Prediction and control of railway-induced vibration

Prediction and control of the vibration or re-radiated noise in buildings and other facilities induced by railway infrastructures or construction activities.

Targeted problem

The existing transport infrastructures in a specific region are sources of noise and vibration, generating an annoyance on the people living near them. Great advances has been achieved in the past three decades on noise control of transport infrastructures. Nowadays it is a well-established and normalized engineering subject. In contrast, vibration control has traditionally remained in the background. However, its importance is growing increasingly once the noise problem has been solved by means of underground infraestructures, the inclusion of acoustic screens, acoustic pavement, etc... Specifically, in recent years, the prediction and control of ground-borne vibration and re-radiated (structural) noise induced railways (especially underground) has become a relevant public concern, leading to many countries all around the world to establish regulations for the maximum ground-borne noise and vibration levels that can be reached in buildings near a railway infrastructure. The rise of high-speed lines has just pushed the concern on this topic a bit more.

Field experience

LEAM has been working for over 15 years on the phenomenology associated with the ground-borne noise and vibration induced by railway infrastructures. In this context, LEAM has formed or currently forms part of research projects focused on the prediction of this vibration impact, such as the CATdBTren, RECYTRACK, ISIBUR, NVTRail and VIBWAY funded by different national and european agencies. Moreover, the group has been providing consultancy services to companies and administrations along these years, resulting on the development of a large amount of impact assessment studies. In order to deal with the increasing demand of consultancy and technology transfer services in this topic, AV Ingenieros spin-off company was created in 2008. The group has established collaboration with research centers in the field such as FEUP (University of Porto), the Dynamics Group of the ISVR (University of Southampton) and LADICIM (University of Cantabria).

Simulation and prediction of railway-induced ground-borne vibration

The experience accumulated during these 15 years has led LEAM to develop a software for the simulation of railway-induced vibrations, called VIBWAY. This software is especially designed to save computational and engineering costs in environmental assessment and detailed studies of traffic-induced ground-borne induced vibrations [1].

Figure 1. Environmental assessment studies in new railway lines.

The VIBWAY software is based on the research outcomes of the group during these years through the following topics:

• Computational enhancements based on new analytical/numerical aspects for the calculation ground response, leading to large computational savings [2,3,4].
• Improvement of the computational cost of the wave progapagation simulation on the ground due to the use of meshless methods and semi-analytical solutions [5,6].
• Simplified modelling of the building structure and the building/soil interaction [7,8].

LEAM is also working in other topics associated to the control of railway-induced ground-borne noise and vibration:

• Intensive research has been conducted to study the specific case of a tunnel with an inner floor partition. This is a tunnel layout solution used in some sections of the new metro line (L9) of Barcelona's underground metro network. A novel modelling approach is probably the most significant contribution of the group on this topic [9].

Figure 2. Tunnel with inner floor partition in L9 of Barcelona's underground metro network.

• Another research topic in where LEAM has been working last years is the mitigation of railway-induced vibrations using dynamic vibration absorbers (DVAs). Theoretical developments [10] together with experimental studies (Fig. 3) has been carried out in order to investigate the problem and its implementation in detail.

• The group has also developed in-house 3D FEM-BEM and 3D FEM-SBM (Singular Boundary Method) solvers that are suitable to study soil-structure interaction problems until 250 Hz in detail.
• Nowadays, the group is directing its efforts on the development of hybrid methods for the prediction railway-induced ground-borne noise and vibration that combine experimental measurements with theoretical models [11]. Developments to include the uncertainty associated to the imperfect knowledge of soil mechanical properties, to the soil-structure interaction, and to the building interior acoustic response due to ground-borne vibration are in progress.

Characterization of elastic components for railway applications.

One of the most important issues to ensure proper predictions is to have reliable input data. In this regard, elastic elements inserted in railway tracks are usually demonstrating highly uncertain mechanical properties. The group has been collaborating with TU Delft and University of Salford in this topic. LEAM is working through two main lines:

• Laboratory characterisation of elastic elements for railway applications. The group is working in advanced methods for the determination of the dynamic stiffness of elastomeric or rubber track components, such us rail pads, under-ballast mats, etc. The group is focusing its effort on improve the procedure described in ISO 10846 in terms of accuracy along the frequency range and on the uncertainty of the stiffness estimation [12].

• In situ characterisation of elastic elements for railway applications. LEAM developed an excitation device capable to excite railway tracks at low frequencies while the input forces are measured. The system can be observed in Fig. 5. The device can be loaded to apply preloads to the track, allowing to better represent the real condition of the track when the train is passing and also to perform studies of the non-linearity of the elastic components of the track due to the preload.

Figure 5. In situ characterisation of railway tracks, with focus on elastic elements.

