Recent light-weighted and structurally-simplified railway vehicle carbodies tend to have the various vertical flexural vibration which causes lowering of the ride comfort. To study techniques for reducing these vibrations, simple numerical analysis models are required. The authors proposed a simple analytical model that can express several flexural vibration modes of a carbody. Along with the modeling technique, determining parameters used in the analysis models (called “model parameters” in this work) is also important. This paper proposes a method to estimate model parameters using particle swarm optimization (PSO) together with running test results. To confirm the validity, eigenvalue analysis and running simulation were performed using the analysis model with the parameters estimated by the proposed method. As the result, the calculated natural frequencies are in good agreement with the measured ones. In addition, within the range of frequencies which present natural frequency of the important vibration mode, good agreement between the calculated acceleration power spectral densities (PSDs) and the measured ones were observed at the measurement points of the centerline of the carbody.

In this study, topology optimization techniques were numerically applied to eigen-frequency structural optimization problems of composite laminated structures with damping layers inserted into the lamina interfaces. General-purpose finite element analysis code, MSC Nastran, and its pre-post processor, Patran, were used in the present study, in which the density method (SIMP method), one of the numerical approaches in the structural optimization discipline, was employed for seeking the most efficient internal structural forms of the present damping layers for eigen-frequency maximization under certain fixed weight reduction constrains. From the results of the present study, certain optimal inner structures or morphologies could be found out for each set of structural and material configurations for each vibration mode, which makes engineers and researchers of the composite material field have a future prospect of the present attempts.

Some of smart phones and tablet computers have a function of vibration feedback, when users touch their panels, in order to improve their input operability. In the present study, the click feeling associating with operability of such panels is evaluated by a questionnaire survey. The smart phone employed here is operated by Android OS, and a piezo-elastic vibration module is attached directly to the back of touch panel. In the experiment, arbitrarily designed input signals are imposed to the module by specially developed software, and vibration responses of the panel are evaluated by examinees. Employed input signals are signals with the constant amplitude and the single frequency that is equal to the fundamental frequency of the piezo module, with the window function for its amplitude, and with chirped frequencies to imitate the S-shaped load-stroke curve that are observed when physical buttons are pushed in. Experimental results revealed that the signal with a constant amplitude and single-frequency is most preferred.

Golf is the sports that have been enjoyed by the people of a wide age group. The many golfers aim to get the high score and hope to getting the longer distance and raising the ball speed by the golf club (Driver). The improvement of the golf club head has been accomplished. In 2008, the upper limit of the coefficient of restitution of the golf club head was regulated. Therefore, the study of the golf club shaft comes to attract more attention. Therefore, in the previous study, the golf swing simulation has already been proposed by the authors. In this simulation, considering the motion and torsion of the grip of the golfer, the golf swing was simulated. Also, this swing simulation consists of the finite element approach using the grip motion obtained by the swing image. In this study, the accuracy of the proposed swing simulation is discussed.

Powerful tsunami attacked to the northeast coast of Japan due to the Great East Japan Earthquake occurred on March 11, 2011. Some aboveground storage tanks (ASTs) were subjected to external pressure due to the tsunami. This paper presents the bifurcation buckling of shell plates in 1,000 m³, 10,000 m³ and 90,000 m³ AST under both internal and external liquid pressure using the axisymmetric shell finite element method. The buckling of cylindrical shells which have the same diameter and thickness as ASTs has been also analyzed for the comparison. The buckling liquid height of an AST is less than that of a cylindrical shell. The reduction ratio of buckling liquid height of an AST from a cylindrical shell is proposed. The buckling liquid height of an AST can be simply obtained from that of a cylindrical shell using the reduction ratio.

The finite element method is applied to linear buckling analysis of cylindrical shells subjected to asymmetric external and axisymmetric internal liquid pressures. The axisymmetric shell element is used and the load distribution, prebuckling and buckling displacements are represented by Fourier series expansion in the circumferential angle. The shells are assumed to stand vertically with the lower and upper ends simply supported. The analyses are performed for a wide range of the geometric parameter Z for asymmetric external liquid pressures and the effects of internal liquid on the buckling liquid height are investigated. The approximate treatment of tsunami pressure acting on tanks is applied to buckling analysis and the effects of internal liquid pressure are obtained.

Carbon fiber reinforced plastics (CFRP) have orthotropic material properties and are usually used as laminated structures. Therefore, their mechanical properties can be varied by changing their fiber orientation angles according to the purpose of their use. However, in the case of CFRP that has poor vibration damping, resonance problems become easily crucial and hence it is necessary to suppress the vibration occurred in the CFRP laminates. The present study proposes to improve the value of coefficient of mode loss by introducing so-called damping sheets. Fiber orientation angle and insert point of damping sheets are decided from numerical results (1280 patterns) in terms of a few lower natural frequencies, modal loss factors and mode shapes numerically obtained by the general purpose finite element method(FEM) code, ANSYS.

