Acoustic pass-by measurements of in-service trains and track characterization
Chalmers Tekniska Högskola Aktiebolag
Request for tender:
Description of goods/services
Chalmers Applied Acoustics is carrying out a research project on rolling noise on slab tracks. In this context, a measurement campaign will be carried out in September 2022 at Trafikverkets demonstrator at Gransjö in Northern Sweden, where a new type of slab track is tested. The measurements are financed by Trafikverket. Tenders are invited here for these measurements, which consist of the measurement of rolling noise and accelerations at the track during pass-by of in-service trains, the measurement of structure-borne transfer functions at the track, the measurement of track decay rates, and a detailed measurement of the rail roughness at the test site.
Requirements specifications of goods/services
The purchase must include the following products/commitments/services:
The measurement location has the address
Trafikplats Gransjö, S-961 92 Boden, Sweden
On google maps
The measurements are planned for week 38.
All measurements are carried out both centrally in the 60-m long slab track section and at a reference section with ballasted track in vicinity to the slab track section. The exact location of the reference section will be decided in situ by Chalmers.
1. Pass-by measurements
Pass-by measurements are carried out during one working day for all passing trains (in total about 30 trains are normally passing within 24h on a weekday). However, at least 5 iron ore line trains, 5 other freight trains (Green Cargo) and 5 passenger trains have to be measured. Measurements in both sections have to be carried out for the same passing trains. All measurements within one section have to be synchronized, but they do not have to be synchronized between the two sections. All data has to be delivered as calibrated temporal raw data (sound pressure, acceleration). If further processed data is required in addition, this is specified below.
The following quantities have to be measured during pass-by:
a) Sound pressure at both the slab track and the ballasted track section:
measurement at one side of the track at 7.5 m from the centre line of the track at the heights 1.2 m, 2.0 m, 3.0 m and 3.5 m above track level; in total 8 microphones; measurement according to ISO 3095 Section 6 but with the difference that vehicle conditions and train speed are ‘as is’. Required valid frequency range at least 20 Hz – 10 kHz. Data delivered as calibrated temporal raw data (i.e. the sound pressure signal over time). In addition, for each pass-by and microphone position, the A-weighted sound pressure level LpAF(t) as a function of time with time weighting F (fast), the A-weighted equivalent continuous sound pressure level LpAeq,Tp, the pass-by time Tp, and the A-weighted sound pressure level as spectrum in one-third octave bands in the range of at least 31.5 Hz to 8 000 Hz are required according to ISO 3095.
b) Vertical and lateral rail acceleration at slab track section:
measurement on the outside of both rails, positions according to EN 15461; vertical and lateral acceleration above a rail seat and mid-span in the middle of a block; in total 8 uniaxial accelerometers; valid frequency range at least 20 Hz – 10 kHz;
c) Vertical Acceleration of block and slab at the slab track section:
measurement of vertical block and slab acceleration on both sides of the track close to a rail seat and in the middle of a block; in total 6 uniaxial accelerometers (2x slab, 4x block); If there is no space on the top of the slab to attach uniaxial accelerometers to measure vertical slab acceleration, two 3-axial accelerometers attached to the side of the block might be required to measure vertical slab acceleration; valid frequency range at least 5 Hz – 3 kHz;
d) Vertical and lateral rail acceleration at ballasted track section:
measurement on the outside of both rails, positions according to EN 15461; vertical and lateral acceleration above sleeper and at midspan; in total 8 uniaxial accelerometers; valid frequency range at least 20 Hz – 10 kHz;
e) Vertical sleeper acceleration at ballasted track section:
measurement of vertical sleeper acceleration next to the rail seats on both sides and in the middle of the sleeper; in total 3 uniaxial accelerometers; valid frequency range at least 5 Hz – 3 kHz;
f) Train speed of each measured train
The positions of accelerometers and microphones are indicated in the attached document measurement_positions_gransjö.pdf.
2. Structure-borne transfer functions
a) Transfer function rail to rail, block, slab and microphones in slab track section:
vertical and lateral excitation on each rail at mid-span and over the instrumented rail seat (8 excitation positions), response using identical accelerometer positions on rail, slab and block and identical microphone positions as used in pass-by measurements (18 responses); 8x18 combinations; valid frequency range at least 20 Hz – 10 kHz for rail-rail, rail-microphones and 5 Hz to 3 kHz for rail-block and rail-slab; data delivered as complex frequency response functions with corresponding coherence and the calibrated temporal raw data
b) Transfer function rail to rail, sleeper and microphones in ballasted track section
vertical and lateral excitation on each rail at mid-span and over the instrumented rail seat (8 excitation positions), response using identical accelerometer positions on rail and sleeper and identical microphone positions as used in pass-by measurements (15 responses); 8x15 combinations; valid frequency range at least 20 Hz – 10 kHz for rail-rail, rail-microphones and 5 Hz to 3 kHz for rail-sleeper; data delivered as complex frequency response functions with corresponding coherence and the calibrated temporal raw data
3. Track decay rate
Measurement of the vertical and lateral track decay rate according to EN 15461 on both rails in both the slab track section and the ballasted track section. Requirements: valid frequency range at least 20 Hz – 10 kHz; data delivered as calibrated temporal raw data for all combinations of excitation and response points, as complex frequency response functions with corresponding coherence for all combinations of excitation and response points, and as track decay rate as spectrum in one-third octave bands calculated according to EN 15461.