Experimental assessment of traffic-induced noise and vibration

For the assessment of vibration impact, LEAM has proper instrumentation to do such studies, carrying out experimental measurement campaigns (mainly with LMS Pimento as multichannel equipment and seismic and piezoelectric accelerometers) as well as in-house computer programs specifically designed to perform the post-processing of the signals acquired according to current regulations and standards.

References

[1] ISO 14837-1. Mechanical vibration. Ground-borne noise and vibration arising from rail systems. Part 1: General Guidance.

[2] Noori, B., Arcos, R., Clot, A., Romeu, J. A method based on 3D stiffness matrices in Cartesian coordinates for computation of 2.5D elastodynamic Green's functions of layered half-spaces. Soil Dynamics and Earthquake Engineering, 114 (2018) 154-158.

[3] Arcos, R., Romeu, J., Clot, A., Genescà, M.. Some analytical aspects of viscoelastic Lamb's problem for improving its numerical evaluation. Wave Motion, 50(2) (2013) 226–232.

[4] Arcos R., Clot, A., Romeu, J., Martín, S.R. Fast computation of an infinite, longitudinally-varying and harmonic strip load acting on a viscoelastic half-space. European Journal of Mechanics - A/Solids, 43 (2014) 58-67.

[5] Liravi, H., Arcos, R., Ghangale, D., Noori, B., Romeu, J. A 2.5D coupled FEM-BEM-MFS methodology for longitudinally invariant soil-structure interaction problems. Computers and Geotechnics, 132 (2021) 104009.

[6] Ghangale, D., Arcos, R., Clot A., Noori, B., Romeu, J. A methodology based on 2.5D FEM-BEM for the evaluation of the vibration energy flow radiated by underground railway infrastructures. Tunnelling and Underground Space Technology, 101 (2020) 103392.

[7] Clot, A., Arcos, R., Romeu, J. Efficient three-dimensional building-soil model for the prediction of ground-borne vibrations in buildings. Journal of Structural Engineering, 143(9) (2017) 04017098

[8] Conto, K.F., Arcos, R., Parente, C., Costa, P.A., Romeu, J. A new semi-analytical approach for dynamic pile-soil interaction problems. Proceedings of the International Conference on Structural Dynamics, EURODYN 2020, 2, pp. 2807-2816.

[9] Clot, A., Arcos, R., Romeu, J., Pàmies, T. Dynamic response of a double-deck circular tunnel embedded in a fullspace. Tunnelling and Underground Space Technology, 59 (2016) 146-156.

[10] Noori, B., Arcos, R., Clot, A., Romeu, J. Control of ground-borne underground railway-induced vibration from double-deck tunnel infrastructures by means of dynamic vibration absorbers. Journal of Sound and Vibration, 461 (2019) 114914

[11] Arcos, R., Soares, P.J., Alves Costa, P., Godinho, L. An experimental/numerical hybrid methodology for the prediction of railway-induced ground-borne vibration on buildings to be constructed close to existing railway infrastructures: Numerical validation and parametric study. Soil Dynamics and Earthquake Engineering, 150 (2021) 106888.

[12] Reina, S., Arcos, R., Clot, A., Romeu, J. An efficient experimental methodology for the assessment of the dynamic behaviour of resilient elements. Materials, 13 (2020) 2889.

• People at LEAM work on the sound characterization of urban and non-urban areas through long-term noise measurements and computer simulations.

• LEAM supports governments in developing and maintaining plans for reducing noise in urban areas making noise maps, capacity maps, action plans and specific proposals for action in coordination with the competent authority.

• LEAM also has expertise in the assessment of the acoustic impact of infrastructures such as roads, railways and airports.

• Researchers at LEAM investigate on new ways of automatically drawing noise maps continuously updated with distributed and mobile sensors optimizing the temporal and spatial sampling.

• LEAM works in the application of active noise control systems in the industrial field, this technique aims to cancel unwanted noise through destructive interference by using an additional acoustic field generated by an electronic control system.

• LEAM members are working on the active window concept, which aims to maintain the sound insulation of walls despite the presence of openings. 

• LEAM are also working on the optimization and implementation of local noise control techniques. This technique allows for reductions in specific areas, without affecting the rest of the acoustic field. LEAM implement this technique both experimentally and using commercial softwares or our own mathematical codes.  For example, this technique is being developed for application in modes of transport or acoustic barriers.