This study performs to evaluate the usefulness of the super-directional loudspeaker in visualizing the vibration mode of single-layer CFRP thin plate. Vibration mode of single-layer CFRP thin plate is excited by acoustic excitation. In order to confirm the vibration mode of the single-layer CFRP thin plate, the laser doppler velocimeter and a time-averaged digital holographic interference device are produced. These devices are able to find the natural frequency and vibration modes of the plate in the same time. In the experiment, it was confirmed that deformation of the torsional vibration of the single-layer CFRP thin plate is affected by positional relationship of the single-layer CFRP thin plate and loudspeaker. In addition, acoustic excitation with super-directional loudspeaker was confirmed that can efficiently measure the vibration mode of the single-layer CFRP thin plate as compared with the conventional.

The present study fabricates fibrous composite with curvilinear fiber shape by using tailored fiber placement machine which is an application of embroidering machine. The composite with curved fibers has variable mechanical properties depending on fiber curvature. First the relationships among fiber density, thickness and curvature are revealed by experimental study with test specimens that has various curvatures. Then, regression equations for stiffness and fiber volume fraction in terms of fiber curvature are estimated by using the mixture rule. Finally, natural frequencies and mode shapes are calculated by finite element analysis with estimated mechanical properties, and those are compared with experimental results. The present calculated results indicated better agreement with experimental results than those without estimated values. Therefore, it was found that the obtained regression equation is effective to predict mechanical behavior of composite with curvilinear fiber.

This paper presents the experimental study for elastic environmental characteristics of thermoplastic fiber reinforced plastics materials. For this purpose, tensile test is carried out for the fiber reinforced plastic material of carbon fibers and the resin of acrylic, nylon and epoxy, and Young's modulus and Poisson's ratio are estimated experimentally for the cases of different environmental temperatures. Furthermore, the experimental modal analysis is conducted for the rectangular plates of the materials, and the numerical calculations for the free vibration problem of the plate are also carried out by using the material properties obtained from the tensile tests.

An inertia force resulting from response of a structure excited by ground motion due to an earthquake excites the structure and generates a seismic force on the structure. The handling of seismic forces has been being discussed in terms of how the seismic force on a piping controls the deformation of the piping, load-controlled or displacement-controlled. A seismic design code for nuclear facilities applied in Japan qualifies this kind of seismic forces as primary stress components which shall be limited to prevent any plastic collapse, on the assumption that the seismic force mainly consists of load-controlled loads and the deformation due to earthquakes is caused by the loads. The authors studied about a condition of plastic collapse occurrence by the relationship between response acceleration and displacement of SDOF system. And it was represented in a previous paper that plastic collapse hardly occurred to soft structure due to an inertia force generated from response acceleration tended to oppose a response displacement. Several simulations for elastic-perfectly-plastic Single mass cantilever model under a combination of alternating load and static load are performed and evaluated. In the model response by the combination load, variations of force components are examined.

This study tries to evaluate the applicability of four candidate indices, those are JMA Instrumental Seismic Intensity, Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV) and Standardized CAV, as Earthquake Hazard Index in the Seismic Probabilistic Risk Analysis (PRA) of mechanical components. As results of parametric elastoplastic earthquake response analyses of one-degree-of-freedom system with bi-linear load-deflection model against 60 near-field earthquake motions selected from NIED's K-NET and KiK-net observed earthquake motion data base in Japan, the correlation between those four indices and Ductility Factor (as Damage Assessment Index) reveals that the index A_JMA, based on JMA Instrumental Seismic Intensity, has similar characteristics with PGV and suggests to be most promising one in the seismic capacity evaluations of mechanical features made by ductile materials.

When piping systems respond under the elastic-plastic region, it is known that the increasing of hysteresis damping and the decreasing of the dominant frequency would occur due to the plastic deformation. But there are few studies that attempt to estimate them quantitatively from the actual excitation test data of piping systems. In this paper, the hysteresis damping ratios and the dominant frequencies under inelastic response behavior region are estimated based on the test data obtained by one-directional shaking table tests on a 3D piping system model. In addition, the strains which were caused on the piping system model are also checked, and correlated with the estimated hysteresis damping ratios. As a result, the estimated damping ratio was about 4% when the one elbow in the piping system model reached to the inelastic region, with about 0.6% strain range. The hysteresis damping ratio was up to more than 10% under the high input acceleration level, when the two main elbows reached to the inelastic region. The dominant frequency was decreased about 3~8% when the one elbow in the piping system model reached to the inelastic region. The decreasing ratio was about 14~18% under the higher input acceleration level.

This paper deals with a new method to estimate the maximum response of the multiple supported (multi -input) nonlinear piping systems. There are many papers concerned with the response analysis of a system having nonlinear properties, such as friction or elastic-plastic characteristics. However, most of them are for the one input nonlinear system because it seems that an application to multiple input nonlinear system is more difficult than that to one input nonlinear system. Although a simple method for estimating the maximum response for multiple input linear systems is also proposed, it cannot use for nonlinear systems. In recent years, the importance of seismic design considering both nonlinear and multiple input problems has been focused. Therefore, we propose a method to estimate the maximum response of multiple input system with elastic-plastic characteristic for rationalization and high evaluation of seismic design of piping systems in the present study. The estimated results are compared with simulated value by numerical simulation and showed the effectiveness of our method.

