Search Results (44)

A numerical investigation is conducted to examine the mechanical properties of a novel three-dimensional (3D) isolation bearing. This device is primarily composed of a lead rubber bearing (LRB), disc springs, and U-shaped dampers. A finite element model is developed and validated against the previous experimental results. Subsequently, comprehensive analyses are performed to evaluate the influence of vertical loadings, shear strains, and the number of U-shaped dampers on the horizontal behavior, as well as the effects of displacement amplitudes and the number of dampers on the vertical performance. Under horizontal loading conditions, the bearing demonstrates reliable energy dissipation capabilities. However, the small lead core design limits its energy dissipation capacity. Compared with the bearing without U-shaped dampers, the bearing’s energy dissipation capacity increases by 628%, 1300%, and 2581% when employing 1, 2, and 4 dampers on each side, respectively. Regarding vertical performance, the innovative disc spring group design effectively reduces the tensile displacement of the LRB under tension, thereby enhancing the overall tensile capacity of the bearing. Furthermore, in comparison to their contribution to horizontal energy dissipation, the U-shaped dampers play a relatively minor role in vertical energy dissipation. Full article

Ensuring the safety of large spherical water storage tanks in seismic environments is critical. Therefore, this study proposed a vibration control device applicable to general spherical water tanks. By utilizing the upper interior space of a spherical tank, a novel tuned mass damper (TMD) system composed of a mass block and four elastic springs was proposed. To enable practical implementation, the vibration control mechanism and tuning principle of the proposed TMD were examined. Subsequently, an experimental setup, including the spherical water tank and the TMD, was developed. Subsequently, shaking experiments were conducted using two types of spherical tanks with different leg stiffness values under various seismic waves and excitation directions. Shaking tests using actual El Centro NS and Taft NW earthquake waves demonstrated vibration reduction effects of 34.87% and 43.38%, respectively. Additional shaking experiments were conducted under challenging conditions, where the natural frequency of the spherical tank was adjusted to align closely with the dominant frequency of the earthquake waves, yielding vibration reduction effects of 18.74% and 22.42%, respectively. To investigate the influence of the excitation direction on the vibration control performance, shaking tests were conducted at 15-degree intervals. These experiments confirmed that an average vibration reduction of more than 15% was achieved, thereby verifying the validity and practicality of the proposed TMD vibration control system for spherical water tanks. Full article

Effective vibration isolation is critical for minimizing the transmission of unwanted mechanical energy from a source to its surrounding environment, especially in precision systems, where even minor disturbances can degrade performance. This study addresses the challenge of low-frequency vibration transmission in lightweight, high-sensitivity audio devices such as turntables with masses below 10 kg. Traditional vibration mitigation strategies—primarily based on increasing system mass to raise the resonant frequency—are unsuitable for such systems due to weight constraints and potential impacts on operational dynamics. Previous studies have identified a critical resonance range of 5–15 Hz, corresponding to the tonearm and cartridge assembly, where transmitted vibrations can compromise signal fidelity and cause mechanical degradation. This research aims to develop an effective and universal vibration isolation solution tailored for lightweight turntables, focusing on external isolation from structural vibration sources such as furniture and flooring. To achieve this, a two-stage experimental methodology was employed. In the first stage, the excitation method with the use of a hammer tapping machine was evaluated for its ability to simulate real-world vibrational disturbances. The most representative excitation methods were then used in the second stage, where the isolation performance of various materials and systems was systematically assessed. Tested isolation strategies included steel springs, elastomeric dampers, and commercial linear vibration isolators. The effectiveness of each isolation material was quantified through spectral analysis and transfer function modeling of vibration acceleration data. The results provide comparative insights into material performance and offer design guidance for the development of compact, high-efficiency anti-vibration platforms for audio turntables and similar precision devices. Full article

To address the seismic vulnerability of high-speed railway bridges (HSRBs) in seismically active regions, this study proposes a hierarchical curved steel damper (CSD) designed to mitigate excessive girder displacements induced by conventional isolation devices. The CSD integrates U-shaped and hollow diamond-shaped steel plates to achieve stable energy dissipation through coupled bending deformation. A finite element model is developed, and its hysteretic behavior is confirmed, with an energy dissipation coefficient of 1.82 and an equivalent damping ratio of 12.7%. An integrated high-speed railway track–bridge-CSD spatial coupling model is developed in OpenSees, which incorporates nonlinear springs for interlayer track interactions. Nonlinear time–history analyses under 40 spectrum-matched ground motions reveal that the CSD reduces transverse girder displacements by 73.7–79.2% and attenuates track slab acceleration peaks by 52.4% compared with uncontrolled cases. However, it increases the maximum bending moment at pier bases by up to 18.3%, necessitating supplemental energy-dissipating components for balanced force redistribution. This work provides a theoretical foundation and practical methodology for seismic response control and retrofitting of the HSRB in high-intensity seismic regions. Full article

