Vibration Limits Research Articles

Acceleration-Displacement Response Spectrum Vibration Limits for Blast Vibrations

This paper proposes a new method to limit vibrations from blasting to avoid damage to residential structures. The evolution of commonly adopted vibration limits and standards adopted for surface blasting operations in close proximity to residential areas is reviewed. The importance of human sensitivity to vibrations is highlighted and vibration limits preventing damage are demonstrated to be influenced by human annoyance. A robust and rational procedure is presented to replace existing vibration standards limiting vibration using the acceleration- displacement response spectrum methodology commonly adopted in earthquake engineering. The proposed approach adopts drift as a measure of damage rather than the current industry accepted measurement of ground velocity.

Vibration isolation measures due to the high sensitive linear accelerator at the Paul Scherrer Institute

The new 735m long linear accelerator “SwissFEL” at the Paul Scherrer Institute (PSI) in Wurenlingen is extremely sensitive against vibrations coming from surrounding equipment (pumps, ventilators, transformers, etc.). The manufacturer’s vibration limit for this linear accelerator is 0.1μm displacement amplitude. Therefore, all vibration sources must strictly be isolated to the highest-possible degree from the rest of the structure. This paper discusses the vibration situation in general for this unique construction (ground vibrations, vibration propagations / structural amplifications, vibration limits, etc.) and as a case study the isolation of a pump located in the building. Steel springs were used and it was achieved to reduce the vibration transmitted to the floor by more than 99%, to a level where the coherent component of the motion recorded on the floor next to the linear accelerator is non-measurable / below the ground motions. The measurements were found to be in good accordance with the FEM model used.

Blast Vibration Analysis by Different Predictor Approaches-A Comparison

Blasting is a majormechanism of rock fragmentation. Explosive usage creates ground vibration, air over pressure as well as fly rock. Blast design is a process which needs to be monitored continuously as the rock mass exhibit many vibrations within the same boundary. Often the quantum of explosive had to be determined within safe vibration limit. Artificial Neural Network approach is also gaining wide recognition for its accuracy to match with the measured values. This paper evaluates the governing relations between PPV at varying explosive quantities and distances using established approaches as well as the results by application of artificial neural network.A total of nine blast events have been analyzed. Indian Standard and ANN approaches exhibit better correlation with the measured values of PPV as compared to that by other approaches.

Seismic Design Research of Simply Supported Rail-Bridge Based on Running Safety

To explore the practical rail-bridge seismic design methods, dynamic response analysis model of the train-rail-bridge system under seismic loads was established, and the widely used simply supported track-bridge in rail transport was taken for the study. By inputting different intensity and frequency artificial seismic waves to the train-rail-bridge system, the whole history of the vehicles running through the bridge is simulated and the dynamic responses of the bridge and the vehicles are calculated. The influence of train type, seismic intensity and spectral characteristics of the earthquake were analyzed. Taking Japanese traffic safety evaluation indexes including derailment coefficient, wheel offload rate and lateral wheel-rail force as evaluation criteria, the allowed lateral bridge displacement limits and acceleration limits that ensuring train running safety under earthquake were obtained, and the bridge vibration limit curve was drawn. Using Lagrange interpolation method, the mathematical expression of the curve was worked out, which can provide a reference to rail-bridge aseismic design.

가속도 크기 변수에 따른 수직진동에 대한 인지수준 고찰

Occupants induced floor vertical vibrations may cause other occupants annoyance and lead to social loss. To help control such floor vibrations, several criteria have been developed mostly based on human perception tests and floor vibration tests. Floor vibration is evaluated by comparison with criteria and vibration parameters of subject floor, such as frequency, damping ratio, acceleration value, vibration duration time and occurrence frequency. Three acceleration value parameters are used in criteria; peak acceleration, rms acceleration and VDV, when a floor vibration serviceability is evaluated. Meanwhile rms acceleration and peak acceleration are adopted as vibration limit value in criteria and researches of human perception for vibration. Occupants induced floor vibration is transient rather than steady state. However, rms acceleration is not reliable parameter for evaluating transient vibration. The objective of this study is to investigate the characters of human perception level according to acceleration value parameters for vibration induced by heel impacts and walking activities.

