Acceleration Transmissibility Research Articles

Analyzing the impact of elastomer spiral bearings as seismic isolators in a reinforced concrete structure in Algeria

Over the past few years, Algeria has experienced numerous seismic events, particularly in the northern region of the country, due to its geographical position between the African and Eurasian tectonic plates. These earthquakes pose significant risks, leading to severe damage to both human life and property, including buildings and infrastructure. In response, civil engineers have increasingly advocated for the adoption of advanced seismic isolation techniques aimed at mitigating the transmission of seismic acceleration from the foundation to the superstructure. As a result, Algeria has seen the implementation of a few key projects incorporating seismic isolators, such as the Grand Mosque of Algiers. This article focuses on the design and analysis of the impact of typical aseismic elastomer spiral bearings in a reinforced concrete building located in the city of Oran, Algeria. The study utilizes ETABS software to evaluate the effectiveness of these bearings in enhancing the seismic resilience of the structure.

A Study of Sliding Base Isolation System: A Review

Seismic isolation systems are crucial for protecting structures by minimizing the transmission of acceleration during seismic events, and among the various types, the resilient sliding system, which combines restoring springs and sliders, is highly effective in mitigating seismic impacts. This system controls structural responses by balancing stiffness and friction, ensuring safety while maintaining the functionality of buildings. However, optimizing the design of this system requires carefully selecting combinations of stiffness and the coefficient of friction to achieve low acceleration levels, while simultaneously managing the relative displacement within the isolation system to protect both the structure and its occupants. Excessive displacement may compromise the integrity of the isolation system or cause damage to the structure it is meant to protect. The challenge lies in finding the optimal friction and stiffness levels that provide sufficient energy dissipation and restore forces without allowing displacement to exceed acceptable thresholds. Studies show that restoring forces generated by springs help limit excessive displacements, while sliders dissipate seismic energy, and adjustments in these parameters must account for variations in ground motion intensity and frequency. Thus, a balance between flexibility and resistance is essential in sliding systems to ensure maximum structural safety and occupant protection during earthquakes. This paper reviews different sliding isolation systems which fulfils the requirements of controlling the earthquake and functioning accordingly. It include systems such as PF, FPS, VFPI , CFPI,VFPS,PFPE, VCFPS,VFFPI etc.

An Investigation of the Effects of a Dynamic Vibration Absorber (DVA) to the Comfort of a Bus's Driver Seat

The frequency weighted acceleration, relative displacement, and Seat Effective Amplitude Transmissibility (SEAT) of a bus driver's seat are investigated by a 4 degrees of freedom (4DOF) vertical dynamic model, including a dynamic vibration absorber (DVA). The Root Mean Squared (RMS) values of the gain responses in the frequency domain are analyzed in the DVA damping ratio domain to help determine the optimal value of the DVA' s suspension. The obtained results show that the comfort evaluation index, in the case of a bus driver's seat with DVA, can be improved by more than 15% and nearly 10%, respectively, with the seat suspension natural frequency of 1~Hz and 4~Hz respectively. The comfort is better with the lower seat suspension natural frequency and vice versa. Especially in the case of both the seat and the DVA suspensions with low natural frequencies, all the three mean of evaluation indexes in the whole damping ratio domain of the DVA, have improved by more than 12%. This is the case with all three evaluation indexes which are the best when the damping ratio of the DVA is greater than 0.6.

Natural Frequency Transmissibility for Detection of Cracks in Horizontal Axis Wind Turbine Blades.

Defects on horizontal axis wind turbine blades are difficult to identify and monitor with conventional forms of non-destructive examination due to the blade's large size and limited accessibility during continuous operation. This article examines both strain and acceleration transmissibility as methods of continuous damage detection on wind turbine blades. A scaled 117 cm offshore wind turbine blade was first designed, 3D printed, and modelled numerically in ANSYS. Transverse cracks were deliberately introduced to the blade at 10 cm intervals along its leading edge. Subsequent changes in the transmissibility, relative to an undamaged baseline model, were measured using different variable combinations at the blade's first three natural frequencies. Experimental results indicated that strain transmissibility was able to locate a 1.0 cm defect at a range of 70-110 cm from the blade hub using the amplitudes of the first natural frequency of vibration. The numerical model was able to simulate the strain experimental results and was determined to be valid for future defect characterization. Acceleration transmissibility was unable to experimentally identify defects sized at 1.0 cm and below but was able to identify 1.0 cm sized defects numerically. It was concluded that transmissibility is viable for continuous damage detection on blades but that further research into other defect types and locations is required prior to conducting full-scale testing.

