Vertical Vibration Research Articles

A new methodology for pre-camber design of a long-span bridge considering dynamic train load and complex environmental effects

This work aims to develop a reasonable pre-camber design method for long-span cable-stayed bridges by investigating the high-speed train-bridge interaction under complex environmental loads, including ambient temperature, concrete creep, and concrete shrinkage (CCCS). First, an integrated dynamic model of the train-track-cable stayed bridge system (TTCSBS) is established using multibody dynamics and finite element theory and validated through field test. Then, the temperature change features at several key positions on the long-span bridge are investigated using long-term monitoring data. Temperature-induced bridge deformation is calculated by applying the established bridge finite element model (FEM) and compared with test results. CCCS-induced bridge deformation is determined through numerical calculations that consider the bridge's structural and material properties. On this basis, the effects of bridge deformation caused by environmental loads on vehicle-bridge dynamic interaction are investigated in detail, and a new bridge pre-camber design method is proposed to counteract the effects of both environmental and train dynamic loads. Results indicate that the proposed model's simulations align well with field test data. The long-span bridge deformation induced by the environmental loads intensifies the dynamic responses of a running vehicle, particularly the wheel-rail vertical force and car-body vertical vibration. However, it has slight influence on train-induced bridge vibration. The proposed pre-camber design method for long-span bridges, which accounts for long-term environmental load action, effectively ensures good vehicle service performance. The research results could provide useful guidance for the design of long-span bridge systems.

Modeling and braking analyses of longitudinal-vertical coupling towbarless aircraft taxiing system

The variation of tire vertical load has effects on the vehicle braking performance, which may lead to the misjudgment of braking distance and increasement of the accident risks. In order to evaluate the braking distance of the towbarless aircraft taxiing system (TLATS) accurately, a longitudinal-vertical coupling model of the TLATS is established, in which the effects of the vertical vibration on braking dynamics is considered. An 11-degrees of freedom (DOF) dynamic model of the TLATS, which consists of the system longitudinal motion, vertical vibration, and an advanced Lugre tire model, is proposed. The tire vertical dynamic loads are obtained by calculating system vibration differential equations as the input for the Lugre tire model, in which an arbitrary pressure distribution function over the contact patch and load related parameters are used. The Lugre tire model parameters are identified based on the virtual experiment results in ADAMS/Car software through a multi-objective optimization (MOO) method. The proposed tire model is more accurate by comparing with the models using other pressure distribution functions. The advanced Lugre model is integrated into the longitudinal-vertical coupling dynamic model of the TLATS, and the fuzzy PID control method is used to achieve the optimal slip rate during the braking procedure. The tire friction and TLATS’s braking performances in terms of the slip rate, braking speed and braking distance are compared between the coupling and uncoupling models under different traction velocities and the road excitations when a same fuzzy control method is used for the system braking. The results show that the proposed longitudinal-vertical coupling TLATS dynamic model could assess the braking behaviors of the TLATS more accurately than the simplified uncoupling model, which could decrease the potential safety risk of the aircraft towing operation on the airport apron.

Chaotic Characteristic Analysis of Spillway Radial Gate Vibration under Discharge Excitation

This paper aims to assess the nonlinear vibration of a radial gate induced by flood discharge; the measured acceleration response data of a spillway radial gate are analyzed using the chaos theory. The results show that the vibration responses of the gate at three opening heights present clear chaotic characteristics, and the chaotic characteristics of the lower main beam point are greater than other points. Moreover, the y-direction (vertical) correlation dimensions of the three measuring points on the supporting arm are larger than those of the x-direction (axial) and z-direction (lateral). The vertical vibration of the supporting arm is more complex and presents more uncertainties, which should be paid attention to in the literature. Under three different gate opening heights, the maximum Lyapunov exponent of each measuring point ranges from 0.0246 to 0.0681. In addition, the flow fluctuation load is the main excitation source of the gate vibration chaotic characteristics.

