Floor Vibration Research Articles

Human-induced vibrations of floors: A probabilistic approach

The current design guidelines for assessing floor vibration performance rely on a simplified approach that considers a single pedestrian as a fixed load with multiple harmonic components applied to the anti-nodes of the floor mode shapes. However, these guidelines do not account for the influence of variability in the walking path on the dynamic response of floors. Moreover, the deterministic approaches used in these guidelines may yield unreliable estimates of vibration response due to the stochastic nature of pedestrian walking force. The aim of this paper is to investigate the dynamic response of floors under a single pedestrian walking load while considering the randomness of the walking path and the walking load itself. A probabilistic perspective is adopted to analyze the dynamic response under different random loading scenarios. Furthermore, the effectiveness of the current guidelines in predicting the dynamic response of floors is critically assessed. The importance of incorporating probabilistic approaches is emphasized to achieve a more comprehensive understanding of the vibration serviceability of floors and to enhance design practices in this context.

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.

Utilizing Artificial Neural Networks and Random Forests to Forecast the Dynamic Amplification Factors of Non-Structural Components

Soft stories in buildings are well-known to present structural vulnerabilities during seismic events, and the failure of non-structural components (NSCs) has been evident in past earthquakes, along with structural damage. This study seeks to investigate how the presence of a soft story in a building affects the criteria for elastic floor acceleration. The soft story is assumed to be at the top, middle, and bottom levels of the structure. To comprehend the behavior of NSCs, the researchers analyze the floor response spectra (FRSs) and component acceleration amplification. Remarkably, the results reveal that the position of the soft story strongly influences the floor response spectra, with structures featuring a middle soft story showing the most significant amplification of component acceleration. In constructing the FRSs, the component dynamic amplification factors (CDAFs) play a vital role as they accurately illustrate how NSCs amplify floor vibrations. Consequently, the study delves into exploring machine learning (ML) models like artificial neural networks (ANNs) and random forest (RF) to map the intricate relationship between CDAFs, the dynamic characteristics of the building, and the behavior of NSCs. Upon comparison of the two models, the random forest model emerges as the superior method in predicting the CDAFs.

Round-robin tests of the different types of sensors for floor impact sounds and vibrations

Recently, floor impact noise monitoring system was introduced for residents to control making noises spontaneously using sound and vibration sensors. The present study aims to investigate the performance and characteristics of various current using sound and vibration sensors which can be eventually compatible with the floor impact noise monitoring system. For measurements of sound sensors, 7 sound microphones were used including 2 condenser types, 4 dynamic types, and 1 electro condenser type. Also, 6 vibration meters were used including 2 MEMS types, 2 Piezo types, and 2 spring types. Sound levels were measured in a semi-anechoic chamber using white noise in the frequency range from 63 Hz to 12.5 kHz. Vibrations were measured using high density wooden panel with an impact ball in the frequency range from 16 Hz to 4 KHz. Round-robin tests were done to confirm the exact performances of all the sensors under same condition. As a result, it was found that dynamic type microphones show the most similar response characterization in comparison with the reference condenser microphone especially in the air-borne sound frequency range from 250 Hz to 2 KHz. Also, it was found that spring type vibration meters show the most appropriate characterization at 63 Hz, most critical structure-borne sound frequency. Thus, the results drawn from the round-robin tests could be used for floor impact noise monitoring systems with the benefit of both economy and performance.

Dynamic Properties of Timber–Concrete Composite Beams with Crossed Inclined Coach Screw Connections: Experimental and Theoretical Investigations

Due to the low density and stiffness of wood, traditional timber floor systems are prone to producing large vibration responses. By combining timber beams with concrete floors, timber–concrete composite (TCC) floor systems show stronger bearing capacity, higher bending stiffness, and better thermal and sound insulation behaviors when compared with traditional timber floor systems. In this study, the vibration performance of TCC beams with crossed inclined coach screw connectors was investigated using dynamic tests. The influence of the screw diameters and slab dimensions on the dynamic performance of the composite beams was evaluated. The test results demonstrated that TCC beams show good dynamic performance when used as a floor component and meet the preliminary requirements of floor vibration comfort for fundamental frequency. The fundamental frequency and damping ratio of TCC beams decreases with the increase in slab dimensions. The bending stiffness and natural frequency of TCC beams decrease smoothly when reducing the screw diameter from 16 to 12 mm. Additionally, two theoretical models were used to predict the natural frequencies of the TCC beams, and the predicted values show good consistency with the measured ones.

