Displacement Amplitude Research Articles

Shaking table tests of a nonstructural freestanding object with variable center of gravity

Freestanding objects have endured seismic damage during major historical earthquakes, but their seismic performance is not fully understood yet. A steel frame was constructed with steel rods and moveable plates to investigate the effect of the center of gravity (CG) on the seismic response of nonstructural freestanding objects. The location of the CG can be tuned to change the CG in the frame. Two groups of shaking table tests were carried out using instrumented floor motion. To verify the shaking table test results, an analytical model was defined based on Housner's rocking model. The experimental response modes were predicted correctly. The experimental kinetic coefficient of friction obtained in the slow-pull tests agreed with the peak acceleration of the steel frame in the shaking table tests. The displacement amplitude generally decreased with increasing height of CG (hcg); however, this trend was not observed when the CG was fixed. Identical properties were observed for the rotational response of the frame. The experimental and analytical rocking responses were in agreement in terms of amplitude, but not in terms of time history and trajectories. The overturing criteria of overturing velocity, spectral velocity, and vulnerability, were evaluated using the experimental results. The overturning spectral acceleration was not accurately predicted using Housner's equation. The overturning probability and ratio were correctly predicted, and they increased with the increase in hcg. The findings of this work enable seismic risk mitigation of nonstructural freestanding objects.

A study on soil propagation mechanism of traffic-induced vibration based on numerical analysis and theoretical approach

In order to clarify soil propagation mechanism of traffic-induced vibration, soil surface responses excited by vertical and horizontal force focused on the frequency characteristics are examined based on numerical analyses, theory of surface wave, and field observations. Relationships between natural frequency of surface soil and frequency at which wave with large amplitude propagates at distant points are examined. In the case of two-layer soil, vertical displacement amplitude excited by vertical point force becomes the largest at twice the natural frequency at distant points. Horizontal displacement amplitude excited by horizontal point force becomes the largest at the natural frequency at distant points.

Design optimization of hybrid isolation bearing for base-isolated buildings catering to multi-level performance fortification criteria

The adaptive seismic isolation system has attracted significant attention from researchers due to its multi-stage behavior and which can be used for multi-staged performance-based design. This paper introduces the configuration and mechanical behavior of a novel hybrid isolation bearing (HIB) combined with sliding bearings and rubber springs. The proposed isolator has three levels of stiffness and can achieve decoupling of horizontal and vertical performance. From the static test conducted on HIB500_R200, it is evident that the HIB displays a three-stage stiffness characteristic. The experimental stiffness values match well with the theoretical values, with a maximal error of 7.18%. Subsequently, an optimal design function for HIB-based isolation structures aiming to satisfy multiple performance objectives is established based on isolation effectiveness and displacement, utilizing the mode-superposition response spectrum and equivalent linear method. The optimization function can effectively and swiftly provide the optimal friction coefficient and the diameter of the rubber spring. A Performing elastoplastic analysis of HIB-based structures adopted for optimization function and traditional design method is performed using Seismostruct software. The numerical analysis reveals that the maximum error between the seismic isolation coefficient and the ratio of shear displacement amplitude values, as well as their theoretical predictions, is only 3.4%. And it also has higher safety redundancy than the traditionally designed isolation structures under mega earthquakes.

The vibration energy dissipation behaviour of 3D-PAM type RVD

Considering that ordinary rubber materials have problems such as insufficient mechanical properties and poor shock absorption effect, a right-angle viscoelastic damper (RVD) based on 3D printed auxetic metamaterial (3D-PAM) is proposed in this paper. According to the refined finite element simulation, a dynamic energy dissipation study was conducted on the RVD. Firstly, the 3D-PAM was fabricated by selective laser sintering printing technique, and its material properties were demonstrated. Secondly, the 3D-PAM type RVD was simulated by ABAQUS to study the characteristics of dynamic energy dissipation and to investigate the stress distribution and displacement variation of the 3D-PAM layer. The results show that the hysteresis curve shape is smooth and full under all working conditions. The hysteresis loop shows linear characteristics under small displacement amplitude. As displacement amplitude increases, a hardening nonlinear response is observed. The maximum loss factor of the 3D-PAM type RVD reaches 0.64. Under the same thickness and loading conditions, the maximum loss factor has increased by 16.4% and 100.0% respectively compared to Polyurethane type RVD and Fluororubber type RVD. In conclusion, results indicate that the 3D-PAM type RVD designed in this project exhibits superior energy dissipation characteristics.