For seismic response analysis of multiple supported piping systems in industrial facilities such as nuclear power plants and petro chemical plants, several simple analysis methods have been proposed and discussed. However, most of them are about one input system because it seems difficult to apply multiple input. Although a simple method for estimating the multiple input response analysis for linear systems is also proposed, we cannot use for nonlinear systems. In recent years, the seismic design considering both nonlinear and multiple input problems has been focused on. Then, the purpose of this study is proposing a new method with considering these two problems. We got the response reduction effect by the difference of phases as a result from the experiment in order to compare with the simulated results and the experimental results.

In recent years, from the purpose of environmental impact reduction and earthquake-proof improvement, even if it carries out an industrial apparatus pair not only in a building, the earthquake-proof performance attracts attention. So the electrical machinery apparatus maker is tackling the earthquake-proof improvement in industrial apparatus. In this research, the FEM analysis model of the iron core structure which is main component parts of a cast resin transformer was built, and comparison verification of the analysis accuracy was carried out with the experiment. Since it united and the technical point required for earthquake-proof improvement was considered, the result is shown.

Japan is earthquake-prone country. Buildings went collapsed by major earthquake, and many people got injured. Therefore, building has been adapted seismic protection. As a result, collapse of buildings was decreased. However, falling of furniture brought about human damages of 30 ~ 50 % by earthquake. It is necessary to prevent falling of furniture. Today, there are a lot of furniture fall prevention devices. Nevertheless, these devices are not popular for people. The reason is difficult to install these devices. Even if these devices are installed, an effect may not be shown. For these reason, easy to install and effective device is needed. In this study, we examined the effectiveness of the furniture fall prevention device by using damper. To examine the effectiveness, it is necessary to know behavior furniture during earthquakes. Therefore, furniture was modeled to expect behavior during earthquakes. This model was excluded the effect of sliding and vertical movement. We analyzed an earthquake response by using this model. In this paper, we conducted vibration experiment, and experiment results were compared with analysis result. We input sine wave in the experiment. The analysis agreed very well with the experiments. As a result, this model can simulate behavior of the furniture.

In the field of marine construction such as off-shore wind power system, traffic ships are used to board/go ashore to the floating structure such as working vessels. However, traffic ships are fluctuated in such environments as tidal waves, and workers face an increased risk of accidents such as falls in the sea and pinched between traffic ships and floating structure. To solve these problems, a new active vibration compensation system on traffic ships is proposed and developed. The system consists of a motion stabilized platform with Stewart Platform type of parallel kinematic mechanism and a catwalk on the platform. The platform is supported on the main hull and kept in a horizontal position by means of the six-degrees-of-freedom hydraulic parallel mechanism which control to absorb motion of the main hull in accordance with the control signal from an on-board computer and motion sensors. System performance has been confirmed by simulation models using the simulation software, MATLAB+Simulink based SimMechanics. A 3/10 scale model of the actual system was developed and stabilized performance of the platform was experimentally verified.

Fukushima nuclear power plant accident occurred from the cause of all the loss of power in the nuclear power plant. Aerogenerator are expected as emergency external power supply of nuclear power plant. However, response control technology of aerogenerator has been still developing stage. In case of application using conventional response control technology to aerogenerator, Tuned Mass Damper may be suitable device now, because of fully effective in harmonious vibration. However, the device can't be expected in impact transient force input such as seismic forces. Therefore, applying a damping element to aerogenerator will be one of solution to reduce responses caused by earthquake or strong wind input. This study has been examined to develop a new suitable response reduction system for aerogenerator using response control device. In this time, the wire type elasto-plastic coil damper is proposed for a vibration control element. In the first step, the evaluation of vibration control effect is conducted from time response analysis using analytical model of TMD and wire type elasto-plastic coil spring damper: CSD based on the restoring force characteristics obtained from loading test used for the test specimens of CSD. In the next step, actual vibration control effect is confirmed from shaking table test.

Japan is one of the most earthquake-prone countries in the world. In the great east Japan earthquake, power plants were severely damaged by strong ground motion and tsunami, and power generation at some power plants had been stopped for a long time. These suspensions of power generation impacted public institutions and industry. Therefore, improving the earthquake resistance of power plants is very important at present. In particular, thermal power plants are important power plants assuming the current Japanese power supply. In current thermal power plants, simple anti-vibration devices made of steel are installed between boiler and its support structure. However these devices do not have enough damping against after shocks following a main shock, because devices made of steel are damaged by repeated deformation. Therefore we propose applying dampers to thermal power plants in order to improve their earthquake resistance. In this paper, boiler structure is modeled to two mass points model at first. Next, earthquake response analysis is carried out in order to compare vibration control performance of dampers (steel damper, friction damper, oil damper, viscous damper, viscoelastic damper). As a result, it was confirmed that the friction damper and the viscous damper have good vibration control performance. The friction damper and the viscous damper suppressed relative displacement between a boiler and its support structure. Additionally convergence of the response after the earthquake was quick.