Prediction of structural vibrations using a coupled vehicle-track–building model

As a result of local factors, limited amounts of land and construction demands, subway lines are sometimes designed to run in close proximity to buildings. Hence, using a real Beijing subway engineering project, we have studied the vibration induced in a building by a moving rail vehicle. A numerical model of the spatially coupled vehicle–track–building system was developed to predict the vibration levels in the structure. The modeling theory was verified by comparison with multi-body system simulations and field test results. Two common types of track, namely, ballasted track and floating slab track were studied and their vibration-mitigation effects were compared in the time and frequency domains. A comparison of the particle peak velocities with the structural vibration limits of the floating floor slab and the first floor of a building revealed a very low possibility of severe damage resulting from vehicle-induced vibration for both types of tracks. We also conducted a one-third octave analysis of the vibration of each building floor and obtained the weighted root-mean-squared acceleration and vibration levels. A comparison of the weighted accelerations with the vibration limits for vibration perception by a human for both types of tracks also revealed that train-induced vibration had no obvious effect on daily human activities on most of the floors. The main exception to this observation was the first floor, which is located close to the vibration source. It is recommended that the first floor should be used for purposes other than residential. Furthermore, a comparison of the vibration levels of each floor for both types of tracks showed that the ballasted track had a better vibration-mitigation effect than the floating slab track for this special engineering case.

CONTROLE E PREVISÃO DE NÍVEIS DE RUÍDO E VIBRAÇÕES GERADOS PELO DESMONTE DE ROCHAS COM EXPLOSIVOS

Air blast and ground vibrations generated by rock blasting have become a major legal and technical problem, mainly due the growing of the cities to the neighborhood of mines and quarries. For many people, the main environmental impacts associated with mining are those generated by rock blasting, and there is a real risk in handling explosives since just around 20-30% of the explosives energy is used to fragment and throw the rock. But the effects of explosives can be precalculated and predicted quite accurately, according the regulations for the use of explosives which are meant to be such a safeguard against accidents. These rules or laws establish that it is necessary to carry out a risk analysis in order to determine, first, what size vibrations the environment will accept and second, how large a charge can be blasted at certain distance without exceeding that vibration or noise limits. This risk analysis has been made in the limestone mines of Cacapava do Sul involving a careful examination of the factors that can affect the blasting operations. At the same time, a mathematical model has been developed in order to reliably predict the noise and vibration levels for a determined distance in the vicinity of the blasting place.

발파진동으로 인한 공작기계 가공정도의 영향 평가

The machine tool is used widely to manufacture and trial manufactured goods in many machinery industries. Blast-induced ground vibration may have an environmental impact, such as damage to the adjacent structures and facilities. This study examined the influence of blast vibration on the accuracy of machine tools. The blast vibration and vibration of machine tools was measured to evaluate the influence of blast vibration on machine tools. Based on the evaluation of the vibration limit of machine tools, the vibration criteria for machine tools in this study were SLIGHTLY ROUGH∼ROUGH. By repeated blast vibration, machine tools are more likely show reduced

Design and Implementation of the System of High Speed Dynamic Balance of Rotor

High-speed dynamic balance is a main method to solve the problem of exceeding the aero engine vibration limit. However, with the development of techniques of high performance engine, the rotating speed of a rotor becomes more and more high, which turns into a challenge to balance it. Therefore, balancing the rotor with high speed effectively is very important. How effective the engine rotor of high speed dynamic balance is very important.

A nonlocal constitutive model generated by matrix functions for polyatomic periodic linear chains

We establish a discrete lattice dynamics model and its continuum limits for nonlocal constitutive behavior of polyatomic cyclically closed linear chains being formed by periodically repeated unit cells (molecules), each consisting of atoms which all are of different species, e.g., distinguished by their masses. Nonlocality is introduced by elastic potentials which are quadratic forms of finite differences of orders of the displacement field leading by application of Hamilton's variational principle to nondiagonal and hence nonlocal Laplacian matrices. These Laplacian matrices are obtained as matrix power functions of even orders 2m of the local discrete Laplacian of the next neighbor Born-von-Karman linear chain. The present paper is a generalization of a recent model that we proposed for the monoatomic chain. We analyze the vibrational dispersion relation and continuum limits of our nonlocal approach. ``Anomalous'' dispersion relation characteristics due to strong nonlocality which cannot be captured by classical lattice models is found and discussed. The requirement of finiteness of the elastic energies and total masses in the continuum limits requires a certain scaling behavior of the material constants. In this way, we deduce rigorously the continuum limit kernels of the Laplacian matrices of our nonlocal lattice model. The approach guarantees that these kernels correspond to physically admissible, elastically stable chains. The present approach has the potential to be extended to 2D and 3D lattices.

