On the brace placement problem in steel framed structure, examples of optimal solutions have been presented in conventional studies. However, there are solution forms that cannot be applied by the purpose of use and design of building. Therefore, the search for the extremal solutions with a high evaluation is important. In this study, simultaneous optimization of brace placement and member cross-section in the framed structure is performed using firefly algorithm (FA). FA is the optimization method to obtain multiple approximate extremal solutions at one trial. We evaluate solutions by implementing two clustering schemes and dimensionless computational parameters to FA.

In the process of design of building structures, it is important to reduce the roof displacement to maintain serviceability of a high-rise building. In the existing optimization methods for seismic performances of building structures, the locations of braces and cross-sections of beams and columns are not simultaneously considered as design variables, and the responses against static design loads defined in design codes are usually considered. In this study, these variables are simultaneously optimized for a braced plane frame to reduce the roof displacement, and new load path is obtained against horizontal seismic loads. The responses are evaluated using response spectrum approach. The properties of optimal solutions are verified using time-history analysis for artificial seismic motions compatible to the design response spectrum.

In order to remove nuclear fuel debris in the Tokyo Electric Fukushima first Nuclear Power Plant, it is necessary to grasp the shape of nuclear fuel debris under water. The properties of nuclear fuel debris are expected to be porous and complicated shapes, and it imposes severe constraint conditions on sensor size and transport that can be used for inspection. In this study, considering these conditions, we reconstruct a shape of steel slag sample by a three dimensional synthetic aperture focusing. So, we evaluated it quantitatively to compare with precise shape data by photogrammetry.

In recent years, a new ultrasonic nondestructive testing that utilezes nonlinear ultrasonic behavior generated in crack or at bi-material interface has emerged. In this research, in order to simulate nonlinear ultrasonic waves, dynamic contact problems of crack surfaces are investigated by MPS method. Numerical results show that higher harmonics are excited by the crack opening and closing states.

Guided wave has been applied to a wide variety of non-destructive testing for a plate, bar and pipe, among others. In this study, we propose a wireless sensing system for the guided wave testing in structural components. Here the guided waves are generated at multi-points with a hammer and received at a fixed position. Using the electrodynamic reciprocity theorem, we visualize the three-dimensional propagation of the guided wave in an I-beam metal specimen. Here, the proposed technique is validated by comparing between the propagation mode extracted from the visualization and calculated with the semi-analytical finite element method.

In recent years, ultrasonic nondestructive evaluation has particularly been important to investigate flaws inside various structural materials. The goal of the ultrasonic nondestructive evaluation is to estimate the position, size, and distribution of flaws. In this study, we attempt to reconstruct the shape of a flaw in the austenitic steels which have the anisotropic property by using the time-reversal method. After the formulation of the FDTD method for obtaining scattered wave data from a flaw and discussion about anisotropic elastodynamic theory, some numerical results are shown to validate the time-reversal method for flaws in the austenitic steel.

Soft and heterogeneous ground is widely distributed in Japan. When embankment is built on soft ground, it is necessary to conduct ground survey and set ground improvement range. The ground improvement range is determined by analysis simulation, and various parameters are necessary for analysis. In this research, we discuss the difference of results by analysis parameters set from the ground survey results.

If edge-opened carbon nanotubes (CNTs) are inserted into polycyclic aromatic hydrocarbon (PAH) atmosphere, PAH molecules spontaneously enter the CNTs and tend to create their stacks. In this paper, encapsulation of coronenes, sumanenes, and corannulenes into a CNT is studied using molecular dynamics simulation. We discuss how these PAH molecules create their stacks, how the tilt angles of the stacks depend on the CNT diameter, and how their stacking morphologies depend on their molecular geometries. Since coronene is a planar molecule whereas sumanene and corannulene are bow-shaped molecules, their stacks have the geometrical characteristics according to their molecular shapes.

