Ground-borne Vibration Research Articles

Vibration isolation performance of quasi constant natural frequency isolation pads associated with test verification

The vibration and noise induced by the operation of subway trains cause disturbances to the adjacent building structures. The serviceability of building structures (i.e., offices and residences) in terms of the annoyance of humans is sensitive to vibration and noise; therefore, it is necessary to conduct an effective vibration control strategy for building structures in terms of the structure-born noise and vibration protection. In serviceability-related vibration control, two issues are considered herein: (a) the irregularity of the controlled structure and (b) the structure uncertainties, such as insufficient knowledge about the structural mass redistributed in the isolation system. A quasi-constant natural frequency (QCNF) pad, mixed with rubber and foam material, is introduced herein to tackle these two issues. Such a system is nonlinear, and its stiffness is associated with the structural mass distribution. In this paper, a single-degree-of-freedom (SDOF) system is employed first to illustrate the property of a QCNF system. Inspired by the ideal load-displacement property of a QCNF system, a streamlined rubber element, an unconstrained cylinder rubber element, and two constrained cylinder rubber elements (including rigidly constrained and flexibly constrained) are designed and simulated with a finite element model. The physical properties of such four designed elements are obtained based on a static testing and an ambient field test. In the end, a quasi-constant frequency isolation pad mixed with rubber and foam material has been comprehensively discussed regarding the finite element simulation and an on-site ground-borne vibration test validation. The results indicate that the flexibly constrained QCNF rubber pad, using a combination of rubber and foam materials, can maintain a nearly constant frequency in the range of 67–1000 kPa load. The test validation based on a real-world application of the QCNF rubber pad indicates its feasibility in serviceability control of a building structure.

The significance of soil–structure interaction in the response of buildings to ground-borne vibration from underground railways

The response of buildings to ground-borne vibration is governed by many physical phenomena. Not least of these is the dynamic soil–structure interaction (SSI) that exists between the various components of the system. The majority of existing models assume that the interaction between a railway tunnel and a building’s foundation is negligible, with the two sub-systems behaving as though they are uncoupled; other components of SSI associated with the foundation and building are accounted for to varying degrees, often with little justification. This paper aims to further our understanding of the SSI between an underground railway tunnel and a nearby building. The response of a typical multi-storey building founded on piles is considered, over the frequency range typically associated with perceptible vibration. A comprehensive numerical model is used to capture the fully-coupled, three-dimensional behaviour of the tunnel–foundation–building system, to investigate the relative significance of four fundamental components of SSI when predicting the overall vibration levels within the building. The effects of building location, relative to the tunnel, pile length and foundation configuration are investigated. Three further building models, of varying complexity, are used to explore the extent to which simplified models can capture the fundamental SSI of the system. The conclusions appear promising for the development of simplified models, particularly those aimed at making overall or relative predictions of building vibration levels to guide the design of mitigation measures.

Attenuation of bulk waves using locally resonant soil-coupled metabarriers

Abstract Low frequency ground-borne vibrations generated by transport infrastructure are one of the most serious causes of disturbance to the general population. One possibility to reduce this problem is to use the wave filtering properties of elastic metamaterials. However, their integration in the soil complicates the prediction of their response, and the influence of soil-structure interaction needs to be correctly evaluated for an efficient design. The aim of this work is to experimentally evaluate the efficiency of metamaterial trench barriers set in soil in attenuating vibrations, using low-frequency local resonance mechanisms. A lab scale model is proposed comprising different resonating structures and a cylindrical encasement is adopted to couple the structure to the soil. The influence of various parameters is evaluated, such as metamaterial structure, geometrical characteristics of the resonator, and constituent materials. Finite Element simulations are used to develop a suitable design, analysing mode shapes and resonance frequencies of structures with and without the surrounding encasement. Experimental modal analysis is then performed on the corresponding fabricated samples, providing both model validation and out-of-soil mechanical characterization. Finally, vibration transmission loss measurements are performed in a setup in which different resonant metamaterial barriers are embedded into the soil sample, allowing the evaluation of barrier performance. Results indicate that the metamaterial structures provide good attenuation of vibrations in selected intervals in the low to high frequency range (1–5 kHz), demonstrating the feasibility of the approach in a scaled sample. Preliminary data regarding the structures providing preferable design characteristics is also obtained. These results can be useful for the design of trench barriers scaled to large dimensions in more realistic applicative settings.