The connected control method (CCM) utilized reaction force between buildings as damping force by using connecting springs and dampers. The effectiveness of CCM has already been established in previous studies. In this paper, integrated connected control method (ICCM) with an experimental high-rise building split into four substructures is presented for a vibration control method to mitigate structural vibration by using internal damping force by CCM. To examine the effectiveness of ICCM, an experimental structure model split into four substructure is build and four dampers are introduced to realize experimental ICCM. Using this model, the effectiveness ICCM is investigated through computer simulations and experiments.

The nuclear power generation does not produce greenhouse gas. In addition, even an aspect of the generation cost is a superior generation method. However, seismic condition in Japan is severe. Therefore seismic design is important for nuclear power facilities. It is useful to adapt a seismic isolation system into nuclear power facility because the seismic loading can be reduced. Because of improvement of horizontal isolation characteristics and restraint of the cardinal number of laminated rubber bearing, the current laminated rubber bearings are used in the longer period and the high surface pressure. In this case, the stiffness of the laminated rubber bearing in the vertical direction decreases. As the result, the response is increased in natural frequency of the principal components. In this paper, we examined the response acceleration of the principal components in the horizontal/vertical frequency of the laminated rubber bearing. The seismic response analysis with one lumped mass model was carried out. The input seismic waves used Kashiwazaki wave and Onagawa wave. As a result of examination, we confirmed that the response amplification of the principal components of the nuclear power facilities was inhibited by using the laminated rubber bearing with the seismic isolation specification of approximately 20 Hz in the vertical frequency and approximately 2 seconds in the horizontal period.

Damage free technologies from unexperienced huge earthquakes arising frequently from far and near field are needed. Hence the pneumatic levitation technology which can isolate perfectly from earthquake ground motion is focused. Into practical use of this, technical points are 1) big area supporting by simple mechanism, 2) less energy and 3) high performance. After fundamental experiments, some important outcomes are obtained. Then we propose a new type seismic isolator with pneumatic levitation which have a small and thin air chamber sealed by resin sheets but slightly leaked to reduce the sliding frictional force. This floating mechanism demonstrates some superior performances of 1) easy supporting large loads, 2) low energy requirements of compressed air, 3) high level isolation for horizontal vibration, 4) stiff spring characteristics for vertical and rotational vibration and so on.

The hysteresis restoring force characteristic of the seismic isolation rubber has the nonlinear characteristics depending on the displacement. A method to reduce the damage of structure in the earthquake with a seismic isolation laminated rubber is discussed and the vibration characteristics of the rubber which minimize the response of the structure in earthquakes is optimized. In this research, PFT-ELS (Equivalent Linear System using the Restoring Force Model of Power Function Type : PFT-ELS) method is applied to the nonlinear vibration analysis of the rubber. And, the building model of 15 layers with the seismic isolation laminated rubber is modeled. Next, the hysteresis restoring force characteristic of the seismic isolation rubber which minimize the response of the structure in earthquakes is optimized by Genetic Algorithms (GA). As earthquakes, Kobe earthquake, the hypothetical Nankai-Tonankai-Tokai connected earthquakes and Kumamoto earthquake (16 April 2016) are used. From these results, we consider about the optimum solutions of the restoring force characteristic by different earthquakes, and we verify the availability and valuable of this optimization method. As a result, it is clarified that the vibration characteristics of the seismic isolation rubber for minimizing the damage of the structure at the design phase through developed optimization system.

This paper describes a cart-type one degree of freedom vibration system using a DC motor and electrical circuit instead of a spring. The stiffness and the damping ratio of the proposed method can be tuned using an LR circuit and an LRC circuit. This proposed method solves the problem of occurring the deflection and buckling of a spring, and occupying the space with the spring. This paper describes the method that uses the proposed vibration systems as a seismic isolator and dynamic vibration absorber. The governing equations of the analytical models were formulated, and the optimum values of the proposed methods were derived. The effectiveness of the proposed methods and theoretical analysis were verified through simulations and experiments.

Japan is the earthquake-prone country. Therefore, structures in Japan require high safety. Base-isolated system satisfies that conditions, so the number of Base-isolated structure shows a tendency to increase. Nevertheless, the number of Base-isolated structure is few in number by comparison with the aseismic structure. Consequently, seismic records of base-isolated structure are insufficient in quantity. Due to reason like this, seismometers are installed in base-isolated structure. In addition, seismic records using seismometers are carried out positively. Seismic records are used for the calculation of structure vibrational properties. Structure vibrational properties are very important in performing the validity examination of the design. Furthermore, These parameters can also be applied to analytical model that replays seismic behavior. It is available for various things such as indication of evacuations, and examination of repair that reproduce seismic behavior of the building. In this paper, we handle a base-isolated structure that continues seismic records. First, we calculated both primary natural frequencies and spectrum intensity by using seismic records of target buildings. Next, we constructed an analytical model that can be changed building stiffness depend on primary natural frequencies and spectrum intensity. Then, using that model carried out earthquake response analysis. Consequently, analysis results that are close to seismic records are obtained.