A Comparative Study on Road Traffic and Metro Train Induced Ground Vibration at CMTI for Establishment of Nano Technology Facilities

Nanotechnology offers enormous potential for discovering new fundamental science, for creating new materials with unique and important properties, and for developing new technology. Nanotechnology deals with particles and system with dimensions of approximately 1 to 100 nanometers. Some aspects of nanomanufacturing technology facilities like nanofabrication, nanometrology requires extremely stable environment with very stringent limits of ground vibration. The ground vibrations induced due to road and rail traffic can affect the nanotechnology research activities, due to disturbances caused by the road and rail traffic induced ground vibrations on the nanotechnology processes and the measurements. The paper presents the study of road traffic and metro train induced ground vibration for establishment of nanomanufacturing technology facilities at CMTI. The road traffic and the metro train induced ground vibration were monitored inside the CMTI campus at surface level to identify the magnitude of ground vibration. The road traffic and the metro train induced ground vibrations are compared in comparison with the CMTI Nanotechnology Lab specifications. The metro train induced ground vibration levels are more in comparison to the road traffic induced ground vibration. The metro train induced ground vibration level exceeds the CMTI Nanotechnology Laboratory ground vibration specifications.

Functional Mode Electron-Transfer Theory.

A solid approach has been developed to ascertain the correlation of electron transfer with molecular vibration in a quantitative manner. Specifically, the reaction coordinate is identified by maximizing the linear Pearson's correlation coefficient between atomic displacement and the diabatic energy gap. In the limit of fast molecular vibration, the rates of electron transfer driven by multiple vibrational modes have been derived respectively under the strong and weak vibronic coupling conditions. Our functional mode electron-transfer theory is then justified by investigating the electron transfer of a betaine-30 molecule from its first excited state to its ground state when being solvated in glycerol triacetate. Among the 210 available vibrational modes of betaine-30, only seven are essential to the electron transfer by cumulatively accounting for more than 60% of the total reorganization energy. Because all essential vibrational modes are significantly faster than thermal fluctuation, the electron transfer is primarily driven by intramolecular quantum tunneling. Interestingly, the calculated reaction driving force of 1.95 eV is substantially greater than the reorganization energy of 0.58 eV, placing the reaction in the inverted Marcus region. Nevertheless, a sizable Franck-Condon factor of 1.58 × 10(-3) eV(-1) is still achieved due to the large vibronically weighted zero-point energy of the essential vibrational modes. After determining the electronic coupling strength as 0.14 eV by the constrained density functional theory, the overall electron-transfer rate at 300 K is found to be 0.30 ps(-1), which agrees nearly perfectly with experimental values.

Impact of Construction-Induced Vibration on Vibration-Sensitive Medical Equipment: A Case Study

Many metropolitan cities suffer from a shortage of land supply, which results in new development in areas with high building density. Construction activities, particularly piling processes, may generate excessive ground-borne vibrations. The nearby sensitive people, facilities and buildings (e.g. hospitals and healthcare institutions) are often vulnerable to such excessive vibrations. However, the impact of construction-induced vibrations on sensitive medical equipment is rarely discussed. The vibration limits commonly adopted by the construction industry are mainly with regard to structural safety, which are considerably greater than the tolerable limits for sensitive medical equipment. This case study evaluates the potential effect of ground vibrations induced by piling activities on sensitive medical equipment. The ground-borne vibrations induced by two piling methods are quantified by field measurements. The indoor floor vibrations are simulated using building models. The vibration limits for a large number of sensitive items of medical equipment are established through questionnaires to the manufacturers. The potential risk to the functionality of the concerned equipment is illustrated by comparing the tolerable vibration limits with the predicted vibration levels.

Modeling of induced seismicity and ground vibrations associated with geologic CO2 storage, and assessing their effects on surface structures and human perception

In this paper, we present model simulations of ground motions caused by CO2-injection-induced fault reactivation and analyze the results in terms of the potential for damage to ground surface structures and nuisance to the local human population. It is an integrated analysis from cause to consequence, including the whole chain of processes starting from earthquake inception in the subsurface, wave propagation toward the ground surface, and assessment of the consequences of ground vibration. For a small magnitude (Mw=3) event at a hypocenter depth of about 1000m, we first used the simulated ground-motion wave train in an inverse analysis to estimate source parameters (moment magnitude, rupture dimensions and stress drop), achieving good agreement and thereby verifying the modeling of the chain of processes from earthquake inception to ground vibration. We then analyzed the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV) and frequency content, with comparison to U.S. Geological Survey's instrumental intensity scales for earthquakes and the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. Our results confirm the appropriateness of using PGV (rather than PGA) and frequency for the evaluation of potential ground-vibration effects on structures and humans from shallow injection-induced seismic events. For the considered synthetic Mw=3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, but would certainly be felt by the local population.