Vibration vulnerability assessment of heritage structures in Lahore: a step towards sustainable conservation

Lahore is among the most important historical cities in Pakistan, and many cultural heritage structures, such as Shalamar Gardens and Lahore Fort, which are recognised as World Heritage Sites by UNESCO, are located there. The rapid increase in transit operations and infrastructure development in Lahore can increase the vulnerability of nearby heritage structures to ground-borne vibrations. In this study, a vibration vulnerability assessment of the heritage structures present in Lahore was performed with the help of the framework provided by the Federal Transit Administration (FTA), USA. A remote survey was carried out to gather valuable information regarding the distance between the heritage structures and potential vibrational sources, as well as the latitude and longitude of the heritage structures, via the web-based mapping tool Google Earth. A vibration vulnerability map of heritage structures was developed on the basis of a vibration vulnerability assessment to make it convenient for policymakers to visualise the present state of heritage structures with respect to vibration vulnerability. The performed vibration vulnerability assessment was validated by experimentally measuring vibrations at the Buddha’s Tomb (Buddha Ka Awa) heritage structure. The study revealed that 17% of the heritage structures present in Lahore are vulnerable to vibrations at present, with potential vibrational sources such as road traffic, metro trains, and rail traffic. The vibration vulnerability assessment revealed that 72% of the vibrationally vulnerable heritage structures in Lahore are most influenced by vibrations from road traffic. The results of this study can aid policymakers in creating intervention packages for vibrationally vulnerable heritage structures in Lahore in relation to their respective needs, which will make it possible to achieve the sustainable conservation of heritage structures.

Study on the effect of mitigation strategies for rail corrugation in metro lines

Rail corrugation appears as a periodic irregularity on the rail running surface that causes severe dynamic loads at the wheel-rail interface. These dynamic forces may generate ground-borne vibrations that propagate from the line to the surrounding buildings causing discomfort to residents. Rail grinding is the most used countermeasure for the mitigation of corrugation. However, this maintenance operation determines high operative costs if frequently performed and must be carefully scheduled. To this end, it is important to assess the effectiveness of other mitigation solutions that may prevent or slow down its growth. The main objective of this study is to investigate the formation of rail corrugation on a sharp curve of the Cityringen underground line in Copenhagen. A wheel-rail interaction model is developed in the frequency domain to identify the root causes of the problem on the specific curve and predict the corrugation wavelength. Once the accuracy of the model is tested against experimental observations on the reference curve, it is used to explore the effectiveness of different mitigation actions, such as the use of friction modifiers, the variation of the speed, track design and track gauge. The results indicate that friction modifiers and speed variation are the most effective measures.

A Novel Application of Computational Contact Tools on Nonlinear Finite Element Analysis to Predict Ground-Borne Vibrations Generated by Trains in Ballasted Tracks

Predictive numerical models in the study of ground-borne vibrations generated by railway systems have traditionally relied on the subsystem partition approach (segmented). In such a method, loads are individually applied, and the cumulative effect of the rolling stock is obtained through superposition. While this method serves to mitigate computational costs, it may not fully capture the complex interactions involved in ground-borne vibrations—especially in the frequency domain. Recent advancements in computation and software have enabled the development of more sophisticated vibrational contamination prediction models that encompass the entire dynamics of the system, from the rolling stock to the terrain, allowing continuous simulations with a defined time step. Furthermore, the incorporation of computational contact mechanics tools between various elements not only ensures accuracy in the time domain but also extends the analysis into the frequency domain. In this novel approach, the segmented models are shifted to continuous simulations where the nonlinear problem of a rigid–flexible multibody system is fully considered. The model can predict the impact of a high-speed rail (HSR) vehicle passing, capturing the key intricacies of ground-borne vibrations and their impact on the surrounding environment due to a deeper comprehension of the occurrences in the frequency domain.

Experimental assessment of isolation performance of a building above metro lines: a case study with dual isolation levels

This paper presents an assessment of the acoustic performance of a five-story residential building constructed directly above a metro line in Prague. The building has been isolated at two levels: first, on top of the distribution beams above the metro tunnel and secondly, at the ground floor. The assessment of the building's performance has been conducted by a direct measurement of ground borne noise radiated inside the rooms and evaluating the vibration transmission loss through the isolation system. The transmission loss assessment was carried out using two different test setups. Firstly, during train pass-byes, ground borne vibrations were simultaneously measured at various locations above and below the vibration cut. Secondly, at the same measurement points, the vibration levels were measured using hammer impacts. Finally, the transmissibility obtained from both test setups was compared and discussed. Additionally, ground borne noise levels were measured inside rooms on different floors above the vibration cut. To identify noise events exclusively associated with train pass-byes, data obtained from synchronized vibration measurements at the center of a room inside an apartment were used. Finally, the measured noise levels were compared with the limit values of noise exposure recommended by the Czech standards.