Dynamic response of axle box bearing for high-speed train considering wheelset flexibility and polygonal wear

In this study, a flexible wheelset was added to a rigid-flexible coupled vehicle dynamics model, in which the axle box bearings are accurately modeled. The measured wheel’s polygon wear profile and Wuhan-Guangzhou track spectrum are used in the model to define the wheel tread and track irregularity, respectively. We conducted a field test on the Wuhan-Guangzhou railway line to validate the model. Then, we investigate how the dynamic properties of the axle box bearing are impacted by the wheelset flexibility and polygonal wear of wheel. We found that the polygonal wheel with a rigid wheelset causes high-frequency vibration in wheelset and axle box, and increases the axle box bearing’s internal contact force. Additionally, the flexible wheelset with a normal wheel tread can alleviate the wheel/rail impact and reduce the axle box’s vertical vibration as well as the axle box bearing’s internal contact force. When the vehicle is running at v = 300 km/h, the excitation frequency caused by the wheel's 20th-order polygon is 576.5 Hz, and the flexible wheelset's 20th-order modal frequency is 577 Hz. The two frequencies are similar, when considering the polygonal wheel and flexible wheelset simultaneously, the wheelset will resonate. And the resonate of wheelset will increase the local deformation of the axle end and deteriorate the bearing operating environment, causing a significant increase in the bearing contact force. Finally, the axle box bearing’s dynamic characteristics are summarized when vehicle velocity varies from 50 to 350 km/h and wheel polygon wear amplitude ranges from 0.01 to 0.05 mm.

Research on the application of inertially stabilized platform in the dynamic measurement of cold atomic gravimeter

Dynamic gravity field measurement based on the cold atom absolute gravity measurement system has important applications in geological exploration, gravity field mapping and other fields. The inertial stabilized platform is the key component of the dynamic cold atom absolute gravity measurement system, which can isolate the interference of carrier angle motion and keep the atomic gravimeter probe in the horizontal attitude during the measurement process. In this paper, according to the dynamic measurement requirements of atomic gravimeter, a high-precision two-axis inertial stabilized platform system is designed. The relationship between attitude angle and gravity measurement error is analyzed, and the stability of the system is enhanced by lead-lag method. Then the static vertical vibration power spectrum of the platform is measured to consider its influence on dynamic gravity measurement. Finally, a dynamic gravity test experiment was conducted in the Yellow Sea to verify the attitude control accuracy of the platform, and the attitude data of the platform under different heading were evaluated. The attitude standard deviation of the platform was better than 4 × 10−5 rad, and the absolute gravity standard deviation of the linear round-trip measurement reached 1.49 mGal. The experimental data show that the inertial stabilized platform can meet the dynamic measurement requirements of the cold atom gravimeter.

Vibration filtering effect of a novel three-dimensional isolation bearing on metro vibration isolation

Three-dimensional (3D) isolation bearings are effective means to reduce the adverse effects of metro vibrations on structures. The current research focuses on the relationship between the vertical stiffness and metro vibration isolation performance of bearings, but neglects the vibration filtering effect resulting from the inherent resonance and material damping effect of them. In this study, a novel 3D isolation bearing was proposed, composed of spring bearings (SBs) and laminated nature rubber bearings (LNR) vertically in series (denoted as 3DSL), and not only its vertical stiffness but also vibration filtering effect on metro-induced vibration isolation performance were fully studied. The design principle and vibration isolation mechanism of the 3DSL were described, followed by the design and test of three specimens. After that, a case study was conducted to investigate the influence of the 3DSL's filtering effect on metro vibration isolation. The results indicated that the 3DSL exhibited high vertical loading capacity and low vertical stiffness. Furthermore, it was found that the vibration amplitude was slightly amplified in the low-frequency range (1–50 Hz), while significantly reduced in the high-frequency range (50–200 Hz) due to the vibration filtering effect of the 3DSL. Altogether, these results demonstrated that the excellent metro vibration isolation performance of the 3DSL was attributed to the low vertical stiffness and vibration filtering effect. It is recommended to consider both the reduction of vertical stiffness and vibration filtering effect of 3D isolation bearings when designing isolation systems for metro vibrations.

