Vibration Comfort Research Articles

Vibration behavior of timber-concrete composite floors under human-induced excitation

The design of timber-concrete composite (TCC) floors is usually subject to the requirement of serviceability rather than strength. Most studies reported so far focus on the dynamic characteristics of the TCC floor. However, there are few studies conducted on the vibration comfort of TCC floors under human-induced excitation. In this paper, dynamic experiments were performed to obtain the fundamental frequency and the damping ratio of a glulam-concrete composite floor under simply supported and fixed support boundary conditions, respectively. Besides, an in-depth investigation was carried out considering the influences of walking path, step frequency, number of pedestrians, arrangement of walking loads and walking mode on the vibration response of the composite floor. Test results showed that the peak acceleration of the floor increased with an increase in step frequency and the number of pedestrians. Regular walking caused a higher peak acceleration compared to irregular walking. At the same step frequency, marking time caused a larger peak acceleration than normal walking. Three existing analytical models were applied to predict the fundamental frequency of the floor, which conformed to the experimental results. In addition, a calculation model and finite element (FE) models were proposed to predict the peak floor acceleration under a single person walking, and the numerical model results agree well with the test results. A double-index was proposed to evaluate the vibration serviceability of TCC floors; the fundamental frequency of the floor is required to exceed 15 Hz and the peak acceleration ought to be less than 0.15 m/s2.

Prediction and Measurement of the Damping Ratios of Laminated Polymer Composite Plates.

Laminated composites materials are mostly used in dynamically loaded structures. The design of these structures with finite element packages is focused on vibrations, elastic deformations and failure control. Damping is often neglected because of its assumed secondary importance and also because of dearth of information on relevant material properties. This trend is prone to change as it is now realised that damping plays an increasingly important role in vibration comfort, noise radiation and crash simulations. This paper shows in a first step how to identify the orthotropic elastic and damping properties of single layer fibre-reinforced composite material sheets using a new extended version of the Resonalyser procedure. The procedure is based on the elastic-viscoelastic correspondence principle and uses a mixed numerical experimental method. In a subsequent step, the complex laminate stiffness values are computed using the identified single layer material properties. To validate this approach, the modal damping ratios of arbitrary laminated plates of different materials at several resonance frequencies are predicted and experimentally verified.

Study on the vibrational comfort of aircraft in formation flight

PurposeThe purpose of this paper is to investigate the passenger comfort changes due to the wake turbulence impact from the formation flight (FF) leading aircraft, which can be a showstopper for the real application of FF to airliners.Design/methodology/approachTaking advantage of the overall aircraft design and optimization framework, as well as the module for FF assessment, the comfort level has been quantified for aircraft in solo flight and in FF according to ISO 2631–1 specifications concerning vibration total value.FindingsThe results showed that atmospheric turbulence intensity is the dominant factor in determining the passenger ride quality in comparison to the impact of formation wake flow. According to the preliminary results of this study, passengers seated away from the aircraft mass center encounter larger discomfort. In comparison to mass center, seats away from mass center also experience slightly stronger discomfort due to FF. The current simulation results show that FF is feasible without remarkably degrading passenger comfort level, which agrees well with the flight test results.Practical implicationsAs passenger comfort is crucial for civil transport application of FF, the study carried out within this manuscript can give a preliminary indication to the showstopper of FF real-world application.Originality/valueThe proposed strategy can provide quantitative values for judging the possible drawbacks of FF, i.e. passenger comfort issues as mentioned in the literature. On the other hand, the aircraft level study based on reliable data and methods can give important insight for this interesting topic and further help the real-world application of FF for commercial aircraft. In addition, it can serve as preliminary studies for further design and operation modifications for aircraft in FF.

Finite Element Analysis of Displacement and Vibration Characteristics of Cantilevered Plate

The cantilever structure will produce a large dynamic response under the vertical load, which will cause the user’s discomfort. Therefore, the vibration characteristics of the structure caused by the vertical load are an important part of the comfort design of the cantilever structure in the normal use limit state. This article takes the vertical displacement of a cantilevered balcony slab on one side of a project under load as an example, and builds a model in the nonlinear finite element software to calculate the structural displacement and the factors of the cantilever length and the tensile reinforcement, and the corresponding comfort evaluation is carried out, which provides a reference for the vibration comfort evaluation of the house cantilever structure.

