scholarly journals Vibration Isolation Mechanism of Concrete Piles for Rayleigh Waves on Sand Foundations

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Jinglei Liu ◽  
Guishuai Feng ◽  
Jian Zhang ◽  
Xiaoyu Zhao ◽  
Chuanqing Yu ◽  
...  
Keyword(s):  
Rayleigh Waves ◽  
Vibration Isolation ◽  
Free Field ◽  
Propagation Path ◽  
Vibration Source ◽  
Single Pile ◽  
Single Row ◽  
Concrete Piles ◽  
Acceleration Amplitude ◽  
Isolation Effects

To study the propagation characteristics of Rayleigh waves and the isolation mechanism of a single-row of piles by isolation effects, in this paper we draw a two-dimensional contour map of ζ (normalized acceleration amplitude relative to a measure close at the vibration source) using a vibration test carried out on a sand foundation. In this experiment, we study, in addition to the free field and the single pile cases, settings with two and three piles. The result shows that the vibration caused by the point source in the free field excites Rayleigh waves in a radial direction along the surface of the foundation. Meanwhile, the vibrations of the points along the propagation path on the surface of the foundation are gradually weakened. There is a steady transition when the ζ drops to 0.6 and a placid decline when ζ decreases to less than 0.25. The vibration-shielded region, the strengthened region, and the strengthened strips will appear on the surface of the foundation. The vibration-shielded region is located behind the piles, and the region presents a trumpet-shaped area that takes the pile as the vertex. Increasing the quantity of piles contributes to increasing the vibration isolation effect, not only that involving the degree of isolation but also for the area of the shielded area. The vibration-strengthened regions include the diffraction regions at the pile corners on both sides of the single-row of piles and the scattering region at the gaps of the piles. In addition, the composite regions are located among the vibration source and the scattering and diffraction-strengthened regions. Increasing the number of piles has little influence on the scattering and diffraction-strengthened regions but can significantly enhance the vibrations of the composite regions. In general, the vibration-strengthened strips are connected with the scattering-strengthened regions. However, in the test of a single pile, the pile is connected to the diffraction-strengthened regions near its two anterior angles.

scholarly journals Numerical Analysis on the Ground Vibration Isolation of Duxseal

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
M. Gao ◽  
S. P. Tian ◽  
R. He ◽  
Y. Wang ◽  
Q. S. Chen
Keyword(s):  
Vibration Isolation ◽  
Damping Ratio ◽  
Free Field ◽  
Three Dimensional ◽  
Ground Vibration ◽  
Vibration Source ◽  
Isolation System ◽  
Vertical Excitation ◽  
Thin Layer Method ◽  
Active Vibration

A new kind of vibration screening material, Duxseal, with a high damping ratio is proposed to be used as an active vibration barrier in the free field. To investigate the influence of width, thickness, and embedded depth of using Duxseal on vibration reduction, numerical studies are performed using a three-dimensional (3D) semianalytical boundary element method (BEM) combined with a thin-layer method (TLM). The isolation effectiveness of Duxseal in ground vibration is also compared with the traditional wave impeding block (WIB). The numerical results show that Duxseal performed exceedingly well in screening ground vibrations in the free field. The effectiveness of the vibration isolation increases with the increase in the width, thickness, and embedded depth of the Duxseal material, within a certain range, under harmonic vertical excitation. In addition, Duxseal is much more effective for isolating ground vibration than the traditional WIB. The performance of Duxseal in isolating ground vibration is relatively stable along the distance away from the vibration source, while the amplitude attenuation ratio bounces upward when the distance away from the vibration source increases for the WIB isolation system.

scholarly journals Isolation effects of vehicle-induced vibration tested by integral floating method

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110449
Author(s):  
Hao Li ◽  
Weiguo Yang ◽  
Pei Liu ◽  
Xiaoguang Zou ◽  
Meng Wang
Keyword(s):  
Vibration Isolation ◽  
Field Measurements ◽  
Dynamic Responses ◽  
Structural Vibration ◽  
Vibration Source ◽  
Frequency Range ◽  
Cultural Center ◽  
Time Frequency ◽  
Isolation Methods ◽  
Isolation Effects

A set of integral floating vibration isolation methods was developed in this study to remedy the lack of effective measures for over-track buildings. The effect of vibration isolation pads was investigated experimentally; the resulting field measurements were used to determine the time-frequency dynamic responses of vehicle-induced vibration and isolation effects. The characteristics of the vibration source appear to significantly affect the frequency domain distribution of vibration inside the building. When no vibration isolation measures are taken, the internal vibration of the cultural center exceeds the limit. BSW vibration isolation pads R480, R550, and R800 are effective in the frequency range of 16–80 Hz. The vibration isolation level in the Z direction is between 5.6 and 7.3 dB. After floating vibration isolation treatment, the maximum Z vibration level of the cultural center is 56.4 dB in daytime hours and 52.9 dB at night, which satisfies the relevant standard. The proposed method is shown to effectively hinder the structural vibration caused by subways on surrounding buildings.