In order to conduct vibration test of nuclear components, high acceleration shaking table system using resonance vibration has been developed. Maximum acceleration of 200 m/s2 with 5 ton specimen weight is achieved. At the trial operation of resonance shaking table, the environmental influence exceeding the regulation value of vibration level has been occurred at the site boundary. In order to suppress vibration of resonance shaking table, the semi-active mass damper (SAMD) has been additionally installed on base of shaking table. Vibration of resonance shaking table was reduced by counterforce of the SAMD. For the confirmation of the earthquake-proof safety for various nuclear facilities, resonance shaking table will be utilized.

Floating Production Storage and Offloading (FPSO) system is now attracting big attention which can develop the natural gas fields under the sea. This paper is related to dynamical design of FPSO system, specially focused on the free surface elevation in the horizontal cylindrical and axisymmetric liquid vessel with end caps induced by the wave. The purposes of this research are to model the sloshing in the horizontal cylindrical container under pitching excitation, and to investigate the damping effect of punching plates. First, the theory on the wave height and the resonant frequency in a horizontal cylinder subjected to pitch external excitation is developed. Then, the theory which is capable of taking account of the damping effect of punching plates installed in the cylindrical vessel is described. Finally, the experimental data of resonant wave height up to the third mode are compared to the theoretically derived results. As a result, we can say that the sloshing theory in a horizontal cylindrical container we built in this paper can demonstrate the wave height response qualitatively and quantitatively especially near the first resonance frequency, and that the damping effect of punching plate can be modeled by using the revised resistance coefficient and the velocity of a flowing fluid.

High rate plate settler modules are solid and liquid separation devices to improve precipitation efficiency of purification in settling tanks in purification plants. In the 2011 off the Tohoku Pacific coast Earthquake, the high rate plate settler module fell off and it was damaged. As a result, supply of the water stopped for a long time. It is considered that liquid sloshing by long period ground motion caused these damages. There are examples of damage as liquid sloshing in the past, fire of an oil tank, and damage of device in a tank, overflow of fluid in storage pool for spent nuclear fuel in a nuclear power plant. From these backgrounds, there are a lot of researches of sloshing for those oil tanks and those nuclear power plants. On the other hand, there are few researches for settling tank in purification plant. Settling tank in purification plant is an important lifeline essential to economy and activity. Therefore, it is necessary to take measures so such kind of damage will not occur again. The purpose of this study is to propose high rate plate settler module with mechanism, which can suppress damage by liquid sloshing and has good repairability. In this paper, we examined that the sloshing occurred by purification plant inclined plates were moved in a long period ground motion. When the inclined plates damaged and falling off, its have became a problem. Therefore, we proposed vibration control devices. Authors performed the sloshing experiment by the miniatures, and investigated the effect of the vibration control devices. Authors carried out the identification of the result based on Housner theory, construction of the analysis model by mass system. Examination of sloshing damage carried out by using the analysis model.

The size of the container crane is recently increasing large, according to the size of container ship which will be large in order to make more international shipping cost efficient. The eigen frequency of it is reduced in proportion to the size which make constraint of weight against the quay structure. Low frequency vibration lead to inhibition of its operation of cargo handling. In this study, we present the method of design for a structure and a control each other, and demonstrate the effectiveness and impact of this method by simulation. Also we indicate the effect of reduce a vibration of real container crane by filer for input operation signals.

In Japan, large number of technologies have been developed to prevent damages of structures from large earthquakes. However, recently not a few building owners request vibration control of their office buildings not only for large earthquakes but also for relatively small earthquakes in order to keep comforts of the buildings. In this study, a new type of Active Mass Damper (AMD) system is developed, which is specialized for small and medium-sized earthquakes. In this AMD system, a feedforward controller is equipped, which implements feedback control simulation using a numerical model of the building and measured earthquake acceleration of the ground. By using this controller, higher vibration modes can be suppressed without control instability. In this paper, effectiveness of the proposed AMD system is verified through hybrid dynamic testing, then the system is applied to a real building. The results are discussed for these experiments.

This paper research an optimal control system design method of the semi-active seismic isolated structure. The semi-active damper has two damping coefficients and be able to change these coefficients by the degree of the control force, but the semi-active damper works only when the velocity of the damper is in the opposite direction of the control force. By this limitation, the building response by the application of the semi-active control is different from the building response by the application of the active control. In this paper, the response which should be reduced is the time which the acceleration response of the building is more than 0.25 m/s², and the purpose of this paper is to design the evaluation function which minimizes the difference of the semi-active control and the active control. To reach this purpose, the optimal control force is plotted on the velocity of damper-control force diagram, and the number of the plot of the optimal control force distributed on each quadrant is shown in histogram. The result is that the peak of the number of the plot of the optimal control force is large in case that the difference of the semi-active control and the active control is minimum.