Thermal radiation in a packed bed is controlled by temperature, emissivity, particle size, and bed structure, including void fraction, particle configuration, and the number of contact points. Thus, thermal radiation plays an important role in higher temperature operation of bed reactors. In this study, effect of the radiation/conduction ratio, namely, the Biot number with a thermal radiation coefficient, on effective thermal conductivity was investigated to clarify heat transfer in a packed bed. The Biot number for thermal radiation was defined as a function of temperature, particle size, emissivity, and configuration factor. The results obtained by the homogenization method showed that effective thermal conductivity with thermal radiation is simplified by the Biot number. Finally, the behavior of thermal radiation in the packed bed can be expressed by a sigmoidal function with the Biot number, even though the bed structure is complex.

The prediction of the hydrocarbon Droplet Size Distribution (DSD) is one of the weaknesses of current underwater oil spill models. In this work, we compare the predictions of empirical DSD models with laboratory mesoscale experiments with and without the application of chemical dispersants. Even after fitting the empirical parameters, the models showed limited accuracy in predicting the droplet median diameter. More robust DSD models are needed for accurate predictions without the dependence on fitting parameters.

A numerical simulation study was carried out to investigate the effect of thermo-solutal Marangoni convection on the flow patterns and the azimuthal wave number in a liquid bridge under zero-gravity. The liquid bridge in the model represents a three-dimensional half-zone configuration of the Floating Zone growth system. Three-dimensional field equations of the liquid zone, i.e. continuity, momentum, energy, and diffusion equations, were solved by the PISO algorithm. The physical properties of the silicon-germanium melt were used (Pr = 6.37×10^-3 and Sc = 14.0). The aspect ratio Asp was set to 0.5. Computations were performed using the open source software OpenFOAM. The numerical simulation results show that the azimuthal wave number changes due to the competing contributions of thermal and solutal Marangoni convective flows.

InGaSb crystals have been grown on the International Space Station using a GaSb (feed) / InSb / GaSb (seed) sandwich-structured sample. To shed light on the experimental results, numerical simulations were carried out to investigate the transport phenomena and mechanisms during the dissolution process of InGaSb crystal under zero-gravity. Simulation results showed that the dissolution lengths of feed and seed crystals were determined by the temperature along the seed interface. The results also indicate a 3 K temperature difference between the inside growth ampoule and the outside cartridge.

The post-K computer development plan under the FLAGSHIP 2020 project launched by the Ministry of Education, Culture, Sports, Science and Technology(MEXT). In the FLAGSHIP 2020 project, nine social and scientific priority issues to be tackled by using post-K computer were widely announced. One of the nine priority issues is “Accelerated development of innovative clean energy systems”. Here, multiphysics simulations for the acceleration of design and development of clean energy systems such as wind farm and coal gasifiers are investigated. In this paper, we would like to introduce current activities of R&D for post-K computer.

This computational study provides useful information for predicting dynamic crack propagation accompany with hydrogen leakage in pressure vessels as an important part of assessing hydrogen as an energy vector. The present study was conducted by using a hybrid of the coupled particle and Euler methods. According to this new computational approach, the hydrogen concentration in outer space was numerically predicted with different boundary conditions and several kinds of crack propagation shapes in the high-pressure tank wall.

A computational method with a multiphase model was applied to the local scour and deposition on a gravel bed, consisting of about 16,700 gravel particles with a diameter of around 7 mm, caused by falling overflows from a rectangular-notch weir. In the computations, representative 26 shapes of gravel particles were modeled with tetrahedron elements and contact-detection spheres. It was confirmed that the predicted heights of gravel beds are in good agreement with those of the experimental results. In addition, a dam-break flow was calculated on a gravel bed, including about 53,500 gravel particles, to demonstrate the applicability of the present computational method to larger problems.

In this research, we consider developing a fluid-structure interaction analysis system involving free surface flows and structures. The conventional serial staggered approach of the particle method and the finite element method is applied for fluid-structure interaction problems. For cost saving in system developing, we attempt to use open source software. Therefore, we utilize the REVOCAP_Couler as a coupling environment and the ADVENTURE_Solid as the FEM software. For a code verification, we demonstrate numerical examples of FSI problems.

We propose a model for mesh-free particle methods to improve conventional ones that analyze the interaction between rigid bodies and free surface flow by using a polygon wall boundary representation. Conventional models allocate rigid particles inside rigid bodies, but the proposed model sets polygon walls only on the surface of the bodies. Consequently, it is expected to reduce the amount of computational cost. In addition, it can improve the robustness and accuracy of the analysis.

