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Publications
Publications (67)
Increasing the operating speed of trains in modern railway networks can induce greater actions on the infrastructure than was previously the case. This is due, in particular, to the occurrence of the resonance phenomenon in railway bridges, which is the focus of this paper and was not traditionally considered as a concern. In this context, the vibr...
The assessment of running safety of railway bridges is conditioned by the Eurocode EN 1990 A2 by limiting vertical deck acceleration. On ballastless track bridges, this value is 5 m/s2. The background for this value is not clear, and it is believed that it originates in the application of an arbitrary safety factor of 2 on accelerations around 1 g...
As far as the authors are aware, the threshold for vertical acceleration of the bridge deck was chosen based on the assumption that the induced dynamic loads would overcome gravity at higher accelerations, resulting in loss of contact between wheels and rail; however, the previous studies do not support this hypothesis. Considering these inconsiste...
This paper presents an efficient 2D beam model of a continuous single-track concrete slab bridge considering the effect of surrounding soil conditions at the location of the retaining walls. A 3D model is used to investigate the backfill soil’s added flexibility for different soil properties. It is shown that for the first bending mode, the additio...
In the field of structural analysis dedicated to the study of vibrations of high-speed railway bridges, one reference load model is the well-known HSLM-A, which limits of validity are stated in Eurocode EN 1991-2, Annex E. In a recent paper published in the Journal of Rail and Rapid Transit, the authors investigated the degree of coverage provided...
This book describes the most recent strategies for the digitalization of railway sector that bring new challenges for the construction, operation, and maintenance of railway infrastructures. These strategies involve the development and application of new technologies and methodologies to enhance the sustainability and resilience of railway infrastr...
There is a growing intent among engineers, stakeholders, and decision makers to use probabilistic methods for infrastructure assessment or design objectives. However, the corresponding limit state for such problems usually requires the construction of complex computational models, usually using commercial software without parallelization capability...
High-speed railway is expanding drastically in Sweden, necessitating new technology, and improvements of existing structures. End-shield bridges are a common and under-tested bridge type in Sweden. Their dynamic performance is significantly impacted by their boundary conditions due to the soil–structure interaction (SSI) and their large masses cant...
Structural damping is an important characteristic in railway bridges, which affects the performance of the structure, especially for bridges with train speeds higher than 200 km/h. The accurate evaluation of damping must be performed properly to correctly assess the structural performance of the bridge under dynamic loading conditions. The present...
Excessive vertical acceleration of ballastless railway bridges subjected to vibrations induced by passing trains is one of the governing design criteria for bridges in high-speed lines. However, to the authors’ knowledge, the corresponding design limit is not based on a solid theoretical or experimental background. Moreover, the traditionally appli...
Railway bridges may experience large vibrations from passing trains if the load frequency of the train coincides with the natural frequency of the bridge. For long and slender bridges on high-speed lines, this may occur within the range of the operational speed. In combination with low inherent damping of the bridge, excessive vibrations during tra...
In this paper, a closed-form solution of the moving harmonic load problem for continuous Euler–Bernoulli beam systems is presented. The generality of the boundary conditions is taken into account by solving the characteristic equation of the system, obtaining its natural frequencies and mode shapes. The undetermined coefficient method is applied to...
The dynamic response of railway bridges is important to consider, as the high velocity loading from the trains increases the risk of resonance. Increasing train speeds and loads result in a need for adaptable properties for railway bridges. One solution is to install magnetorheological dampers, as the response of the structure originating from movi...
This paper presents results from experimental testing of a railway bridge. Forced vibration tests was performed using a hydraulic actuator with variable load amplitude. The estimated modal properties show that the increased load amplitude results in lower natural frequency and higher damping, especially for the first mode of vibration. Despite this...
The operational speed of the trains is intended to be significantly increased forthcoming; which consequently questions the safety level of the current design concepts concerning different performance limits. Thus, the reliability of the simply supported single-span bridges is assessed in the current article adopting the first-order reliability met...
One approach for upgrading existing high-speed railway bridges which are susceptible to excessive vibrations is to install damping devices. In this article, a model of a simply supported bridge with supplemental fluid viscous dampers installed between the superstructure and the abutments is derived based on an arbitrary mode of vibration. The aim i...