Intelligently optimized arch-honeycomb metamaterial with superior bandgap and impact mitigation capacity

Engineering applications concurrently face challenges related to vibration, impact, load-bearing and energy absorption. Here, an arch-honeycomb metamaterial with split-ring resonators is proposed for wave attenuation and impact mitigation, with better energy absorption and lower initial peak stress. The split-ring resonators effectively induce bandgaps below 3 kHz, and the mechanisms of bandgap generation and polarization are studied through mode shapes, frequency contours and equivalent mass densities. Subsequently, a machine learning-based optimization framework is introduced to tailor the bandgaps, leading to a 155.59% increase in bandgap width. Furthermore, superior vibration isolation and impact mitigation are confirmed through experiments. Obvious attenuation peaks are observed in the bandgaps of the acceleration transmission spectrum in frequency domain. In time domain, the impact test demonstrates peak weakening and delay. The metamaterials offer advantages in wave attenuation, impact mitigation, load-bearing and energy absorption, providing valuable insights for the advancement of multifunctional metamaterials and their practical engineering applications.

On the displacement control performance of base-isolated structures incorporating nonlinear negative stiffness device

Low-frequency dominant far-field harmonic-like long period ground motions (FGMs) excitations have the potential to amplify the seismic response of base-isolated structures (BIS) and may result in isolator displacements exceeding their maximum limits. The application of negative stiffness devices (NSD) in isolated structures primarily focuses on SDOF systems, which fails to capture the displacement response of the superstructure on the isolation story. To address this issue, this study proposes the application of NSD to a 2DOF system in a BIS, with root mean square value as the metric for displacement transmissibility. Firstly, the displacement transmissibility of base-isolated structures with negative stiffness devices (BIS-NSD) and BIS is derived using the triple-harmonic balance (T-HB) method and the single-harmonic balance (S-HB) method, respectively. Subsequently, the applicability of the T-HB method and the S-HB method in obtaining analytical solution for the displacement transmissibility of BIS-NSD and BIS is revealed and validated through numerical solution. Parameters are selected based on fixed-point theorem for comparative analysis of the displacement and acceleration transmissibility between BIS-NSD and BIS. Finally, a comparative analysis between BIS-NSD and BIS under FGMs confirms the application advantages of NSD. The results indicate that compared to BIS, BIS-NSD significantly reduces the displacement transmissibility of the superstructure and the isolation story in the low-frequency range. As the primary resonance frequency decreases, NSD widens the vibration bandwidth of BIS. BIS-NSD effectively mitigates the increase in displacement caused by low-frequency ground motions. The acceleration transmissibility demonstrates that, without sacrificing the acceleration of the superstructure, it effectively controls the displacement of the isolation story.

Application of improved particle swarm optimization algorithm in the proportional integral differential-controlled semi-active suspension system

To enhance the control performance of semi-active suspension systems, this research proposes a particle swarm optimization algorithm (PSO) with adaptive nonlinear correction of inertia weights, which is then integrated with a proportional integral differential (PID) algorithm. To this end, this research establishes quarter semi-active and passive suspension models of automobiles by utilizing the Matlab/Simulink simulation platform. In this foundation, this research further compares the advantages and disadvantages regarding performance indexes of semi-active suspension controlled by the adaptive inertia weighted particle swarm optimization (APSO) algorithm and the PID algorithm, as well as the PID-controlled semi-active suspension and passive suspension through simulation. Simulation results indicate that performance indicator values for different suspension types increase with higher pavement grades. Compared with passive suspension, the semi-active suspension controlled by APSO and PID algorithms presents significantly improved performance indexes, with reductions of at least 31.61% in root mean square (RMS) concerning body vertical acceleration, 1.78% in suspension dynamic deflection, and 22.13% in tire dynamic loads. Moreover, analysis of suspension system frequency response characteristics demonstrates a significant decrease in droop acceleration transmission rate for the semi-active suspension with APSO and PID algorithms across the whole frequency range compared with that of the PID-controlled suspension and passive suspension. On the same note, despite the higher values of suspension dynamic deflection and tire dynamic load transfer rate in certain frequency bands, they are generally within acceptable suspension limits. Simply put, the findings confirm the feasibility of applying the APSO algorithm in PID-controlled semi-active suspension systems, which effectively improves both vehicle ride comfort and handling stability.