Experimental and Numerical Study on Dynamics of Two Footbridges with Different Shapes of Girders

The paper presents the experimental and numerical results of the dynamic system identification and verification of the behavior of two footbridges in Poland. The experimental part of the study involved vibration testing under different scenarios of human-induced load, impulse load, and excitations induced by vibration exciter. Based on the results obtained, the identification of dynamic parameters of the footbridges was performed using the peak-picking method. With the impulse load applied to both structures, determination of their natural vibration frequencies was possible. Then, based on the design drawings, detailed finite element method (FEM) models were developed, and the numerical analyses were carried out. The comparison between experimental and numerical results obtained from the modal analysis showed a good agreement. The results also indicated that both structures under investigation have the first natural bending frequency of the deck in the range of human-induced excitation. Therefore, the risk of excessive structural vibrations caused by pedestrian loading was then analysed for both structures. The vibration comfort criteria for both footbridges were checked according to Sétra guidelines. In the case of the first footbridge, the results showed that the comfort criteria are fulfilled, regardless of the type of load. For the second footbridge, it was emphasized that the structure meets the assumptions of the guidelines for vibration severability in normal use; nevertheless, it is susceptible to excitations induced by synchronized users, even in the case of a small group of pedestrians.

Analysis of motorcycle vibration comfort based on rigid-flexible coupling model

Based on the rigid-flexible coupling model, this article utilized ADAMS to establish a dynamics model of a motorcycle, in which the engine excitation and road excitation were determined. According to the ISO5349 and ISO2631 standards, the vibration of the motorcycle at 60 km/h was analyzed. The results showed that the high-frequency vibration of the engine accounted for the most vibration at the handle when driving on the B-class road at 60 km/h, and the vibration level was uncomfortable. In contrast, the low-frequency vibration of the road roughness was the main excitation of the cushion vibration, and the vibration level was relatively uncomfortable. These results were in accordance with the subjective impression on human observers, indicating that the vibration comfort analysis method based on the rigid-flexible coupling model was correct and effective to provide theoretical basis for the subsequent improvement and modification early in the design stage.

Two-step dynamics of a semiactive hydraulic engine mount with four-chamber and three-fluid-channel

Semiactive hydraulic engine mounts (HEMs) offer better noise, vibration and harshness (NVH) performance in a wider frequency band than passive HEMs and provide acoustic and vibrational comfort for passenger cars that rivals that of active engine mounts (AEMs); these advantages lead to the wider use of HEMs than AEMs. In limited control modes, broadening the vibration isolation band as much as possible is the fundamental purpose of semiactive HEMs. This paper focuses on an analytical and experimental study of a unique semiactive HEM with four-chamber and three-fluid-channel whose lengths shorten successively while the cross-sectional areas increase successively. The semiactive HEM presents dynamic characteristics in a two-step style and thus can offer good NVH performance in a relatively wider band. The first step is induced by the resonance of the longest fluid channel, and the second step is induced by the resonance of the shortest fluid channel corresponding to a separate decoupling membrane (DM) fluid chamber. The relationship of bulk stiffness between the DM and the main rubber spring is switched from an in-series connection for the first step to an in-parallel connection for the second step, which is an intrinsic reason for effectively widening the vibration isolation band. To better clarify the two-step dynamics, the influence of the DM is further investigated by introducing frequency-dependent bulk stiffness in-series and in-parallel. Moreover, two additional HEMs and their experimental two-step dynamics are illustrated to validate the frequency-dependent bulk stiffness. The ideal control strategies for semiactive HEMs with four-chamber and three-fluid-channel are developed and numerically verified by minimizing the force transmissibility in a wider frequency band. The findings of this paper can facilitate the design of dynamics for HEMs with a DM. Proper matching and relationship switching of the bulk stiffness between the DM and the main rubber spring can effectively improve NVH performance for passenger cars.

Vibration analysis of the F-segment car exhaust system

The paper considers the problem of improving the comfort and environmental friendliness of a modern f-segment car with an internal combustion engine by reducing the noise and vibration levels of the exhaust system. Gas-dynamic and mechanical excitations from the car engine and road surface cause vibrations in the exhaust system, which are transmitted through the body and the bracket structure to the body causing discomfort of the driver and passengers. To reduce the negative impact, when designing the exhaust system, it is necessary to ensure such a location of the exhaust system suspension elements that will meet the maximum operation requirements for the vibration comfort. An important task is to build a numerical experiment for the entire assembly structure to determine the nature of the similar systems loading. The solution of the above tasks is aimed at the insurance of specific strength and durability of both the entire system as a whole and the most important support elastic elements. This calculated study is of practical importance not only for reducing the vibration load of car exhaust systems and the car body, but also for improving the vibro-acoustic comfort of passengers.

