For the purpose of improving measurement accuracy of bender element test, the vibration characteristics of several bender element and self-monitoring bender elements with different dimensions and geometries were evaluated at multiple points by a laser displacement sensor. The elements exhibited damped vibration following multi-degree-of-freedom system with several natural frequencies. As a result of experimental modal analysis, an unexpected eigen mode consisting of transverse bending motion, which is beyond the assumption was observed in all the elements. Considering modelization of the element vibration using modal approximation, responses of the elements were reconstructed based on frequency responses which were approximated by superposition of the eigen modes, and compared with the observed responses. The responses reconstructed using the two main eigen modes well reproduced the observed ones, and resulted in mean error through the whole element surface of approximately 10% in the respective elements.

In this study, a free vibration analysis method for anisotropic laminated plates using the region-wise zig-zag theory has been proposed. This theory is a theory that combine improved zig-zag theory and layer-wise theory in order to apply it to structures reinforced with composite materials. By setting the region in the plate thickness direction, accurate natural frequencies can be calculated effectively not only for out-of-plane vibration modes but also for in-plane vibration modes. The accuracy of this theory for moderately thick plates is investigated, and the method using virtual lamina is applied to the region-wise zig-zag theory to verify the accuracy for thick plates.

The pulsed laser beam irradiation of a material induces the rapid rise of the thermal stress, and then the stress wave generates and propagates into the material’s interior. This phenomenon is known as the photoacoustic effect, and the generation of the elastic waves in the ultrasonic frequency range has been confirmed experimentally. This study aims to develop a numerical model to simulate the generation and propagation of ultrasonic waves due to the photoacoustic effect. Here, the heat conduction and the elastic wave problems are solved in a coupled manner using the discretization by the finite integration method. For the water immersion non-destructive inspection, a propagation simulation in the wave field, including the interface between solid and liquid, must be considered. The simulation result showed that the intensity of longitudinal waves toward the bottom of the material from the laser irradiation through water was higher than the one through the air. The validation by an experimental measurement was conducted, and the same phenomenon was observed.

The performance of existing structures varies over time due to aging and damage caused by various environmental factors. Therefore, it is necessary to properly assess the residual performance for their lifecycle management. For this purpose, it is essential to calibrate the numerical model based on observations, so that the model responses are tuned as close as possible to the actual behaviors. In this study, we propose a hierarchical Bayesian model updating framework using the Bhattacharyya distance and staircase density functions to quantify uncertainties in the model parameters. Through simple numerical examples, the proposed method is compared with the conventional Bayesian inference. The results demonstrate that the proposed method is robust to various distribution shapes and capable of quantifying various types of uncertainties such as measurement errors or/and model parameter uncertainties.

This paper analyzes the factors in the shear fracture behavior of reinforced concrete beams using numerical simulation based on experimental design. The non-linear finite element analysis with a damage model is applied to the fracture simulation of reinforced concrete beams. The shear fracture behavior, similar to the experimental results, is simulated by the numerical experiments with an orthogonal array. The influential factors in the shear fracture behavior of reinforced concrete are quantitatively analyzed by the analysis of variance and the response surface methodology. The results reveal that the material strength of concrete strongly influences the shear fracture behavior of reinforced concrete beams.

In this study, ultrasonic measurements and simulations are performed to show that the time-reversal imaging works well with the reverberating wave fields and hence useful for ultrasonic testings. In the experiment, ultrasonic echoes from an artificial crack in a T-joint specimen are measured. The measured waveforms are then time-reversed and re-emitted into a finite difference numerical model for the investigation of focusing in a reverberating environment. It is found as a result that the path of the scattered waves can be traced in the time-reversed field back to its origin though their presence is hardly recognizable in the original signals. Moreover, the scattering source can be located accurately in the reverse-time migration images, thus highly robust nature of the time-reversal focusing concept has been demonstrated in a ultrasonic testing context.

Structural members of a transmission tower in a deep-snow district might be damaged due to snow cap. However, the mechanism of member deformation has not been investigated in detail because of the bad accessibility to the transmission tower in a winter season. Therefore, in this study, a remote monitoring has been conducted over 16 months in order to watch a developmental process of snow cap and measure inclination of structural members. The results of observation and numerical simulation shows that the snow cap grows asymmetrically around a structural member and that the eccentric load generates larger stress around the end of member. Another type of snow cap is developed on a joint of members. This load occurs a buckling of push-up members.

The distribution of bending stress along the direction perpendicular to the bridge axis on the flange of beams with a wide flange is not uniform due to shear lag. In the design of beams, the additional stress due to the shear lag is considered by reducing the bending rigidity by the effective width. However, it has been known that the shear lag is not caused by bending but by cross-sectional deformation associated with shear deformation. In this context, a beam theory with a degree of freedom of cross-sectional deformation due to shear is proposed to evaluate shear lag effect. While the beam theory considering cross-sectional deformation has been known to estimate shear lag effect accurately, a finite element analysis of representative volume of cross-section is required to obtain a couple of additional cross-sectional parameters. In this study, we propose a method to estimate the additional parameters using LASSO regression and Gaussian process regression. The accuracy of the proposed method is confirmed by a set of test data.