On the reduction of FEM models dealing with vibrations propagation from ground to buildings

The problem of ground-borne vibrations in contact with a building's basement is crucial to the comfort of people living in buildings located very close to roads or railway tracks. The numerical finite elements models used to describe this situation are heavy to compute: it must combine the complexity of the building with the large dimensions of the soil. We propose a method to reduce the model computation cost while keeping accurate results. The goal of our study is to remove the ground from the model by applying efforts and boundary conditions to the building foundation to reproduce the soil/structure interactions. The full model of a simple building with a basement on a single-layer soil is studied to extract the coupling stresses. Corresponding efforts are applied to the building alone, with several boundary conditions tested. The results show similar vibration levels on the building floors, for a far lower time of computation.

Coupling model between building post structure and floors with the spectral element method

With the densification of urban area and public transport, the structure-borne noise disturbance due to railway traffic is a major issue. In order to mitigate it, ground-borne vibration propagation in building has to be investigated. The case of post-beam constructions necessitates 3D modeling with choices between complex, precise and computationally time-consuming approaches (3D finite element method for example), and fast but less accurate approaches like the statistical energy analysis (SEA) which need a strong modal density. For such post-beam constructions, the spectral element method (SEM) appears to be a good compromise. This method allows reducing the number of elements to represent the truss structure compared to the finite element method. However, the building walls and floor are difficult to consider with the SEM. In this paper, the challenge of coupling post-beam structures and floors is examined, a method is proposed and results are discussed. The aim is to develop a method applicable to different buildings while keeping advantage of SEM low discretization.

Guiding near-source elastic waves in a semi-infinite medium.

In this work, we propose elastic metamaterials with phase discontinuities to steer the propagation of near-source bulk waves in a semi-infinite elastic medium. Our design exploits an array of embedded subwavelength resonators with tailored masses to attain a complete phase shift spanning [Formula: see text]. This phase control allows for diverse wave functionalities, such as directional refraction and energy focusing. Through the use of dispersion diagrams and the generalized Snell's law, along with a multiple scattering formulation, we analytically demonstrate the effectiveness of our design in achieving the desired wavefront manipulation. The proposed design has the potential to advance the field of guiding elastic waves using metamaterials and find practical applications in areas such as isolating ground-borne vibrations in densely urbanized regions and energy harvesting. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Numerical prediction of ground-borne vibrations due to continuous vibratory driving of circular closed-ended piles

Various types of pile driving work may induce high-intensity ground-borne vibrations. Predicting vibration intensity before adopting mitigation measures is vital for minimizing the impact of vibration on nearby structures and occupants. Vibratory pile driving is a commonly applied foundation construction method. However, numerical simulation models for ground vibrations during a complete process of vibratory driving have rarely been studied. This study introduces an axisymmetric finite element model that utilizes the arbitrary Lagrangian-Eulerian technique to simulate the continuous vibratory driving of a circular closed-ended pile penetrating from the ground surface to a target depth. The model validity was confirmed by assessing the calculated ground vibrations against the findings documented in earlier research. The results showed that the critical penetration depth of piles, at which the maximum peak particle velocity (PPV) occurs, varied with the radial distance and depth of points of interest, contradicting a common preconception. Moreover, the maximum PPV did not always occur on the ground surface across all radial distances. Parametric analysis revealed that an increase in the soil cohesion strength, pile diameter, or soil-pile friction, or a decrease in the driving frequency or soil damping ratio would increase ground vibrations due to vibratory pile driving.

