To ensure the compatibility between rolling stock and infrastructure when dynamically assessing railway bridges under high-speed traffic,the damping properties considered in the calculation model significantly influen...To ensure the compatibility between rolling stock and infrastructure when dynamically assessing railway bridges under high-speed traffic,the damping properties considered in the calculation model significantly influence the predicted acceleration amplitude at resonance.However,due to the normative specifications of EN 1991-2,which are considered to be overly conservative,damping factors that are far below the actual damping have to be used when predicting vibrations of railway bridges,which means that accelerations at resonance tend to be overestimated to an uneconomical extent.Comparisons between damping factors prescribed by the standard and those identified based on in situ structure measurements always reveal a large discrepancy between reality and regulation.Given this background,this contribution presents a novel approach for defining the damping factor of railway bridges with ballasted tracks,where the damping factor for bridges is mathematically determined based on three different two-dimensional mechanical models.The basic principle of the approach for mathematically determining the damping factor is to separately define and superimpose the dissipative contributions of the supporting structure(including the substructure)and the superstructure.Using the results of a measurement campaign on 15 existing steel railway bridges in the Austrian rail network,the presented mechanical models are calibrated,and by analysing the energy dissipation in the ballasted track,guiding principles for practical application are defined.This guideline is intended to establish an alternative to the currently valid specifications of EN 1991-2,enabling the damping factor of railway bridges to be assessed in a realistic range by mathematical calculation and thus without the need for extensive in situ measurements on the individual structure.In this way,the existing potential of the infrastructure with regard to the damping properties of bridges can be utilised.This contribution focuses on steel bridges,but the mathematical approach for determining the damping factor applies equally to other bridge types(concrete,composite,or filler beam).展开更多
A realistic and economical dynamic assessment of railway bridges requires input parameters that correspond to reality.In this context,the applied damping properties of the structure have a decisive influence on the re...A realistic and economical dynamic assessment of railway bridges requires input parameters that correspond to reality.In this context,the applied damping properties of the structure have a decisive influence on the results in the prediction of resonance effects and further in the assessment of the compatibility between rolling stock and railway bridges.The standard prescribes damping factors depending on the type of structure and the span to be used in dynamic calculations.However,these factors can be regarded as very conservative values which do not represent reality.Thus,in situ measurements on the structure are often necessary to classify a bridge categorised as critical in prior dynamic calculations as non-critical.Regarding in situ tests,a measurement-based determination of the damping factor is inevitably accompanied by a scattering of the generated results due to the measurement method used and as a result of the individual scope of action of the test-evaluating person and this person’s interpretation of the measurement data.This paper presents novel evaluation methods and analysis tools for determining the damping factor based on measurements in the frequency and time domains,intending to reduce the scatter of the results and limit the scope of action of the person evaluating the test.The main aim is to provide simple and easy-to-use evaluation algorithms for practical applications without additional data transformations and to define clear principles of action for the data-based evaluation of realistic and high damping factors.Based on in situ tests on 15 existing railway bridges,the data-based procedure for determining the damping factor is explained,and the methods are compared in the time and frequency domains.It is shown that a clearly defined evaluation algorithm can significantly reduce the scattering of results.Furthermore,it is demonstrated that forced vibration excitation and evaluation in the frequency domain provide the best results in reliable,reproducible,and high damping factors.展开更多
基金funded by the Austrian Federal Railways(ÖBB Infrastruktur AG)in the context of the research project‘VeMoDiss’(acronym)。
文摘To ensure the compatibility between rolling stock and infrastructure when dynamically assessing railway bridges under high-speed traffic,the damping properties considered in the calculation model significantly influence the predicted acceleration amplitude at resonance.However,due to the normative specifications of EN 1991-2,which are considered to be overly conservative,damping factors that are far below the actual damping have to be used when predicting vibrations of railway bridges,which means that accelerations at resonance tend to be overestimated to an uneconomical extent.Comparisons between damping factors prescribed by the standard and those identified based on in situ structure measurements always reveal a large discrepancy between reality and regulation.Given this background,this contribution presents a novel approach for defining the damping factor of railway bridges with ballasted tracks,where the damping factor for bridges is mathematically determined based on three different two-dimensional mechanical models.The basic principle of the approach for mathematically determining the damping factor is to separately define and superimpose the dissipative contributions of the supporting structure(including the substructure)and the superstructure.Using the results of a measurement campaign on 15 existing steel railway bridges in the Austrian rail network,the presented mechanical models are calibrated,and by analysing the energy dissipation in the ballasted track,guiding principles for practical application are defined.This guideline is intended to establish an alternative to the currently valid specifications of EN 1991-2,enabling the damping factor of railway bridges to be assessed in a realistic range by mathematical calculation and thus without the need for extensive in situ measurements on the individual structure.In this way,the existing potential of the infrastructure with regard to the damping properties of bridges can be utilised.This contribution focuses on steel bridges,but the mathematical approach for determining the damping factor applies equally to other bridge types(concrete,composite,or filler beam).
基金funded by the Austrian Federal Railways (ÖBB Infrastruktur AG) in the context of the research project ‘Ve Mo Diss’ (acronym)
文摘A realistic and economical dynamic assessment of railway bridges requires input parameters that correspond to reality.In this context,the applied damping properties of the structure have a decisive influence on the results in the prediction of resonance effects and further in the assessment of the compatibility between rolling stock and railway bridges.The standard prescribes damping factors depending on the type of structure and the span to be used in dynamic calculations.However,these factors can be regarded as very conservative values which do not represent reality.Thus,in situ measurements on the structure are often necessary to classify a bridge categorised as critical in prior dynamic calculations as non-critical.Regarding in situ tests,a measurement-based determination of the damping factor is inevitably accompanied by a scattering of the generated results due to the measurement method used and as a result of the individual scope of action of the test-evaluating person and this person’s interpretation of the measurement data.This paper presents novel evaluation methods and analysis tools for determining the damping factor based on measurements in the frequency and time domains,intending to reduce the scatter of the results and limit the scope of action of the person evaluating the test.The main aim is to provide simple and easy-to-use evaluation algorithms for practical applications without additional data transformations and to define clear principles of action for the data-based evaluation of realistic and high damping factors.Based on in situ tests on 15 existing railway bridges,the data-based procedure for determining the damping factor is explained,and the methods are compared in the time and frequency domains.It is shown that a clearly defined evaluation algorithm can significantly reduce the scattering of results.Furthermore,it is demonstrated that forced vibration excitation and evaluation in the frequency domain provide the best results in reliable,reproducible,and high damping factors.