Model of the Secondary Path between the Input Voltage and the Output Force of an Active Engine Mount on the Engine Side

The active engine mount (AEM) provides an effective solution to improve the acoustic and vibration comfort of a car. The same AEM can be installed for different engines and different vehicle bodies and attenuates the engine vibration, which is one of the most pressing challenges. To study this problem, this paper develops a mathematical model of a secondary path between the input voltage and output force of the AEM on the engine side considering the frequency-dependent characteristic of the stiffness, which includes the structure parameters of the AEM as well as the dynamics of the actuator, the fluid in the inertia track, the foundation (vehicle body), and the attenuated vibrating object (AEM preload or engine). The proposed model is validated by three test cases without vibration excitation, which are performed with different AEM preloads and foundations. The AEM is considered as an active part and passive part, the mass of which is determined experimentally. Parameter effect on the dynamic characteristics of the secondary path of the AEM is studied based on three tests and a numerical simulation.

A seated human model for predicting the coupled human-seat transmissibility exposed to fore-aft whole-body vibration

Occupant discomfort, induced by vibration transmitted through a vehicle seat, can be evaluated by measuring vibration on the contact interface between the occupant and seat. In the previous study (Ittianuwat et al., 2016), measuring five contact points of the back-backrest, including centre point (ISO 2631-1), was considered as an important factor for assessing occupant comfort in frequencies where seat structure resonances occur. To enhance occupant vibration comfort in the early seat design stage, predicting the dynamic response of the coupled human-seat system on various contact locations is necessary. In this study, a low order seated human body Finite Element (FE) model was developed for predicting vibration transmissibility of the human-seat system in frequencies up to 30 Hz. Throughout the optimization process, the parameters of the model were obtained by comparing measured transmissibilities of the occupied vehicle seat system. The human-seat system vibration modes were also compared and verified with measured data by calculating MAC (Modal Assurance Criterion). The results showed that two human body vibration modes coupled with foam were observed below 10 Hz, and two coupled human and seat structure fore-aft modes were observed at around 20.1 Hz and 21.9 Hz. Fore-aft transmissibility of the model at various locations of contact provided reasonable correlation with the measured data. The developed low order human model enables the prediction of the fore-aft transmissibility on various back-backrest contact locations up to 30 Hz. This showed the capability of improving occupant's vibration comfort by predicting transmissibilities of the human-seat system in the early stage of developing a new vehicle seat.

A Fuzzy AHP‐Based Method for Comprehensive Blasting Vibration Comfort Evaluation Forecast

Blasting vibration comfort evaluation (BVCE) is an emerging interdisciplinary multilayer and multifactor issue that involves explosion mechanics, structural dynamics, biodynamics, statistics, psychology, and many other disciplines. The evaluation index system of blasting vibration comfort is divided into three levels: target level, criterion level, and index level. The absorption blasting vibration energy (ABVE) value is calculated based on triangular membership function, while the value of residual subjective evaluation index is obtained based on evaluation standard. The weight of each index is determined using the analytic hierarchy process. By developing the mathematical models, defining and quantifying the BVCE indices, and analyzing the factors that influence blasting vibration comfort in a hierarchical manner, this study proposes an exploratory fuzzy AHP‐based method for comprehensive BVCE. The feasibility\reliability of this method is verified on the basis of 166 groups of comfort survey data. It is found that more than 85% and 62% of forecast results had an error of less than 1.0 and 0.5, respectively. The aim of combining qualitative and quantitative approaches to evaluate and forecast blasting vibration comfort can be initially realized. Further sensitivity analyses show that the absorbed blasting vibration energy (ABVE) index had the most significant influence, followed by environmental vibration, environmental noise, blasting noise, and lastly other factors on blasting vibration comfort. The presented results can provide a reference and guidance for actively creating the favorable conditions in blasting construction practice to improve the resident comfort and to realize the goal of “undisturbing, safe, and harmonious blasting construction.”