Using tire derived aggregates (TDA) as infill material for wave barriers

Ground-borne vibrations caused by construction activities and highway and railway traffic may disturb adjacent structures and sensitive machines. Thus, studies on isolating this type of vibrations have accelerated in recent years. Few experimental work investigated the use of rubber-soil mixtures as infill material for vibration mitigation. However, despite its high damping capacity, almost no experimental work has been conducted to evaluate the use of Tire Derived Aggregates (TDA) as infill material for trench barriers. This paper aims to investigate the use of TDA trenches as a wave barrier. Also, the performance of buried TDA trenches was considered in this work. A series of vibration tests were conducted in a steel tank with dimensions of 2.75 m long, 2.25 m wide, and 1.80 m deep. The trench depth and frequency varied from 0.2 to 0.6 m and 100–200 Hz, respectively. The results showed that TDA trenches had a superior performance compared to open trenches. TDA trenches could reduce the vertical vibration amplitude by up to 30 % more than open trenches. Also, open and TDA trenches performed better in mitigating the vertical vibrations compared to the other directions. Furthermore, for optimum design of open and TDA trenches, the normalized trench depth should be between 1 and 1.3 D. Covering TDA trenches with soil was found to decrease their vibration isolation significantly at normalized burial depth larger than 0.15.

Impact of Train-Induced Vibrations on Residents’ Comfort and Structural Damages in Buildings

AbstractThe rapid growth of urbanization and the progress of industrialization have resulted in the construction of over or near-track buildings. Train-induced ground-borne vibrations have attracted attention because they can damage buildings and cause residents discomfort. This study conducted a series of finite element analyses on three 5-story concrete framed buildings, which were subjected to the passage of trains at various speeds. One of the buildings was modeled as an over-track building, whereas the other two buildings were located in close proximity to the track but at different distances. The present study investigated the impact of train speed and track-to-building distance on the acceleration and velocity responses of buildings. The comparison of residents’ comfort levels and the structural safety of buildings against potential damages was conducted using international standards as the controlling criteria. Furthermore, an efficient mitigation technique was implemented, involving the utilization of open trenches with different depths between buildings and the railway track. This approach was employed with the aim of minimizing the detrimental impacts caused by trains-induced vibrations. The findings indicated that the over-track building was impacted by the train-induced vibrations more than near-track buildings. Furthermore, it was shown that although the passage of high-speed trains can disturb the comfort of building residents and potentially cause some structural damage to buildings, it did not lead to any significant story drifts in the structures. Finally, the minimum required depth of open trenches to mitigate train-induced vibrations was computed for every type of buildings and train speeds.

Comparison of train noise and vibration measurements with U.S. Department of Transportation model predictions

Wayside noise and ground-borne vibration measurements of freight and light rail train operations were carried out in Denver, CO in support of the Burnham Yard Transportation Planning Study being pursued by the Colorado Department of Transportation (CDOT). This study was intended to evaluate various track layout alternatives for the Consolidated Main Line (CML) freight railroad alignment and enhancement of Regional Transportation District (RTD) light rail operations while maintaining options for Front Range Passenger Rail (FRPR) within Burnham Yard and the surrounding areas. The objective of the measurements was to compare measured train noise and vibration levels with predictions using models sanctioned by the U.S. Department of Transportation (USDOT) in order to validate the use of these models to assess the noise and vibration impacts of the project alternatives. The models included the Federal Railroad Administration (FRA) Chicago Rail Efficiency And Transportation Efficiency (CREATE) freight noise model, the FRA Horn Noise Model, and the models included in the Federal Transit Administration (FTA) Transit Noise and Vibration Impact Assessment Manual. Based on a comparison of measured and modeled results, it was concluded that the USDOT models could be used to assess noise and vibration from train operations in the Burnham Yard Study Area.

Investigating the effects of in-track countermeasures to reduce ground-borne vibration from underground railways

Investigating the effects of in-track countermeasures to reduce ground-borne vibration from underground railways

Criticality and chaos in auditory and vestibular sensing

The auditory and vestibular systems exhibit remarkable sensitivity of detection, responding to deflections on the order of angstroms, even in the presence of biological noise. The auditory system exhibits high temporal acuity and frequency selectivity, allowing us to make sense of the acoustic world around us. As the acoustic signals of interest span many orders of magnitude in both amplitude and frequency, this system relies heavily on nonlinearities and power-law scaling. The vestibular system, which detects ground-borne vibrations and creates the sense of balance, exhibits highly sensitive, broadband detection. It likewise requires high temporal acuity so as to allow us to maintain balance while in motion. The behavior of these sensory systems has been extensively studied in the context of dynamical systems theory, with many empirical phenomena described by critical dynamics. Other phenomena have been explained by systems in the chaotic regime, where weak perturbations drastically impact the future state of the system. Using a Hopf oscillator as a simple numerical model for a sensory element in these systems, we explore the intersection of the two types of dynamical phenomena. We identify the relative tradeoffs between different detection metrics, and propose that, for both types of sensory systems, the instabilities giving rise to chaotic dynamics improve signal detection.

