Initial situation, problem statement and motivation: In urban areas, the emmission of traffic-related noise increases as a consequence of the concentration of living areas and infrastructure. The noise emission due to rail traffic increases on railway bridges due to structure-borne noise of the vibrating bridge, e.g. due to large sound-radiating surfaces or small vibration attenuation in case of missing ballast bed. Common measures such as noise barriers can sometimes even increase the noise emission because of their large sound-radiating surfaces.
This proposal addresses noise reduction measures for existing railway bridges. Existing solutions include e.g. rail dampers or sub-ballast mats (measures on superstructure). Other measures such as rails embedded in bridge structure affect the bridge structure itself and, are thus not suited for reconstruction. Known problems include underestimation of sound emissions, not sufficiently known mutual interaction between several measures, or missing adjustment of the measures to account for bridge structure-borne noise.
Goals and innovation compared to the state of art: The aim of the project is to explore the effectivity of optimized of vibro-acoustic measures for railway bridges. The project focuses on application on existing railway bridges, and thus primarily on measures at track superstructure. Combination of several measures and their mutual influence will be analysed using a realistic computation model. Properties of vibration-damping materials will be tested across an extended frequency range and will be used in the simulation. Requirements for optimized material properties will be stated and an effective combination of several measures will be proposed.
Expected results and findings: This investigation explores the optimization potential for measures against structure-borne railway bridge noise and quantifies their attainable efficiency. Obtained results will serve as a basis for a subsequent research project.
The following questions will be answered:
- Quantification of the expected noise reduction by application of individual measures
- What is the effect of local stiffeners and integrated noise barriers?
- How can existing measures for the superstructure be improved (construction, material properties)?
- Should a subsequent research project on the optimization of specific measures for the superstructure be carried out?
- What noise reductions could be expected after successful completion of a subsequent research project?