Adopting a probabilistic framework, this study quantifies train-induced aerodynamically fatigue loading in bolted connections between noise-barrier steel posts and concrete edge beams on high-speed railway bridges. Train passages generate a sinusoidal pressure and suction shock load that causes cyclic loading and preload losses of the bolted connections. Defective installation conditions - primarily inclined bolts and insufficient bolt preload - locally increase fatigue stress and connection uncertainties, thereby shortening the structural service life. The paper presents an assessment methodology that enables the integration of structural health monitoring data. The proposed framework combines probabilistic fatigue modelling with parameters calibrated through numerical simulations and experimental investigations, explicitly accounting for deviations from ideal installation conditions. The database comprises laboratory measurements on preload evolution, bolt misalignment, and load-induced response quantities within the bolted connection. The probabilistic fatigue analyses are expressed in terms of reliability indices aligned with consequence classes, allowing for condition-based maintenance planning and resource-efficient strengthening measures. By enabling the integration of monitoring data into a probabilistic fatigue framework calibrated by experiments and simulations, the study provides a scalable, reliability-based methodology applicable to both existing and newly constructed noise barriers on high-speed railway lines.

Forced vibration tests are applied to railway filler beam bridges of different span length, bearing condition and construction type, aiming to determine the bridge specific dynamic parameters. The main focus of the research is the determination of the actual present vibration mode dependent damping ratios, whereby a statistical method is applied to account for the regularly observed scattering of experimentally determined damping ratios of real structures. The first part of the paper describes the method applied to extract the dynamic parameters by application of forced vibration tests and in the second part a representative number of measured railway bridges is presented and discussed in detail. It is shown that the application of forced vibration tests lead to reliable and reproducible results for the experimentally determined dynamic parameters of real railway bridges, especially of the damping ratios, and that the applied statistical method accounts sufficiently for the spreading of the determined damping values. In addition, the experimentally gained results show that both, the natural frequencies and especially the damping ratios of the considered railway filler beam bridges depend highly on the executed bridge specific bearing conditions. A continuous line bearing contributes highly to the energy dissipation and lead to significant higher damping ratios of railway bridges compared to the common executed elastomeric point bearings. The experimentally determined damping ratios are compared with the values given in the Eurocode and based on the gained results the aim is to develop and define an additional damping applicable to increase the normative lower limit damping ratios for filler beam bridges.

The dynamic response of a bridge to a train crossing needs to be assessed when planning new railway bridges on tracks with a line speed above or equal 120 km/h and when recalculating existing bridges for new train configurations planned to put into operation or when increasing the locally permissible line speed. In the assessment, the model trains HSLM-A and HSLM-B need to be applied as a sequence of moving loads on two- or three-dimensional mechanical models of the bridge structure as defined in Eurocode EN 1991-2. However, these load models were developed in the 1990s while in the last 25 years many new trains have been developed and put into operation with different configurations compared to the normative model trains in terms of axle distances and axle loads. As a result, the dynamic bridge response for actually operating trains can significantly exceed the permissible values, in particular the vertical bridge acceleration. The normatively regulated model trains HSLM-A and HSLM-B are therefore no longer adequate for the dynamic assessment of railway bridges, and there is an urgent need to develop new load models for passenger and freight trains, to cover the trains currently operating on the European railway network. For the reasons mentioned above, an international consortium consisting of TU Darmstadt, KU Leuven, AIT and REVOTEC was commissioned by the German Centre for Rail Transport Research (DZSF) in 2019 to develop new dynamic passenger and freight train load models for the dynamic calculation of railway bridges. This article presents the development steps carried out, the optimization methods used herein, as well as the validation of the newly developed load models on a large set of existing railway bridges.

The high-speed load model (HSLM-A) was developed more than 20 years ago.Since 1999, the vehicle technology and bridge design have developed accordingly.So new vehicle types, which are not always covered by the standardized load model, must be examined additionally.Within this paper the need of a new dynamic load model for dynamic analysis of railway bridges will be demonstrated.Investigations were done based on currently running passenger trains, which results into a train database of about 3200 train configurations of operating trains within central Europe.To cover possible future train configurations, fictitious parameterized train sets were created.Two different methods the train signature and FEM-computations on a large-scale set of bridges demonstrated that the existing HSLM-Model does not cover real operating passenger trains.510 relevant trains could be identified as relevant and define a refence line for operating trains.On top 67 fictitious resonance trains were found on the variation of different geometric train vehicle parameters which could be a worstcase scenario All this demonstrates, the need for a new high-speed load model.