We have been developing a series of fluid–structure interaction (FSI) models, in which structural analysis is conducted by the finite element method and the free-surface flow is done by mesh-free particle methods. In this study, we conduct two-dimensional simulation, which reproduce a sloshing tank experiment with elastic beam, as a validation test of the proposed FSI model. We compare result of the proposed FSI model with the experimental one.

In this study, a FSI design approach of an insect–inspired MEMS wing is proposed. Similar to actual insects, the proposed design actively uses the FSI to create the passive wing motion. Each design solution has a so-called 2.5–D structure for the MEMS technology. The 3–D unsteady monolithic FSI equation system is solved to find the satisfactory design solutions using a projection method. An area of satisfactory design solutions in a design parameter space is found. Each design solution in this area can generate the thrust sufficient to support the weight of the model insect.

A strongly coupled multiphysics analysis of the electric-structure-fluid interaction in micro electro mechanical system (MEMS) using the finite element method is presented. The strongly coupled electric-structure interaction is based on the block Gauss-Seidel (BGS) iteration scheme, while the strongly coupled structure-fluid interaction is based on the projection scheme. A novel translation algorithm for the electric force and the structural displacement accurately takes into account the electric-structure interaction in MEMS. Therefore, this algorithm combines these schemes to analyze the strongly coupled electric-structure-fluid interaction in MEMS. The proposed method is applied for a flexible piezoelectric bimorph actuator in a channel to demonstrate its performance.

This paper presents a time dependent enrichment for an interface-reproducing extended finite element method (XFEM) for flow with sharp interfaces and deformable thin structures such as shells, beams, and membranes. The enrichment is formulated to be consistent to the Lagrangian time derivative of the enrichment function. The numerical data with and without the time dependence are compared to the interface-tracking computation using arbitrary Lagrangian-Eulerian (ALE) coordinates. We found the time dependent enrichment enhances stability and accuracy of the interface-reproducing XFEM for fluid-thin structure interactions.

Resistance spot welding is widely used in manufacturing industry. Analysis of resistance spot welding is required for examination of welding mechanism and determination of welding parameters such as weld current, electrode force and weld time because welding parameters are obtained empirically. In this paper, effect of structure–electric current–thermal conduction triply coupled model on resistance spot welding analysis results are examined to make analysis more efficient. Statistically similar representative volume element size and resolution of finite element analysis model are also discussed for microscale electrical contact resistance analysis of multiscale resistance spot welding analysis.

To develop new FRP products with high design freedom, enormous experiments such as coupled and multiphysics phenomena are required. Due to strength anisotropy and nonlinearity in fiber direction, CAE design utilised mixturing rule and homogenization / localization analysis was not convenient. In this paper, focusing on unit cells, auther introduced a simple and straightforward exclusive finite element model for FRP with high-strength material as continuous elastic beam, and base matrix material as isotropic solid element, and made a prospect for coupled and multiphysics analysis.

On unpaved road, we often encounter the washboard-like corrugation that forms spontaneously. A counterintuitive fact is that the corrugation is not flattened but grows with time under heavy traffic volume. In the present work, we have considered the formation mechanism of the spontaneous road corrugation. Our analysis is based on a series of partial differential equations that involve several soil parameters; we thus performed consolidation tests for unsaturated soil and evaluated the values of the parameters. The numerical simulation allowed us to reveal the sufficient conditions associated with characteristics of cars and soil, under which the surface corrugation grows with time.

In this study, shaking table tests were conducted on a model of seismic isolation building to observe responses due to collision with a retaining wall. The test results indicated that the relationship between the maximum story shear force and collision velocity was linear. In addition, large floor acceleration occurred during the collision and it depended on the wall rigidities.

We proposed a new damper called an on-off damper that can vary the damping force depending on the response displacement and response velocity. The on-off damper reduces the damage of seismic-isolated structures which undergo excessive deformation during huge earthquakes, without lowering the performance of the seismic-isolation system during medium to small magnitude earthquakes. We investigate the effects of using the proposed attenuator on the responses of a superstructure model to seismic motion that causes collision with retaining walls. An experiment using a shaking table is conducted, and the results from the test are compared with those from numerical analyses.