Serviceability Evaluation of High-Rise Buildings Exposed to Typhoon Proximity Effects Using ISO10137 and ISO6897

This study evaluates the vibration data of high-rise buildings during a typhoon by measuring the vibration data and using international serviceability standards. In order to do this, the horizontal vibration serviceability evaluation standards of each country were surveyed, but the standards that could be applied were limited to ISO10137 and ISO 6897. Despite the trend that the discomfort of residents increases as the number of high-rise buildings increases, the current standards are for high-frequency vibrations, such as machine vibrations or vertical floor vibrations, so there is an urgent need for research on new evaluation methods for low-frequency horizontal vibrations. As a result of analyzing the effects of typhoons on buildings, the study’s target building had low natural frequencies of less than 1 Hz, and the highest acceleration was observed to be amplified up to about 160 times due to the effects of Typhoon Danas and Chaba, but there was no change in the natural frequency. When this result was applied to the horizontal vibration serviceability evaluation, it was found that the likelihood of residents perceiving vibration was low during constant vibration, but during strong winds, the size of the top-floor horizontal vibration exceeded the average level of vibration perception proposed by ISO standards, so most residents of high-rise buildings would be likely to perceive the vibration as uncomfortable.

Tire and Engine Sources Contribution to Vehicle Interior Noise and Vibration Exposure Levels

The main objective of the research presented in this paper is to enhance driver-passengers comfort of a vehicle that in turn leads to better vehicle safety and stability. The focus was put on studying the interior vibration and noise contributions originated from tire-road and engine-transmission subsystems, due to their significant impact on the dynamic performance of the vehicle. The noise and vibration measurements were recorded at the driver’s head position and on the driver legs room. Furthermore, the influence of different tire types and road surface textures on the vehicle interior noise and vibration were considered. The results indicate that the widely used conventional engine mounts and tires in commercial vehicles cannot fulfill the conflicting requirements for the best isolation concerning both road surface and engine-transmission induced excitations. The values of driver’s head position sound pressure level and floor vibration acceleration broadband averages originate for engine-transmission are lower than that for tire-road interaction. Furthermore, the values of RMS, crest factor, kurtosis and IRI for the vehicle waveform were estimated for vehicle speeds, tire types and road surface textures. Moreover, the percentage contribution for both interior noise and vibration originated from tire-road interaction is higher than the one from vehicle engine-transmission system in all the vehicle speed range, tire type and road surface texture considered.

Vibration of Timber and Hybrid Floors: A Review of Methods of Measurement, Analysis, and Design

Floor vibration, although not a safety concern, is a prevalent performance complaint in multi-story structures. With the increasing use of mass timber construction, various types of long-span timber floors (LSTFs), including plain cross-laminated timber (CLT), CLT with secondary beams (ribbed-deck), and hybrid systems such as timber–concrete composite (TCC) and CLT on-steel-support beams, are gaining popularity. However, due to limited knowledge regarding their vibration characteristics and acceptance criteria, these construction types are often overlooked during the design stage by architects, engineers, and builders. Existing standards and guidelines primarily calibrated for steel and concrete floors lack a validated and calibrated method for evaluating the vibration performance of LSTFs. Nonetheless, it is essential for structural engineers to address vibration concerns during the design stage and potentially investigate excessive vibration in existing buildings, providing mitigation solutions. This article provides a comprehensive overview, discussion, and analysis of the measurement, analysis, design, perception, and acceptability of vibration of timber floors as outlined in international standards and commonly used guidelines. Experimental and theoretical case studies, including vibration measurements of a CLT floor and a comparison of vibration acceptability in lightweight timber floors using different methods, are reported. The results highlight discrepancies between simplified equation calculations and modal analysis observations, underscoring the limitations of relying solely on simplified equations. Furthermore, it is observed that current modal superposition methods tend to be conservative in predicting floor acceleration and velocity responses. Recommendations are provided for future research in the field to enhance floor vibration assessment techniques, aiming for improved design optimization and occupant comfort.