Rock drilling performance of rotary ultrasonic tools incorporating PZT piezoceramic and Mn:PIN-PMN-PT piezocrystal

High performance Mn:PIN-PMN-PT piezocrystal material is investigated to understand if its extraordinary properties can replace the traditional hard piezoceramic material for space exploration applications. A bolted Langevin-style ultrasonic drill tool incorporating a pair of Mn:PIN-PMN-PT piezocrystal rings is built to compare with a same configuration ultrasonic drill tool actuated with a pair of hard piezoceramic rings, which are tuned to the first longitudinal mode (L1) at around 20 kHz. From the characterisation results, it is observed that the piezocrystal material presents significantly greater values of relative permittivity, electromechanical coupling coefficient, and piezoelectric charge coefficient than the hard piezoceramic material. Despite these outstanding properties, the piezocrystal driven ultrasonic drill tool shows similar displacement amplitudes to its counterpart. Nonetheless, the impedance magnitude of the piezocrystal driven ultrasonic drill tool at resonance is a magnitude lower than the piezoceramic actuated drill tool, due to the large piezoelectric charge coefficient d33. Ultrasonic rock drilling experiments suggest that the cutting force for sandstone and marble are greatly reduced, but limestone and tuff are less affected.In general, the piezocrystal driven ultrasonic drill tool demonstrates a marginally improved cutting performance than the piezoceramic actuated drill tool, in terms of lower cutting force and motor power consumption, however, the tool wear appears slightly poorer. The research outcome of this paper indicates that the thickness mode of the piezocrystal rings might not be the optimal form of excitation, which could be due to the piezoelectric losses at high excitation levels, so other excitation conditions and vibration modes will need to be explored to fully adopt the extraordinary material properties of the piezocrystal material.

Influences of inclined crack defects on vibration characteristics of cylindrical roller bearings

Crack initiation and propagation directions on the raceway surface of cylindrical roller bearings (CRBs) can generate different forms of excitation patterns and affect the vibration level of CRBs. For inclined crack defects on the raceway surface, the direction of a roller passing through the cracked raceway determines the order and amplitude of time-varying displacement (TVD) excitation and time-varying stiffness (TVS) excitation. In this study, two different excitation modes are proposed to simulate the interactions between the roller and the raceway. Then, the excitation modes are integrated into the dynamic model of CRB and used to study the effects of crack inclination and propagation direction on the vibration characteristics of CRBs. The results show that the bearing vibration acceleration caused by excitation mode I is greater than that caused by excitation mode II. The distribution direction of the inclined crack defect on the CRB raceway has a great influence on its vibration level. It can provide useful guidance for early bearing fault detection and diagnosis.

Horizontal vibration characteristics of offshore twin–pile foundations

Accurately estimating the horizontal dynamic parameters of offshore pile groups plays a critical role in offshore foundation engineering. Most of the current research ignored the hydrodynamic force applied to the piles, making it difficult to accurately simulate the operational conditions of offshore pile groups. This study considered the dynamic soil resistance and hydrodynamic pressure induced by pile horizontal vibration, providing a more accurate and comprehensive dynamic analysis of offshore twin–pile foundations. By incorporating the determined pile–soil and pile–water interaction forces and solving the horizontal vibration equations of piles, the dynamic impedance and displacement amplitude of the offshore twin–pile system were derived. After validating the rationality of the proposed solutions, the effects of hydrodynamic force, pile arrangement, and pile geometrical dimensions were extensively discussed. The main conclusions are as: (1) The influence of hydrodynamic force on the dynamic stiffness of the twin-pile system becomes gradually significant as the load frequency increases; (2) Neglecting the effects of hydrodynamic force leads to an overestimation of the natural frequency of twin–pile foundations; (3) Compared to a single pile, the natural frequency of twin–pile foundations is less sensitive to the changes in geometrical dimensions.