An efficient pile-group foundation model to deal with ground-borne vibration problems

An efficient pile-group foundation model to deal with ground-borne vibration problems

Minimal Conditioned Stiffness Matrices with Frequency-Dependent Path Following for Arbitrary Elastic Layers over Half-Spaces

This paper introduces an efficient computational procedure for analyzing the propagation of harmonic waves in layered elastic media. This offers several advantages, including the ability to handle arbitrary frequencies, depths, and the number of layers above an elastic half-space, and efforts to follow dispersion curves and flag up possible singularities are investigated. While there are inherent limitations in terms of computational accuracy and capacity, this methodology is straightforward to implement for studying free or forced vibrations and obtaining relevant response data. We present computations of wavenumber dispersion diagrams, phase velocity plots, and response data in both the frequency and time domains. These computational results are provided for two example cases: plane strain and axisymmetry. Our methodology is grounded in a well-conditioned dynamic stiffness approach specifically tailored for deep-layered strata analysis. We introduce an innovative method for efficiently computing wavenumber dispersion curves. By tracking the slope of these curves, users can effectively manage continuation parameters. We illustrate this technique through numerical evidence of a layer resonance in a real-life case study characterized by a fold in the dispersion curves. Furthermore, this framework is particularly advantageous for engineers addressing problems related to ground-borne vibrations. It enables the analysis of phenomena such as zero group velocity (ZGV), where a singularity occurs, both in the frequency and time domains, shedding light on the unique characteristics of such cases. Given the reduced dimension of the problem, this formulation can considerably aid geophysicists and engineers in areas such as MASW or SASW techniques.

Analysis and intelligent prediction of subway train-induced vibration in the building with pile foundation

The rapid development of subway construction inevitably leads to the subway lines traversing through or adjoining the buildings. However, current research primarily focuses on the train-induced ground-borne or building with shallow foundation vibrations, with a relatively limited investigation into the vibration pertaining to the building with pile foundation. A vibration analysis model of a building with pile foundation adjacent to a subway is established in this study using the finite element method, and the effects of various factors on the vibration of the building are analyzed, then the prediction of building vibration characteristics is also carried out by combining artificial intelligence methods. The results show that the building floor has an amplifying effect on the vibration acceleration level and Z-vibration level in the high frequency range, and the vibration energy attenuation at high frequencies is faster in the building with pile foundation compared to the building with shallow foundation. In the meantime, it shows that the GA-BP model is capable of effectively capturing the vibration characteristics of the building with pile foundation within the dominant frequency range. and the vibration of the building with pile foundation can be predicted not only by parameters such as train speed, soil and structure parameters but also by train-induced ground-borne vibration, which provides the possibility of simplifying the process of vibration prediction process and enhancing the practical application.

Experimental Study on Reutilization of Waste Rubber Chips with Sheetpiles as a Coupled-Wave Barrier to Reduce Ground-Borne Vibrations

Abstract Purpose Environmental and man-made vibrations due to various sources have become an environmental issue in recent years. Wave barriers such as open and in-filled trenches have been commonly used in the mitigation of these vibrations. Even though the open trench has exhibited better performance than the others, it may not be applicable or feasible in many cases. Therefore, soft and stiff barriers have been used for the same purpose. The present study aims to reveal the vibration isolation performance of not only single barriers such as rubber chips in-filled trenches and sheetpiles but also a novel barrier, rubber chips-sheetpile coupled barriers. Methods Rubber chips and sheetpiles were employed as soft and stiff wave barriers, respectively. The screening effectiveness of rubber chips, sheetpiles and their coupled form was examined through comprehensive field tests. Vibrations having frequencies in the range of 10–80 Hz were generated by a state-of-the-art mobile seismic shaker and measured by highly sensitive acceleration and velocity pickups in the absence and presence of these wave barriers. The effectiveness of the wave barriers was quantitatively determined. Results and conclusion While the sheetpile was more effective than rubber chips at low frequencies, the case was vice versa at higher frequencies. However, the coupled wave barrier outperformed other barriers in each case. If one barrier could not provide the required amount of isolation or is only effective within a limited range of frequency, using a coupled barrier with the installation of the other may significantly provide better vibration isolation.