Vibration Limits Research Articles

A Study on the Mast Structure Vibration Limits considering the Operating Time of Naval Ships

The mast structure of a naval ship has a lot of expensive equipment attached and is easily exposed to strong vibration due to its structural characteristics, so it is necessary to manage vibrations well to prevent equipment failure and increase operating time. Since September 2015, the Navy has been managing the vibration of the ship's mast structure with a separate tolerance standard from the local vibration, but this standard is set at 1/2 of the vibration limits for mast-mounted equipment without any engineering basis. So the establishment of new vibration limits based on the operating conditions of naval ships is required. In this study, the mast structure vibration limits were reviewed considering the actual operating time of naval ships, and the results were compared with the standards of major overseas classification societies and the actual measurements of a ship that had mast structure vibration problems.

Identification of amplitude-dependent aerodynamic damping from free vibration data using iterative unscented kalman filter

This study presents an innovative approach employing an iterative Unscented Kalman Filter (IUKF) for the identification of amplitude-dependent nonlinear aerodynamic damping using wind tunnel free vibration data. The wind-structure interaction system is represented as a single-degree-of-freedom system, with the amplitude-dependent aerodynamic damping modeled as a polynomial function of structural displacement and velocity. The augmented state variables, encompassing structural vibration frequency and polynomial coefficients for aerodynamic damping, are concurrently estimated from free vibration data using the UKF technique. To enhance the robustness of the identification results against variations in initial conditions, the UKF is applied iteratively by assigning the estimated polynomial coefficients as new initial values for the state variables. Validation of the IUKF-based method is performed through a numerical example featuring a typical bridge deck sectional model, as well as experimental data from two spring-suspended sectional models experiencing vertical vortex-induced vibration (VIV) and torsional post-flutter limit cycle oscillation. The feasibility of identifying amplitude-dependent aerodynamic damping for amplitude range not covered by the displacement signal is examined.

Operational risk assessment of hydropower units based on PSSCA-VMD-CNN-GBiLSTM and multi-feature fusion

Hydroelectric units are an essential part of hydropower plants nowadays, and assessing and predicting the operating conditions of hydroelectric units is of great significance for the reliable operation of hydropower plants. Firstly, an optimization method based on polynomial regression with Pearson and Spearman fusion and Sine Cosine Algorithm (SCA) algorithm (PSSCA) is proposed to optimize the parameters in the variational modal decomposition (VMD), so as to suppress the influence of noise on the vibration signals of hydroelectric units. Then, the sample entropy and root-mean-square fusion of the VMD decomposed modal functions are reconstructed into a hybrid feature vector set so that this vector set can maximally contain the feature information of the vibration signals of the hydroelectric units. Finally, the CNN-GBiLSTM assessment model is constructed by combining the Convolutional Neural Network (CNN) model, the Bi-directional Long Short-Term Memory (BiLSTM) model, and the global average pooling layer, which is used to predict the upper and lower limits of the healthy vibration of the hydropower unit, and to construct the risk indicator of the hydropower unit operation by combining the values of the upper and lower limits. The results of simulation and comparative experiments show that the method proposed in this study can visually represent the three operational risk scenarios of a hydropower unit: low risk, medium risk, and high risk. It can effectively accomplish the operational risk assessment of hydropower units and improve the assessment accuracy and assessment speed, thus proving the effectiveness and superiority of the method.

Case study of construction noise and vibration monitoring at an elementary school

Construction noise and vibration monitoring was performed for long-term construction activities occurring directly adjacent to an elementary school and playground area. Noise and vibration limits were determined based on measurements taken indoors and outdoors during preliminary construction activities, and in discussions with the school. Noise and vibration alerts during monitoring were provided in real-time to the construction managers during the activities, and notices of exceedances provided as methods of administrative controls. Various temporary noise mitigation barriers erected on-site were also assessed.

