Anders Rønnquist

Implications of the operation of multiple pantographs on the soft catenary systems in Sweden

Trains operating with several pantographs are used in Sweden and other countries. The more complex operational conditions, however, cause additional difficulties, i.e. low quality of current collection, increased mechanical wear and electromagnetic interference, due to the poor dynamic behaviour of the system. In order to address these problems, a three-dimensional model for the computational analysis of the interaction between catenary and pantograph is presented and validated in this paper, and the dynamic behaviour of the multi-pantograph system, based on Swedish soft pantograph/catenary systems, is analysed. Parametric studies are performed to investigate cases with different distances between pantographs and with up to three pantographs in use. The relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, is studied. The results show that an appropriate distance between pantographs and a given type of catenary allow operation on the existing infrastructure with up to three pantographs while maintaining an acceptable dynamic performance at the desired speed.

Dynamic assessment of existing soft catenary systems using modal analysis to explore higher train velocities: a case study of a Norwegian contact line system

Significant advances made on the rolling stock have considerably increased the possibility of higher speeds in existing railways. Thus, it is important to explore higher speeds and potential limiting factors of existing soft catenary systems. The present paper investigates procedures to assess the dynamic behaviour of these systems using response sampling and modal analysis. The assessment evaluates and quantifies dynamic response along the section. To verify the approach, a case study is conducted and the following assessment methods are used: lengthwise track correlation estimating dynamic predictability, power spectral density estimations before and after passage and short-time Fourier transforms and spectrograms. The combination provides detailed information on the dynamic behaviour. The first part introduces necessary considerations for suggested modal analysis. The second part describes an existing Norwegian section. The case study is conducted using a finite element model including a straight and a given section between Oslo-Trondheim, providing detailed evaluations and system limitation detections.

The use of dynamic response to evaluate and improve the optimization of existing soft railway catenary systems for higher speeds

An increasing demand for reduced travel times requires the exploitation of the full capacity of existing overhead railway catenary systems. This need has become an issue in Norway, as the majority of existing catenary systems are designed for a maximum speed of 130 km/h. In many regions, plans to reconstruct the railway line do not exist. Therefore, existing catenary sections must be optimized to increase a train’s velocity and reduce the total travel time. In this paper, the dynamic response is evaluated in an optimization investigation of an existing soft catenary system. A dynamic investigation that considers finite element models of existing soft railway catenary sections with original tension forces, current tension forces and suggested new tension forces for velocities at and above the design speed is conducted. The dynamic response is quantified by the interpretation of spectral densities and variations in their peak values. Due to more movement at mid-span than at the pole support, the effects from altering the tension forces and increasing the speed can be more accurately described and estimated by considering the dynamic content of the response at mid-span instead of the peak uplift at the pole support. A 23% increase in speed is possible for the system with the best tested new tension force setting, in which only the dynamic response and uplift at the pole support are considered.

Modal Analysis of a Floating Bridge Without Side-Mooring

The Norwegian Public Roads Administration is currently planning a ferry-free Coastal Highway Route E39. Floating bridges represent feasible options in this project with already two long span floating bridges in function, i.e. the Bergsoysund and Nordhordaland Bridges. In connection with this project, one of the main objectives is to quantify the accuracy of the numerical methods used to predict dynamic behaviour of floating bridges. An extensive monitoring system is installed to measure structural response as well as environmental actions from wind and waves on an existing floating bridge: the Bergsoysund Bridge. These measurements are used to estimate the modal system properties of the structure. The system identification is performed using a parametric time-domain Stochastic Subspace Identification method as well as the Frequency Domain Decomposition method. Challenges of system identification for highly damped structural systems, such as a floating bridge, are especially emphasized. The results are also compared with numerical predictions from a two part combined linear frequency-domain model set-up. The first part consists of a hydrodynamic model, including wave excitation as well as fluid-structure interaction, and relies on linearized potential theory. The results from this are thereafter introduced into a finite element model, for a complete structural dynamic analysis.

Variation in predicting pantograph–catenary interaction contact forces, numerical simulations and field measurements

ABSTRACT The contact force between the pantograph and the contact wire ensures energy transfer between the two. Too small of a force leads to arching and unstable energy transfer, while too large of a force leads to unnecessary wear on both parts. Thus, obtaining the correct contact force is important for both field measurements and estimates using numerical analysis. The field contact force time series is derived from measurements performed by a self-propelled diagnostic vehicle containing overhead line recording equipment. The measurements are not sampled at the actual contact surface of the interaction but by force transducers beneath the collector strips. Methods exist for obtaining more realistic measurements by adding inertia and aerodynamic effects to the measurements. The variation in predicting the pantograph–catenary interaction contact force is studied in this paper by evaluating the effect of the force sampling location and the effects of signal processing such as filtering. A numerical model validated by field measurements is used to study these effects. First, this paper shows that the numerical model can reproduce a train passage with high accuracy. Second, this study introduces three different options for contact force predictions from numerical simulations. Third, this paper demonstrates that the standard deviation and the maximum and minimum values of the contact force are sensitive to a low-pass filter. For a specific case, an 80 Hz cut-off frequency is compared to a 20 Hz cut-off frequency, as required by EN 50317:2012; the results show an 11% increase in standard deviation, a 36% increase in the maximum value and a 19% decrease in the minimum value.