The objective of this study is to evaluate the vibratory response of two-span continuous beams subjected to moving loads and, in particular, to investigate the maximum resonance and cancellation of resonance phenomena. The main practical interest is the evaluation of the maximum acceleration response in railway bridges, which is one of the most dem...
In this work, the effect of the surrounding soil condition on the fundamental modal characteristics and dynamic response of railway bridges with integral abutments is studied. Due to the computational cost of the full FE models and the lack of reliable simplified models, the effect of the soil-structure interaction is usually neglected in the vibra...
The influence of dynamic soil–structure interaction (SSI) on simply supported railway bridges is investigated. Impedance functions are calculated considering shallow foundations in soil strata limited by bedrock. The impedance functions are coupled to bridge models, and the assembled soil–bridge systems are investigated addressing the modal propert...
The information contained in this paper will be of interest not only to bridge engineers, but also to train manufacturers. The article provides practical insight into the degree of coverage of real articulated trains (ATs) that Eurocode EN1991-2 guarantees. In both the design of new railway bridges, as well as in the assessment of existing ones, th...
The influence of model assumptions on the dynamic impedance functions of shallow foundations is investigated using finite elements in two studies. The first investigates the effects of model assumptions in different combinations including embedment of the foundation, variation of modulus with depth, and permanent load acting on the foundation. The...
The train running safety on non-ballasted bridges is studied based on safety indices from the vertical wheel–rail forces. A 2D train–track–bridge interaction model that allows for wheel–rail contact loss is adopted for a comprehensive parametric study on high-speed passenger trains. The relation between bridge response and vehicle response is studi...
This paper presents a full-scale dynamic testing on a simply supported railway bridge with integrated end-shields, by using a hydraulic exciter. Experimental frequency response functions are determined based on load controlled frequency sweeps. Apart from accurate estimates of natural frequencies, damping and mode shapes, the experimental testing a...
Short-span portal frame bridges are predominant in Swedish railway lines. Although it is well known that the dynamic response of these partially-buried rigid structures is governed by the surrounding soil, the effect of the soil is usually neglected in the train-induced vibration analysis due to the expensive computational costs. This paper focuses...
This article presents preliminary theoretical results on the influence of dynamic soil-structure interaction (SSI) of slab foundations. Impedance functions, representing the dynamic SSI, were obtained from FE-models depicting the soil for a few cases of different geotechnical preconditions. The obtained impedance functions were attached to single-s...
Mainly because of the infamous incident with excessive vibrations of the London Millennium Bridge, the behavior of lively footbridges has been thoroughly studied lately. The liveliness of such bridges is strongly connected to various interaction effects between the pedestrians and the bridges. One such effect is the variation in the modal propertie...
p>Due to an increasing interest in recreational running, groups of jogging people becomes a more frequent load case on footbridges. The studies related to runners on footbridges are very limited and according to current design guidelines, running loads can be neglected. This study aims at investigating if the effect of running pedestrians on a foot...
The railway track, being discretely supported at each sleeper, has a varying stiffness. The periodic loading from the wheels passing the sleepers at a certain speed introduces the sleeper passing frequency. This excitation of the track is a well-known source of vibration for track embankments. However, the interaction between the sleeper passing fr...
Several bridges along the Bothnia railway line in Sweden do not fulfil the Eurocode requirements regarding the maximum vertical bridge deck acceleration. The aim of this study is to investigate the possibility of reducing the acceleration of one of these bridges to an acceptable level by using post-installed viscous dampers. The bridge-damper syste...
p>The dynamic response of structures is an important aspect to consider, especially at resonance. Particularly, bridges traversed by trains are at risk, due to the repeated loading with regular interval from the axle and bogie spacings. If the risk of resonance is not accounted for in the design, the vertical acceleration of the bridge deck may exc...
Due to a trend in designing light and slender structures, many modern footbridges are prone to excessive vibrations. Severely vibrating footbridges can give rise to discomfort for the pedestrians. Therefore, during the last decades, pedestrian-induced vibrations of footbridges have become a subject of great interest. In this study, the performance...
p>Short and stiff bridges are generally quite sensitive to the dynamic effects arising from train-bridge interaction. In the Swedish landscape, such bridges are common and represent 60-70% of the total bridge stock. Recent research has clearly shown that simple structural models may result in highly conservative predictions of the dynamic response...