BORS/BJR TRAVELLING FELLOWSHIP: A COMPARISON OF THE EFFECTS ON BONE TISSUE OF TWO ULTRASONIC CUTTING DEVICES OPERATING AT DIFFERENT FREQUENCIES

AbstractIntroductionUltrasonic cutting in surgery has great potential. However, a key limitation is heat created by friction between the bone and the blade. Bone has poor thermal conductivity which hinders the dissipation of heat, causing cell death near the cut site In addition, ultrasonic vibration may create microcracks. It was hypothesised that these effects on bone would vary with the frequency and displacement of the ultrasonically powered blade. Therefore varying frequencies and displacements of the tip of the blade were studied to find the combination with fewest microcracks and lowest temperature rise at the bone-tool interface.AimTo explore the effect of different frequencies and tip displacements of ultrasonic cutting devices on the amount of thermal and mechanical damage.MethodsIn vitro tests were conducted on fresh rat femoral shafts using two different frequencies; 20kHz and 35kHz.Two displacement amplitudes of two different frequencies were used: 23.9 μm (p-p) and 7.5 μm (p-p) both at 20kHz and 18.7 μm (p-p) and 27 μm (p-p) both at 35kHz and. Cooling was used to emulate clinical conditions. Histological examination (H & E and TUNEL) was performed to identify live and dead cells. Further rat femoral shafts (n=6) were exposed to the same number of cuts by each tool to identify any micro-damage induced by different electrical currents using Micro-CT and confocal Laser scanning microscope. All experimental data were expressed as mean ± standard deviation. Statistical analysis was performed using one-way ANOVA, followed by Post Hoc multiple comparisons test. Differences between groups were considered statistically significant at p < 0.05.ResultsThe cut site at 7.5 μm (p-p) in 20kHz displayed only indentation instead of a cut, and was excluded. Histological examination revealed a high incidence of cell death at the cutting edge, in both frequencies. At 35kHz and 27 μm (p-p) some charring was evident, while at 20kHz and 23.9 μm (p-p) more irregularities were seen on the surface of the cut indicating instability during cutting when this setting was used. In contrast, the 35kHz at 18.7 μm (p-p) resulted in a smoother cutting surface. The highest cell death percentage ranged from 25% (at 35kHz, 18.7 μm (p-p)) to 44 % (at 35kHz, 27 μm (p-p)). Most of the tool's effect was located within 25 µm of the cut surface. There was a significant decrease to < 5 % at 200 µm. No cell death was found over 200 µm from the cut surface in both frequencies (35 kHz and 20 kHz). No significant difference in total percentage cell death was found between cutting at 35kHz and 18.7 μm (p-p) and at 20kHz and 23.9 μm (p-p). No microcracks were detected along the depth of the cut site at either frequency.ConclusionOf the 2 ultrasonic cutting frequencies tested, the combination of the higher vibration frequency (35kHz) and the lower displacement amplitude (18.7 μm (p-p) demonstrated least damage to the bone tissue. No microcracks were displayed when using either of the ultrasonic cutting frequencies.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