 

 

 

Description of the topic

The recent progress made in ultra-low-power devices like wireless sensor networks for structural health monitoring, which are primarily battery-powered, has increased the interest of industries for substituting batteries with other power systems with non-hazardous disposal, non-periodical replacement, and low-maintenance as offered by the vibration energy harvesting systems. These technologies transform kinetic energy from vibrations into electrical energy by means of an electromagnetic, piezoelectric or electrostatic transducer mechanism. Mechanical vibration is the most common type of mechanical energy for harvesting. It is ubiquitous in built and natural environments and is not affected by radio wave, solar or thermal conditions. Manmade sources of mechanical energy (e.g., machinery, infrastructures, and transportation) can emit high levels of harmonic vibrations or low levels of random vibrations, these last ones being challenging to harvest efficiently. Moreover, natural mechanical energy is usually related to vibrations induced by wind or water flow.

Developments at the LEAM

At LEAM, we are working on the design, development and improvement of electromagnetic vibration energy harvesting technologies. For these aims, analytical, numerical and experimental methods are used to understand the physical behavior of these type of electromechanical systems, perform different simulations of uncoupled and coupled systems, and execute different laboratory and field tests, respectively. The following is a list of topics that are studied at the moment at LEAM:

• Design, optimization and testing of a high-performance electromagnetic vibration energy harvester (EMVEH) based on Halbach magnet arrays (Fig. 1).
• Investigation of electromagnetic vibration energy harvesting on water distribution control valves (Fig. 2).
• Investigation of electromagnetic vibration energy harvesting for railway-induced vibrations (Fig. 3).
• Analysis of the influence of the electromagnetic coupling between the magnets, the springs and the environment for different electromagnetic vibration energy harvesting configurations.
• Study of the mechanical transmissibility and voltage response of different electromagnetic vibration energy harvesting configurations.
• Wideband and self-tuning electromagnetic vibration energy harvesters.

Figure 2. Application of vibration energy harvesting to water distribution valves.

Figure 3. Measurements of the power electrical output of the LEAM's prototype at L9 of Metro Barcelona.

 Predictive Maintenance

Predictive facility maintenance is a strategy that is based on the early detection of system failures, so that it is possible to change the affected component during a scheduled shutdown, before the failure occurs.

Among the existing technologies for prematurely detecting faults, the one based on acoustic emission is perhaps the one with the most potential both in a variety of applications and with detection capability, but it is still in a very initial state of its development due to the complexity of the phenomenon to be detected.

Physical principle

Any modification in the state of a material such as the appearance and growth of cracks, local plastic deformation, corrosion or phase changes, etc. is accompanied by a release of energy in the form of pulses of elastic waves that propagate within the material. These pulses contain information from the source that generated them, and the EA technique is based on the detection and analysis of these. The advantages of this strategy over more established ones are:

- Ability to detect multiple phenomena in early stages

- Ability to detect invisible faults

- Ability to detect under normal operating conditions

- Ability to determine the origin of the failure

The release of vibratory energy is different for each phenomenon and for each material, with the identification of the parameters of the vibrating pulses associated with each type of fault and material being the main difficulty and challenge of this strategy.

Signals from an AE system.

Applications

Industrial applications of EA are still limited:

- Inspection of pressure vessels

- Detection of fluid leaks in valves and pipes

- Corrosion detection

- Bridge monitoring (under development)

But research on this topic shows great potential for application in other fields:

• Degradation of materials: increasing defects, crack propagation, plastic deformations, rupture of inclusions or precipitates, surface degradation [3], both in structures and mechanisms. This gives it great potential for application in the aerospace industry, in the processing industry, in infrastructure maintenance or in wind turbines.

• Reversible processes: phase crystallographic transformations, solidifications, thermoelastic effects, friction between surfaces, etc.

• Manufacturing processes: defects in welding, forging processes, milling, turning, etc.

• In fluids: detection of suspended particles, evolution of the gas, boiling point.

• Ability to predict the time between the detection of the onset of the fault and the macroscopic fault.

• Understanding the breaking mechanisms in non-homogeneous materials, such as steels or composite materials.

Experience

The LEAM has worked successfully with the characterization of the failure mechanisms in tool steels in order to design a predictive maintenance system in forming tools within the MOUSICOSYS project. EA has been applied in monotonic flexion, flexion fatigue, contact fatigue, and nanoindentation assays.

The ability to detect damage to biological material has been demonstrated, opening the door to the detection of injuries and programming of high-performance training or in concrete-based composite matrices, allowing to identify the mechanisms of occurrence of fail.

And finally, within the framework of the LOOMING FACTORY project, a low-cost system for the acquisition and analysis of EA-based faults and application to gear trains is being developed, which could be autonomous taking advantage of parallel development. in energy harvesting based on the transformation of vibratory energy.

Examples of internal fractures detected by AE in steels. Note the size of the fractures detected.

AE testing on organic tissues.

Detection of faults in concrete-based composite material. A vibrating pulse can be seen on the screen.

Monotonous bending test in steel test tubes for tools.