In recent years, the vehicle-based indirect Structural Health Monitoring (iSHM) method has been increasingly used to identify the dynamic characteristics of railway bridges during train crossings, and it has been shown that this method has several advantages compared to traditional SHM methods. A major advantage is that sensors are just mounted on the vehicle, and no sensors or data acquisition systems need to be installed on the railway bridge. In this paper, the application of the vehicle-based iSHM method is demonstrated numerically and experimentally for determining the natural frequencies of railway steel bridges during train crossing. The coupled linear equations of motion of the train-bridge multi-body system are derived, and train crossing simulations are conducted numerically, considering different train speeds. Three different railway bridges are considered, and the train-induced vibration responses are calculated for both the train multi-body system and the railway bridge models. Different representative evaluation points are chosen for the wheelsets, bogies, and car bodies of the considered vehicle. To calibrate the numerical model, the resonance frequencies of an existing single-span steel bridge are measured in situ by the application of forced vibration tests. Besides the executed in situ measurements of the bridge, the considered crossing vehicle is also instrumented with several accelerometers at the wheelsets, bogies, and car bodies, and the vibration responses of both the bridge and the crossing vehicle are measured simultaneously during the duration of several train crossings with different train speeds. The recorded vibration responses are analyzed in the frequency domain and compared with numerical simulation results. It is shown that the first bending frequency of the considered railway bridge can be clearly identified from the computed frequency response spectra and that the vehicle-based iSHM method provides a promising tool for identifying the dynamic characteristics of railway bridges.

Dynamic calculations of train crossing of railway bridges must be carried out in Europe in accordance with current valid standards for both new and existing bridges. The high-speed load model (HSLM) trains to be used are defined in the Eurocode, denoted as HSLM-A1 to -A10. In the near past, the results gained from these dynamic calculations of train crossing have shown, that the current valid HSLM model trains do not cover the bridge vibration response level for certain real operating trains. It turned out that the application of the HSLM-A trains might lead to an unsafe design of new railway bridges and destabilization of the ballast layer may occur, leading to safety critical track position defects and eventually to train derailments. Hence, in 2019 the consortium TU Darmstadt, KU Leuven, Austrian Institute of Technology and REVOTEC was commissioned by the German Federal Railway Authority to develop a completely new European high-speed train load model for dynamic calculations of railway bridges that should account for almost all current running operating trains in the European railway network. The project ended in June 2023 and this paper presents the steps carried out to develop the high-speed train load model, denoted as HSLM-C, and the results of validation calculations considering more than 300 existing railway bridges of different construction type.

This concept paper discusses the effects of the installation condition of fasteners on the life‐cycle performance of noise barriers. Noise barriers that are erected along high‐speed railway lines are loaded by aerodynamic pressure and suction waves due to the passing trains. As an integral part of railway infrastructures their level of safety must be maintained throughout their entire lifetime. On basis of this concept and study, a potential monitoring‐based approach for the assessment of the life‐cycle performance of NBs is briefly introduced. That monitoring‐based approach finds its place in a holistic four‐stage assessment framework, in other words a progressive four‐stage model in which the information content increases with each model stage and thus successively increases the accuracy of the determined structural conditions at the time of observation and the prediction for the remaining service life of the structure. The objectives of this paper should bring relevant insights for the whole holistic four‐stage model. Depending on how far the degradation of the considered noise barrier has already progressed, the corresponding stage of the holistic assessment concept is activated, which enable infrastructure managers to plan their future investments regarding maintenance, retrofit or rebuilt of noise barriers more economically.

The train-induced forced vibration responses of railway bridges are investigated and evaluated under consideration of nonlinear effects.The considered nonlinearities refer to the amplitude dependency of the natural frequencies, which was observed during in-situ measurements conducted by the authors for several existing railway bridges of different construction type.The nonlinearities detected during dynamic measurements on existing railway bridges are presented and discussed.The focus is on single-span steel and concrete slab bridges with ballasted superstructure.Numerical simulations of train crossings are carried out under assumption of nonlinear beam models for the considered railway bridges.The amplitude dependency of the natural frequencies is considered in these nonlinear simulations and the structural responses during train crossing are presented in the form of resonance curves.For comparison purposes, the calculations are also carried out on linear beam models with constant natural frequencies and the resulting deviations are discussed.The influence of the investigated nonlinearities on the vibration response behavior of railway bridges is highlighted and recommendations for the future consideration of these effects in dynamic calculations of train crossing are given.