THE USE OF AN ULTRASONIC TOOL TO CUT HUMAN BONE: CUTTING SPEED AND FORCES OF ORTHOPAEDIC SURGEONS

AbstractBackgroundUltrasonic cutting of bone boasts many advantages over alternatively powered surgical instruments, including but not limited to: elimination of swarf, reduced reaction forces, increased precision in cutting and reduced adjacent soft tissue damage, reduced post-operative complications such as bleeding and bone fracture, reduced healing time, reduced intra-operative noise and ease of handling. Despite ultrasonic cutting devices being well established in oral and maxillofacial surgery, applications in orthopaedic surgery are more niche and are not as well understood. The aim of this study was to investigate the cutting speed (mm/s) and cutting forces (N) of orthopaedic surgeons using a custom-designed state of the art ultrasonic cutting tool to cut fresh human bone samples.MethodsA setup based on the Robot Operating System (ROS) and AprilTag was designed to track and to record the real time position of the ultrasonic cutting tool in space. Synchronised load cell axial force readings of three separate orthopaedic surgeons during ultrasonic cutting were recorded. Each surgeon was asked to find a comfortable position that reflects as close as possible their clinical handling of a cutting instrument used in surgery, and to perform two cuts in each of three samples of human cortical bone. Bone samples were obtained following ethical approval from an institutional review board (ethics approval number: SR1342) and prior informed consent was obtained from all patients. Bone samples were extracted from the femoral neck region of three hip osteoarthritis patients. During cutting, surgeons were allowed a total cutting time of one minute and cutting was conducted using an ultrasonic tool with frequency of a 35kHz (35.7 µm peak to peak displacement amplitude) under constant irrigation using a MINIPULS® 3 Peristaltic pump (38 revolutions per minute) using Phosphate-Buffered Saline (PBS) at 25°C. From the recorded data, the average instantaneous cutting velocity was calculated and the maximum cutting force was identified.ResultsAll surgeons assumed a back-and-forth cutting motion, variation in the applied cutting force was observed. The average vertical cutting speed, axial cutting force and cutting depth across all surgeons and all samples was 1.64 mm/s, 1.91 N and 0.73 mm, respectively. While increasing the axial cutting force resulted in a deeper cut, overloading of the ultrasound transducer occurred when the tool advanced too quickly into the bone tissue during cutting. The exact force threshold, or the optimal speed at which the surgeon can maintain a constant force during cutting, requires further investigation.ConclusionsIn this study, all surgeons cut using a back-and-forth cutting motion, with variation in the applied cutting force which may ultimately inform which clinical applications in orthopaedic engineering are most suitable for this technology. Applying too much force caused overloading of the ultrasound transducer, which is a limitation with the current cutting tool. The results from this study may facilitate the eventual uptake of ultrasonic cutting tools for application in orthopaedic surgery.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

The influence of physical activity and sex on carotid artery longitudinal wall motion in younger healthy adults.

Carotid artery longitudinal wall motion (CALM) is a novel preclinical marker for atherosclerosis that describes the axial anterograde and retrograde motion of the intima-media complex. While regular physical activity and sex are known to independently influence arterial stiffness, their roles on axial arterial wall behaviour are unknown. The purpose of this study is to examine whether physical activity and sex impact CALM. We hypothesized that CALM retrograde displacement and total amplitude would be greater in females and active individuals, as a function of arterial stiffness. Fifty-seven young healthy adults (30 females; aged 22±3 years) were evaluated for CALM outcomes and arterial stiffness and grouped by physical activity based on active (V̇O2=44.2±8.9mL/kg/min) or sedentary (V̇O2=33.7±6.7mL/kg/min) lifestyles defined by the Canadian 24-Hour Movement Guidelines. Arterial stiffness and CALM were measured by carotid-femoral pulse wave velocity (cfPWV) and vascular ultrasound at the right common carotid artery with speckle tracking analysis, respectively. cfPWV was greater in males (p<0.01) with no interaction between sex and physical activity (p=0.90). CALM anterograde displacement was greater in males (p=0.03) resulting in a forward shift in total CALM pattern, which became less prominent when controlling for mean arterial pressure (p=0.06). All other CALM outcomes were not different between activity and sex. V̇O2max was not correlated to any CALM outcome (all p>0.05). Apparent sex differences in vascular function extend to novel CALM outcomes but may be confounded by blood pressure. We recommend sex-balanced design and reporting in future studies due to possible anterograde-shifted CALM patterns in healthy males.

Modeling a Fluid-Coupled Single Piezoelectric Micromachined Ultrasonic Transducer Using the Finite Difference Method.