Vibration source properties of cargo trains: free field vibration and trackside measurement analysis

2021 ◽  
Vol 263 (2) ◽  
pp. 4652-4659
Author(s):  
Eliam Vlijm
Keyword(s):  
Free Field ◽  
Vibration Measurement ◽  
Vibration Source ◽  
Mean Square ◽  
Vibration Level ◽  
Vibration Signals ◽  
Measurement Analysis ◽  
Train Speed ◽  
Rail Deflection

Annoyance caused by railway operations has gained increasing attention in the Netherlands. This has led to a multimillion research project into different aspects of train passages as a source of vibration. The project is initiated by the Dutch railway operator ProRail. In advance of this project a study has been performed on vibration signals at free field caused by cargo train passages at four different sites. The signals have been compared to trackside measurements. The trackside measurements consist of fibre optic measurements of the rail deflection at pre-installed locations different from the free field vibration measurement sites. Different vibration level indicators have been studied like train speed, axle loads and wheel roughness indicators and their correlation with vibration levels. Vibration levels are defined in several ways, a frequency weighted running mean square value (so-called Veffmax), a 2-second RMS level (unweighted) and levels per frequency band. Special attention is given to the variation in time of the measured vibration signals during the train passage to see whether 'bad quality' wheel passages can be identified. The results give valuable input for a future case study in which wheel quality and its influence on vibration levels will be studied further.

scholarly journals Dynamic Response of Single Pile Subjected to Different Frequencies in Gypseous Soil

2020 ◽  
Vol 13 (4) ◽  
pp. 50-57
Author(s):  
Noor D. Abd ◽  
Safa H. AbidAwn
Keyword(s):  
Experimental Study ◽  
Dynamic Response ◽  
Slenderness Ratio ◽  
Vibration Source ◽  
Single Pile ◽  
Collapsible Soil ◽  
Dynamic Movement ◽  
Steel Container ◽  
Gypsum Content ◽  
Gypseous Soil

This paper exhibits an experimental study on dynamic response of a single pile under dynamic load which comes from motor placed on cap pile called a vibration source. This study used the effect of the dynamic movement of vibration on one pile, collapsible soil (gypseous soil) used in this study with 30% gypsum content. The experiment is performed in a dry and soak state. A solid steel pile with a slenderness ratio of 27 was inserted into the soil after preparing it in layers in a steel container (30 * 30 * 60) cm. The test was performed under a dynamic response to the different frequencies 10, 15, 20, and 25 Hz. The results showed that the speed, acceleration and displacement increase with increasing frequency of the vibration source in addition to that the values of speed, acceleration and displacement amplitude are less in the case of soaking compared to their values in the dry state.

scholarly journals Design, Experiment, and Improvement of a Quasi-Zero-Stiffness Vibration Isolation System

2020 ◽  
Vol 10 (7) ◽  
pp. 2273 ◽  
Author(s):  
Shuai Wang ◽  
Wenpen Xin ◽  
Yinghao Ning ◽  
Bing Li ◽  
Ying Hu
Keyword(s):  
Vibration Isolation ◽  
Damping Ratio ◽  
Excitation Amplitude ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Linear Spring ◽  
Isolation Effects ◽  
Magnetic Rings ◽  
The Relationship ◽  
Force Displacement

This paper proposes a new kind of quasi-zero-stiffness (QZS) isolation system that has the property of low-dynamic but high-static stiffness. The negative stiffness was produced using two magnetic rings, the magnetization of which is axial. First, the force–displacement characteristic of the two coupled magnetic rings was developed and the relationship between the parameters of the magnetic rings and the stiffness of the system was investigated. Then, the dynamic response of the QZS was analyzed. The force transmissibility of the system was calculated and the effects of the damping ratio and excitation amplitude on the isolation performance were investigated. The prototype of the QZS system was developed to verify the isolation effects of the system based on a comparison with a linear vibration isolation platform. Lastly, the improvement of the QZS system was conducted based on changing the heights of the ring magnets and designing a proper non-linear spring. The analysis shows the QZS system after improvement shows better isolation effects than that of the non-improved system.

scholarly journals Vibration-Isolation Performance of a Pile Barrier in an Area of Soft Soil in Shanghai

2020 ◽  
Vol 2020 ◽  
pp. 1-27
Author(s):  
X. F. Ma ◽  
M. Y. Cao ◽  
X. Q. Gu ◽  
B. M. Zhang ◽  
Z. H. Yang ◽  
...  
Keyword(s):  
Numerical Model ◽  
Vibration Isolation ◽  
Soil Layer ◽  
Isolation Effect ◽  
Normal Operation ◽  
Vibration Source ◽  
Filling Material ◽  
Vibration Measurements ◽  
Pile Diameter ◽  
Environmental Vibration