Railway noise barrier constructions are subjected to high aerodynamic loads during the train passages, and the knowledge of their actual structural condition is relevant to assure safety for railway users and to create a basis for forecasting. This paper deals with deterministic and probabilistic approaches for the condition assessment and prediction of the remaining lifetime of railway noise barriers that are embedded in a safety concept that takes into account the damage consequence classes. These approaches are combined into a holistic assessment concept, in other words, a progressive four-stage model in which the information content increases with each model stage and thus successively increases the accuracy of the determined structural conditions at the time of observation and the forecast of the remaining service life of the structure. The analytical methods used in the first stage of the developed holistic framework are based on common static calculations used in engineering practice and, together with expert knowledge and large-scale fatigue test results of noise barrier constructions, form the basis for the subsequent stages. In the second stage of the data-driven condition assessment and life cycle analysis approach, linking routines are implemented that combine the condition assessments from the visual inspections with the additional information from temporary or permanent monitoring systems with the analytical methods. With the application of numerical finite element methods for the development of a digital twin of the noise barrier in the third stage and the probabilistic approaches in the fourth stage, a maximum determination accuracy of the noise barrier condition at the time of observation and prediction accuracy of the remaining service life is achieved. The data-driven condition assessment and life cycle analysis approach enables infrastructure operators to plan their future investments more economically regarding the maintenance, retrofitting, or new construction of railway noise barriers. Ultimately, the aim is to integrate the presented four-stage holistic assessment concept into the specific maintenance and repair planning of infrastructure operators for aerodynamically loaded railway noise barrier constructions.

In recent years the application of vehicle-based indirect Structural Health Monitoring (SHM) to railway bridges has increased significantly and it has been shown that this method provides several advantages compared to traditional SHM methods. However, vehicle-based indirect SHM still entails several challenges that require further research. In this paper, the application of the vehicle-based indirect SHM method is demonstrated numerically and experimentally for determining the natural frequencies of an Austrian railway bridge. At first, the coupled equations of motion of the train-bridge multi-body model are presented and train crossing simulations are conducted numerically considering different train speeds. The vibration responses during train crossing are evaluated for both the train multi-body system and the considered railway bridge model. Different representative evaluation points are chosen at the wheelsets, bogies, and car bodies of the considered train. At second, the resonance frequencies of the bridge are measured in-situ by executing forced vibration tests applying closed-loop controlled electrodynamic shakers. Besides in-situ measurements of the bridge, the considered moving train is also equipped with accelerometers, and the vibration responses of both the bridge and the moving train are measured simultaneously during the duration of several train crossings. The recorded vibration responses are analyzed in the frequency domain and compared with the numerical simulation results. It is shown that the first longitudinal bending frequency of the considered railway bridge can be clearly identified from the computed frequency response spectra.

The high safety requirements for railway infrastructures are a basic demand that the railway user places on the railway operator. Noise barriers that are erected along high-speed railway lines are loaded by aerodynamic pressure and suction waves due to the passing trains. Noise barriers are an integral part of railway infrastructures, and their level of safety must be maintained throughout their entire lifetime. This concept paper discusses deterministic and probabilistic-based approaches for condition assessment and prognosis of remaining service life of railway noise barriers, embedded in a safety concept that takes damage consequence classes into account. These approaches are combined into a holistic assessment concept, in other words a progressive four-stage model in which the information content increases with each model stage and thus successively increases the accuracy of the determined structural conditions at the time of observation and the forecast for the remaining service life of the structure. The analytical methods used in the first stage of the developed holistic framework are based on common static calculations used in the engineering practice and, together with expert knowledge and large-scale fatigue test results of noise barrier constructions, form the basis for the subsequent stages. Linking routines that combine the condition assessments from the common executed visual inspections and additional information from permanent monitoring systems applied to failure-critical elements with the analytical methods of the first stage are implemented in the second stage of the holistic framework. With application of numerical finite element methods in the third stage and finally the probabilistic approaches in stage four, the highest degree of determination accuracy of the noise barrier condition at the time of observation and prediction accuracy of the remaining lifetime shall be achieved. Depending on how far the degradation of the considered noise barrier has already progressed, the corresponding stage of the holistic assessment concept is activated, which enable infrastructure managers to plan their future investments regarding maintenance, retrofit or rebuilt of noise barriers more economically. The aim is to integrate the project results into a supranational framework, which is established through orientation towards Europe-wide preliminary projects.

In this paper, parametric forced tuned solid ball dampers (TSBD) are considered for vibration control of engineering structures in an untypical way. The special feature of the presented investigation is to evaluate the potential application of parametric forcing of the rolling cylindrical or spherical body in the runway for reducing the vertical vibrations of a vibration-prone main system. Typically, tuned solid ball dampers are applied to structures that are prone to horizontal vibrations only. The coupled nonlinear differential equations of motion are derived and the phenomenon of parametric resonance of the rolling body in the runway is analyzed. A criterion for avoiding parametric resonance is given to achieve the optimal damping effect of the TSBD. In the second part of the article, a method for the targeted use of parametric resonance to reduce the vertical vibrations of engineering structures is presented and verified, considering a biaxially harmonic excited pedestrian bridge. It is shown that, with a suitable choice of damper parameters, a stable vibration of the rolling body in the runway is formed over the course of the vibration despite the occurrence of parametric resonance and that the maximum vertical vibration amplitudes of the main system can be reduced up to 93%. Hence, the here presented untypical application of parametric forced TSBD for reducing the vertical forced vibrations of vibration-prone main systems could be successfully demonstrated.