A complete model was developed to simulate the behavior of a circular clamped axisymmetric fluid-coupled Piezoelectric Micromachined Ultrasonic Transducer (PMUT). Combining Finite Difference and Boundary Element Matrix (FD-BEM), this model is based on the discretization of the partial differential equation used to translate the mechanical behavior of a PMUT. In the model, both the axial and the transverse displacements are preserved in the equation of motion and used to properly define the neutral line position. To introduce fluid coupling, a Green's function dedicated to axisymmetric circular radiating sources is employed. The resolution of the behavioral equations is used to establish the equivalent electroacoustic circuit of a PMUT that preserves the average particular velocity, the mechanical power, and the acoustic power. Particular consideration is given to verifying the validity of certain assumptions that are usually made across various steps of previously reported analytical models. In this framework, the advantages of the membrane discretization performed in the FD-BEM model are highlighted through accurate simulations of the first vibration mode and especially the cutoff frequency that many other models do not predict. This high cutoff frequency corresponds to cases where the spatial average velocity of the plate is null and is of great importance for PMUT design because it defines the upper limit above which the device is considered to be mechanically blocked. These modeling results are compared with electrical and dynamic membrane displacement measurements of AlN-based (500 nm thick) PMUTs in air and fluid. The first resonance frequency confrontation showed a maximum relative error of 1.13% between the FD model and Finite Element Method (FEM). Moreover, the model perfectly predicts displacement amplitudes when PMUT vibrates in a fluid, with less than 5% relative error. Displacement amplitudes of 16 nm and 20 nm were measured for PMUT with 340 µm and 275 µm diameters, respectively. This complete PMUT model using the FD-BEM approach is shown to be very efficient in terms of computation time and accuracy.

Magnetic haptic device using miniature SmFeN powder magnets in PCB-on-MEMS system

This paper reports a magnetic microactuator for haptic applications. The actuator consists of a Si chip and two printed circuit boards (PCBs), and the total size of the device is 7.8 mm × 7.8 mm × 2.4 mm. A tiny magnet is embedded into the Si chip and actuated by a current flowing in the PCBs. The mechanical and electrical parts are separated on the Si chip and the PCBs, respectively, and there is no electrical connection between them, allowing simple fabrication and assembly. The magnet, made from a mixture of SmFeN magnetic powder and wax, exhibits a large magnetic field of 0.4 T. The magnet is supported by soft springs of parylene, enabling a large displacement amplitude, a low resonance frequency, and high mechanical robustness. The measured resonance frequency and amplitude are 139 Hz and 62 µm, respectively. The rise and fall times of the vibration of the device at 100 mA drive are 19 ms and 52 ms, respectively. Sensory analysis revealed that the haptic device created the haptic sensation on a scale of three, weak, medium, and strong intensity, with input currents from 50 mA to 200 mA.

Static Mechanics and Dynamic Analysis and Control of Bridge Structures Under Multi-Load Coupling Effects

With the rapid development and wide application of large-span bridges, the problem of dynamics and safety control of bridge structures under multiple loads is becoming more and more prominent. To realize the dynamic analysis and mechanical control of the girder structure, this paper designs a new type of magnetorheological (MR) mechanical damper based on the mechanistic analytical method and establishes a coupled dynamics model of the vehicle-rail-MR mechanical damper. The simulation and validation results show that the error between the semi-analytical method and the finite element theory calculation results is only 1.0%, while the kinetic simulation is consistent with the measured frequency domain trend. The analytical results show that: After applying MR mechanical damper for mechanical control, the moment live load and shear values of side spans were reduced by 27.68% and 10.79%, respectively; and the maximum moment and shear values generated at the center pivot were reduced by 28.19% and 10.81%, respectively. After applying the mechanical damper, the stress distribution of the cable-stayed bridge is more balanced, and the maximum diagonal stress of the overall structure is reduced from 3.8 MPa to 2.9 MPa. After safety control, the root-mean-square (RMS) value of the mid-span displacement amplitude was reduced by 59.32% and the maximum value was reduced by 11.46%, which improved the stability of the girder dynamics. After mechanical control, the dynamic acceleration response of the beam within the span decreased between 2 and 8 seconds and increased between 8 and 10 seconds. The overall response fluctuated around −5 m/s2 with a relatively smooth trend.