4. Acoustic rail roughness with trolley
Rail roughness measurements have to be carried out both in slab track section and in the ballasted track section
- Measurement on both rails in both sections over a distance of at least 60 m
- Measurement in parallel lines with 1 mm lateral distance. At least the whole running band needs to be measured and at least 30 parallel lines
- The spatial resolution along the rail must be <= 1mm
- The measurement needs to be synchronized between the different lines on one rail and between the two rails in one section. Our aim is to combine the measurements in different lines to obtain a 3D roughness profile.
- Roughness wavelength range covered at least 2 mm – 100 cm
- Amplitude resolution <=0.1 micrometer
- Delivery of the data as calibrated spatial raw data of displacement
Further information and requirements:
- Delivery of data as calibrated temporal/spatial raw data (and processed data in some cases as specified above) with all necessary information for continued processing, analysis, and evaluation; The delivered data format has to be readable in Matlab.
- Time to plan the measurements with Chalmers Applied Acoustics before departure and in situ needs to be included in the contract.
- Trafikverket takes care of the security arrangements during the measurements.
- Trafikverket will arrange access to electric power 220V 16A. They will put up boxes to provide electricity.
- The measurements are planned for week 38. However, as the measurements are weather dependent (rain, wind, snow), it can become necessary to postpone the measurements with short notice. A postponement will be decided by the consultant in consultation with Chalmers. It is the responsibility of the consultant that all measurements are carried out under suitable weather conditions. All measurements must be carried out as close in time to week 38 as possible (week 38 or later). The different measurements (1)-(4) must also be carried out as close in time as possible to each other. Preferentially, all measurements should be carried out within the same day. The maximum acceptable delay between the measurement of roughness (4) and the pass-by measurements (1) is one week. Likewise, the maximum acceptable delay between the measurement of track decay rate (4) and the pass-by measurements (1) is one week. The measurement of structure-borne transfer functions (2) must be carried out for the same mounting of accelerometers and microphones as the pass-by measurements (1), i.e. the sensors are not to be removed between the measurements.
- In case the measurements cannot be carried out in autumn 2022 due to an early onset of winter, they will be postponed to May or June 2023.
- During weekday nights, there are time windows of about 5 hours where there is no regular train traffic, which could be suitable to carry out the roughness measurements. However, these time windows are also used for maintenance work that can involve maintenance-related traffic.
- Maximum price 230 000 SEK. This price includes all costs of the assignment including costs caused by rescheduling the measurements due to bad weather as described above.
Price shall be submitted in SEK excluding VAT and include all related costs requested in this request for tender.
The supplier must accept all agreement terms.
The tender must be received no later than 2022-06-24.
The tender shall be valid until 2023-07-01.
Questions during the tender period
Questions should only be asked via the function "Questions and answers" in Mercell Direct Procurement.
OBSERVE: Last day for questions will be 2022-06-16. Questions will be answered 6 days before the last day for tender at the latest.
Evaluation of tenders
The most economically advantageous tender (i.e. an assessment of price, quality, service etc.) will be chosen.
Description of the criteria that will be assessed (in the prioritized order):
1. Competence and capability to carry out pass-by measurements according to ISO 3095, measurement of accelerations at the railway track, measurement of structure-borne transfer functions at the railway track, measurement of track decay rate according to EN 15461, and continuous measurements of acoustic rail roughness over distances of several tens of meters as specified in this document. Competence and capability must be demonstrated by providing the educational background and a CV of the person(s) that will carry out the measurements and by demonstrating previous experience with such measurements (describe your previous experience with such measurements and provide three reference projects with contact details of corresponding reference persons). To demonstrate the capability to carry out the requested rail roughness measurements provide in addition the technical specifications of the measurement device including spatial resolution, amplitude resolution, wavelength range and achievable documented accuracy and precision, and describe how the synchronization between different lines on one rail and between the two rails is carried out.
2. Competence and capability to cooperate with academia in the planning and execution of measurements demonstrated with references
The evaluation will be carried out by a reference group from Chalmers Applied Acoustics.
Confidentiality and the freedom of information principle
After the procurement has been terminated the principle of public access to official records applies. This means that all documents related to the procurement process become public and may be disclosed to anyone who requests access to them. Exceptions may only be made if there is any specific reason to believe that the Tenderer may suffer damage if the information is disclosed.
If you have information that you feel is of such nature, your tender shall include precise details of which information should remain confidential, and how you would suffer damage in case of the public disclosure of this information. Chalmers will evaluate your request and determine whether confidentiality in accordance with Swedish law may be deemed to apply.
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