research and development project. In the paper, the developed structural details and the push-out experimental program are presented with general results and statements besides a detailed evaluation of a specified specimen type.

Stockbridge dampers are widely used to mitigate the vibrations of cable-stayed bridges and of many other cable-suspended or cable structures exposed to the action of pedestrians, traffic or wind load. Within the current research work, one of the most effective and likely used damper types, the Stockbridge damper, was investigated to support its design and application within the daily engineering praxis. The Stockbridge damper has a relatively simple structural layout, which ensures its modular design allows it to easily adapt the damper to cables having different dynamic properties (eigenfrequencies, mass, etc.). This paper focuses on two main research areas: (i) to understand the static and dynamic behaviour of the damper and the stay cable interaction to investigate the effectiveness of its damping; (ii) to study the sensitivity of the natural frequencies of the damper to the design parameters. The final aim of the research is to develop a simple design method that is easy to apply in engineering practice and allows the efficient adaptation of the Stockbridge damper to different cable-stayed bridges. Key findings include the recommendation to position the damper at approximately 20% of the cable length for optimal attenuation, the importance of detuning to maintain effectiveness under varying cable forces, and the observation that increasing the damper mass improves efficiency, particularly for detuned elements.

A temporary monitoring system was installed on the 175-year-old historical Széchenyi Chain Bridge during its reconstruction. The bridge is in the downtown area in the capital city of Hungary and plays a significant role in the city life of Budapest. Six-month-long measurements were conducted during the reconstruction process of the bridge, yielding crucial insights into the structural behaviour of the historical structure. The measurement results were evaluated; the findings encompass the rotation capacity of the pins between the chain elements and the structural response to temperature changes. This information helped the decision-making between 2021 and 2023 by the designers and construction company during the reconstruction. For instance, daily temperature fluctuations resulted in increased bending moments in the chain elements, rising up to 158% compared to the values observed during a proof load test in 2018. Furthermore, the measurements reveal an approximate 42% increase in normal forces compared to the proof load test, which highlights the high sensitivity of chain bridges to temperature fluctuations, where geometric stiffness plays a crucial role. Reconstruction, namely reducing self-weight, notably intensifies the impact on normal forces and bending moments. These outcomes strongly emphasize the dominance of the dead load and self-weight in the case of chain bridges.

The demountable shear connector is the most important component of sustainable composite structures, as it allows the elements to be reused. The ongoing research and development project – in the cooperation of the Budapest University of Technology and Economics and KÉSZ Group, bim.GROUP Ltd., Hungary – aims to design a new demountable steel‐concrete composite structural system. In the current research, bolted shear connectors with embedded bolts and threaded rods, which can fit the applied technology of the industrial partner, are being developed and studied. One of the main aspects of this connection is to consider the bolt hole clearance – to decrease initial slip and stiffness reduction – and also to provide the proper strength and ductility features. A push‐out experimental programme was designed and completed to study the behaviour of the developed shear connections. It is observed that the examined shear connectors have proper structural behaviour with adequate resistance and ductility, which is applicable according to the Eurocode 4 standard and fits the objectives of the current research project. This paper presents the developed structural details, the observations and the evaluation of the push‐out experimental results with the conclusions and statements.