| 1. |
- Liu, Zhendong, et al.
(författare)
-
Implications of the operation of multiple pantographs on the soft catenary systems in Sweden
- 2015
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : Sage Publications. - 0954-4097 .- 2041-3017. ; 53:3, s. 341-346
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 2. |
- Liu, Zhendong, et al.
(författare)
-
Possible speed increase on soft catenary system with help of auxiliary pantograph
- 2016
-
Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015. - : CRC Press. ; , s. 927-936
-
Konferensbidrag (refereegranskat)abstract
- Stiffness variations and wave propagation in the catenary system cause high dynamic variations in the contact force between pantograph and catenary at high operating speeds. In order to increase the operational speed on an existing catenary system, especially on soft catenary systems, technical upgrading is usually required to keep the current collection quality within an acceptable range. Therefore, it is desirable to explore a more practical and costsaving method to achieve higher operational speed. With the help of a 3D pantograph-catenary finite element (FE) model, a parametric study on two-pantograph operation at short spacing distances is carried out. Results show that although the leading pantograph suffers from deterioration of dynamic performance, the trailing pantograph achieves a better dynamic behaviour by using a proper spacing distance between pantographs. To avoid the additional wear caused by poor dynamic performance on the leading pantograph, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current. In this way, the operational speed of the existing system can be increased while still sustaining a good dynamic performance without large modifications on the existing catenary system.
|
|
| 3. |
- Abrahamsen, Rune, et al.
(författare)
-
Dynamic Response of Tall Timber Buildings Under Service Load : The DynaTTB Research Program
- 2020
-
Ingår i: EURODYN 2020, XI international conferece on structural dynamics. - : National Technical University of Athens. - 9786188507210 ; , s. 4900-4910
-
Konferensbidrag (refereegranskat)abstract
- Wind-induced dynamic excitation is becoming a governing design action determin-ing size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and meas-ured to estimate their key dynamic properties (natural frequencies and damping), no systematic evaluation of dynamic performance pertinent to wind loading has been performed for the new and evolving construction technology used in TTBs. The DynaTTB project, funded by the Forest Value research program, mixes on site measurements on existing buildings excited by heavy shakers, for identification of the structural system, with laboratory identification of building elements mechanical features coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and pro-vide key elements to FE modelers.The first building, from a list of 8, was modelled and tested at full scale in December 2019. Some results are presented in this paper. Four other buildings will be modelled and tested in spring 2020.
|
|
| 4. |
- Abrahamsen, Rune, et al.
(författare)
-
Dynamic response of tall timber buildings under service load : results from the dynattb research program
- 2023
-
Ingår i: World Conference on Timber Engineering 2023 (WCTE 2023). - : Curran Associates, Inc.. - 9781713873297 ; , s. 2907-2914
-
Konferensbidrag (refereegranskat)abstract
- Wind-induced dynamic excitation is a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway, i.e. vibration serviceability problem. Although some TTBs have been instrumented and measured to estimate their key dynamic properties (eigenfrequencies, mode shapes and damping), no systematic evaluation of dynamic performance pertinent to wind loading had been performed for the new and evolving construction technologies used in TTBs. The DynaTTB project, funded by the ForestValue research program, mixed on site measurements on existing buildings excited by mass inertia shakers (forced vibration) and/or the wind loads (ambient vibration), for identification of the structural system, with laboratory identification of building elements mechanical features, coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and provide key elements to finite element models. This paper presents an overview of the results of the project and the proposed Guidelines for design of TTBs in relation to their dynamic properties.
|
|
| 5. |
- Colmenares, Daniel, et al.
(författare)
-
On the quantification of the human-structureinteraction effect on a random vibration framework
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The focus in this work is on evaluating the structural response to verticalpedestrian excitation using a spectral loading model for pedestrian-inducedforces that accounts for the randomness of human excitation and the increasedcorrelation between pedestrians as the pedestrian density increases.To account for the effect of human-structure interaction (HSI), the quantificationof the expected value of the response of the coupled pedestrianbridgesystem with respect to the expected value of the response of the samestructure under the same Gaussian spectral load density is presented. Aparametric analysis is presented and the influences of the ratio between themean step frequency and the natural frequency of the support structure, theratio of the natural frequency of the pedestrians to the natural frequency ofthe support structure, the modal mass ratio of the coupled system, and thecoefficient of variation of the considered Gaussian power spectral density ofthe load are studied. In addition, the correlation between pedestrians underunconstrained and constrained pedestrian traffic is investigated using thecoherence function. The study shows that further experiments are neededto avoid minimising the contribution of higher modes under restrictive trafficconditions on pedestrian bridges due to near-perfect correlation betweenpedestrians. Finally, an equivalent damping model and an equivalent forcemodel are presented to calculate the expected value of the response of thecoupled pedestrian-bridge system under a Gaussian-load power spectral density starting from the expected value of the response of only the consideredsupport structure.
|
|
| 6. |
- Liu, Zhendong, 1983-, et al.