A novel OPR-free method for blade tip timing based on adaptive variable reference blades

Monitoring rotor blade vibrations is imperative in aero-engine testing and service. Blade tip timing (BTT), a promising technique for such monitoring, assesses the operational status of rotor blades through non-intrusive measurement of blade tip displacement. Traditional BTT technology relies on the Once-Per-Revolution (OPR) probe, which poses installation challenges and introduces measurement uncertainties in practical applications. This paper introduces a novel OPR-free approach, employing Adaptive Variable Reference Blades (AVRB) for non-intrusive measurement of rotor blade vibrations. The method assumes a stochastic mistuning of blades within the same stage, resulting in non-simultaneous resonance of blades at a given speed. In each revolution, the vibration level of individual blades is determined by assessing the deviation between the average speed of a blade, as measured by two adjacent BTT probes, and the average speed across the entire circumference. Consequently, a non-vibrating blade is adaptively identified and selected as the reference blade. The relative vibration levels among blades vary dynamically during different revolutions, influenced by mistuning features, leading to variability in the reference blades. These adaptive variable reference blades can then replace the OPR probe, aiding in the computation of vibration displacement and further parameter identification of blades. To validate the effectiveness of the proposed method, a five-degree-of-freedom numerical model is utilized for simulation. Additionally, experiments involving both a five-bladed disk and an eight-bladed disk are conducted to validate the proposed approach. Numerical simulations and two sets of test results demonstrate a fundamental agreement between the blade vibration displacement calculated using the proposed method and the outcomes obtained through the traditional BTT method with OPR. The relative error in the identified blade vibration frequency derived from the blade vibration displacement, as determined by both methods, does not exceed 1 %. Additionally, the relative error in the amplitude of the blade vibration displacement is within the range of 10 %.

What is the Resonance of a Linear Mechanical Resonator, Peak Amplitude of Displacement or Peak Amplitude of Velocity?

What is the Resonance of a Linear Mechanical Resonator, Peak Amplitude of Displacement or Peak Amplitude of Velocity?

Bedrock Fractures Control Groundwater‐Driven Mountain Slope Deformations

AbstractSeasonal deformation of mountain rock slopes can be driven by groundwater infiltration and depletion. Such processes could explain our field observation in the Aletsch Valley, Switzerland, where GNSS‐derived 3D annual displacement amplitudes reach 3.4 cm. However, the physical mechanisms behind such groundwater‐driven surface displacements are not well understood. Here, we develop a fully coupled hydromechanical model to simulate the relevant processes in a valley slope embedded with numerous fractures of variable sizes. The magnitude and orientation of transient annual slope surface displacement obtained from our model are in overall agreement with the field observations. The key geological factors controlling the type and magnitude of reversible mountain slope deformations are fracture network geometry, fracture aperture, and regional stress field. We show that the heterogeneity and anisotropy of bedrock hydromechanical responses, originating from depth‐dependent variations of fracture properties, play a critical role in groundwater recharge and valley slope deformation. During recharge events, pore pressure perturbations migrate downward from the groundwater table and toward the receiving stream and the deep subsurface. This process driven by pressure diffusion and poroelastic stressing develops in the subsurface with a great reach of up to a few kilometers, called critical hydromechanical response zone, and controls surface deformation patterns. During groundwater recession, this hydromechanical response zone expands downward and ground surface displacement vectors rotate upwards. Our results suggest that slope surface deformation can inform about subsurface permeability structures and pore pressure fluctuations, which have important implications for understanding groundwater flow in fractured bedrock slopes.

Effect of a Conical Extension on Aerosol Sedimentation in the Case of Acoustic Small-Amplitude Oscillations in a Tube

The effect of acoustic low-intensity oscillations in a homogeneous tube and in a tube with a conical extension is experimentally investigated for the same resonator volumes. The resonator shape is shown to have an effect on the oscillation spectrum and intensity and the pressure wave shape at constant values of the resonance frequency and the piston displacement amplitude. An increase in the resonator Q-factor is observable, when the resonator has a conical extension. An accelerated aerosol sedimentation in tubes is revealed in the case of acoustic oscillation with the resonance frequency. In the presence of a conical extension the aerosol drop concentration is reduced by a factor of 1.2 more rapidly than in the case of a uniform tube and three times more rapidly as compared with natural sedimentation. The results obtained can be used for increasing the efficiency of acoustic methods of gas purification from the disperse phase

Investigation on the Damping Effect of FST System under Moving Load Using the Track–Tunnel-Layered Saturated Ground Model