Bouldering & chronic traumatic encephalopathy – That is repeated mild traumatic brain injury from climbing

Mild traumatic brain injury (mTBI) is one of the most common neurological conditions resulting from linear accelerations in the range of 60 gravity. Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative syndrome. Its etiopathology is attributed to repeated blows to the head and the transmission of acceleration and deceleration forces to the brain. There are several types of climbing, the most popular are lead climbing, speed climbing and bouldering. Athletes involved in the latter sub-discipline (bouldering) appear to be most at risk of mTBI. Bouldering takes place on artificial walls or natural rock and involves climbing without a rope on routes up to several metres in height. We hypothesised that climbers in the bouldering sub-discipline are at risk of frequent mTBI and, as a consequence, may suffer from chronic traumatic encephalopathy. In the paper we presented physical formula to support our thesis, a verification of this formula and a survey of boulder climbers. The physical model was verified in a practical test. Differences in the range of ≈ 2g were demonstrated (MAE = 1.86, RMSE = 2.51). There is evidence in the form of a physiological model that boulderers are able to achieve accelerations that cause mTBI. The study population had a 12 % incidence of repeated falls and reported symptoms associated with mTBI during bouldering training sessions. Given the diagnosis of CTE, which can only be made after death, future research should focus on diagnosing and treating symptoms of mTBI and CTE (including depression, progressive memory loss, suicidal behaviour, cognitive impairment) in boulder climbers.

A novel multi-resonator honeycomb metamaterial with enhanced impact mitigation

Local resonant metamaterials show significant promise in applications involving the attenuation of impact waves. This paper introduces a honeycomb metamaterial featuring a circular distribution of multiple mass-beam resonators designed to enhance impact mitigation by broadening low frequency bandgaps. The bandgaps of unit cells with different number of mass-beam resonators (MBR) are calculated. It is found that the unit cell with circularly distributed resonators (C-MBR) has strong low frequency local resonance in all directions, thus opening a complete wide bandgap in about 500–1200Hz. Then, a method of equivalent stiffness reduction related to the corresponding mode shapes is used to research the negative effective mass density characteristic, explaining the generation of the low frequency bandgaps. Subsequently, the impact protection capacity of local resonant metamaterial is compared with that of ordinary honeycomb metamaterial through experiment and simulation. Interestingly, the maximum acceleration values under the impact load of local resonant metamaterial are about 45% lower than that of honeycomb metamaterial, and the reaction force under the blast load is about 80% reduction. Besides, by analyzing the acceleration curve waveform and transmission spectrum, the local resonant metamaterial is found to exhibit continuous short period vibration, which blocks the wave in low frequency band. Finally, the energy dissipation performance of the local resonant metamaterial explains that it converts more impact energy into the kinetic energy of the core with resonators, thereby reducing the energy transferred to the bottom panel. These results underscore the potential application of the proposed metamaterial with multi-resonators in impact mitigation and energy dissipation.

Optimization and biodynamic modelling of a 3D-printed honeycomb cushion and double-diamond seating suspension system for vibration isolation

Extended periods of driving, lasting up to 8 hours, can have a severe impact on a driver's health due to the presence of low-frequency vibrations caused by uneven road surfaces. This paper presents a novel biodynamic system modelling method for investigating how the human body responds to low-frequency vibrations. The lumped biodynamic parameter model predicts time-domain head acceleration and frequency-domain transmissibility ratio. This paper's design innovation involves a three-dimensional printed cushion composed of honeycomb cells and a seating suspension system featuring six double-diamond isolators. Using the Design of Experiments, Response Surface Method, and Genetic Algorithm methods, the structural parameters of the seating suspension system and cushion in the model are optimized for the minimum peak transmissibility ratio. The uniqueness of this paper's approach lies in its sensitivity analysis and optimization of the seat cushion and seating suspension system design parameters within a quarter-vehicle suspension system environment, which sets it apart from other literature. Furthermore, this paper explores the connection between the negative Poisson's ratio and quasi-zero stiffness as a means of reducing vibration transmission.

EFFICIENCY EVALUATION: EPOXYURETHANE DAMPING INSERTS IN VIBRATION PROTECTION SYSTEMS

The article contains experimental studies of the efficiency of the developed epoxyurethane compositions, which are designed to minimize vibration acceleration transmission coefficients in vibration protection and impact protection systems in the range frequencies from 20 to 2000 Hz. Determined that they have a high damping capacity and shorter technological cycle for preparing the composition. Keywords: epoxyurethane insert, vibration protection and impact protection systems, amplitude and frequency characteristics.