On the Implementation of an Auxiliary Pantograph for Speed Increase on Existing Lines

ABSTRACT The contact between pantograph and catenary at high speeds suffers from high dynamic contact force variation due to stiffness variations and wave propagation. To increase operational speed on an existing catenary system, especially for soft catenary systems, technical upgrading is usually necessary. Therefore, it is desirable to explore a more practical and cost-saving method to increase the operational speed. Based on a 3D pantograph–catenary finite element model, a parametric study on two-pantograph operation with short spacing distances at high speeds shows that, although the performance of the leading pantograph gets deteriorated, the trailing pantograph feels an improvement if pantographs are spaced at a proper distance. Then, two main positive effects, which can cause the improvement, are addressed. Based on a discussion on wear mechanisms, this paper suggests to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current, to minimise additional wear caused by the leading pantograph. To help implementation and achieve further improvement under this working condition, this paper investigates cases with optimised uplift force on the leading pantograph and with system parameter deviations. The results show that the two positive effects still remain even with some system parameter deviations. About 30% of speed increase should be possibly achieved still sustaining a good dynamic performance with help of the optimised uplift force.

Global Buckling Reliability Analysis of Slender Network Arch Bridges: An Application of Monte Carlo-Based Estimation by Optimized Fitting

Network arch bridges are extremely slender bridge structures with a very efficient load-carrying structure. This configuration can carry loads that are several times greater than traditional tied-arch bridges with vertical hangers. These bridges are seen as an attractive structure due to their slenderness, which potentially also make them vulnerable to global system buckling. Thus, the buckling reliability of network arch bridges is here further investigated with emphasis on geometric and load uncertainties. In principle, the reliability of structural systems can be accurately predicted by standard Monte Carlo simulation. This method has several attractive features for structural system reliability. One is that the system failure criterion is easy to control, almost irrespective of the complexity of the system. However, the computational cost involved may be prohibitive for highly reliable structural systems if standard Monte Carlo simulation is used. In this chapter a recently developed enhanced Monte Carlo method has been applied for calculating the reliability. This method drastically reduced the computational burden of the standard Monte Carlo approach and thereby made it practically feasible to estimate the reliability of the bridge against buckling.of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Preface Communities face a number of risks from natural and anthropogenic hazards. Risk and reliability analysis provide essential information for risk determination (the quantification of the probabilities of potential consequences in various hazardous scenarios), evaluation (the decision of whether actions are necessary, under conditions of uncertainty), and mitigation (the decision of how to act). Over the past few decades, risk and reliability analysis have gone from a specialty topic to a mainstream subject in engineering, becoming essential tools for informed decision-making, hazard mitigation and planning. This book presents the state of the art in risk and reliability with a unique collection of contributions from some of the foremost scholars in the field. Combining the most advanced analysis techniques with practical applications, this book is one of the most comprehensive and up-to-date references available on this subject, makes the state of the art in risk and reliability analysis accessible to a large audience, and helps make risk and reliability analysis the rigorous foundation of engineering decision-making. The fundamental concepts needed to conduct risk and reliability assessments are covered in detail, providing readers with a sound understanding of the field and making the book a powerful tool for students and researchers alike. The book is a tribute to one of the fathers of modern risk and reliability analysis, Prof. Armen Der Kiureghian. During his career, Prof. Der Kiureghian has made fundamental and …

Covariance-Driven Stochastic Subspace Identification of an End-Supported Pontoon Bridge Under Varying Environmental Conditions

The Bergsoysund Bridge is currently being extensively monitored with accelerometers, anemometers, wave radars and GNSS sensors. By applying Covariance-driven Stochastic Subspace Identification (Cov-SSI), the modal parameters of the bridge are estimated. The results are interpreted in the context of the environment, represented by significant wave heights. The problem is characterized by the fact that modes are closely spaced in frequency and have high damping. Two weighting algorithms for the Cov-SSI are applied, to assess their performance for application on structures with these characteristics.

Monitoring Wind Velocities and Dynamic Response of the Hardanger Bridge

The Hardanger Bridge is the longest suspension Bridge in Norway and among the top 10 longest suspension bridges in the world. A comprehensive monitoring system was installed after it was completed in August 2013. The monitoring system is designed to provide data that can be used to verify the numerical methods used to predict wind induced dynamic response of slender bridges located in complex terrain. The monitoring system is outlined in this paper together with preliminary analysis of the accuracy of the model used to describe the self-excited forces acting on the bridge deck. Extensive wind tunnel testing was performed in the design of the Hardanger Bridge to achieve an excellent aerodynamic behaviour of the cross-section of the bridge deck. The experimental results of the aerodynamic derivatives that describe the self-excited forces have been combined with a finite element model of the bridge to predict the in-wind natural frequencies and damping ratios of the combined structure and flow system. The numerical predictions have been compared to results obtained from measured data using data-driven and covariance-driven stochastic subspace identification. It is concluded that the model for the self-excited forces provides in-wind frequencies and damping ratios that corresponds well to the observations from measured data.

Experimental evaluations of material damping in timber beams of structural dimensions

Understanding the inherent damping mechanisms of floor vibrations has become a matter of increasing importance following the development of new composite floor layouts and increased span. The present study focuses on the evaluation of material damping in timber beam specimens with dimensions that are typical of common timber floor structures. Using the impact test method, 11 solid wood beams and 11 glulam beams made out of Norway Spruce (Picea abies) were subjected to flexural vibrations. The tests involved different spans and orientations. A total of 420 material damping evaluations were performed, and the results are presented as mean values for each configuration along with important statistical indicators to quantify their reliability. The consistency of the experimental method was validated with respect to repeatability and reproducibility. General trends found an increasing damping ratio for higher modes, shorter spans, and edgewise orientations. It is concluded from the results that material damping of timber beams of structural dimensions is governed by shear deformation, which can be expressed more conveniently with respect to the specific mode shape and its derivatives.