| 1. |
- Ait-Ali, Abderrahman, 1991-, et al.
(author)
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Evaluating the mix of maintenance activities on railway crossings with respect to life-cycle costs
- 2024
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In: European Journal of Transport and Infrastructure Research. - : TU Delft. - 1567-7141 .- 1567-7133. ; 24:1, s. 1-29
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Journal article (peer-reviewed)abstract
- Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time, this makes them critical since they can cause costly delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both the life-cycle costs (LCCs) of the assets and socio-economic transportation costs for passengers and freight customers. In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) for the crossing panel – an S&C subsystem – is investigated using a combination of mechanical and econometric modelling. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle– turnout interaction. Long-term mechanical degradation of the crossing panel is simulated for different maintenance strategies that correspond to different timing of the associated maintenance measures (crossing repair welding and tamping). This provides the basis for analysing the interdependence between preventive and corrective activities using econometric modelling. Based on a case study of a common type of S&Cs in the Swedish infrastructure, the impact of different maintenance strategies on LCC and transportation costs is analysed. Opportunities and challenges in the development of more economically effective maintenance strategies of S&Cs are discussed.
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| 2. |
- Andersson-Sköld, Yvonne, 1957-, et al.
(author)
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Ramverk för att prioritera och bedöma nyttan av klimatanpassningsåtgärder
- 2023
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Reports (other academic/artistic)abstract
- Klimatförändringarna är idag påtagliga och även om vi snabbt får ner utsläppen av växthusgaser kommer fler, mer omfattande och mer kostsamma klimatrelaterade händelser att inträffa alltmer ofta. Kostnaderna inom den svenska transportsektorn för klimatrelaterade händelser som skadar gator, vägar, spår-/järnväg, med flera sårbara delar av infrastrukturen är stora redan idag och förväntas öka. Översvämningar, bränder och skador till följd av väderrelaterade händelser på anläggningar resulterar bland annat i minskad framkomlighet och en ökad risk för olyckor. För att upprätthålla transportsystemets funktion är det därför viktigt att vi vidtar riskreducerande åtgärder för att minska sannolikheten och omfattningen av negativa konsekvenser av både dagens klimat- och väderrelaterade händelser men framför allt för att hantera framtida klimatrelaterade händelser. Det är nödvändigt att säkerställa transportsystemets funktion vid extrema väderhändelser, och under perioder av långvarig nederbörd, långvariga värmeböljor och förändrade nederbördsmönster. Det gäller också att redan idag möjliggöra anpassningsåtgärder för att hantera långsiktiga förändringar som höjd havsvattennivå och grundvattennivåer, som påverkar infrastrukturens framkomlighet och livslängd.I denna rapport presenteras sammanfattande resultat och en sammanfattning av hur ett ramverk för att utvärdera klimatrelaterade effektsamband har använts. Med effektsamband avses att identifiera, bedöma och värdera klimatrelaterade risker och riskreducerande åtgärder. I denna rapport är fokus på att identifiera, bedöma och utvärdera effektiviteten av klimatrelaterade åtgärder. Resultatet av det framtagna ramverket kan användas för att analysera riskreducerande åtgärders effekter, det vill säga för att bedöma om det är relevant att genomföra en åtgärd, när i tiden den bör genomföras samt för att bedöma vilken åtgärd som är mest relevant att genomföra. De risker som beaktas genom fallstudier innefattar brandrisk, olycksrisk på gator och vägar på grund av nollgenomgångar eller värme, översvämning, erosion och skred och påverkan på vägkonstruktionen (spårbildning, bärighet och utmattning), solkurvor och risker vid kraftiga vindar. Testerna har innefattat faro- och riskidentifiering, riskanalys, identifiering och utvärdering av möjliga åtgärder. Exempel på fallstudier är Gävleregnet 2021, ett skyfall i Kungsbacka kommun 2019, erosionsrelaterade förändringar under lång tid vid Österdalälven och beräkningar av påverkan av temperatur, fuktighet och förändringar i tjälförändringsmönster på vägkonstruktionen vid E10 vid Svappavaara. I en av de fallstudier som sammanfattas i rapporten redovisas även en monetär värdering och känslighetsanalys. Ramverket har också legat till grund för en diskussion avseende klimatrelaterade risker kopplade till elförsörjning.
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| 3. |
- Carlberger, Andreas, 1992, et al.
(author)
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Numerical prediction of rail corrugation growth on curves
- 2016
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In: Proceedings of the 19h Nordic Seminar on Railway Technology, September 14 - 15, Luleå, Sweden (2016).