Predictive Analytics-Based Methodology Supported by Wireless Monitoring for the Prognosis of Roller-Bearing Failure

Roller mills are commonly used in the production of mining derivatives, since one of their purposes is to reduce raw materials to very small sizes and to combine them. This research evaluates the mechanical condition of a mill containing four rollers, focusing on the largest cylindrical roller bearings as the main component that causes equipment failure. The objective of this work is to make a prognosis of when the overall vibrations would reach the maximum level allowed (2.5 IPS pk), thus enabling planned replacements, and achieving the maximum possible useful life in operation, without incurring unscheduled corrective maintenance and unexpected plant shutdown. Wireless sensors were used to capture vibration data and the ARIMA (Auto-Regressive Integrated Moving Average) and Holt–Winters methods were applied to forecast vibration behavior in the short term. Finally, the results demonstrate that the Holt–Winters model outperforms the ARIMA model in precision, allowing a 3-month prognosis without exceeding the established vibration limit.

Evaluation of human-induced vibration in floors of modular hospitals

Construction of modular hospitals has gained significant attention since the global pandemic. One important design requirement for hospitals that is critical for their safe operation is to control floor vibration. Floors in modular buildings are often more prone to vibration because they are lightweight and less restrained. This study first presents a standardized design layout for modular hospitals developed based on Canadian code requirements. Then, the human-induced vibration of various floor systems designed for this sample modular hospital is investigated using different analysis methods including a new method developed by the authors. It is found that conventional floor designs may not be suitable for modular hospitals considering the strict vibration limits for hospitals and the need for lightweight construction. Using detailed finite element analysis, it is shown that the proposed method can accurately predict the vibration response of various floors including those that have frequencies well beyond the application range of existing design methods.

Active Microvibration Control of Tool Platforms Installed on the Floors Subjected to Moving Vehicles in Industrial Factories

The vibration responses of tall flexible tool (or equipment) platforms subjected to floor excitations at the platform base are considered more crucial than those of the short ones. This study examined the microvibration control performance of the proposed active piezoelectric mass damper (APMD) or driver for tall platforms subjected to internal automated guided vehicle- (AGV-) induced floor vibrations with larger intensity and broader bandwidth in liquid-crystal-display (LCD) fabrication factories (fabs). The APMD did not require auxiliary spring and damping elements to tune the natural frequency and reduce the stroke of the mass block as required by typical active tuned mass dampers (ATMDs). The motion equation of the proposed analytical model including a continuous three-span beam (or floor) system and an active-controlled tool platform under the action of the AGV moving forces was derived. The APMD, consisting of piezoelectric stacks and a mass block, was installed on the platform subjected to the base rotation excitation, which could be attributed to the uneven vertical floor vibrations induced by AGVs. Moreover, the direct output feedback control algorithm was adopted to determine the optimal feedback gain matrix for calculating the active control force. Time history analyses of the continuous beam-platform model under different AGV weights moving at the same speed were performed, and the corresponding velocity vibration spectra of the floor and platform were further obtained through one-third octave band spectrum analysis. Numerical simulation results revealed that the microvibrations of the platform without APMD generally exceed the VC-A level regardless of the AGV weight. Significant reductions of over 90% on the platform microvibrations could be achieved after the platform was implemented with the APMD, and vibrations met the desired vibration limit (VC-B). Moreover, the APMD exhibits comparable microvibration control performance to the ATMD and requires less mass of the mass block, stroke, and applied voltage under the same active control force. In real-life high-tech production fabs, AGV-induced platform microvibrations occur all the time; therefore, the proposed APMD with less power consumption could be an economical and feasible approach for persistent microvibration control of tall platforms in LCD fabs.

Allowable Limit of Human Annoyance Towards Ground-Borne Vibration Velocity Induced by Rail Traffic: A Review

Many industrialized nations have created their own standards for determining and grading the dangers posed by ground-borne vibration, notably in terms of human irritation. Excessive vibrations created by trains have an impact not only on individuals, but also on sensitive machinery and buildings. The authority as well as practitioners have critical responsibilities in managing and accessing vibrations. This study discusses the differences between the standard and the limit of vibrations caused by trains that can irritate people. The local standard guideline was compared to the standards used by the US, Norway, Sweden, California, Germany, and the Netherlands. This study was mainly interested in the limitations of vibration velocity in residential settings.