The purpose of this paper is to present a novel single tube semi-active tuned liquid gas damper (SA-TLGD) for suppressing horizontal vibrations of tower-like structures and to study its damping effectiveness. The main difference to the well-known state-of-the-art tuned liquid column damper (TLCD) is the special geometric shape of the developed SA-TLGD. Contrary to the TLCD, the presented SA-TLGD only consists of a single horizontal tube that is partially filled with water. A large deformable elastic membrane with neglectable stiffness is used as the interface between the liquid and the air. Both ends of the horizontal tube are sealed and the resulting gas spring is used as the restoring force and frequency tuning parameter, respectively. The developed SA-TLGD is a semi-active vibration damping device, where its natural frequency and magnitude of energy dissipation can be re-adjusted during operation. Due to the lack of any vertical tube parts, this new type of vibration absorber requires significantly less installation space compared to the classical TLCDs. The equations of motion of the SA-TLGD and the coupled main system are derived by the application of conservation of momentum. The procedure of optimal tuning of the SA-TLGD is presented, and computational numerical studies are performed to demonstrate the damper effectiveness. It is shown that the application of the developed SA-TLGD provides a large reduction in the maximum horizontal forced vibration amplitudes of tower like-structures and that its semi-active functionality enables the possibility of re-adjustment any time during the operation life of the structure.

Die bei Zugfahrten in Eisenbahntunneln auftretenden druckwellen‐ und strömungsinduzierten aerodynamischen Belastungen werden dargelegt und in Bezug auf die Beanspruchungswirkungen der in modernen Bahntunneln ausgeführten unterschiedlichen Einbauten diskutiert. Es wird gezeigt, dass die in den derzeitigen Richtlinien und Normen angegebenen Belastungsgrößen tw. unvollständig sind und insbesondere die Effekte einer Wirbelablösung am Heck des fahrenden Zugs mit der daraus sich einstellenden hochgradig dynamischen Wirbelschleppe nicht abdecken. Im Zuge von mehreren Messkampagnen und begleitenden numerischen Simulationsberechnungen wurden in Österreich die in der Realität bei Zugfahrten in Eisenbahntunneln tatsächlich auftretenden aerodynamischen Belastungen abgeleitet und darauf aufbauend für unterschiedliche Einbauten die bei der Bemessung anzusetzenden Belastungswerte formuliert. Bei den Simulationsberechnungen wurde insbesondere auch die bei langen Tunneln maßgebende Fahrt von mehreren Zügen dicht hintereinander untersucht. Die Durchführung dieser numerischen Simulationsberechnungen und Messkampagnen unter realen Betriebsbedingungen in schnell befahrenen eingleisigen Eisenbahntunneln sowie die erzielten Ergebnisse werden dargelegt.

As part of the research project MTE 2.0 initiated by OBB-Infrastruktur AG, extensive investigations into the actual temperature loads on railway bridges were carried out. As part of the project, measurements on bridge structures as well as evaluations of statistical meteorological climate data over a period of 50 years, probabilistic evaluations and both analytical and numerical calculations were carried out. Based on the results of the project, the design model for temperature loads according to Eurocode 1 was adapted for railway bridges (concrete or composite structures) and a proposal for an optimized temperature load model was newly developed, which is summarized in the following article. Comparative calculations for railway bridges have shown that the elongation of the bridges in the ultimate limit state according to the optimized load model are 25 % to 45 % lower than those based on ONORM EN 1991-1-5 or ONORM B 1991-1-5, respectively. Taking into account the partial safety factors and the characteristic values, the actual elongations of existing bridges can be described much more realistically using the newly developed load model.

In this article, the vibration response of railway bridges due to train crossing is investigated and evaluated under consideration of nonlinear effects. The considered nonlinearities refer to the amplitude dependency of the natural frequencies, which was observed for several real railway bridges. In the first part, the nonlinearities detected during dynamic measurements on real railway bridges are presented and discussed. The focus is on single-span reinforced concrete slab bridges with ballasted superstructure. In addition, the basics of the nonlinear duffing oscillator with sublinear spring characteristic are presented and the special effects of nonlinear oscillations are explained. In the second part, numerical simulations of train crossings are carried out under consideration of nonlinear beam models. The amplitude dependency of the natural frequencies is taken into account in the simulations and the structural responses during train crossing are presented in the form of resonance curves. For comparison purposes, the calculations are also carried out on linear beam models with constant natural frequencies and the resulting deviations are discussed. The influence of the investigated nonlinearities on the vibration behavior of railway bridges is highlighted and recommendations for the future consideration of these effects in dynamic calculations of train crossing are given.