Shaking table test of vertical isolation performances of super high-rise structure under metro train-induced vibration

Metro systems are integral to improving transportation efficiency and providing convenience to the public; however, they cause environmental vibrations. To analyze the metro vibration propagation law and vibration isolation performance of a 120 m super high-rise structure positioned directly above two metro tunnels, a shaking table test at a 1/30 scale ratio is conducted in this study. First, a model for the shaking table test is designed and manufactured, and measurements of metro train-induced ground vibrations obtained on site are input into the model. Subsequently, vertical vibration tests are performed on the models with and without laminated rubber isolation bearings. Finally, their dynamic characteristics, vibration propagation law, and vibration isolation effect are analyzed, and the vertical vibration isolation mechanism of the structure is discussed. The results indicate that the metro vibration exerts a resonance effect on non-isolated super high-rise structures, thus resulting in the progressive amplification of the metro vibration response along the floors of the structure. The vibration isolation layer formed by the laminated rubber isolation bearings significantly reduces the vertical modal frequency and increases the vertical damping ratio of the super high-rise structure, thus effectively attenuating the vertical metro vibration. Unlike the non-isolated structure, the vibration-isolated structure can avoid severe structural resonance responses in the dominant frequency band of the metro vibration. This study aims to offer insightful considerations for evaluating metro vibrations in super high-rise structures and may serve as essential reference for vertical vibration isolation.

Vibration behavior of innovative discretely connected precast concrete sandwich floors

This paper investigates the vertical vibration behavior of an innovative discretely connected precast concrete sandwich floor (DCPCF) in orthogonal slab laying direction (OSLD). An experimental program included the full-scale tests of seven DCPCF specimens and two cast-in-situ floor (CISF) specimens was conducted. In order to evaluate the vertical vibration behavior of the DCPCF, the parameters considered the number of slabs, the number of connectors, the position of slab joints and loading condition were studied according to the vibration mode, fundamental frequency, damping ratio and acceleration response. The test results indicated that the first two vibration modes of DCPCF specimens and CISF specimens were basically the same. The fundamental frequency of the DCPCF was negatively correlated with the number of slab joints and overlying loads, and positively correlated with the number of connectors and the distance of slab joints to the mid-span. The damping ratio of the DCPCF decreased with the decrease of the number of slab joints, the increase of the number of connectors and the distance of slab joints to the mid-span. The vibration response of DCPCF specimens was slightly larger than those of CISF specimens under the same excitation. The peak acceleration increased with the increase of the loading frequency and the number of pedestrians. The closer the loading distribution was to the mid-span, the greater the peak acceleration would be. Based on the vertical vibration theory of elastic thin slab, the calculation methods for predicting the first mode natural frequency and peak acceleration of the DCPCF in OSLD were proposed. The calculated results obtained by the proposed formula showed good agreement with the experiment results.

Coordination control between vibration suppression and energy regeneration for vehicles driven by in-wheel motors under regenerative braking condition

In this paper, focusing on regenerative braking condition, a coordination control method is proposed to achieve the vibration suppression and braking energy recovery of vehicles driven by In-Wheel Switch Reluctance Motor (IWSRM). Firstly, a vehicle vertical dynamic model, including SRM drive system, vehicle braking system, and quarter SRM-suspension system, is established based on the analysis of the generating and vibration characteristics of IWSRM. Then, after analyzing the effects of eccentricity and electromagnetic excitation, the vertical unbalanced radial force is used as control signal in design of the control method. Moreover, for ensuring the recovered energy and reduce vertical vibration, the optimal key control parameters varying with the vehicle speed and braking strength are obtained by genetic algorithm. To achieve verification of the control method, the several vehicle performance indexes are selected as observation objects, which are analyzed and compared to other control methods, and the results indicate the control method can effectively weaken the vertical acceleration and improve the vehicle ride comfort without significantly decreasing regenerative braking energy. Finally, a hardware in the loop experiment is conducted, and the effectiveness and real-time ability of the proposed method can be verified.