These days, there are a lot of high-rise buildings in Japan. These buildings don't vibrate so strongly with the short period earthquake, but they are weak for the long period earthquake. When a long period earthquake happens, they will vibrate in large amplitude and continue for long periods. So it is important to make buildings stronger to the long period earthquake. Most of these buildings already have some damping devices to reduce the vibration excited by wind, but these devices won't work effectively for earthquake. In this study, the effectiveness of the active brace added for each layer of the building which already has Tuned Mass Damper (TMD) is verified. After that, the optimal number of active braces and their places to set are discussed.

A dynamic vibration absorber is used for the purpose of preventing resonance phenomena of structures. But a passive mass damper is not effective except for the specific frequency. Therefore, if there exists several modes, it is generally used several passive mass damper to suppress two or more modes of vibration. In this paper, it aims at restraining the primary and secondary modes by one semi-active dynamic absorber installed on the top of the two degrees of freedom structure. The semi-active dynamic absorber consists of a mass, springs, and air dampers. The air damper can be changed the damping and stiffness by changing the aerial inflow amount. In this paper, vibration control is performed by switching two parameters which aims at restraining the primary and secondary modes by H infinity norm.

This paper considers the optimal design of double-mass dynamic vibration absorbers (DVAs) attached to an undamped single-degree-of-freedom system. Three different optimization criteria (H_∞ optimization, H₂ optimization, and stability maximization criteria) were considered for the design of the DVAs. First, the analytical models of vibratory systems with double-mass DVAs were considered, and seven dimensionless parameters were defined. Five of these parameters must be optimized to minimize or maximize the performance indices. Assuming that all dimensionless parameters are nonnegative, the optimal values of one parameter for a double-mass DVA arranged in series (series-type DVA) was proven to be zero. The optimal adjustment conditions of the other four parameters were derived as simple algebraic formulae for the H₂ and stability criteria and numerically determined for the H_∞ criterion. For a double-mass DVA arranged in parallel (parallel-type DVA), all five parameters were found to have nonzero optimal values, and these values were obtained numerically by solving simultaneous algebraic equation for each of the optimization criteria. Second, a comparison of the optimized values of the performance indices revealed that for all optimization criteria, the performance of the series-type DVA is the best among the three DVAs and that of the single-mass DVA is the worst.

In order to confirm the earthquake proof safety of the nuclear power facilities, the resonance shaking table which realize the maximum acceleration 20G have been developed. Because of generating a large acceleration, the resonance shaking table have caused environmental vibration problem. As a countermeasure, the Semi Active Mass Damper (SAMD) has been developed. However, in the conventional controller design of SAMD, the parameters of the controller have to be determined by trial and error in order to get satisfactory results. Therefore, if the experimental condition is changed, it is necessary to perform trial and error again. To remove this complex procedure, an adaptive digital filter called Filtered-X is adopted to the controller design of SAMD. In this study, shaking tests were done using the resonance shaking table under 20G acceleration, then effectiveness of the proposed adaptive controller is shown that the site boundary vibration level was lower than the regulation value , and also better performance was obtained compared to the conventional method.

The structure causes a resonance at the natural frequency and large vibration occurs. As a method to shift the resonance frequency, the dynamic absorber using the additional mass is known well. It is known that the dynamic absorber is effective at the specific frequency, but is ineffective in the other frequency band. Because the resonance frequency depends on the stiffness, it is necessary to devise a semi-active dynamic absorber to change the stiffness by the frequency of the structure. In prior research, there was a problem of ”the occurrence of acceleration disturbance.” In order to improve the problem, a variable stiffness mechanism is realized by meshing the rack gear using the solenoid actuator which has a small operating range. The stiffness of the dynamic absorber is changed according to the frequency of the structure, and it is verified that the effect of the semi-active dynamic absorber by simulations and vibration experiments with some seismic waves.

This paper proposes a new design method of a position control system (PD controller) for active mass damper systems including neural oscillators. Our previous system provided rectangular desired values for the auxiliary mass of active mass damper in the neural system. Due to the rectangle shape, the AMD system generated appreciable acceleration as the direction of motion of the auxiliary mass changed during operation. In order to reduce the impulsive acceleration, a new neural system, which could generate smooth desired values, was proposed. However, the proposed new system acquires appropriate control gains to drive the auxiliary mass to the desired value. Therefore, the new design method of the PD controller is proposed and verified in numerical simulation.