Tolerable Limits of Construction Vibrations

Construction impact and steady-state vibration sources such as pile driving, dynamic compaction, and other machinery generate ground and structural vibrations that may detrimentally affect diverse adjacent and remote structures, people, and sensitive devices. Vibration effects on structures depend on numerous factors. Vibration limits developed in the blasting industry are often used for evaluation of the construction vibration effects on structures. However, these vibration limits were derived only for specific combinations of blasting, soil conditions, and structures. Soil deformations and soil-structure interaction determine soil and structure responses to vibration excitation. Soil and structure vibration responses should be the basis for applied tolerable limits. Diverse tolerable limits are proposed for various soil and structure vibrations. In addition to vibration measurements, condition surveys should be performed for analysis of the causes of the existing damage to structures.

Multi-Objective Structural Optimization Design of Horizontal-Axis Wind Turbine Blades Using the Non-Dominated Sorting Genetic Algorithm II and Finite Element Method

A multi-objective optimization method for the structural design of horizontal-axis wind turbine (HAWT) blades is presented. The main goal is to minimize the weight and cost of the blade which uses glass fiber reinforced plastic (GFRP) coupled with carbon fiber reinforced plastic (CFRP) materials. The number and the location of layers in the spar cap, the width of the spar cap and the position of the shear webs are employed as the design variables, while the strain limit, blade/tower clearance limit and vibration limit are taken into account as the constraint conditions. The optimization of the design of a commercial 1.5 MW HAWT blade is carried out by combining FEM analysis and a multi-objective evolutionary algorithm under ultimate (extreme) flap-wise load and edge-wise load conditions. The best solutions are described and the comparison of the obtained results with the original design is performed to prove the efficiency and applicability of the method.

Physical risk associated with vibration at cycling

The vibrations undergone by men are a well-known and widely studied risk factor in the industrial world. They are transmitted to the whole body or the upper limbs and they are measured, and limited, according to international standards. Disorders resulting from exposure to vibration are varied in nature: osteoarticular, muscular, vascular, and neurological. In this context, an European Directive 2002/44/EC to the protection of workers exposed to vibration, precises thresholds for vibration exposures and defines the procedure for risk prevention. Nevertheless, the effect of vibration is little studied in sports despite the ubiquity of these. Vibration can induce discomfort, degrading performance or causing musculoskeletal disorders. This paper makes an overview of the studies involving the vibrations during cycling. At first, this paper will summarize the different standards and guidelines relating vibration in humans, which present a guide for the measurement and evaluation of the vibration and exposure limits. Secondly, this paper presents a state of the art vibration effects: (i) the physiological and pathological disorders in athletes, (ii) and the performance. A third part will be devoted to the synthesis of numerical studies that represent the biodynamic response and help to predict the effects of human body vibration. Finally, new research and innovations will be discussed based on studies in other sports.

Dynamic modeling of injection-induced fault reactivation and ground motion and impact on surface structures and human perception

We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about Mw = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzed the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic Mw = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO2 leakage, but would certainly be felt by the local population.

Floor vibration testing in hospital operating rooms

Operating rooms in several hospitals have been studied for their in-situ floor vibration properties. The motivations ranged from identifying the cause of unstable images observed in a surgical microscope to determining whether a portion of a long span floor in a hospital parking garage could be adapted for a future surgical center. As part of these studies, several types of floor excitation techniques were employed including a vibration exciter, a “heeldrop,” and a human walker. The input magnitudes from the first two of these excitation sources can be measured at a given location using a calibrated force plate. The human walker, however, is a “wild card” source since the location of the footfall is constantly changing; moreover, the nature of the applied force pulse is unknown under field conditions. Thus, one cannot easily quantify the dynamic force of the test signal that is most germane to the assessment of floor vibration in the field. The paper will review the literature governing floor vibration limits in sensitive buildings and summarize the utility of information obtained by various floor testing protocols.

Research on Vibratory Behavior Assessment and Maintenance of Drilling and Threading Machine VA20A

Vibrations due to mechanical defects,are transmitted within the entire structure of the equipment, are amplified during its dynamical operation, having a direct impact on the accuracy of the processed surfaces. Spectral components need vibration analysis is required. In order to determine the operation state and the vibration level caused by the mechanical failures , the FFT (Fast Fourier Transform Method) method has been used. The vibrations measurements is repeated at constant intervals; It specify the measured vibration limits; It compares the values in ISO-sites exist for determining optimal predictive maintenance intervals.