In 2015, the Architectural Institute of Japan design concept against accidental actions was published as the book titled “Introduction to Shock-Resistant Design of Buildings”. In this design concept, a single-degree-of-freedom (SDOF) model is used as a basic tool for calculating peak responses of individual structural members under the identified action. It seems to be prudent for practical design purposes to adopt approximate methods that permit rapid analysis of complex structures with reasonable accuracy. In this report, to confirm the validity of the response analysis results from the SDOF model, a collision analysis is performed on the same column using finite element model.

This Paper presents a simulation for a full scale falling rock protection net by using 3D distinct element method (DEM). Collision experiment of full scale falling rock protection net has been carried out in advance The dynamic deformation process of wire net is recorded by video and high speed camera and the deformation process of wire net is recorded by video and high speed camera, and the tension of anchorage wire-ropes are measured. On the other hands, the steel net and wire ropes are modeled by cylindrical and spherical elements in 3D-DEM. An elastic-plastic constitutive law which has cut-off point associated with the broken wires to express limit state is adopted.

Many empirical formulas have been proposed for evaluating local damage to reinforced concrete (RC) structures caused by impacts of rigid missile. Most of these formulas have been derived based on impact tests perpendicular to the target structures. Up to now, few impact tests oblique to the target structures have been carried out. This study has been conducted with the purpose of proposing new formula for evaluating the local damage caused by oblique impacts based on previous experimental and simulation results. In this paper, the results of simulation analyses for evaluating the local damage to a RC Structure subjected to normal and oblique impacts by missiles, by using the simulation method that was validated using the results of previous impact experiments. Based on the results of these simulation analyses, the effects of the rigidity of the missiles as well as the impact angle on the local damage to the target structures are clarified.

Window glass destruction due to impact objects can cause serious human injury, thus to consider of window glass property placed on building facade is important for shock-resistant building design against impact actions. In this study, destruction moment of glass windows due to flying objects is observed with high-speed camera through the impact loading experiments, and behavior of scattering glass window pieces is quantitatively estimated. Test specimen and test situation are simulated FEM analyses. As a results, it is assured that numerical simulations can adequately reproduce window glass behavior broken into pieces and their scattering as recording in the experimental tests.

A new method of earthquake robustness evaluation is proposed for an elastoplastic base-isolated high-rise building considering simultaneous uncertainties of structural parameters. Since it is difficult to evaluate the earthquake robustness of elastoplastic structures due to heavy computational load on the time-history response analysis, the closed-form expression of the critical response of a single-degree-of-freedom elastic-perfectly plastic structure under double impulse is used. To evaluate efficiently the degree of robustness in terms of the robustness function proposed by Ben-Haim, an upper bound of the critical elastic-plastic response is derived under the structural uncertainties.

In recent years, studies on the collapse behavior of structures when column loss occurs have been conducted. However, there exists no study on optimization of member cross-sections of a frame structure considering column loss. In this study, an optimization method for structural redundancy is proposed. The collapse load factors in case of loss of each column are calculated by the limit analysis. The minimum value of these collapse load factors is maximized by a genetic algorithm (GA). The usefulness of optimization considering column loss has been studied through the numerical experiments.

The purpose of this study is to propose a systematic enumeration method of various optimal truss topologies considering structural redundancy against member fracture. In the present paper, this problem is formulated as a truss topology optimization problem, which is to find the configuration of truss members such that the structural volume should be minimized. This problem can be solved by the branch and bound method with heuristics method. The applications of the proposed method are illustrated in some numerical examples with discussion on characteristics of design results.

The austenitic steel which has the acoustic anisotropic property is generally used as structural material of nuclear power plants. It is known that the stress corrosion cracking (SCC) occurs in the austenitic steel on high temperature and pressure corrosive environment conditions. Therefore, it is essential to develop an ultrasonic non-destructive testing technique for early detection of defects. In this research, a linearized inverse scattering technique with the aid of the convolution quadrature time-domain boundary element method (CQBEM) has been developed for the reconstruction of a defect shape in an austenitic steel.

