# Modernization of Heavy Loaded Tram Radial Effect on Noise and Vibration
## 6 Findings from the Vibration Measurements
Extreme values of \(v_{rms}\) vibration amplitudes in the **B2V** location were achieved by bridge deck oscillating in the vertical direction \(z\) and the horizontal \(y\) (**B2V**) during tram passages on the K1 track (approximately 1.65 m from B2V). Here, the max \(v_{rms}\) value was reached for the vibration direction \(z\) = 41.37 mm/s and the max value \(v_{rms}\) = 46.71 mm/s for the \(y\) direction. During the passage of trams on the track K2 (approximately 4.05 m from **B2V**), the value \(v_{rms}\) = 20.04 mm/s was reached for the direction of vibration \(z\) and the value max \(v_{rms}\) = 21.07 mm/s for the direction \(y\). The results of the spectral analysis at point **B2V** pointed to the fact that the maximum values of vibration levels at the foundations of the building occurred mostly in the band of dominant frequencies \(f_{D1}\) = 55 to 70 Hz (\(f_{D2}\) = 170 to 220 Hz). The detected frequency bands exclude the occurrence of resonant phenomena during the vibration of buildings on Stur Street, as the values of their basic natural frequencies \(f_{0i}\) are considerably below (\(f_{0i}\) \(<\) 20 Hz) these detected excitation frequency bands. The mentioned frequency bands exclude the occurrence of resonant phenomena during the vibration of the Old Bridge generated by the tram operation on the modernised line, as the values of the fundamental natural frequencies \(f_{0i}\) are considerably below (\(f_{0i}\) \(<\) 10 Hz) these detected excitation frequency bands. Periodic monitoring of noise and vibration is necessary to reduce the environmental impact of tram traffic. Baseline or initiation measurements must be performed just after the construction of the traffic route. It is also necessary to make measurements after major modifications to the track. Major structural modifications of the tramway include the upgrading of individual sections. In Bratislava, the most loaded radial of the tramway transport system has been modernised due to its unsatisfactory structural and technical condition. A gradual increase in the noise and vibration effects of the tram line in poor condition also contributed to the modernisation. The measurements showing this increase were essential for the decision of the city council to upgrade this radial. A large number of reports of experimental measurements are in the electronic resource [27]. The last measurements before the reconstruction [38] carried out in different sections of the tramway transport system of Bratislava led to the following findings:  
* The noise from tram operation is primarily generated by two sources--the construction of the tram track and the tram vehicles. * Noise from the rolling motion of the wheels of the vehicles on the rails is dominant. At standard tram speeds in urban areas, rolling noise represents 80-90% of the total noise emitted. * A substantial reduction in noise levels on the modernised sections of track can be expected compared to the current situation (before modernisation). Reference noise values resulting from measurements before the radial modernisation were in the range of \(L_{Aug}\) = 87 to 92 dB [38]. The results of the measurements after the retrofit, reported in Chapter 3 and in the summary section of the conclusions, reported values of \(L_{Aug}\) = 68 to 76 dB. However, even with the track modernisation, the reduction of noise levels below the \(L_{Aug}\) = 70 dB value reported in the national legislation was not achieved [38]. Faster upgrading of tram vehicles will contribute to the reduction of levels. Monitoringmeasurements are currently in progress confirming these assumptions (decrease on average to \(L_{Aeq}\) = 6 dB). In the aspect of vibrations, the measurements before the modernisation in the monitored locations reached the values of the parameter \(v_{rms}\) = 5-15 mm/s. The results of the measurements after the modernisation, presented in Chapter 3 and in the summary section of the conclusions, reached values of \(v_{rms}\) = 1-3.5 mm/s.