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Conference paper (other academic/artistic)abstract
- Rail corrugation (periodic surface irregularities at distinct wavelengths) is a problem experienced by many railway networks worldwide. Corrugation induces a pronounced dynamic wheel‒rail contact loading that leads to increased generation of noise and in severe cases even damage to vehicle and track components. The large magnitude creep forces and sliding between wheel and rail make corrugation especially prone to develop on curved track. The current work summarizes the results from a Master Thesis project performed in collaboration between Chalmers, ÅF Industry, Bombardier Transportation and Stockholm Public Transport. A time-domain model for the prediction of long-term growth of rail roughness has been developed, see Figure 1. Dynamic vehicle‒track interaction in a broad frequency range (at least up to 300 Hz) is simulated using the commercial software SIMPACK. Wheelset structural flexibility is accounted for by using modal parameters calculated for a finite element model. Non-Hertzian and non-steady wheel‒rail contact and associated generation of wear are calculated in a post-processing step in the software Matlab. Archard’s law is applied to model the sliding wear. A large number of train passages is accounted for by recurrent updating of the rail surface irregularity based on the calculated wear depth. The proposed prediction model is applied to investigate a curve on the Stockholm metro network exposed to severe corrugation growth.
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| 4. |
- Nielsen, Jens, 1963, et al.
(author)
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Switch panel design based on simulation of accumulated rail damage in a railway turnout
- 2016
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In: Wear. - : Elsevier BV. - 0043-1648. ; 366-367:SI, s. 241-248
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Journal article (peer-reviewed)abstract
- A methodology for numerical prediction of accumulated rail damage in railway turnouts is presented. Based on simulation of dynamic vehicle-track interaction followed by a discretisation of the conditions in each wheel-rail contact, distributions of rail wear are calculated by the Archard model of sliding wear, while surface initiated rolling contact fatigue (RCF) damage is evaluated by the Palmgren–Miner rule and an index building on shakedown theory. Partial slip in the wheel-rail contacts and variable amplitude loading are considered. For freight traffic in the diverging route, the influence of rail inclination and switch rail elevation on damage in the switch panel is investigated in a demonstration example. Two-point contact situations with one contact on the switch rail and one on top of the stock rail induce relative motion and slip between wheel and rail leading to high energy dissipation. In agreement with field observations, it is concluded that wear is the dominating damage mechanism on the gauge side of the switch rail while the risk for RCF is higher on the crowns of the switch and stock rails. For accurate prediction of rail life for given combinations of wheel/rail materials and traffic conditions, the methodology needs to be calibrated by field measurements.
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| 5. |
- Nielsen, Jens, 1963, et al.
(author)
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Switch panel design based on simulation of accumulated rail damage in a railway turnout
- 2015
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In: Proceedings of the 10th International International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Colorado Springs, USA, August-September 2015.
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Conference paper (peer-reviewed)abstract
- A methodology for numerical prediction of accumulated rail damage in railway turnouts is presented. Based onsimulation of dynamic vehicle‒track interaction followed by a discretisation of the conditions in each wheel‒railcontact, distributions of rail wear are calculated by the Archard model of sliding wear, while surface initiated rollingcontact fatigue (RCF) damage is evaluated by the Palmgren-Miner rule and an index building on shakedown theory.Partial slip in the wheel‒rail contacts and variable amplitude loading are considered. For freight traffic in the divergingroute, the influence of rail inclination and switch rail height on damage in the switch panel is investigated in ademonstration example. Two-point contact situations with one contact on the switch rail and one on top of the stock rail induce relative motion and slip between wheel and rail leading to high energy dissipation. In agreement with fieldobservations, it is concluded that wear is the dominating damage mechanism on the gauge side of the switch rail whilethe risk for RCF is higher on the crowns of the switch and stock rails. For accurate prediction of rail life for givencombinations of wheel/rail materials and traffic conditions, the methodology needs to be calibrated by fieldmeasurements.
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| 6. |
- Torstensson, Peter, 1981-, et al.
(author)
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Wheel–rail impact loads and noise generated at railway crossings : Influence of vehicle speed and crossing dip angle
- 2019
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In: Journal of Sound and Vibration. - : Academic Press. - 0022-460X .- 1095-8568. ; 456, s. 119-136
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Journal article (peer-reviewed)abstract
- Wheel–rail impact loads and noise at railway crossings are calculated by applying a hybrid prediction model. It combines the simulation of non-linear vertical dynamic vehicle‒track interaction in the time domain and the prediction of sound pressure level using a linear frequency-domain model. The two models are coupled based on the concept of an equivalent roughness spectrum. The time-domain model uses moving Green's functions for the linear vehicle and track models, accounting for wheel structural flexibility and a discretely supported rail with spatially-varying beam properties, and a non-Hertzian wheel–rail contact model. Three-dimensional surface geometry of the wheel and crossing is accounted for in the solution of the wheel–rail contact. The hybrid model is compared against field measurements and is demonstrated by investigating the influence of vehicle speed and crossing geometry on the radiated impact noise. Based on simulation results, it is concluded that the impact loads and noise can be mitigated by reducing the effective dip angle at the crossing, which is determined by the vertical trajectory of the wheel when making the transition between wing rail and crossing nose.