The following paper discusses different aspects of railway bridge dynamics, comprising analysis, modelling procedures and experimental testing. The importance of realistic models is discussed, especially regarding boundary conditions, load distribution and soil-structure interaction. Two theoretical case studies are presented, involving both determ...
This paper describes the development of a hydraulic bridge exciter and its first pilot testing on a full scale railway bridge in service. The exciter is based on a hydraulic load cylinder with a capacity of 50 kN and is intended for controlled dynamic loading up to at least 50 Hz. The load is applied from underneath the bridge, enabling testing whi...
This article presents numerical and experimental analyses of a steel truss railway bridge. The main feature of this work is that dynamic experiments have been performed before and after the ballasted track was placed on the bridge. Consequently, it has been possible to quantify the effect of the ballast and the rails on the dynamic properties of th...
In this article, the use of external damping systems for vibration mitigation of railway bridge dynamics is studied. For a presented case study bridge, the performance of different tuned mass damper systems (TMDs) is studied. During train passage, the change in dynamic characteristics of the bridge may produce a significant detune to a passive TMD....
The dynamic response from passing trains at high speed is studied for a short span soil–steel composite bridge. Field measurements have been performed, comprising steel strains, vertical crown displacements and accelerations in the steel and the backfill. Soil material damping properties are estimated through analysis of the field measurements. App...
The Swedish government is considering upgrading the train speed along three railway lines in the Southern part of Sweden from 200 km/h to 250 km/h. According to the current design code, this requires that the bridges be examined with dynamic simulations to avoid excessive vibrations. This paper employs a method that can be used at an early stage to...
In this paper, a load capacity assessment and strengthening measures of a multi-span railway arch bridge with backfill are presented. The bridge is located in Stockholm, Sweden, and constitutes a vital link for the national railway network. The bridge consists of 20 concrete arches with overlying backfill, each with a span of 20 m. After more than...
In this paper, fatigue assessment of a steel railway bridge is presented. The bridge is located in central Stockholm, Sweden, and is one of the most vital links for the railway network. The bridge service both freight trains and commuter trains with more than 500 passages per day. The main load bearing structure is designed as a steel grillage of w...
In this paper, the advantage of an adaptive damping system is presented. A damper with variable stiffness is tuned based on estimates of the real-time frequency response, facilitating optimal vibration mitigation. The performance of the developed routines is investigated on an existing tied arch railway bridge. Based on previous field measurements,...
In this paper, dynamic analyses and field measurements of a tied arch railway bridge is presented. Excessive vibrations of the hangers were obtained, caused by resonance during train passages. The resulting increase of the stress level and number of stress cycles were shown to decrease the fatigue service life significantly. The most critical secti...
During routine inspections of the Söderström Bridge in central Stockholm, one of Sweden’s most important railway bridges, cracks were found in the web of the main steel beams. The finding initiated theoretical studies which showed that the cracks developed mainly due to poorly designed connections of the cross beams and out-of-plane bending of the...
During annual inspections of one of Sweden's most important railway bridges, the Söderström Bridge in central Stockholm, cracks in the web of the main steel beams have been discovered. Extensive theoretical work has been undertaken to assess the remaining service life of the bridge. Furthermore, the bridge has recently been instrumented to enhance...
This paper deals with the dynamic effects on a tied arch railway bridge during train passages. The bridge is located in Ånge municipality in central Sweden. Large vibrations of the hangers were observed during train passages and field measurements have been performed to study the train induced vibrations of the hangers. According to the Palmgren–Mi...
The aim of this thesis is to analyse the effects of train induced vibrations in a steel Langer beam bridge. A case study of a bridge over the river Ljungan in Ånge has been made by analysing measurements and comparing the results with a finite element model in ABAQUS. The critical details of the bridge are the hangers that are connected to the arch...
In this paper, results from full-scale tests on a corrugated soil-steel flexible culvert for railway traffic are presented. The bridge was instrumented with strain gauges, acceler-ometers and displacement gauges, measuring the response from passing trains. The aim of the measurement campaign was to gain knowledge of the dynamic behaviour due to tra...