Vibration-assisted material damage mechanism: From indentation cracks to scratch cracks

Vibration-assisted grinding is one of the most promising technologies for manufacturing optical components due to its efficiency and quality advantages. However, the damage and crack propagation mechanisms of materials in vibration-assisted grinding are not well understood. In order to elucidate the mechanism of abrasive scratching during vibration-assisted grinding, a kinematic model of vibration scratching was developed. The influence of process parameters on the evolution of vibration scratches to indentation or straight scratches is revealed by displacement metrics and velocity metrics. Indentation, scratch and vibration scratch experiments were performed on quartz glass, and the results showed that the vibration scratch cracks are a combination of indentation cracks and scratch cracks. Vibration scratch cracks change from indentation cracks to scratch cracks as the indenter moves from the entrance to the exit of the workpiece or as the vibration frequency changes from high to low. A vertical vibration scratch stress field model is established for the first time, which reveals that the maximum principal stress and tensile stress distribution is the fundamental cause for inducing the transformation of the vibration scratch cracking system. This model provides a theoretical basis for understanding of the mechanism of material damage and crack propagation during vibration-assisted grinding.

Load-suspended power backpack for labor saving and energy harvesting from human walk

Long-distance walk with a heavy load such as hiking and field rescue, often leads to accumulative fatigue. And continuous energy support for wearable electronics is often demanded in remote areas. Here, we report a new load-suspended power backpack that can realize labor saving and energy harvesting from human walking. An innovative suspended system is designed to decouple the synchronous movement of backpack and body, which consists of two elastomer-pulley block units and two linear sliding rod units. It also utilizes a new charge pumping technology of triboelectric nanogenerator (TENG) for high-efficient energy conversion, achieved by a specially designed main TENG and two buffer capacitors (BFCs). The main TENG has one top electrode but two bottom ones to build two separated plate variable capacitors for charge storage. The new technology is characterized by using one top electrode to synchronously drive shuttling charges in four pathways between main TENG and BFCs, and generating electricity based on shuttling charges. Consequently, it can reduce the remarkable 32.6% vertical vibrations of load and 26.7% wearing force and provide a high voltage of 820 V and a current of 103.2 μA. The average power in one current pathway is calculated to 84.1 mW (336.4 mW for four ones) with an effective power density of 29.96 mW/g, high enough to light 354 small LEDs, 235 large LEDs, the electronic watch and thermos-hygrometer. The backpack can not only be applied to relieve accumulative fatigue, but also has great potential to be an energy source for continuously driving wearable electronics for various applications.

Elevator vibration signal denoising by deep residual U-Net

Vibration signals from elevators contain critical information pertinent to condition monitoring and fault diagnosis. However, the presence of noise in real-world data acquisition environments invariably contaminates these signals, thus compromising the effectiveness of condition monitoring and fault diagnosis. This study proposes a novel denoising method based on deep residual U-Net to mitigate noise in the vertical vibration signals of elevator cabins. The proposed network is a convolutional neural network with skip connection and multi-scale convolution structure, which can automatically learn the potential mapping between noisy and clean signals. The robustness and effectiveness are verified through experiments using real-world vibration signals compared with three conventional denoising methods in both linear and non-linear systematic indicators. Moreover, the proposed method exhibits higher accuracy and promising prospects in practical applications when applied to elevator travel distance monitoring.