Due to the complex mechanical structure of the spring-operated mechanism, its failure mechanisms often exhibit a multi-faceted nature, involving various potential failure sources. Therefore, conducting a failure mechanism analysis for multi-source faults in such systems is essential. This study focuses on the design of composite faults in combination operating mechanisms and develops simulation scenarios with varying levels of fault severity. Given the challenges of traditional simulation methods in performing quantitative analysis of core jamming faults and the susceptibility of the core’s motion trajectory to external interference, this paper innovatively installs a spring-damping device at the extended core position. This ensures that, during the simulation of core jamming faults, the motion trajectory remains stable and unaffected by external factors, while also enabling precise control over the degree of jamming. As a result, the simulation more accurately reflects real fault conditions, thereby enhancing the accuracy and practicality of diagnostic model outcomes. This study employs the Morlet wavelet transform to convert the current and displacement signals in the time series into time-frequency spectrograms. These spectrograms are then processed using the ResNet50 deep residual neural network for feature extraction and fault classification. The results demonstrate that, when addressing the diagnostic problem of small-sample data for operating mechanism faults, ResNet50, with its residual structure design, exhibits significant advantages. The convolutional layer strategy, which first performs dimensionality reduction followed by dimensionality expansion, combined with the use of the ReLU activation function, contributes to superior performance. This approach achieves a fault recognition accuracy of up to 91.67%. Full article

In practice, the structural analysis and design of pedestrian systems subjected to human-induced vibrations is often based on simplified biodynamic models that can be used in place of even more complex computational strategies to describe Human-Structure Interaction (HSI) phenomena. Among various walking features, the vertical reaction force that a pedestrian transfers to the supporting structure during motion is a key input for design, but results from the combination of multiple influencing parameters and dynamic interactions. Robust and practical strategies to support a realistic HSI description and analysis have hence been the object of several studies. Following earlier research efforts, this paper focuses on the optimised calibration of the input parameters for the consolidated Spring-Mass-Damper (SMD) biodynamic model, which reduces a single pedestrian to an equivalent SDOF (with body mass m, spring stiffness k, and viscous damping coefficient c) and is often used for vibration serviceability purposes. In the present study, this calibration process is carried out with smartphone-based acquisitions and experimental records from the Centre of Mass (CoM) of each pedestrian to possibly replace more complex laboratory configurations and devices. To verify the potential and accuracy of such a smartphone-based approach, different pedestrians/volunteers and substructures (i.e., a rigid concrete slab or a timber floor prototype) are taken into account, and a total of 145 original gaits are post-processed for SMD modelling purposes. The analysis of the experimental results shows a rather close match with previous findings in terms of key pedestrian parameters. This outcome poses the basis for a more generalised application of the smartphone-based strategy to a multitude of similar applications and configurations of practical interest. The validity of calibration output and its possible sensitivity are further assessed in terms of expected effects on substructures, with a critical discussion of the most important results. Full article

Vibration control has emerged as a significant concern in civil engineering, aiming to minimize the displacement and stress exerted on structures during seismic events. The accelerated oscillator damper (AOD), which is a damping device that depends on acceleration, has been demonstrated to be highly effective. However, in the case of traditional bridges, it is difficult to accurately place the secondary mass, spring, and damping components at the piers. Additionally, it has been found that as a general single-degree-of-freedom (SDOF) damping device, a significant limitation of the AOD system is its insufficient damping effect in the near-resonance region. This study presents a strengthened AOD with a liner spring (SAOD-LS), in which the secondary spring and damper are linked to the primary structure rather than being attached to the piers. This design not only provides enough space for the secondary system but also has a higher amplification factor of secondary spring and damping components compared with the original layout. In addition, we suggest a nonlinear spring device (NSD) that includes connecting rods and inclined linear springs arranged in a diamond configuration. This innovative design is intended to introduce nonlinear stiffness characteristics into the equivalent stiffness, thereby improving the device’s performance and providing effective anti-resonance features in the near-resonance region. We have confirmed the motion equations for the SAOD-LS and used finite element (FE) analysis to validate the formulation of the equivalent external force and deformation of the NSD. We have thoroughly investigated both the SAOD-LS and the strengthened AOD equipped with NSD as the secondary spring (SAOD-NSD) for their potential implementation in a bridge project. These damping systems demonstrate exceptional performance and robustness, making them highly suitable for enhancing structural resistance to seismic activity. Full article

