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Uncertainty in Prediction of Rail-Induced Ground-Borne Vibration
Published in Robert Peters, Uncertainty in Acoustics, 2020
Figure 12.9 illustrates a dynamic model of a commuter train running on a conventional track that ensures that all relevant parameters, except for the rail pad stiffness, are known. Assuming the rail pad stiffness to be 200 MN/m per metre of track and accepting that the rail pad stiffness may range from 50 to 500 MN/m per metre of track, a 17-dB uncertainty interval (−10 to 7 dB, as shown in Figure 12.9) should then be expected. The figure maps out the potential variation in terms of free-field vibration levels for a range of rail pad stiffness. It is important to note that these insertion gain curves are dependent on the base case and may therefore be less representative if the base case is to vary substantially.
Components, Emission Reduction Techniques, and Noise Immunity
Published in David A. Weston, Electromagnetic Compatibility, 2017
The use of an AC and transient circuit analysis program like SPICE is invaluable in the design or selection of filters. The program allows the modeling of the filter and noise sources and is especially useful in the analysis of complex load and source impedances. As an example, consider a single-section filter with a 500-μH inductance, a 2-μF capacitance, and a 72-Ω load. The filter response to an AC waveform, supplied from a low-impedance source, peaks (resonates) at 5 kHz. At this frequency it exhibits 13 dB of insertion gain. Changing the filter to a three-section type with equal-value inductances and capacitances does not change the insertion gain but changes the frequencies at which insertion gain is a maximum (i.e., 2–6.3 kHz). When a second section is added, with a 100-μH inductance and a 1-μF capacitance, the original resonance occurs at 4 kHz, with a second resonance at 20 kHz. In filter selection the magnitude of the load capacitance must be considered. For example, a low-Q filter may exhibit a high Q when used at the output of a supply that is loaded by a number of on-board decoupling capacitors.
Filters
Published in Geoff Lewis, Communications Technology Handbook, 2013
Insertion gain or loss. When a network is connected between a generator and a load then assuming that both impedances are correctly matched, there may be a gain or loss of signal power at the load, depending on the nature of the network. The ratio of the output power to input power, usually quoted in decibels, is described as the system insertion gain or loss, respectively.
Evaluation of the soil layering and soil lens effect on the ground-borne vibrations induced by twin metro tunnels
Published in European Journal of Environmental and Civil Engineering, 2022
R. Heidary, M. Esmaeili, M. Gharouni Nik
In order to investigate the effect of the top layer thickness on the surface vibrations, at each step, the thickness of the upper layer is increased equal to the tunnel radius. Then the vibrations level imposed on the ground surface are compared with that obtained from the homogeneous model. The concept of Insertion Gain (IG) defined by Eq. (3) is used for this compression (Hung et al., 2013). where x1 and x2 are the PPV calculated by the homogeneous model and the modified model, respectively. The elastic modulus and the upper layer thickness are varied in the modified model. According to previous studies (Real et al., 2015), overestimating results are predicted by 2 D models. It is noteworthy that in this paper, this uncertainty is eliminated by comparing the single and twin tunnel results and using the above concept (Eq. (3)). In other words, the obtained results are qualitative or comparative.
Effects of train operational parameters on ground-borne vibrations induced by twin metro tunnels
Published in International Journal of Rail Transportation, 2021
Ramin Heidary, Morteza Esmaeili, Morteza Gharouni Nik
The paper is organized as follows. In section 2, the 3D FE model of twin tunnels is briefly summarized. This section considers all aspects of the twin tunnels such as material properties, element size, and boundary conditions to cover all important aspects of the twin tunnel model. Verification of the proposed model is compared with the results from Hamad et al. article [14] to show the accuracy of the developed model. Then, a parametric study has been done in section 3 to investigate the effect of train's speed and axle load on the free filed vibrations. In this section, Insertion Gain (IG) concept is applied to assess the determined results.
Hybrid analytical-numerical modelling of ground vibrations from moving loads in a tunnel embedded in the saturated soil
Published in European Journal of Environmental and Civil Engineering, 2022
Zonghao Yuan, Danting Xu, Li Shi, Xiaodong Pan, Ben He, Minyun Hu, Yuanqiang Cai
Figure 6 shows the insertion gain at r = 6 m, θ = 0 and z = 0 versus the load frequency (c = 40 km/h). Insertion gain becomes less than zero above f0 = 25 Hz, indicating vibration isolation. However, isolation is not achieved at load frequencies around the natural frequency of the slab. Similar results can be observed for other points in the free field.