Sandwiched electromagnetic energy harvester based on the alternating north- and south-orientation magnet array

Vibration mechanical energy may be highly destructive in many scenarios, such as bridges, pipelines, precision instruments and subways. These energies may convert into electrical power to apply not only to power the wireless sensor nodes but also to serve to protect vibrating objects. However, in pipelines complex vibration environments, the mechanical energy harvesting from a single direction is insufficient. In this study, a sandwiched electromagnetic energy harvester is designed with an alternating north- and south-orientation magnet array to convert both horizontal and vertical vibration mechanical energy into electrical power. Experimental results have shown that the device is capable of collecting vibration energy from both horizontal and vertical directions, and the collection of vibration energy from both directions can be performed simultaneously. This innovative energy harvester has the potential to convert pipeline vibration energy from multiple directions into electricity, which can both protect the pipelines and self-power to the detection of pipeline working conditions.

Linear permanent magnet electrodynamic suspension system: Dynamic characteristics, magnetic-mechanical coupling and filed test

This study investigates the dynamic electromagnetic characteristics and thermo-mechanical coupling effect of the linear permanent magnet electrodynamic suspension system (PMEDS) via high-speed test rig. Besides, a physical prototype weighing 1.5 tons along with a 50-m linear copper guideway is developed and tested. Firstly, the topology structure along with fundamental operation model is introduced, followed by establishing the analytical model. Subsequently, a multi-functional test rig is utilized to experimentally determine its speed characteristics, lateral stability, and vertical vibration, while also validating the simulation and analytical models. Additionally, thermo-mechanical coupling analysis is conducted through co-simulation, experimentation and calculation to determine the dependence of temperature on the levitation and drag forces. Finally, a prototype vehicle integrated with auxiliary components, is fabricated and tested on a copper guideway. The vehicle is suspended freely via levitation force in the air above 30 mm, with tested suspension height generally aligning with dynamic simulation results.

Physics-based Data-informed Prediction of Vertical, Catenary, and Stepped Riser Vortex-induced Vibrations

Physics-based Data-informed Prediction of Vertical, Catenary, and Stepped Riser Vortex-induced Vibrations

Particle dynamics in vertical vibration-driven immersed granular systems: A study with resolved computational fluid dynamics-discrete element method

Vibration-driven immersed granular systems (VIGSs) are ubiquitous in nature and industry. However, particle dynamics in 3D VIGSs is hard to obtain directly from experiments. The resolved Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) is introduced to study a cylindrical VIGS subjected to vertical vibration focusing on particle dynamics. A Voronoi-weighted Gaussian interpolation (VWGI) method is used to convert the discrete particle information into a continuous field. The VWGI method enables the estimation of the continuous field for granular systems, especially for those with large-scale non-uniformity and heterogeneity particle distribution in local cells. The results show that the periodic variation of the system's kinetic energy is caused by the collision between the lower particles and the vibrating wall, and the particle kinetic energy decreases with height rising. A velocity spatial structure of convection, moving from the cylinder center to the sidewall, is observed in both immersed and dry systems away from the bottom. Vibration-driven particles can exhibit a similar flow structure to natural convection. Compared to the dry system, the convection strength and momentum transfer in the VIGS are higher, while the momentum diffusion is lower. The fluid restrains the particle energy acquisition and enhances the energy dissipation of the “heated” particles, while the formation of the fluid convection benefits the particle convection directionality. This resolved CFD-DEM study with the VWGI method provides useful results of the particle dynamics in VIGSs, which could provide guidance for some practical applications in minerals processing involving vibration-driven immersed granular systems.

