# Modernization of Heavy Loaded Tram Radial Effect on Noise and Vibration
## 6 Findings from the Vibration Measurements  
The main objective of experimental vibration measurements in **B1** and **B2** sites was to determine the levels of vibration generated by the standard operation on the tram track in the modernised sections. In the tram zone on Stur Street, in the densely built-up area of the city, vibration levels were measured on the cell wall of building no. 20 (building of the Police of the Slovak Republic) at point **B1V** and in the third field on the bridge structure at points **B2V**, during the standard traffic operation in the given line section. As a relevant comparison parameter of vibration levels, the effective value of the amplitudes of the vibration velocity \(v_{rms}\) (mm/s) is considered in the given case. On the basis of the findings, the following can be stated:  
1. The results of experimental vibration measurements in the location on Stur Street were obtained from measurements of vibration levels in different traffic conditions, creating multi-source excitation vibration fields with random characteristics--during different tram speeds, their acceleration and retardation from distant tram stops, etc. (trams in the given sections moved at speeds from 20 to 50 km/h). For the number of measurements performed at point **B1V** (in the \(x\) and \(z\) directions), in order to determine the vibration conditions in this location, it was possible to select the relevant characteristic passages of trans on tracks K1 and K2. Extreme values of \(v_{rms}\) vibration amplitudes in the **B1V** location were achieved by the vibration of foundation structures in the vertical direction (**B1 Vz**), during tram passages on the K1 track (approximately 4.2 m from **B1V**). In the cases of older types of trans, the achieved value of \(v_{rms}\) = 1.76 mm/s, and in the case of new types of trans, the value max \(v_{rms}\) = 2.29 mm/s. 2. During the tram passages on the track K2 (approximately 6.6 m from **B1V**), the value max \(v_{rms}\) = 1.73 mm/s was reached on the older track. In the new track cases, the value max \(v_{rms}\) = 1.90 mm/s was achieved. Extreme values of amplitudes of vibrations \(v_{rms}\) in the **B1V** location were achieved by the vibration of foundation structures in the horizontal direction y (**B1 Vy**), during the passage of trans on the track K1 (approximately 4.2 m from **B1V**), where in the case of older types of trans, the value max \(v_{rms}\) = 3.31 mm/s was reached. In cases of new types of trans, the value max \(v_{rms}\) = 3.43 mm/s was achieved. During the tram passages on the K2 track (approximately 6.6 m from the **B1V**), the value of max \(v_{rms}\) = 3.26 mm/s was reached for the new tram types. The absolute extreme value of the amplitude of the vibration velocity during all measurements was achieved in the case of a passage of a new type of tram on K2, namely, max \(v_{(t)}\) = 26.24 mm/s. The results of the spectral analysis at the **B1V** point pointed to the fact that the maximum values of vibration levels at the building foundations in the case of older types of trams occurred mostly in the band of dominant frequencies \(f_{D}\) = 60 to 80 Hz. In the case of new types of trams, it was in the band of dominant frequencies \(f_{D}\) = 75 to 100 Hz. 3. The results of experimental vibration measurements on the Old Bridge in the location of the tram line **B2** were obtained from the vibration levels on the steel-concrete bridge deck at point **B2V** (approximately 1.5 m from K1), generated by the standard tram line operation (tram speeds in the given sections ranged from 30 to 50 km/h). For the performed number of measurements at the measuring point **B2V**, it was possible, in order to determine the vibration conditions, to select suitable passages of trams on the track K1 and K2. The effective value of the vibration velocity amplitudes \(v_{rms}\) (mm/s) is considered to be the relevant noise comparison parameter in the given case.