Cylindrical hydraulic dampers are commonly utilized to mitigate vibrations in machinery and structural applications. These devices generally feature a single linear stroke and are often linked to rotary joints to handle complex loading conditions. However, their installation in confined spaces, such as vehicle suspensions, poses considerable difficulties. In this research, we introduce an innovative bifurcated origami hydraulic damper with nonlinear damping capabilities. Initially, we formulated the collapsible conditional equations essential for the design of the bifurcated origami hydraulic dampers. We then examined the fluid dynamics within the damper and its flow channels, determining that the damping force is proportional to the square of the velocity. Furthermore, we developed motion equations based on the derived damping force and suggested vibration analysis methods using the Runge–Kutta approach. For the mass-spring vibration system, we created an experimental setup with the bifurcated origami hydraulic damper and performed vibration tests using noise signals recorded from a vehicle traveling on a gravel road, thus validating its damping performance and efficacy. Additional tests, which varied the orifice size at the end of the origami structure, as well as the type and temperature of the internal fluid, showed that the orifice size had a more pronounced effect on damping efficiency than the fluid type and temperature. This confirmed the vibration-damping effectiveness of the bifurcated origami hydraulic damper. Full article

A special vibration damper is proposed for Young’s modulus and hardness identification through a scratching process on extruded aluminum. This paper presents the design and working principle of a scratching damper based on a scratching device. A non-contact electromagnetic shaker is used to generate the shaking force for test sample vibration. The required forces on the scratched material during the scratching process are generated by an adjustable compression spring. The proposed damper is designed and tested on an extruded aluminum 3004 sample for the determination of its Young’s modulus and hardness, and validation is performed using the standard test instruments. The physical dimensions of the scratching tracks are measured using a microscope and utilized to compute the scratching energy factor. Load curves are obtained at different divisions of the scratching process. The loop energy during the scratching process of the tested object is measured and used for the determination of sample material properties. Furthermore, the energy conservation law, scratch energy release rate of semi-conical scratch head, and loop energy release rate are established to determine the Young’s modulus and hardness of the sample. Their estimation accuracies are evaluated. The proposed method has several advantages over the traditional methods, including low cost, directness, and high repeatability. The results suggest this to be used as an alternative to the standard modulus and hardness tester. Full article

In recent years, rehabilitation robots have been developed and used in rehabilitation training for patients with hemiplegia. In this paper, a rehabilitation training robot with variable damping is designed to train patients with hemiplegia to recover upper limb function. Firstly, a magnetorheological joint damper (MR joint damper) is designed for the rehabilitation training robot, and its structural design and dynamic model are tested theoretically and experimentally. Secondly, the rehabilitation robot is simplified into a spring-damping system, and the rehabilitation training controller for human movement is designed. The rehabilitation robot dynamically adjusts the excitation current according to the feedback speed and human–machine interaction torque, so that the rehabilitation robot always outputs a stable torque. The magnetorheological joint damper acts as a clutch to transmit torque safely and stably to the robot joint. Finally, the upper limb rehabilitation device is tested. The expected torque is set to 20 N, and the average value of the output expected torque during operation is 20.02 N, and the standard deviation is 0.635 N. The output torque has good stability. A fast (0.5 s) response can be achieved in response to a sudden motor speed change, and the average expected output torque is 20.38 N and the standard deviation is 0.645 N, which can still maintain the stability of the output torque. Full article

Due to their weight, the seismic response control of buildings needs a large-scale damper. To reduce the consumption of shape memory alloys (SMAs), this study proposed a dual self-centering pattern accomplished by the coil springs and SMA, which could drive the energy dissipation device to recenter. Combined with the friction energy dissipation device (FD), the dual self-centering friction damper (D-SCFD) was designed, and the motivation and parameters were described. The mechanical properties of D-SCFD, including the simplified D-SCFD mechanical model, theoretical index calculations of recentering, and energy dissipation performance, were then investigated. The seismic response mitigation of the steel frame adopting the D-SCFDs under consecutive strong earthquakes was finally analyzed. The results showed that a decrease in the consumption of SMA by the dual self-centering pattern was feasible, especially in the case of low demand for the recentering performance. Reducing the D-SCFD’s recentering performance hardly affected the steel frame’s residual inter-story drift ratios when the residual deformation rate was less than 50%, which can help strengthen the controls on the steel frame’s peak seismic responses. It is recommended to utilize the D-SCFD with not too high a recentering performance to mitigate the seismic response of the structure. Full article