Transforming farming with intelligence: Smart vibration monitoring and alert system

During the evolution towards digital agriculture, the pivotal role of tractor riding necessitates a focus on improving operator performance and well-being. While most research has centered around vibration analysis, tangible solutions to control elevated vibration levels remain rare. The study aims to introduce an intelligent ThingSpeak-Enabled IoT (Internet of Things) solution that provides real-time monitoring and generates prompt warning alerts for tractor operators when vibrations exceed safe thresholds. The initial phase involved the real-time measurement of WBV (whole-body vibration) and SEAT (seat effective amplitude transmissibility). Following this, the secondary phase encompassed the analysis and validation of the system in cases where WBV and SEAT exceeded the recommended limits. The experimental design comprised 135 trials by systematically varying tractor ride parameters, including average speed (m/s), average depth (m), and pulling force (kN) levels. Daily vibration exposure response ranged from 0.43 m/s² to 0.87 m/s² with a mean exposure of 0.64 m/s2, surpassing the EAV (exposure action value) threshold of 0.5 m/s². The SEAT values ranged between 91.37 and 133.08 with a mean of 108.35, that indicates insufficient seat isolation capacity, i.e., < 100. Statistically, the study ascertained a significant influence of average speed and average depth WBV and SEAT responses at a 5% significance level. It underscores the potential efficacy of altering speed and depth parameters to attenuate vibration exposure levels. Further, the effectiveness of the system was tested through the automatic transmission of warning alerts via emails, text messages, and flashing red LED light on the IoT system. This critical feature provides considerable utility for tractor operators to adjust ride settings, ensuring that the ride remains within safe vibration limits. Furthermore, adopting such an advanced warning system in tractor manufacturing signifies a pioneering step towards sustainably enhancing operator well-being.

Limits of permissible vibrations of vehicles for different driving conditions and norms of vibration load

A method for constructing regulatory boundaries for the amplitude-frequency characteristics of sprung vehicles is presented using the parameters of the road micro-profile and the regulations of vibration load. Formulas are given for calculating the standard spectral dispersion densities for the boundaries of labor productivity decrease, comfort boundaries and boundaries that ensure safety and health, with a duration of vibration exposure of 8 hours, 4, and 1 hour. The graphs of the regulatory spectral densities of dispersions for the boundaries of the decrease in labor productivity for the same duration of exposure are given. The method for calculating the spectral density of the dispersion of the road profile based on its correlation function is presented. Formulas for calculating spectral dispersion densities for 8 types of road profile are given. The examples of the regulatory boundaries of the amplitude-frequency characteristics obtained on the basis of the presented method are given. Keywords: vehicle suspension, road micro-profile, spectral density of road micro-profile, correlation function of road microprofile, regulatory boundaries, amplitude-frequency characteristics

Structural Optimization of Lightweight Composite Floors with Integrated Constrained Layer Damping for Vibration Control

Due to current architectural trends, contemporary public buildings are becoming open-plan spaces with much less weight and damping. Consequently, Vibration Serviceability Limit State (VSLS) due to human-induced vibrations has become an increasing concern for structural engineers, especially when designing offices, hospitals, or gymnasiums. When dealing with resonant vibrations, a slight increase in the floor-damping enables decreasing considerably the vibration level. The damping strategy studied in this work is usually known in the literature as Constrained Layer Damping (CLD) and consists of a viscoelastic layer constrained between the concrete slab and the steel beam of a lightweight composite floor. In this paper, a complete structural checking methodology has been developed for analyzing all the limit states that determine the final sizing of a steel–concrete composite floor treated with CLD, including a detailed analysis of the VSLS. The methodology has been used for setting a structural optimization problem for floors with and without CLD treatments. Thus, it has been demonstrated that the integration of CLD treatments at the design stage of the building allows the development of lighter floor structures with a smaller embodied carbon (EC) footprint, especially for long-span schemes with restrictive vibration limitations.

Field investigation on the impact of vehicle traffic on the vibration of ancient seawalls in Qiantang River

To investigate the vibrational impact of vehicular traffic on the ancient Qiantang River seawall, on-site measurements of the seawall’s pulsation and forced vibrations under different vehicle speeds and axle loads were conducted. The acquired data were analyzed in the time domain, frequency domain, and 1/3 octave bands, revealing the time-frequency vibrational characteristics of the ancient seawall structure. The results indicate that the characteristic frequencies of the ancient seawall are 3 Hz and 10 Hz, with the primary frequency band of the structural vibrations induced by vehicular traffic ranging from 0 to 30 Hz. Vehicle traffic primarily caused vertical vibrations in the seawall structure, with along-dike horizontal vibrations being significantly higher than cross-dike vibrations. Based on the measurement results, an empirical relationship between the peak vibration velocity of the ancient seawall and variations in vehicle speed and axle load was established. It was found that, compared to axle load, increased vehicle speed had a more pronounced amplification effect on the structural vibrations of the ancient seawall. To ensure the vibrational safety of the ancient seawall relics, maximum vehicle speeds for different loading conditions of tri-axle trucks were provided based on vibration limits: for an axle load of 10 t, speeds should be below 34 km/h; for 11.52 t, below 24 km/h; for 13.04 t, below 20 km/h; and for 14.56 t, below 15 km/h.

