Reducing environmental impact of vibrations from metro trains and assessing the structural safety of railway bridges.

Environmental impact of vibrations from metro trains. In support of developing a sustainable urban mobility, this work package will address the environmental impact of vibrations from metro trains. To this purpose, a numerical model will be used that has been developed at K.U.Leuven in collaboration with other European partners. 1. Using the model available at K.U.Leuven, an elaborate parametric study will be set up to assess the relative importance of determining parameters. Vibrations levels in buildings will be assessed in terms of vibration norms. 2. This parametric study should result in a decision tree to support rational track and tunnel design and to identify when vibration countermeasures should be taken, what vibration countermeasures can be effective and under what conditions a detailed numerical study is certainly needed. 3. The parameteric study will particularly address the vibration isolation efficiency of different track structures as they are commonly used on the Beijing metro network. This study will also support the future extension of the test tunnels as BJTU will have a full three dimensional of the coupled track-tunnel-soil system. 4. The possibility of structural damage to buildings due to large number of vibration cycles generated by railway traffic will be evaluated. Structural safety of railway bridges. This work package will apply dynamic system identification and health monitoring to steel railway bridges as an efficient tool to assess their safety, durability and serviceability. Based on the common experience of both partneers, dynamic train-bridge interaciton analysis based on a validated finite element model will be applied to determine the stress and strain history of structural components of a railway bridge during the passage of a train. This will allow determining the fatigue load of the bridge and to assess its safety, serviceability and life time. 1. Selection of a steel railway bridge in the Beijing area, that is potentially affected (damaged) by increasing axle loads and train speeds. 2. performing vibration measurements on the instrumented bridge and its components under ambient loading (wind, micro-tremors), during the passage of trains (forced excitation involving dynamic train-bridge interaction), and during the free vibration followint the passage of a train. 3. Dynamic system identification is applied to the ambient data and/or the data extracted from the free vibration part immediately following the passage of a train. 4. Construction of a finite element model of the railway bridge. When monitoring is applied on a continuous or periodic basis, deviations of the dynamic system characteristics can be interpreted in terms of damage. Different damage indicators have been proposed. One of the most powerful methods consists of simulating damage in the finite element model of the bridge and, subsewuently, finding the damage pattern which produces dynamic system characteristics as close as possible to the measured dynamic system characteristics. 5. The forced excitation data will be used to validate three-dimensional dynamic train-bridge interaction models. Stress and strain histories in structural components are evaluated and the real fatigue load on critical details (shear studs, welds, ...) as well as the lifetime and serviceability of the railway bridge can be determined.

Keywords:Damage assessment, Train-bridge interaction, Buildings, Vibrations, Bridges, Soil-structure interaction, Environmental impact, Metro trains

Disciplines:Construction engineering, Earthquake engineering, Geotechnical and environmental engineering, Water engineering, Wind engineering, Mechanics, Modelling, Biological system engineering, Signal processing, Structural engineering, Other civil and building engineering