In the vertical floor isolation system, rocking vibration of seismic isolated equipment is excited by horizontal earthquake motion. This paper deals with a dynamic absorber applicable to rocking vibration reduction of the vertical seismic isolated equipment. The proposed system is a rolling pendulum type dynamic absorber using magnetic damper, which is composed of circular rails, a rolling body including magnets and a conductor plate. The design method for the dynamic absorber and the evaluation method for vibration reduction effect are showed in this paper. The dynamic characteristics are also examined by vibration test. It is confirmed from the vibration tests using a rocking model apparatus that the proposed dynamic absorber is effective for rocking vibration reduction.

The optimal design method of double-mass dynamic vibration absorbers (DVAs) is discussed with respect to the minimization of the maximum amplitude magnification factor. The performance of a double-mass DVA is superior to a single-mass DVA with the same mass ratio, although the design methods are still the subject of studies. The design optimizations of double-mass DVAs that are arranged in parallel or series are formulated precisely using an optimality criteria approach in which the optimal parameters are obtained as the numerical solutions of simultaneous algebraic equations. The primal equations are derived using Vieta's formula with the assumption that the optimal design is realized with three resonant points of equal height. The additional equations are derived as the determinants of Jacobian matrices that are defined using the primal equations. After rearrangement, these formulations realize the direct numerical solution of the design optimization via the solution of simultaneous algebraic equations. Examples are provided that prove the effects of double-mass DVAs. The formulations used in this study are variants of the algebraic approach developed by O. Nishihara that realized the closed-form algebraic exact solutions to a popular design optimization of a single-mass DVA. The well-known design formulae that use the fixed points by J. P. Den Hartog and J. E. Brock correspond to an approximate solution to this problem.

One of effective ways to suppress vibration of a mechanical system is using a dynamic vibration absorber. The dynamic vibration absorber consists of a mass, a spring and a damper. The optimal tuning of natural frequency and damping ratio of the dynamic vibration absorber is required to suppress vibration. So, to add an adjustable mechanism of stiffness and damping of the dynamic vibration absorber becomes easy to tune. This paper proposes a new design method of an adjustable dynamic vibration absorber consisted of an adjustable mechanism of stiffness and damping. The adjustable mechanism of stiffness consisted of an arm, coil springs and a rotatable spring holder. Restoring force of coil springs was changed by rotating the spring holder. The adjustable mechanism of damping consisted of a copper plate, magnets and a linkage. Damping was changed by rotating the driving link. We made the proposed adjustable dynamic vibration absorber and verified whether the proposed adjustable mechanism is valid by experiments. In addition, we study the effect of mass of base, spring and damping in a dynamic vibration absorber on vibration control characteristics. We found the optimal tuning in consideration of that mass and confirmed the effect of the optimal tuning in consideration of that mass by experiment.

This study proposes a high-performance linked fluid inertia mass damper. The damper (LFIMD) has three distinguishing properties; the first one is the damping effect by viscous fluid, the second is inertia mass effect by high-speed moving fluid, the third is ability to make deformation distribution uniform by hydraulic link system. In this study, we define “high-performance of the damper” as exerting relatively greater inertia force than viscous damping force. In the first part of this paper, we try to improve the performance by changing working fluid with different density. The test shows inertia force and negative stiffness increase as the density of the fluid increase. Next, we demonstrate how the negative stiffness works to improve seismic response control performance by shaking table test.

The author developed a vibration suppression device that utilized magneto-rheological fluid (MR fluid) and long bypass pipe in order to get an effect of series inertia mass. The inertia effect due to the series inertia mass makes natural frequency of 1DOF system lower, and it also cut off vibration at anti-resonance frequency. Amplitude of the effect depended on not only a cross sectional area of bypass pipe but also fluid density and length of bypass pipe. If the cross sectional area can be switched when diameter of the bypass pipe makes virtually changeable for clustering particles of MR fluid under strong magnetic field by electromagnets; the variable inertia effect which acts as the series inertia mass might be artificially derived. In this paper, to confirm the variable inertia effect, trial damper which had twelve electromagnets along the bypass pipe was manufactured and dynamic properties of the damper were measured in some current cases of electromagnets. Finally, variable inertia effect was confirmed experimentally.

Eddy currents are generated by the relative motion of a conducting plate and a magnet. Magnetic damper is a device that utilizes the magnetic drag force produced by the eddy current. The author call the magnetic damper moving parallel to the conducting disk the parallel-motion type magnetic damper. The author previously proposed the vector potential method for magnetic damper. The method has a good point that magnetic damping force can be calculated accuracy when a parallel-motion type magnetic damper is composed of rectangular magnets with alternating directional magnetic poles and a conducting plate. Generally ferromagnetic metal, for example a steel plate (S45C), has a property known as concentrating magnetic flux into itself. In this paper, using image method, we propose the new vector potential method for the magnetic damper with steel plates outside the rectangular magnets with alternating directional magnetic poles. The image method is a method for calculating a magnetic field by adding image currents in order to satisfy the boundary conditions between a magnetic material area and an air area in the magnetic field and the vector potential field. Damping ratios calculated by the new vector potential method are compared to the tests. As a result, analytical results are in good agreement with the experimental results.