Лингвистические средства выражения ускорения и замедления времени в различных типах художественной речи (на материале произведений англо-американских авторов)

The paper examines linguistic means that express slowed and accelerated flow of time in the novels by American and British authors. The aim of the research is to demonstrate the fact that such types of literary speech as description and narration can effectively express different speed of time in combination with linguistic means. The scientific novelty of the work consists in determining the atypical meaning of Future Simple and Present Progressive in the context that reveals the character’s perception of time, as well as in identifying the specific contents of narration that can contribute to the transmission of time acceleration by linguistic means: changes in the size of objects, their rotational movement, illusion of counter motion, the character’s rapid movement in space. The results of the study showed that polysyndeton can create opposite effects: slow down (description of subjects) and accelerate time (narration about planned actions). It was also found that Present Progressive, if used unconventionally in the narration about events of the distant past, renders the slowing down of time.

Tracking-Differentiator-Based Position and Acceleration Feedback Control in Active Vibration Isolation with Electromagnetic Actuator

In order to improve the performance of the active vibration isolation system (AVIS) with electromagnetic actuator, several problems of vibration control are studied. Position control is a critical component in suspension systems, and the position sensor noise can extremely affect the stability of the system, so a tracking differentiator (TD) is proposed to obtain effective differential signal from relative position sensor. In vibration control, the feedback of acceleration combined with PD position feedback is presented to suppress transmission of periodic vibrations. Then, taking the acceleration transmission as the evaluation index, the acceleration transmission under the presented control method is derived, and the influence of control parameters on vibration isolation performance is discussed in detail. The vibration isolation performance is improved from 24.47 dB to 2.4 dB at resonance frequency, and −34 dB attenuation is achieved at 100 Hz with respect to vibration isolation mount system tested on the ground. The experimental results demonstrate that the performance of active vibration isolation system are improved by the proposed acceleration feedback control.

Development of a Water Transmission Rate (WTR) Measurement System for Implantable Barrier Coatings.

While water vapor transmission rate (WVTR) measurement is standardly used to assess material permeability, a system able to quantify liquid water transmission rate (WTR) measurement is highly desirable for implantable thin film barrier coatings. Indeed, since implantable devices are in contact or immersed in body fluids, liquid WTR was carried out to obtain a more realistic measurement of the barrier performance. Parylene is a well-established polymer which is often the material of choice for biomedical encapsulation applications due to its flexibility, biocompatibility, and attractive barrier properties. Four grades of parylene coatings were tested with a newly developed permeation measurement system based on a quadrupole mass spectrometer (QMS) detection method. Successful measurements of gas and water vapor and the water transmission rates of thin parylene films were performed and validated, comparing the results with a standardized method. In addition, the WTR results allowed for the extraction of an acceleration transmission rate factor from the vapor-to-liquid water measurement mode, which varies from 4 to 4.8 between WVTR and WTR. With a WTR of 72.5 µm g m-2 day-1, parylene C displayed the most effective barrier performance.

Configurable trunk shaker for the mechanical harvesting of different fruit branches

Trunk shakers perform a forced vibration that should be set according to tree species and architecture to efficiently detach fruits. However, manufacturing companies produce designs that are poorly customisable according to different trees. This work presents a prototype that is configurable in amplitude and frequency of vibration, which has been developed to generate the different vibration patterns required by various fruit trees. To study the feasibility of the developed technology, we built a test bench with a post, to which we fixed olive, almond and orange tree branches, and tested different configurations of the machine (frequencies from 12.25 to 20.75 Hz and eccentricities from 58 to 86 mm). Acceleration values were recorded at different points: the trunk shaker, the post in the grip, the top of the post, and in each branch. We recorded a large loss of acceleration transmissibility between the shaker and the post (20%–60%) due to existing frictions that dissipate energy through heat loss. There is a non-linear increase between vibration frequency and the resultant acceleration value recorded, as well as with increasing eccentricity. The shaker was able to provide a different vibration pattern in each configuration, affecting the transmission of vibration in each of the branches studied, for which mean acceleration transmissibility ranged between 82% (almond), 104% (olive) and 136% (orange).

Development of an electrorheological elastomer isolator working in shear-squeeze mixed mode

The vibrating screen equipment will resonate through the resonance region during startup and shutdown stage. However, the stiffness and damping of the traditional passive vibration isolator cannot be adjusted in use, which leads to the unsatisfactory vibration isolation effect of that on the installation foundation of vibrating screen. In this paper, based on the characteristics of electrorheological elastomer (ERE) with tunable storage modulus, a variable stiffness ERE isolator in shear-squeeze mixed mode is developed. At the first step, the EREs used for the isolator was prepared, and the dynamic viscoelastic properties were measured. After that, the structure of ERE isolator was designed, and the vibration isolation effect of the ERE isolator for vibrating screen was analyzed by simulation. The simulation results demonstrate the resonance amplitude and stopping time of the vibrating screen in startup and shutdown stage will decrease with the ascending electric field strength. Finally, the shear-squeeze mixed-mode ERE isolator was tested on electro-dynamic shaker. The experimental results indicate that the ERE isolator has a better effect of vibration reduction with increased electric field strength in startup and shutdown stage of vibrating screen, and the acceleration transmissibility by ERE isolator is reduced 37.6% under 3 kV mm−1.