An efficient three-dimensional dynamic stiffness-based model for predicting subway train-induced building vibrations

The prediction of train-induced vibration in buildings constructed above the subway is a challenging problem due to its sophisticated system and time-consuming calculation. This paper proposes an efficient three-dimensional (3D) dynamic stiffness-based model (DSM) to predict subway train-induced building vibrations. The DSM has the capability to analytically explore the axial, bending, and torsional vibrations of columns and beams, as well as the flexural and in-plane vibrations of floors and walls induced by the moving train, which few studies have focused on before, and has high computational efficiency compared to the traditional finite element method (FEM). In the DSM, the dynamic stiffness matrices of floors, walls, columns and beams are formulated by the stiffness theory firstly. Then, the global dynamic stiffness matrix of the building is determined following an assembly procedure and the vibration responses of the building can be calculated by the dynamic stiffness equation in the frequency domain. Further, the calculation accuracy and efficiency of the DSM are validated by comparison with a 3D finite element model. Finally, the DSM is used to predict the train-induced vibrations of a building constructed at a subway station based on a subway train-slab track coupled dynamics model. Results show that the building vibrations induced by the moving train are significant in both vertical and horizontal directions and the steel-spring floating-slab track can effectively suppress the train-induced building vibrations.

Application of multiple dynamic vibration absorbers in reducing low-frequency vibration of a floor-like lightweight joist structure: Comparison of experimental and computational results

Typical solutions to reduce excessive floor vibration and radiated sound to the room below include increasing floor mass, stiffening floor structure, and adding a floating floor in the source room. However, these methods may not be effective for lightweight floors at low frequencies. The use of dynamic vibration absorbers (DVAs) to reduce low-frequency structural vibration has attracted the attention of researchers in recent years. In this paper, an analytical model is proposed to study the effect of DVAs on the vibration of a lightweight joist structure by combining the bending modes of the plate with the bending and torsional modes of the beams. The analytical model is compared with the results from finite element models and measurements on a scaled wooden joist floor structure with fabricated spring-mass-type DVAs. A good consistency between the analytical results with results from the latter two are found in terms of the structural vibration and the DVAs’ effects.

Floor vibrations and rectification

Excessive floor vibration due to human excitation is a significant serviceability concern in buildings and other long span structures. The use of lightweight materials, nominal furniture and open plan layouts is resulting in lighter floors with lower damping than traditional older floors and hence an increased risk of excessive vibration response. This paper provides insights into walking excitation, floor response and remedial actions for floors with excessive vibrations.

Vibration modeling of buildings with composite floors

Profiled composite floors (ribbed concrete slabs on corrugated steel decks) are commonly used in steel framed buildings. However, complicating the dynamic modeling of such floors is their apparent stiffness anisotropy due to the periodically spaced ribs. In this paper, approaches are presented to obtain the effective, flat-plate properties of composite floors to predict floor vibrations for two building case studies. Measured floor vibrations for the case studies are then compared to the models.

Vibration Reduction in Passenger Vehicle by Optimization of Propeller Shaft Design

In Passenger segments, vehicles floor vibration is one of the major cause which leads to discomfort for passengers. There are several locations for vibration, one of the location is Floor of the bus where passengers will feel the vibration directly while sitting on the seats and while standing on the Gangways. So acceleration levels in passenger segment should be as per AIS 153 standard. The objective of this paper is, of all the available causes for vibration, we will discuss about the middle floor vibrations raised by Propeller shaft and how to mitigate the problem by various focused design proposals on Propeller shaft. Here, we will be reviewing the Bus segment which has a Double Piece Propeller shaft design configuration.

Human Perception of Lightweight Floors Vibrations, New Investigations to Improve Wood Building Performances (GIVILIF Project)

The present paper aims to highlight the first findings of the GIVILIF project (Group Induced Vibrations on LIght Floors). The primary purpose of this project is to improve the existing standards around the vibrations of timber floors induced by group activities. It presents the first part of the applied methodology for the subjective and objective evaluation of vibrations. First, a survey among inhabitants was conducted better to understand the vibrational discomfort of existing buildings’ occupants. Then, tests on a shaking table explored the perception of individuals to define thresholds of perception, discomfort and intolerance. It was found that the acceleration graph assures certain conformity with the thresholds offered by the ISO2631 standard concerning offices and residences, purpose of this study.