Vibration Analysis of the Base Structure Supporting a Centrifuge–Motor Assembly in a Petroleum Oil Refinery

A structure carrying a centrifuge and motor in a petroleum oil refinery has been vibrating above the alarm limit of vibration. This has been a recurring problem. The maintenance work undertaken at regular intervals on the basis of time waveform and spectrum analysis could provide only a temporary solution. To investigate the causes of vibration above the acceptable limits, pre-stressed modal analysis of the structure was undertaken by using Finite Element Analysis software ANSYS™ and natural frequencies and mode shapes were extracted. Pre-stressing was done by considering the self-weight of the structure, centrifuge and motor. The structure was analyzed using a combination of beam elements, shell elements and mass elements. The operating deflection shape (ODS) technique which helps to observe the deflection pattern of structure in real time at operating or other frequencies from the measured vibration data was employed to validate the analytical results. ME’scopeVES™ software employing the ODS technique was used in this work. Analytical results obtained from ANSYS™ software are compared well with the ODS test results. The analysis of analytical and experimental results has revealed that the structure was operating in the resonance band.

Field measurement and evaluation of vibrations inside buildings above metro tunnels

The buildings above metro tunnels have developed rapidly in China in recent years because it can make comprehensive use of land resources. However, buildings are closer to the vibration source, which makes them sensitive to train-induced vibration and adversely affect the living quality of the building occupants. Based on field-measured vibration data of buildings above metro tunnels, the response characteristics of train-induced vibrations at the basement and floor slabs of buildings were investigated herein. The results showed that the vertical acceleration was much larger than the horizontal acceleration. The vertical acceleration of the floor slabs was greater than that of the basement, and the main frequency band of vertical vibration was 50–70 Hz. In this case, with an increase in the floor, the vertical acceleration of the buildings first increased, decayed rapidly, and finally increased slightly; that is, a vibration amplification phenomenon on the top three floors of the buildings was observed. The maximum vertical acceleration appeared on the 4th floor and the minimum vertical acceleration appeared on the floor, which was three floors below the top. The horizontal distance between the building and tunnel has a significant effect on the amplitude of vertical acceleration. The vibration levels caused by different trains have little difference, with a maximum variance of 2.3 dB. The Z vibration levels of all the measuring points were significantly lower than the first-level vibration limit (73 dB) specified in Chinese standard for limits and measurement methods of vibration in the room of residential building (GB/T 50355-2018).

Design of cross-laminated timber (CLT) floors for human-induced vibrations

Cross-laminated timber (CLT) is an innovative engineering wood product made by gluing layers of solid timber boards placed in an orthogonally alternating orientation to the neighbouring layers. CLT panels provide an efficient solution for floors in single and multi-storey buildings. Due to their light weight and often long-span, the design of these floors is generally governed by serviceability limit state criteria, that is, deflection or vibration limits. Vibrations induced by dynamic actions, such as people walking and their everyday activities, cannot result in structural failure but may cause discomfort to occupants if vibrations are not properly controlled. This paper gives an overview of some available methods for the vibration serviceability design of residential CLT floors. Differences between these methods are discussed through the consideration of criteria and their limit values. Although some criteria are common to certain methods, it may happen that the same criteria take into account different factors. In order to get a better description of the actual behaviour of floor structure, certain classifications of floors based on vibration serviceability performance were introduced in design methods.