Analysis of vertical vibrations affecting a child transported in a child seat during a car passing over the release speed bump

The article presents the results of research on the assessment of vibrational comfort of children carried in child seats. The work analyzes the impact of the child's mass and the speed of the car passing through the speed bump on the level of vibration to which the passenger (child) transported in the child seat mounted on the rear seat of the car is exposed. The tested car seats were installed in a passenger car using the ISOfix base. During the tests, the measured values were the acceleration of the seat child seat, the backrest of the child seat, the rear seat of the car and the child seat ISOfix base. As part of the research, car drive through the speed bump were carried out at different car speeds and with different mass simulating the mass of a child. The test results were analyzed in order to determine the magnitude of vibrations generated during car drive through the speed bump. Based on the results obtained, the level of vibrational comfort of a child trip in a child seat was assessed.

Analysis of dynamic properties and vibration comfort of large-scale stands

ABSTRACT Large grandstands provide areas for human activities and leisure pursuits. The degree of vibration comfort for people has an important effect on the functionality of grandstands. In this paper, the changes of the dynamic properties of the stand owing to different human postures are demonstrated. The comfort degree for human vibration in the large stand is also examined by full-scale measurements and questionnaire surveys. In addition, the analysis of the influence of different parameters on acceleration responses of the stand is presented via numerical simulation. Thereafter, it has been observed that ISO10137-2007 and BS6472 are more suitable than GB10070 and AISC-11 for evaluating vibration serviceability owing to crowd jumping loads during football matches in the large grandstand environment. Moreover, it has been observed that females and the staff are more likely to feel uncomfortable during matches, whilst students younger than 30 years old are the least sensitive group to vibrations of large stands. When the frequency of the jumping loads is close to the fundamental frequency of the stand or the synergy rate is high, the resonance is more likely to occur, which should be avoided by designers and users.

Experimental and numerical investigations on timber-concrete connections with inclined screws

In new and existing buildings, it is important that floors are sufficiently strong and stiff in plane. In comparison with pure timber floor systems, timber–concrete composite structures are often used as floor solutions to better combine acoustic separation with both greater load-carrying capacity and increased stiffness, also resulting in significant improvement of the serviceability vibrational comfort. The choice of a structurally effective yet inexpensive shear connection between the concrete topping and the timber joist is crucial to make the composite floor a viable solution that can compete with reinforced concrete and steel floors. The use of inclined screws to connect the timber beam to the concrete topping represents a possible solution to maximize the slip modulus of the connection and, at the same time, to keep the construction cost within acceptable values. In this paper, the mechanical behavior of such a type of timber to concrete connection is explored via experimental pushout tests and numerical investigations. The specimens tested were made of an inner timber block connected to two outer concrete slabs by means of two 8 mm diameter screws per side. To reproduce the timber flooring used in real practice as permanent formwork for the placement of the concrete topping, an OSB layer was introduced between the timber block and the concrete slabs of the specimens. Experimental results were statistically assessed to compute the mean slip moduli and the characteristic values of the shear strength. A mathematical model of an inclined elastic beam on an elastic foundation capable to provide the slip modulus of the system was developed. The dependency of the slip modulus upon the screw inclination and the interlayer flooring thickness was also investigated. The accuracy of the theoretical results was assessed through comparisons with experimental results.

Influence of particle damping on ride comfort of mining dump truck

Abstract Mining dump truck produces strong vibrations for a long time during driving, which will reduce the comfort of the drivers and even affect their health. With the advantages of not changing the original structure and good damping effect, the particle damping technology is suitable for the cab with narrow space. The plinth between the cab floor and the seat was transformed into a particle damper, and the discrete element model of the damper was established. For different damper schemes, energy dissipation analysis based on discrete element model was used to find out the optimum one. Finally, through the field test, the results indicated that at the speed of 40 km/h, the Root-Mean-Square (RMS) value of acceleration in the X direction (Front After), Y direction (Cross Car), and Z direction (Up Down) at the measurement point of the seat were reduced by 26.8%, 46.8%, and 38.4%, respectively; at 6.3 Hz, the comfort duration was increased by 85% after the particle damper was used. This research has important engineering value for damping in the cab of mining dump truck to improve its vibration comfort.