Experimental study on structure-borne noise of vertical concrete noise barriers sitting on the ground

To investigate the relationship between the structure-borne noise and the vibration of vertical concrete noise barriers sitting on the roadside of the railway, the time-frequency characteristics of the accelerations and sound pressure level of the barrier slab under train crossing events were analyzed by in situ vibration and noise testing. The results show that (1) the vertical vibration level in the mainline area is approximately 94.7 dB, while it is approximately 104.4 dB in the turnout area, and the average increase effect of the vibration level is approximately 9.7 dB. (2) The sound pressure level of the structure-borne noise in the mainline area is approximately 66.4 dB(A), while it is approximately 70.0 dB(A) in the turnout area, and the average increase effect of the sound pressure level is approximately 3.6 dB(A). (3) The vibration is amplified significantly at approximately 40-60 Hz. In summary, the structure-borne noise of the barrier slab is affected by the forced vibration amplification of the barrier slab, and the sound and vertical vibration amplified analysis of the noise barrier under ground motion excitation caused by train operation brought out the related relationship between the vertical vibration and the structure-borne noise.

Study on vibration measurement and sensory evaluation of combined vibration for detached houses

Sensory and psychological content accounts for 90% of all vibration complaints in Japan. Therefore, evaluation based on vibration sensation is very important. Traffic vibration is the most common source of vibration that causes complaints, when limited to detached houses. If traffic vibration is the source of complaints, occupants will suffer from vibration for a long period of time. Vibration transmitted by traffic to housing floors may not be either vertical or horizontal, but rather a combination of both vertical and horizontal vibration that exceed perceptual thresholds. Japanese standards include "JIS C 1510" and "AIJES-V0001-2018". However, they do not describe methods for sensory evaluation of combined vibration. Although ISO 2631 series describes it, it is necessary to consider whether it can be applied to Japan as it is. Considering that traffic networks will continue to develop in Japan, especially in urban areas, it is assumed that the vibration generated inside houses, mainly from traffic vibration sources, will not be a single vibration of vertical or horizontal vibration, but a combined vibration that is perceived in multiple directions. Therefore, in this paper, vibration measurement and sensory evaluation of combined vibration were examined using a real house vibrated by traffic.

The impact of accelerometer location and frequency weightings on the prediction of pleasantness ratings for vertical whole-body vibrations on an aircraft seat bench

Noise and vibration are two physical factors that can reduce the perceived comfort of passengers during a flight. In this application context, vibrations are often measured using accelerometers placed at the seat rail or with a seat pad between the seat surface and the buttock of a sitting person. To develop pleasant aircraft cabin environments, it necessary to know which measurement location best reflects subjective ratings and whether the application of a frequency weighting as proposed in the ISO 2631 standard is beneficial. In this study, 40 participants rated the pleasantness of sinusoidal whole-body vibrations in the vertical direction while seated on a typical aircraft seat bench and listening to a synthetic broadband aircraft cabin noise over headphones. The vibration signals covered seven frequencies and four vibration levels and ratings were made on a verbally anchored scale. The results showed that an increase in vibration level leads to more unpleasant ratings for each of the tested frequencies, independent of the accelerometer position. Although the ISO frequency weighting underpredicts the ratings for high frequencies in both cases, applying it to the seat rail measurements seems to reflect the pleasantness ratings better than the seat pad measurements proposed in the ISO 2631 standard.

Experimental study on reading disturbance by combining two-axis vibration and noise

We conducted an experimental study for the combined effect of noise and vibration. This study shows two results of the experiments. The first is the result of an experiment on activity disturbance by a combination of horizontal and vertical vibration stimuli from automobiles and trains, and the second is the result of an experiment combining dual-axis vibrations and noise stimuli. The vibration stimuli were four levels and noise stimuli were two levels. Noise-vibration combination experiment was used sound stimuli with peak levels of 50dB and 60dB. Thirty or twenty students participated in these experiments. Both railway stimuli and automobile stimuli in the high vibration condition, reading disturbance on the combined stimuli of horizontal (lateral direction) and vertical vibration stimuli were higher than that on the only one axis vibration stimulus. As a result of ANOVA, the reading disturbances in the including noise condition were higher than that in the condition of vibration stimuli only. In addition, the reading disturbances were high in the large vibration stimuli conditions.