Guidelines for the field-based vibration assessment of pressure vessel nozzles

Vibration analysts rely on industry guidelines and international standards for the “screening” of piping vibration datasets, i.e., to differentiate locations of high piping vibration (usually high dynamic stress) from acceptable piping vibration. Despite the abundance of piping vibration criteria, analysts continue to develop advanced screening methods to discard “false positives” at the data collection stage, i.e., measurement locations with high vibration (exceeding vibration limits) but with acceptable dynamic stress. The present work is a contribution to the growing body of advanced screening methods and aims to identify the most suitable vibration limit curves for the field-based vibration assessment of pressure vessel nozzles. This sub-category of process pipework requires special attention due to the relative flexibility of the parent pressure vessel and the relatively stiff geometry of nozzles compared to general pipework. The harmonic response problem of a cylindrical nozzle radially intersecting a thin-walled cylindrical pressure vessel and vibrating at its fundamental bending modes is solved using a three-dimensional Finite Element (FE) model. The results of the parametric FE study suggest that frequency-dependent vibration velocity criteria, such as the Energy Institute (EI) guidelines, are more suitable for assessing vibration severity on pressure vessel nozzles than constant vibration velocity criteria, such as the ISO 20816-8.

The effect of a seismic wave on a two-span beam on rigid supports interacting with the ground

The transverse vibrations of a two-span beam bridge, the shore supports of which interact with the surrounding soil during seismic action, are considered. The condition is accepted that the deformations of structures do not go beyond the limits of elasticity and vibrations are linear in nature. The bridge supports are assumed to be submerged in the ground and interacting with a rigid body under the action of non-stationary dynamic influences. The case is considered when the left, middle and right supports have equal masses and interact with the surrounding soil in the same way. The symmetry condition is applied, and it is sufficient to consider the equation of the right half of the beam. The problems are solved by the analytical Fourier method under the given boundary conditions. The results obtained are presented in the form of stress distribution over time and length of bridge structures, and their analysis is also presented.

Rectifying an Excessive Vibration Issue in Shallow Foundation with Permeation Grouting: A Case Study

Large vibrating machines are integral part of industrial facility. This paper describes the case example of excessive vibration, encountered in one of the machine foundations in such facility, as well as the corresponding rectification works. This vibrating machine was built on shallow foundation sitting on compacted sand fill layer; the foundation self-weight is more than eight (8) times of the equipment weight. The block foundation dimension is about 7.0 x 1.7 x 1.7 m3. The vibrating machine frequency (which sits above the foundation) is 450 rpm, with a relatively large impulsive cyclic load. In this paper, firstly, the potential root cause of this vibration issue is explored. Thereafter, considerations for the rectification works are described; in this case, a permeation grouting technique, using low-viscosity cement grout is chosen. The work method for this ground improvement works, including the completion criteria are described. Post-improvement vibration measurement indicates that the measured vibration is within the accepted vibration limit, indicating a successful improvement work.

A Calculation Model for Vibration Effect Induced by Resonance-Free Vibratory Hammer Method

Buildings close to the ground treated by the resonance- free vibratory hammer method are often vulnerable to excessive vibrations. An in situ test of an urban soft site was carried out to investigate the resonance-free vibratory hammer induced vibration effects during construction. Vibration pickups were set at the positions with distances of 15 m, 30 m, 50 m, and 100 m away from the vibration source. On the basis of the results obtained from this investigation, vibration effects of the resonance-free vibratory hammer and safe construction distances were systematically analyzed. The testing results indicate that the vibration in the vertical direction is stronger than that in the other two horizontal directions. The vertical vibration should be the main reference quantity for the foundation treatment by using the resonance-free vibratory hammer method. The predominant frequency of each measuring point in the same direction decreased with an increase of the distance from the vibration source (DFTVS). In terms of the measuring point with a DFTVS of 30 m, the peak values of velocity in all directions were within 5 mm/s, which meet the requirements of the allowable limit of building vibration. According to the in situ testing results, a model for calculating the acceleration exponent of the vibration caused by the resonance-free vibratory hammer technology was established by comprehensively considering the amplitude of acceleration, the attenuation coefficient of THE DFTVS, and the vibration correction factor. Finally, the reliability of the calculation model was verified through the comparison between the calculated results and field vibration experimental results, in which all the correlation coefficients of validation example were above 0.9.

Dynamics of the Rotor System of a Vibrational–Centrifugal Separator with an Elastic Vibration Limiter

Dynamics of the Rotor System of a Vibrational–Centrifugal Separator with an Elastic Vibration Limiter