The phase-field (PF) model has been used for simulating microstructure evolutions in various materials. However, likewise other simulation methods, since the PF model needs immeasurable parameters and unknown simulation conditions, the data assimilation (DA) attracts attention for reproducing realistic microstructure evolution by integrating experimental data to the PF simulation. In this study, we implement the ensemble Kalman filter to two-dimensional PF simulation of dendrite growth in Al-Cu alloy and estimate the strength of interfacial anisotropy which characterizes the morphology of dendrite. Our DA methodology is validated by conducting twin experiments and the true value of the interfacial anisotropy is successfully estimated.

Reconstruction of impact force history from corresponding impact responses such as strain, acceleration, displacement, etc. is useful when measuring impact force acting on structures. In this study a wavelet deconvolution technique was applied to the impact force reconstruction. First, deconvolution technique using Haar wavelet was formulated. Then finite element simulation on the impact crushing of thin-walled square column was conducted. Comparisons of the reconstructed impact force to the one obtained by the finite element analysis demonstrated effectiveness of the wavelet deconvolution technique.

In Japan, the proportion of rubella susceptible person's is currently near the threshold above which a major epidemic may occur. During 2012/13 the number of rubella cases in Japan was relatively large in recent years. The maximum number of weekly reported cases was 168 in Tokyo Prefecture and 268 in Osaka Prefecture while 1-2 or no cases are reported per week in usual years in each prefecture. This epidemic is almost limited to the metropolitan area while below ten cases per week were reported in 30 prefectures. Such a geographical contrast in reported cases reflects that the susceptibility is very close to the threshold of major outbreak. It is necessary to take into account a spillover of the disease via the person's movement and stochastic nature of transmission in order to reproduce such an infection trend. In the present study, it is shown that the 2012/13 epidemic is reproduced better well by a stochastic meta-population model. Using this model, we have compared the final size (total number of cases over an epidemic) between equal and weighted distribution of vaccines and found that concentration to the largest three prefectures minimize the final size.

The multi-material structure in which steel members support high load and the other members are made of light metal such as aluminum alloy is becoming mainstream in automobile industries. The bolted joints in the structure are required to apply proper jointed load. This study has proposed a novel method to extract the surface texture parameters based on the data set of the jointed load and the natural frequency of the target by using the data assimilation. Moreover, applying the proposed method, the jointed load was estimated from the arbitrary natural frequency by using a few sample of the data set.

In recent years, small earthquakes repeating on subduction zones of crustal plates have attracted much attention for earthquake prediction. Small repeating earthquakes are analyzed for monitoring interplate slip because their recurrence times reflect the quasi-static slip rate around their fault patches. Thus, we propose a space-time model extended from a renewal process to estimate the spatio-temporal distribution of slip rate on plate boundaries and apply it to a repeating earthquake catalog in Northeastern Japan.

Space debris is an artificial and useless object orbiting around the Earth. Fragments generated by breakup events is the most common in observed and tracked objects. The history of orbit is opened for public. However, the physical properties of orbiting object are not disclosed. The aim of this study is to estimate physical properties of fragments generated by breakup events using history of these orbits. Particle Markov chain Monte Carlo methods is adopted for estimating physical properties of fragment.

Structural system identification was performed for three story frame structural model using the projection filtering algorithm as inverse procedure. Natural frequencies were used as the observations in the inverse analysis. In this study, 1st vibration mode was just adopted as the observations from viewpoint of practical. In this paper, possibility of inverse analysis using lower vibration mode as the observations are made clear through some simulation inverse analysis.

A newly built ship is required to conduct several examinations due to understand the performance such as the speed, the maneuverability and so on. Espetially, the result of the speed trial is very important for the owner of the ship, because the ship’s speed is directly related to profit. In this case, a tidal flow and a ocean current become important factor. To remove these effect, nternational Towing Tank Commitee (ITTC) and International Standardization Organization (ISO) decided the procedure. However, the procedure is complex. To solve this difficulty, we attempt to estimate the tidal flow and the ocean current from ship motion.