In this paper, a single-tier beam-spring-damping system and a two-tier beam-spring-damping system are adopted to simulate the FT (fixed track) and FST (floating slab track) system, respectively. The tunnel is modeled as an infinitely long Euler—Bernoulli beam embedded in the layered saturated soil. By solving the governing equations of the saturated soil and employing the TRM (transmission and reflection matrices) method, the frequency response function of the tunnel-layered saturated soil model is obtained. Making use of the interaction between the tunnel and track systems, the track system is coupled with the tunnel-layered saturated ground model. The solutions for the dynamic response of the track system–tunnel-layered saturated ground model under moving loads in the time–space domain are obtained using the inverse Fourier integral transform. To evaluate the damping effect of the FST system on the vibration of tunnel and soil, four damping coefficients are defined and the vibration results of the FT system–tunnel-layered saturated soil model are compared with those of the FST system–tunnel-layered saturated soil under different moving loads and soil conditions. The numerical results show that both the vibration displacement and acceleration amplitude are attenuated after using the FST system, and the damping coefficient of acceleration is about 30% greater than that of the displacement. In addition, the damping effect of the FST system on the ground surface vibration is associated with the embedded depth of the tunnel and the soil stiffness.

Seismic performance evaluation of a five-story column-and-beam glulam frame with steel-timber buckling restrained braces

This paper summarizes the results of numerical simulation and fragility analysis of a five-story column-and-beam glulam frame with chevron steel-timber buckling restrained braces (BRBs). Key parameters of the rotational behavior of the bolted beam-to-column connections and column base connections were modeled and calibrated using shaking table test results. Prediction methods of the stiffness and capacity of the steel-timber BRBs were proposed and validated with the test results. An FEM model of the glulam frame with steel-timber BRBs was developed to capture the frame seismic response and validated using shaking table test results. The FEM model which considered damping change and damage accumulation achieved good agreement with shaking table test results, with the modelling errors of displacement amplitude for most conditions less than 15 %. Fragility analysis of the frame was conducted based on the validated FEM model. The probability of exceeding the collapse prevention limit state under the VII-rare earthquake excitations was reduced to close to zero when steel-timber BRBs were used. This study demonstrates the potential for using glulam frames with steel-timber BRBs in Chinese VII seismic regions.

Evaluation on the possibility of sound conduction independent of tympanic air cavity for severe tympanic adhesion patients by finite element analysis.

Background: For patients with severe tympanic adhesion, reconstructing the tympanic air cavity is often challenging, resulting in poor hearing reconstruction outcomes. Therefore, establishing a sound conduction pathway independent of the tympanic air cavity may be a viable method for reconstructing hearing in these patients. Purpose: The objective of this study was to evaluate the feasibility of sound conduction independent of the tympanic air cavity (i.e., replacing the original cavity with a tympanic vibrating material) using finite element analysis. Methods: We established a sound-structure coupling finite element model of the tympanum vibration conduction system, which included the tympanic membrane (TM), ossicular prosthesis, and tympanic vibrating material. This model was used to simulate middle ear vibrations under sound pressure, and we extracted the frequency response curve of the ossicular prosthesis' vibration displacement amplitude to evaluate the sound conduction effect of the middle ear. Next, we adjusted the structural and mechanical parameters of the tympanic vibrating material to analyze its impact on the sound conduction effect of the middle ear. Finally, we compared the frequency response curve of the stapes footplate in normal subjects to evaluate the feasibility of sound conduction independent of the tympanic air cavity. Results: The Shell tympanic vibrating material had a better vibration conduction effect compared to solid or porous tympanic vibrating material. The vibration amplitude decreases with the increasing elastic modulus of the tympanic vibrating material. Implantation of 40kPa-shell tympanic vibrating material had the lowest hearing loss less than 5dB, and the hearing loss with 1MPa-porous tympanic vibrating material was largest and less than 25dB. Conclusion: Our study suggests that replacing the tympanic air cavity with a tympanic vibrating material is feasible. The establishment of a sound conduction pathway independent of the tympanic air cavity could potentially provide a method for hearing reconstruction in patients with severe tympanic adhesion.