Annoyance-rate-and-casualty-reality-based method of comfort evaluation of military ambulance

The objective of this paper is to explore a new comfort evaluation method, which is suitable for studying the comfort of casualty transported by a military ambulance. The paper applies existing vibration evaluation methods to quantitatively obtain comfort of non-ambulatory casualty, stimulates the patients with different vibrational conditions, and analyses the annoyance rates with psychophysics knowledge as well as the ratio of war to disaster injuries and susceptibility of the wounded. The road test proves that this new method is feasible for vibrational comfort evaluation of non-ambulatory casualty and gains quantitative advantages over the traditional methods.…

Research on Design of Vibration Comfort of Large Span Roof Based on structural scheme

This article focuses on the layout of three types of large-span floor slabs with ordinary concrete ribbed beams, restressed beams, and box-shaped slabs combined with specific engineering projects. By using finite element software, the vibration comfort of the three kinds of structural schemes was evaluated from the aspects of structural dynamic characteristics, jump load response and so on. The analysis results show that the common ribbed beam system can meet the vibration comfort requirement of the slab under reasonable plane layout. Restressed beam system has little effect on the frequency of natural vibration of the floor slab. The box beam system can increase the natural vibration frequency of the vertical vibration of the floor and improve the vertical vibration performance of the floor.

Impact of selected sources of transport vibrations on the perception of vibrations by people in buildings

Vibrations propagating through the soil into the building can not only be harmful to the building structure or cause its accelerated wear, but can also effect on the vibrational comfort in the rooms. They can also be annoying for residents and building users, and in extreme cases can lead to sleep disorders, headaches and neurotic conditions. Especially vibrations from the low frequency range from 5 to 25 Hz are undesirable, because there are resonance frequencies of human internal organs in this frequency range. The human perception of vibrations in buildings, despite many researches made in the past, despite standards and requirements in this area, is still a topic not fully understood mainly due to the subjective nature of the perception of vibrations by various people. It is widely known that the type of transport vibration source has an impact on human perception. Vibrations generated by above-ground sources are more felt on the upper floors as opposed to vibrations generated from the underground. In this paper three types of transport vibrations are analyzed on one chosen building located in Warsaw. Human perception of vibration is evaluated according to two methods: root mean squared (RMS) and vibration dose value (VDV).

Costs Analysis of the Floors that Can Ensure the Comfort in the Buildings

The aim of this article is to check comfort in the passive buildings located in Libertow (close to Cracow). The two aspects of comfort are described: a thermal comfort with tightness and humidity and a vibrational comfort. The main results of measurements of the comfort aspects are described and shown. Passive buildings which were investigated are very tight and well insulated. It is good for the energy saving and for the budget of the owners but it could be a problem for the humidity requirements. In such buildings, there also could be a problem with solar energy excess which could provide that the rooms are overheated. The vibrational aspect is also often neglected on the design stage, but it also could be a problem when the residents live in their homes. The problem is that when a house is built, the costs of changes to adapt the rooms to the appropriate comfort level are much higher than in the design stage. The alternative may be a properly designed floor which shall meet all thermal and vibrational aspects of comfort. In order to improve the quality of multi-faceted comfort, three types of flooring have been proposed. All three are clearly described and their advantages and disadvantages are shown. The main goal of this article is a detailed cost analysis of these three types of floor. Cost analysis was made according to the Polish requirements so-called Catalogs of Material Inputs in the NormaPRO. Costs were estimated using detailed, simplified and mixed methods. The most effective and economically justified type of floor was also chosen.

Measurement and Interpretation Methodology for Determining Comfort in Passive Buildings and NZEB Buildings

The article contains good practise recommendations related to the proper performance of measurements of comfort in passive buildings. Passive building is a high-quality building due to impeccable construction in terms of building physics. The passive building is so well insulated that it can only be heated by supplying fresh ventilation air. Such buildings have certain features such as: balanced temperatures, there is no overheating of the rooms in summer due to the high insulation of the partitions, high insolation due to the optimal positioning of the windows, acoustic comfort, reducing pollution in the interior, high quality of thermal comfort, no aeration, high indoor air quality, permanent protection against moisture and fungiculation of partitions, etc. In all the features listed above, there was no vibration comfort, which could be a problem especially in the city centers with extensive transport infrastructure. This kind of comfort is mostly neglected during the design process, not only in the passive buildings. In this article comfort in passive buildings for all its aspects is described. The main emphasis in the article was put on the guidelines relating to the measurement of thermal comfort and measurements of vibration comfort. The recommendations contain all stages of the measurement process from the preparation of measurements with the local vision and the measurement plan, through the in-situ measurement to pre-processing and analysis of measurement data. All measurement stages are shown on the real example of passive building located in Poland. The good practise guidelines for comfort measurements could be very useful in the diagnosis of passive buildings and NZEB buildings.