In this talk, we will discuss the numerical analysis of the time harmonic Kelvin-Voigt type viscoelastic equation in order to realize MR Elastography, which is one of modalities to identify the stiffness of human tissue. The minimizing problem of a certain cost function is proposed for the identification and it requires numerical computation of direct problem of the equation. However, accurate computation by the conventional finite element method is hard in this situation. In this presentation, we will show that the nonconforming finite element method is efficient by some numerical examples.

The elastic stiffness constants are fundamental information for ultrasonic nondestructive testing of carbon fiber reinforced plastic (CFRP). In this research, the elastic stiffness constants are determined using wavefield data of ultrasonic propagation on surfaces of a unidirectional CFRP. First the ultrasonic wave propagation is experimentally visualized by a non-contact ultrasonic generation method using scanning laser excitation. Then the direction-dependent phase velocity distribution is obtained from the wavefield data processed by the time-space Fourier transform. By optimizing the elastic stiffness constants in the Christoffel equation using the measured phase velocity in several directions, five independent components of the elastic stiffness constants of the unidirectional CFRP are determined.

The second-harmonic generation characteristics at solid-solid contact interfaces subjected to an obliquely incident longitudinal wave are analyzed based on a nonlinear spring-type interface model. The interface is characterized by two linear stiffness parameters and three nonlinearity parameters. Using a perturbation method, the response of the interface is divided into the linear part (fundamental wave component) and the perturbation part (stationary and second-harmonic components). The amplitudes of the second-harmonics are obtained as functions of the incident angle, and the influence of the interfacial parameters is examined.

This paper presents a general numerical procedure for multiple scattering analyses of flexural waves on a Kirchhoff plate with arbitrary arrangements of circular holes. The time-harmonic deflection field of the plate is given as the sum of the incident wave fields and the scattered wave fields by the embedded holes. Considering the vanishing bending moment and shear force at the periphery of holes, we construct a set of linear algebraic equations with respect to wave expansion coefficients of the exciting field alone using the multiple scattering theory and the numerical collocation technique. These linear algebraic equations are solved by the periodicity assumption of the hole arrangement perpendicular to the propagation direction of the incident wave. Using the proposed method, propagation characteristics of flexural waves are analyzed for hexagonal arrangements of circular holes with different concentrations. The energy transmission spectra of flexural waves are shown to capture the detailed features of the stop band formation.

An upper and lower bounds analysis method of eigenvalue problems by the nodeless element method has been proposed in this paper. At first stage, the upper bound of eigenvalues and eigenvectors of problem are analyzed by the variational principle of strong form of the nodeless element method. Next stage, the lower bound of any one pair of eigenvalue and eigenvector is given by inverse analysis for the eigenvector of the first stage using the weak forms of variational principle of the nodeless element method. This method is particularly effective for the broadband frequencies of solid mechanics. An example of analysis of the natural vibration of flat plate is shown in this paper.

This paper studies an axisymmetric elastic contact problem of an elastic layer bonded on elastic substrate indented by a rigid flat-ended cylindrical and spherical indenter. The analytical solutions are obtained by solving an infinite system of simultaneous equations. The accuracy of values of present numerical results is verified by comparison with the results of some previous studies. Additionally, we presents not only the distribution of the dimensionless normal contact stress under cylindrical and spherical indenters but also the distribution of the dimensionless normal displacement at the upper surface of the elastic layer and the stress singularity factor.

The ballast settlement of a ballasted track with a railjoint is simulated using a coupling method of wheel-track vibration analysis and ballast settlement analysis. The wheel-track vibration is modeled as an assembly of beams, masses and dashpots, while the ballast settlement phenomena is modeled with elastoplastic FEM with cyclic densification model. The influence of the existence of a rail irregularities around a railjoint on the simulated ballast settlement is investigated through numerical tests. The rail irregularities with a typical shape observed in a rail around a railjoint causes a relatively large permanent displacement of ballast surface near a railjoint. In the track without rail irregularities, the ballast settlement at the railjoint is smaller than one beneath the sleepers near a railjoint.

In order to investigate the characteristics of radiation behind reflected air shock waves, shock tube experiments were performed systematically. The radiation behind the shock wave was observed by a high-speed video camera. The composed chemical species behind the shock waves were examined by using narrow band-pass filters. Also, we analyzed radiation spectra by using the basic radiation theory, and we compared the theoretical results with the experimental ones.