The motion of a heavy mass on a bridge span causes vibrations whose magnitude and frequency content depend on the mechanical properties of the structural system, including the magnitude of that mass and its speed of traverse. In order to limit vibrations that could potentially cause damage, a simple passive device configuration, namely the tuned mass damper (TMD), is introduced and its effect on the beam vibrations analyzed. Specifically, a TMD in the form of a single-degree-of-freedom (SDOF) unit comprising a mass and a spring is placed on the span to act as a secondary system for absorbing vibrations from the primary system, i.e., the bridge itself. A Lagrangian energy balance formulation is used to derive the governing equations of motion, followed by an analytical solution using the Laplace transform to investigate the transmission of vibratory energy between primary and secondary systems. Results are given in terms of time histories, Fourier spectra and spectrograms, where the influence of the TMD in reducing vibratory energy is demonstrated. The TMD is placed in the region where the beam’s transverse motion is at a maximum, while its mechanical properties are sub-optimal, in the sense that there is no separate damper present and minimal damping is provided by the spring element itself. In parallel with the analysis, a series of experiments involving a simply supported model steel bridge span traversed by a heavy mass are conducted to first gauge the analytical solution and then to confirm the validity of the proposed passive scheme. Full article

In the mine hoisting system, rigid guide failures and the influence of internal and external airflow intensify vessel transverse vibration, heightening demands on operational safety and equipment reliability. This paper focuses on integrating magnetorheological dampers and disc springs as the roller cage shoe buffer for vibration control, resulting in an innovative buffer device. The structure and magnetic circuit were meticulously designed. Using Maxwell simulation, we analyzed the impact of magnetic circuit parameters—specifically the damping gap and core radius—on the magnetorheological damper. We optimized these parameters through orthogonal testing to enhance damping and vibration reduction. This led to a notable 58% increase in the damper output force. A virtual prototype of the lifting system under actual working conditions was established. A simulation analysis verified the vibration-damping performance of the optimized roller cage shoe. The results indicate that the new roller cage shoes effectively inhibit transverse vibration, surpassing traditional roller cage shoe performance. This is scientifically and practically significant for ensuring safe cage shoe lifting system operation. This paper can provide a crucial theoretical basis for the design of roller cage shoes in ultra-deep mine lifting systems. Full article

The membrane-type air spring can be used to suppress lateral vibration of a vibration isolation table. However, compared to voice coil actuators, pneumatic actuators are difficult to use for precise vibration control, because servo valves have nonlinear dynamic characteristics. Therefore, actuators, such as voice coil actuators, can be placed in parallel with air springs, allowing force-type actuators to provide additional force to the system. These actuators generate force. In the case of a ball-screw mechanism device or a linear servomotor, it is an actuator that generates displacement. These actuators are represented as serial active systems. Serial active systems are structurally simpler than parallel active systems. However, there are very few studies on vibration isolation systems using serial active systems compared to parallel active systems. As the two are different types of systems, a new control algorithm suitable for the serial active system is needed. This study proposes a system in which an actuator capable of accurately controlling displacement is connected in series with a support spring-damper. A new active vibration control algorithm for the proposed control system is also developed, which is termed the position input and position output. The proposed control algorithm uses the displacement of the system as an input and outputs the desired displacement of the actuator installed in series with the damper and spring. The proposed control algorithm increases the damping at the target frequency and reduces the response of the system. Numerical studies and experiments were conducted on the single-degree-of-freedom and multi-degree-of-freedom systems. The results show the efficacy of the proposed control system and the novel control algorithm for the vibration suppression of the lateral vibration of a vibration isolation table. Full article

The paper presents the experimental characterization, the formulation of a numerical model, and the evaluation, by means of non-linear analyses, of a new friction damper conceived for the seismic upgrade of existing building frames. The damper dissipates seismic energy through the friction force triggered between a steel shaft and a lead core prestressed within a rigid steel chamber. The friction force is adjusted by controlling the prestress of the core, allowing the achievement of high forces with small dimensions, and reducing the architectural invasiveness of the device. The damper has no mechanical parts subjected to cyclic strain above their yield limit, thereby avoiding any risk of low-cycle fatigue. The constitutive behavior of the damper was assessed experimentally, demonstrating a rectangular hysteresis loop with an equivalent damping ratio of more than 55%, a stable behavior over repeated cycles, and a low dependency of the axial force on the rate of displacement. A numerical model of the damper was formulated in the OpenSees software by means of a rheological model comprising an in-parallel system of a non-linear spring element and a Maxwell element, and the model was calibrated on the experimental data. To assess the viability of the damper for the seismic rehabilitation of buildings, a numerical investigation was conducted by performing non-linear dynamic analyses on two case-study structures. The results highlight the benefits of the PS-LED in dissipating the largest part of seismic energy, limiting the lateral deformation of the frames, and controlling the increase in structural accelerations and internal forces at the same time. Full article