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| 7. |
- Ait-Ali, Abderrahman, 1991-, et al.
(author)
-
Evaluating the mix of maintenance activities on railway crossings with respect to life-cycle costs
- 2023
-
Reports (other academic/artistic)abstract
- Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time, this makes them critical since they can cause costly delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both the life-cycle costs (LCC) of the assets and socio-economic transportation costs for passengers and freight customers. In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) is investigated using a combination of mechanical and econometric modelling. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Long-term mechanical degradation of the S&C is simulated for different maintenance strategies that correspond to different timing of the associated maintenance measures (crossing repair welding and tamping). This provides the basis for analysing the interdependence between preventive and corrective activities using econometric modelling. Based on a case study of a common type of S&Cs in the Swedish infrastructure, the impact of different maintenance strategies on LCC and transportation costs is analysed. Opportunities and challenges in the development of more socio-economically effective maintenance strategies of S&Cs are discussed.
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| 8. |
- Ait-Ali, Abderrahman, 1991-, et al.
(author)
-
Evaluating the mix of maintenance activities on railway crossings with respect to life-cycle costs
- 2024
-
In: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 405-406
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Conference paper (other academic/artistic)abstract
- Switches and crossings (S&Cs) are critical assets in the Swedish rail infrastructure, with a density of 0.8 S&C per track-km and renewal costs of up to 4.5 million SEK/S&C. The efficiency of maintenance strategies for S&Cs is vital from a (socio-)economic perspective. The focus of this study is on the importance of the mix of maintenance activities performed on a S&C with respect to its life-cycle costs (LCCs). The study investigates the interdependencies between the deterioration mechanisms, preventive and corrective maintenance activities, and expected LCCs, including transportation costs due to traffic disruptions/delays. One or a combination of different approaches are often used in the literature, such as engineering or LCC methods. In this research, a novel approach is introduced that combines mechanical simulations, data analysis, econometrics, and LCC calculations to compare the efficiency of different maintenance strategies. The mechanical simulations consider one S&C on the Swedish railway network. The selection criteria were that the S&C is located on the main line, installed in 2014 (generates the longest observation period given the availability of data), and had no extreme values with respect traffic volume, maintenance activities and failures. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Further, the relationship between frequency of preventive and occurrence of corrective maintenance activities is analyses using an econometric model. Implications of a specific mix of maintenance activities on the S&C lifetime and LCC are evaluated using different cost parameters. Results obtained from mechanical simulations reveal the correlation between poor crossing geometry and higher rates of ballast settlement. The econometric analysis finds a statistically significant impact of (cumulative) preventive maintenance on corrective maintenance, i.e., more preventive maintenance leads to fewer corrective activities. Based on a standard mix of maintenance activities (inferred using econometric regression across all S&Cs), the lifetime of the selected S&C is estimated to 10 years with a lower associated LCC than that resulting from the record of performed maintenance activities at the site. The LCC evaluations highlight the potential to improve the efficiency of S&C maintenance by adopting proactive strategies.
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| 9. |
- Ait-Ali, Abderrahman, 1991-, et al.
(author)
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Evaluation of long-term maintenance of switches & crossings with respect to life-cycle costs and socio-economic impact
- 2022
-
Conference paper (other academic/artistic)abstract
- Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time this makes them critical, and they can cause major delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both life-cycle costs (LCC) of the assets and other additional socio-economic costs (e.g., transportation costs for passengers and freight customers). In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) is investigated using a combination of mechanical and econometric modelling.The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Changes in the timing of the associated maintenance measures (crossing repair welding and tamping) are performed to investigate the impact on damage modes. This is then linked to LCC and transportation costs, which requires a distribution between preventive and corrective activities with respect to the simulated maintenance strategy. This relationship is investigated by means of regression modelling: ??????????=?(??????????,?)where Corrective and Preventive represent the number of failures and the scheduled actions to prevent these failures, respectively. ? holds variables related to the traffic (volume, type of traffic, axle load, etc.) and the infrastructure (type of S&Cs, etc.).
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| 10. |
- Andersson, Robin, 1986, et al.
(author)
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An efficient approach to the analysis of rail surface irregularities accounting for dynamic train–track interaction and inelastic deformations
- 2015
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In: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 53:11, s. 1667-1685
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Journal article (peer-reviewed)abstract
- A two-dimensional computational model for assessment of rolling contact fatigue induced by discrete rail surface irregularities, especially in the context of so-called squats, is presented. Dynamic excitation in a wide frequency range is considered in computationally efficient time-domain simulations of high-frequency dynamic vehicle-track interaction accounting for transient non-Hertzian wheel–rail contact. Results from dynamic simulations are mapped onto a finite element model to resolve the cyclic, elastoplastic stress response in the rail. Ratcheting under multiple wheel passages is quantified. In addition, low cycle fatigue impact is quantified using the Jiang–Sehitoglu fatigue parameter. The functionality of the model is demonstrated by numerical examples.
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