Heavy-weight floor impact sound of a pure framed structure by field measurement and numerical calculation

Examples of poor heavy-weight floor impact sound performance of pure framed structures with reinforced concrete were observed relative to the floor slab thickness. To investigate the cause of the poor performance, the floor vibration characteristics of several examples of actual pure framed structures were measured during heavy-weight impact. As a result, the floor vibration characteristics of the displacement of the girders and coupled vibration of the girders and floor slabs not seen in conventional floor structures surrounded by girders with reinforced concrete walls were observed. The propagation of the vibration of the floor slab was observed in more than the range surrounded by girders and in the next slab beyond the girders owing to the vibration of the girder itself. That these physical phenomena can be evaluated using a numerical calculation method was confirmed, and the vibration of the girder itself and the actual vibration range when the floor slab is subjected to heavy-weight impact must be considered to accurately predict the heavy-weight floor impact sound performance.

Toward Device-free and User-independent Fall Detection Using Floor Vibration

The inevitable aging trend of the world’s population brings a lot of challenges to the health care for the elderly. For example, it is difficult to guarantee timely rescue for single-resided elders who fall at home. Under this circumstance, a reliable automatic fall detection machine is in great need for emergent rescue. However, the state-of-the-art fall detection systems are suffering from serious privacy concerns, having a high false alarm, or being cumbersome for users. In this article, we propose a device-free fall detection system, namely G-Fall, based on floor vibration collected by geophone sensors. We first decompose the falling mode and characterize it with time-dependent floor vibration features. By leveraging Hidden Markov Model (HMM), our system is able to detect the fall event precisely and achieve user-independent detection. It requires no training from the elderly but only an HMM template learned in advance through a small number of training samples. To reduce the false alarm rate, we propose a novel reconfirmation mechanism using Energy-of-Arrival (EoA) positioning to assist in detecting the human fall. Extensive experiments have been conducted on 24 human subjects. On average, G-Fall achieves a 95.74% detection precision on the anti-static floor and 97.36% on the concrete floor. Furthermore, with the assistance of EoA, the false alarm rate is reduced to nearly 0%.

Measurement and application of walking models for evaluating floor vibration

For light and long-span structures, human-induced vibration may present a serviceability issue. To study the vibration serviceability problem, it is important to have a better understanding on human-induced forces, such as walking. To this end, the load-time histories of walking excited by 25 test participants were measured using a force-measuring plate. Totally, 300 walking force–time histories were recorded; and the peak load factors were compared in detail. The correlation analysis shows that there is a weak correlation between the three directional components of walking load, i.e., the walking component can be modeled independently. Then, the Fourier series functions for walking were derived; and the relationships between the dynamic loading factors, phase angles and the duration time Tp of single-step walking were developed, giving the forcing functions. The load-time history extension method was used to establish the forcing function for continuous walk. Lastly, the proposed continuous walking model was validated with the test and finite element results.

Numerical prediction method for vibration characteristics of steel-framed ALC floor structure

The prediction of floor vibration is of great importance from the viewpoint of accurate prediction of sound environment. In this paper, applicability of the finite-element analysis to the vibration simulation of autoclaved lightweight aerated concrete (ALC) floor structure on a steel-framed structure was verified. The results of a numerical case study has confirmed that the numerical coupling scheme of the ALC floor panels and the steel-framed structure had a significant influence on the simulated vibration characteristics of the ALC floor panels. Then, the validity of the proposed method was finally confirmed by comparison with the measurement results.

Relation Between Seated Person Vibrations and the International Roughness Index

Vertical vehicle feet/floor interface vibrations are typically not used to indirectly estimate road roughness. The relation for vehicle floor vibrations, the International Roughness Index (IRI), vehicle speed, and road roughness vertical displacement spectrum according to the ISO 8608: 2016 standard was previously derived only for the simulation of a reference quarter-car model. It was estimated using the in situ measurement of vibrations of a person sitting in a passenger car for different vehicle and road categories, vehicle speed, and road roughness. Vibrations at the feet/floor interface and seat surface of a seated passenger were evaluated with the frequency-weighted root-mean-square vertical acceleration according to the ISO 2631-1: 1997 standard. The results indicated that the simulated results for the quarter-car model may have substantially underestimated the ratio between the vehicle floor vibrations of a seated person and the IRI, but they were similar to seat surface vibrations.

Abnormal behavior detection of solitary elderly people using floor vibration

Abnormal behavior detection of solitary elderly people using floor vibration