In recent years, elevators to be installed in the building by the high-rise buildings are long stroke, thus elevator ropes are longer. Consequently, the natural period of elevator rope increases and gets closer to the natural period of buildings. As a result, the elevator rope hooked to the equipment of shaft wall when the elevator rope vibrates by an external force, such as an earthquake or wind. Secondary damage such as containment of passenger and elevators service stop may occur. It has become a problem. For example, The Great East Japan Earthquake in 2011, 2015cases of problem such as catch and damage of elevator ropes have been reported. Therefore, it is necessary to analyze the behavior of the elevator rope vibration in order to prevent hooked of the rope. Analysis of the elevator rope is carried out in each manufacturer. Each manufacturer has own analysis techniques. Consequently, unified evaluation and comparison is difficult. Therefore, this study is aimed at construction of analysis techniques that can be unified evaluation and comparison of the elevator rope. In this report, we examine the behavior of the elevator rope in consideration of the collision when changing the tension.

In order to estimate the vibration damping characteristics of the elevator rope, basic experiments using piano wire were executed. There are three causes of vibration damping of the rope. The first one is viscous damping which is proportional to vibration speed. The second is vortex damping which is proportional to velocity squared, and the third is mechanical damping of the wire end. The transfer function of displacement between the end of the wire and the center of the wire are measured, while changing both the atmospheric pressure and the vibration excitation amplitude. Velocity square damping becomes dominant when the vibration amplitude is large.

In the 2011 off the Pacific coast of Tohoku Earthquake, four fall accidents of the escalators occurred. These accidents, the escalator that linked the third floor from second floor dropped, occurred in the commercial facilities of the low-rise, steel-frame building. In general, the escalator is installed with one side of the leg or both sides as non-fixed style in order not to restrict motion of the escalator. However, the escalator truss might come off from the beams of the building, because interlaminar deformation with more than assumption was caused in the building where the accident happened. In new public notice about the reinforcement of the falling off prevention structure of the escalator after these accidents, the structure that an escalator never fall off was determined, 1 Structure to make enough overlap allowance, 2 Structure to take backup measures for. To make enough overlap allowance for, the escalator truss come off from the beam of building and is less likely to drop. However, it is considered that a non-fixed part collides with the beam of building by the big rolling of the earthquake; the collision may give compression and residual displacement to the escalator. From the above-mentioned background, the object of this research is to construct of an analytical model grasping behavior at earthquake for an escalator, which considered collision with the beam of building. In this paper, I perform earthquake response analysis in using the restoring force characteristics model, was built by the compression experimental value using the escalator truss of the original size, and Bi-linear model in this study until now, and I examine behavior at an earthquake for an escalator.

In previous study, the research and development of laminated type base isolation device using urethane elastomer was carried out to upgrade a seismic safety for various structures. The fundamental characteristics was investigated from several loading test by using various experimental devices, and the design formula for the stiffness and equivalent damping coefficient is formulated as an approximate expression of mechanical characteristics until now. The mechanical characteristics based on the loading test up to 500% shear strain using experimental specimen with 100 × 100 mm cross-sectional shape. It was confirmed that urethane elastomer is not hardening up to 500% shear strain. Moreover, the experimental examination for aged deterioration in the urethane material has been continuously carried out. As the results, it was confirmed that the laminated type seismic isolation device using urethane elastomer is possible to develop as a practicable device from the stable mechanical properties as considering in design step. In this study, the small-scale laminated type base isolation device using urethane elastomer is advanced to the direction of further technical upgrading and of scale down for light-weight structure as a sever rack. The first stage, basic properties of the urethane elastomer has been investigated by loading test. The second stage, the compression creep test with laminated type base isolation device has been investigated to confirm an effect on light-weight mechanical devices.

Damping properties of foamed plastics is analyzed experimentally using an impulse technique. To investigate the influence of expansion ratio on vibration damping characteristics, vibration tests are implemented. The damping capacities of foamed plastics are identified by using the experimental result. These results show that it is important to take the effect of the expansion ratio on the material damping into consideration.

Magneto-rheological elastomer (MRE) is a class of smart material whose rheological or viscoelastic properties can be varied by applying external magnetic fluid. The MRE is the solid analogue of magneto-rheological fluid (MRF) and expected to overcome the disadvantages of the fluid such as the particle deposition and the sealing problems. When such MRE is exposed to external magnetic field, the strength of the inter-particle force will change and thus their apparent elastic modulus is changed depending on the magnitude of the field. In this paper, the MRE is then applied to the vibration isolating mounts along with variable stiffness control scheme. Before designing the vibration isolator, the magnetic field analysis was performed by the finite element method (FEM) in order to find out how much magnetic field is applied to MRE. Then, three type variable-stiffness vibration isolator applied the MRE are developed, and evaluate each of the transmission characteristics. Experimental investigations suggested that the proposed anti-vibration mount with variable stiffness property may be possible to suppress the vibration than conventional one in a wide range of frequency band.