(författare)
-
Application of tuned-mass system on railway catenary to improve dynamic performance
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Finding a simple and practical method to improve the dynamic behaviour of a specific structure is always desirable in civil and mechanical engineering. The railway catenary system is the overhead power line above the track, interacting with the train-based pantograph to transfer electric power. Due to vertical stiffness variation and a propagating wave along the catenary, the fluctuation of the contact force becomes significant with operational speed increasing. Therefore, this has become one of the key factors which limits the operational speed and service life of key components. Wire misalignment, structural errors and uneven mass distribution of the catenary can further deteriorate the contact stability. In order to achieve a higher speed on existing lines, the catenary needs large-scale modification implying long out-off-service time. From the designing aspect, all components directly fixed to the catenary, like clamps, steady arms and other fittings, are made as light and small as possible to minimize disturbances. However, in other engineering applications, some well-designed additional mass systems are adopted aiming to improve their dynamic performance. In order to take advantage of these unavoidable masses on the catenary, an investigation on lumped-mass distribution in single-pantograph and multi-pantograph operations is performed with help of a 3D pantograph-catenary finite element (FE) model. The results show that a rightly-tuned mass, here the implementing location and the elasticity of its connection, can positively change the dynamic performance without implementing large-scale modification to the existing system. Through a brief discussion on the mechanism of this positive effect, this paper proposes that applying some artificial tuned-mass system can be a possible method to overcome unfavourable working conditions or even allow speed increase on existing lines.
|
|
| 7. |
- Liu, Zhendong, 1983-, et al.
(författare)
-
Dynamic optimization of railway catenary system by turning unwanted lumped-mass into tuned-mass
- 2018
-
Ingår i: Dynamic optimization of railway catenary system by turning unwanted lumped-mass into tuned-mass. - : CRC Press/Balkema. - 9781138035713 ; , s. 675-680
-
Konferensbidrag (refereegranskat)abstract
- The railway catenary is suspended to its supports with droppers, clamps and oth-er fittings. These lumped-masses are made light and small to minimize disturbances. The mass-es cannot be completely removed but can be adjusted during maintenance. In other technical systems, artificial mass is used to improve the dynamic behaviour. Therefore, in this study the relationship between the lumped-mass distribution and its dynamic behaviour is investigated. Based on a 3D pantograph-catenary finite element (FE) model, a parametric study on the lumped-mass distribution on the Swedish soft catenary system is performed by applying addi-tional lumped-mass to different positions. It is shown that the mass distribution affects the dy-namic performance and in some cases, can improve the dynamic performance. The influence becomes stronger in multi-pantograph operation. Installing these masses on the messenger wire can avoid hard-point effects. In this way, the artificial mass can be used to improve the dynamic performance or correct some structural defects.
|
|
| 8. |
- Liu, Zhendong, et al.
(författare)
-
Numerical study on pantograph raising and lowering in multi-pantograph operation
-
Ingår i: The international Journal of railway technology. - 2049-5358 .- 2053-602X. ; :3
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Multi-pantograph operation is a convenient and efficient way to operate railway rolling stock, but the influence between the pantographs makes the system more sensitive and vulnerable than a single-pantograph system. When a train passes through special sections or in an emergency condition, it is necessary to lower one or all of the pantographs and then raise them up again. In these circumstances, the motion of the pantographs can introduce a sudden impact to the catenary that may change the pantograph configuration, then disrupting the dynamic stability. To address the dynamic performance during pantograph raising and lowering, a numerical study on multi-pantograph operation is carried out with help of a 3D pantograph-catenary finite element (FE) model under the conditions: up to three pantographs, various pantograph raising/lowering orders and different operating positions in a span. The results show that the leading pantograph is little influenced by the raising and lowering movement of any pantograph behind it. However, any trailing pantograph is significantly affected by any operation taking place ahead of it. The dynamic performance of the system depends on the pantograph spacing distance and the operational speed, but is little affected by the operating position in a span. To study auxiliary-pantograph operation where the leading pantograph works as an auxiliary pantograph, this paper shows how an optimal setting of the leading pantograph benefits the trailing pantograph and suggests specifying the speed where the leading pantograph gets into or out of service to avoid disruption.
|
|
| 9. |
- Nåvik, Petter, et al.
(författare)
-
Variation in predicting pantograph-catenary interaction contact forces, numerical simulations and field measurements
- 2017
-
Ingår i: Vehicle System Dynamics. - : Taylor & Francis. - 0042-3114 .- 1744-5159. ; 55:9, s. 1265-1282
-
Tidskriftsartikel (refereegranskat)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 80Hz cut-off frequency is compared to a 20Hz 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.
|
|
| 10. |
- Reymert, Sebastian, et al.
(författare)
-
A characterisation of vehicle-driver response to lateral disturbances when passing through bridge tower wakes
- 2024
-
Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105 .- 1872-8197. ; 246
-
Tidskriftsartikel (refereegranskat)abstract
- Some of the strongest wind -induced lateral perturbations of the vehicle -driver system on bridges are observed when passing the towers. Occupants may feel uncomfortable or unsafe as a result. The aims of this work are to characterise the wind velocity profile observed in the wakes of bridge towers and understand the mechanisms through which the vehicle -driver system responds. A test vehicle was repeatedly driven across 5 cable -supported bridges with towers, of which 4 have been studied. Observed changes in wind speed were between 7 and 20 m/s with reference wind speeds of 14 to 25 m/s. The spatial periods of the wind profiles varied between 1.0 and 3.5 vehicle lengths giving disturbances at frequencies of 0.7 to 3.2 Hz at 60 to 80 km/h. The results show that the driver overcompensates for the changes in aerodynamic loading at the towers and the handling response of the vehicle is dominated by steering input - rather than aerodynamic input - once the driver initiates steering compensation. It is also shown, in agreement with an existing conceptual model, that the amplitude of the driver's steering response is linearly related to the change in the vehicle's yaw rate immediately preceding the compensation attempt.
|
|