Investigation of the Vibration Transmission Characteristics of the Aero-Engine Casing System by Rotating Force Exciter

This work aims to study the dynamic characteristics of an entire aero-engine casing by experiments using a new type of rotating exciter. New vibration sensor layout rules are proposed according to experimental results and vibration transmission characteristics. The vibration response of the aero-engine casing is carried out, and the vibration response of different casing measuring points is also studied. The finite element model of the engine casing’s structure is established to obtain the natural frequency of the whole aero-engine casing, which agrees well with the experimental measurement. We find that the vibration acceleration transmission value of the radial measuring point of bearing No. 1, but not the fan sensor, is more suitable for detecting the running state of the fan rotor. In addition, the sensor in the intermediate casing can detect the vibration of the high-pressure rotor. Bolt loosening of the flange has little effect on the vibration transmission characteristics of the casing. This work aims to provide experimental data of whole aero-engine vibration characteristics with a new rotating exciter for the vibration test, which can help optimize the location of the vibration transducer for the engine and the assembly technology design for the whole engine structure.

The Two-Stage Suspension System of the Fiber Optic Vector Hydrophone for Isolating the Vibration from the Mooring Rope

The two-stage suspension system (TSSS) is designed for the fiber optic vector hydrophone (FOVH) to isolate the vibration from the mooring rope. The acceleration transmissibility of the TSSS is studied theoretically and experimentally. The results show that the TSSS has a major advantage over the traditional one-stage suspension system (OSSS). Typically, the vibration isolation of the TSSS is demonstrated to be over 25 dB higher than that of the OSSS at 100 Hz. Meanwhile, it is demonstrated that the TSSS has little negative influence on the in-band acceleration response of the FOVH. The TSSS has the prospect of reducing the mechanical noise of the FOVH, which is conducive to suppressing the self-noise and enhancing the ability of weak signal detection.

Effect of leaves in the dynamic response of olive tree branches and their computational model

The application of vibration in the mechanical harvesting of fruit trees is a determining factor to achieve fruit detachment. The acceleration required to do so is experimentally determined in expensive tests using different machines and configurations. A simple, appropriate model that could predict the vibration response of plant matter might facilitate these simulations of different conditions and optimise the process. Several mathematical and computational models exist that employ great simplifications and produce uncertain results. We propose a computational model for simulating the dynamic response of branches with and without foliage under forced vibration, applied to the case of the olive tree. We also present a method for characterising the mechanical properties necessary to conduct the simulation using commercial software, Ansys, and the experimental determination of the properties. To do so, we propose some simplifications in the modelling. Next, computational simulations replicate the same conditions as the real vibration tests conducted in the laboratory, and the accelerations produced at the origin and ends of the branches are determined. The results offer a good degree of similarity between the calculated and experimental values in terms of natural frequencies, although some dispersion of transmissibility exits between the origin and ends of the branches, above all for larger branches and when considering their foliage. Branches without leaves had lower natural frequencies. The damping coefficient of branches with leaves was almost twice than ones without although the acceleration transmissibility is much bigger.

Influential Article Review — The Effect of Seismic Excitation on the Passive Stiffness of a Seismically Isolated Bridge Deck

This paper examines the performance of modified bridge elements under simulated earthquake excitations. We present insights from a highly influential paper. Here are the highlights from this paper: This study is on the seismic performance assessment of a seismically isolated bridge structure with passive stiffness modification implementation. Performance of the passive stiffness modification approach is compared with semi-active control implementation on the bridge deck. El Centro NS (north-south) and Kobe EW(east￾west) earthquake excitations are used for the dynamic simulations of the passive case. Results are given in a comparative way for the uncontrolled bridge deck, passive stiffness modification implemented and semi￾actively controlled, seismically isolated bridge deck (Yanik & Aldemir, 2018). Frequency dependent acceleration, velocity and displacement response transmissibility ratios are defined to examine the results. For our overseas readers, we then present the insights from this paper in Spanish, French and German.