Environmental vibration caused by traffic can affect the normal operation of precision instruments, and vibration-isolation measures should be taken to reduce such negative effects. The engineering background of this paper is a hard-X-ray tunnel under construction in Shanghai, China. First, field vibration measurements are used to study the characteristics of the ground traffic, maglev, subway, and other vibration sources near the tunnel, as well as the laws governing the propagation of vibration waves in the surface and soil layer. The finite-element modelling is then used to establish a two-dimensional numerical model for the field conditions, and the numerical results are compared with the field vibration measurements to validate the applicability of the numerical model for assessing the effects of environmental vibration. Finally, how the parameters of a pile-barrier vibration-isolation system, a vibration-isolation measure used widely for tunnels, influence its performance is studied. The results show the following: with increasing distance from the vibration source, the amplitude of the vibration acceleration decreases gradually, and the high-frequency part of the vibration wave is attenuated rapidly, whereas the low-frequency part is attenuated very little. The vibration-isolation effect of the pile barrier is directly proportional to the elastic modulus of the pile body, the pile length, and the hollow ratio of the pile, and inversely proportional to the stiffness of the filling material. The pile diameter, pile row number, and row spacing have little influence on the vibration-isolation effect. Increasing the pile diameter attenuates the acceleration amplitude somewhat around 10 Hz but has no effect on it around 5 Hz. Overall, the present numerical method is well suited to evaluating environmental vibration problems.

scholarly journals Influence of the phase difference between kinematic and inertial loads on seismic behaviour of pile foundations in layered soils

2020 ◽  
Author(s):  
Thejesh Kumar Garala ◽  
Gopal Madabhushi
Keyword(s):  
Natural Frequency ◽  
Free Field ◽  
Phase Relationship ◽  
Phase Variation ◽  
Bending Moment ◽  
Pile Group ◽  
Pile Foundations ◽  
Single Pile ◽  
Seismic Behaviour ◽  
Soil Layers

A series of dynamic centrifuge experiments was conducted on model pile foundations embedded in a two-layered soil profile consisted of soft-clay layer underlain by dense sand. These experiments were specifically designed to investigate the individual effect of kinematic and inertial loads on a single pile and a 3×1 row pile group during model earthquakes. It was observed that the ratio of free-field soil natural frequency to the natural frequency of structure might not govern the phase relationship between the kinematic and inertial loads for pile foundations as reported in some previous research. The phase relationship obtained in this study agrees well with the conventional phase variation between the force and displacement of a viscously damped simple oscillator subjected to a harmonic force. Further, as expected, the pile accelerations and bending moments can be smaller when the kinematic and inertial loads act against each other compared to the case when they act together on the pile foundations. This study also revealed that the peak kinematic pile bending moment will be at the interface of soil layers for both single pile and pile group. However, in the presence of both kinematic and inertial loads, the peak pile bending moment can occur either at the shallower depths or at the interface of soil layers depending on the pile cap rotational constraint.

Model and Simulation for Two-Axis Vibration Isolator

2013 ◽  
Vol 655-657 ◽  
pp. 521-525
Author(s):  
Yong Liang Zhang ◽  
Bai Wei Guo ◽  
Xiu Yun Meng
Keyword(s):  
High Resolution ◽  
Vibration Isolation ◽  
Spatial Dynamics ◽  
Observation System ◽  
Vibration Source ◽  
Isolation Technique ◽  
Model And Simulation ◽  
Satellite Platform ◽  
Combined Simulation ◽  
Object Of Study

The satellite platform in the orbit, as the payload carrier, always suffers from the complex spatial dynamics disturbances. The disturbances affect the LOS stabilization of the high resolution optical payload and then affect the quality of the image from the high resolution earth observation system. In order to solve the problem, the vibration isolation technique-placing the appropriate vibration isolators between the vibration source and system to isolate the direct transmission of the vibration is adopted. In the paper, we take the two-axis isolator as the object of study, build its dynamic model and design the controller for the two-axis isolator. We use ADAMS which is used for the mechanical dynamics and MATLAB to do the combined simulation to verify the controller’s effects.

The Influnce of Velocity for a Moving Load on the Vibration Isolation Using Pile Group

2012 ◽  
Vol 204-208 ◽  
pp. 210-214
Author(s):  
Man Qing Xu ◽  
Bin Xu
Keyword(s):  
Integral Equation ◽  
Fundamental Solution ◽  
Frequency Domain ◽  
Half Space ◽  
Vibration Isolation ◽  
Moving Load ◽  
Free Field ◽  
Isolation Effect ◽  
Moving Loads ◽  
Patch Load

Based on Biot’s theory and integral transform method, the velocity of moving loads impact on the vibration isolation effect of pile rows embedded in a poroelastic half space is investigated in this study. The free field solution for a moving load applied on the surface of a poroelastic half space and the fundamental solution for a harmonic circular patch load applied in the poroelastic half space are derived first. Using Muki’s method and the fundamental solution for the circular patch load as well as the obtained free field solution for the moving load, the second kind of Fredholm integral equation in the frequency domain describing the dynamic interaction between pile rows and the poroelastic half space is developed. Numerical solution of the frequency domain integral equation and numerical inversion of the Fourier transform yield the time domain response of the pile-soil system. Numerical results of this study show that the same pile rows can achieve a better vibration isolation effect for the lower load speed than for the higher speed. Also, the optimal length of piles for higher speed moving loads is shorter than that for lower speed moving loads.

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