One of the primary screening methods to evaluate the damage probability and health of bridges is the VBISI(Vehicle-Bridge Interaction System Identification) method, which simultaneously estimates vehicle and bridge mechanical parameters(mass, damping, stiffness) and road surface roughness based only on vehicle vibration and position data. In the ideal case without noise, the method has been shown to have excellent efficiency and accuracy in mathematical models. However, in the presence of noise, the estimation accuracy of mechanical parameters decreases. In this study, we propose a new algorithm for estimating mechanical parameters of vehicles and bridges from big data, and attempt to improve the estimation accuracy against noise. The obtained results show that VBISI method with multiple runs improves the estimation accuracy compared to the models in the previous studies. However, it has not yet reached the level of application to field experiments. Further improvement of the estimation accuracy and its application to field experiments are considered in the future.

With the rapid increase in torrential rainfall disasters and associated landslides, the demand for predictive numerical simulations has been growing. Due to computational limits, one needs to introduce approximations, however, the parameters to link detailed and approximated simulations (e.g. drag / bed friction coefficients) are determined empirically, and their applicability remains vague. In this context, this paper presents the application of a deep learning model, PINN (Physics-Informed Neural Network) to inverse analysis. This work assumes a scenario where one has an access to limited data (which is the case for real-site observation), and proposes utilizing data’s spatial features extracted from POD (Proper Orthogonal Decomposition) instead of conventional random number-based method. We found that proposed method supports PINN for faster training convergence and efficient parameter identification.

This study proposes a method for determining an optimal shooting condition of the digital image correlation (DIC). The method is formulated based on the response surface methodology. The explanatory variables in the response surface take the F-number, the shutter speed, and ISO speed, each of which is the parameter related to the amount of light taken into the camera and strongly affects the shooting accuracy. The response surface is defined according to the central composite design and Box-Behnken design. The comparison between the optimal shooting condtion and the other conditions demonstrates that the DIC with the proposed method allows measurements with the highest accuracy.

In recent years, the importance of improving the resilience of infrastructure facilities against unexpected large-scale disasters has been pointed out. This study is fundamental research for the development of a monitoring design method to contribute to the improvement of resilience performance from the structural design side. The basic framework of the sensor placement optimization method and the adaptive real-time prediction method is proposed for the case of an embankment on a liquefiable sand layer. A set of spatial basis functions is derived from the numerical analysis results, and a method that effectively utilizes the characteristics of the spatial basis functions is proposed. For the sensor placement optimization, we confirm that the greedy method with QR-pivoting provides valuable information from an engineering viewpoint. For adaptive real-time prediction, we proposed a method that uses the marginalized likelihood to immediately select the number of spatial basis functions for prediction (model selection) and then predicts the component coefficients using a Kalman filter. Finally, the numerical results of the input seismic ground motions for validation are compared with the adaptive real-time prediction by the proposed method. It was confirmed that the proposed method improves the prediction accuracy by selecting appropriate models in real-time according to the input seismic ground motion characteristics.

In a previous study, the authors clarified the physical phenomena of concrete defects and digital hammering inspection results through experiments and FEM analysis, and developed a forward analysis model that outputs digital hammering inspection results from the defects state. In this study, an in-verse analysis model was developed to quantitatively evaluate the defects state of concrete from the digital hammering inspection results by machine learning the database created by the forward analysis model, and the accuracy of the evaluation and the effectiveness of the approach using the database were summarized.

There is concern about high-frequency vibration in steel bridge members with rail joints. However, modal damping for higher-order local vibration modes over 100 Hz is still an open program. In this study, the existing modal identification method using multi-point hammering and the reciprocity theorem that can be used in the field test is improved. A simulated generation method of free vibration responses measured synchronously at multiple sensors is developed by the inverse Fourier transform of the transfer function. The proposed method is applied to full-scale railway steel I girder bridge web members. As a result, the modal characteristics of the web members up to 2,000 Hz are clarified. In addition, the resulting modal damping ratios and natural frequencies relationship indicate that most high-order local vibrations over 300 Hz have a small modal damping ratio below 1 %.

In recent years, along with heavy rainfall, damage to bridge foundations caused by scouring has increased. Even if residual displacement occurs in the foundation, early emergency restoration is realizable if the residual bearing capacity can be retained. A Bayesian inference method for load–settlement curves of shallow foundation after scouring has been proposed previously. This method allows residual bearing capacities to be predicted using light loads. In this study, we use the abovementioned method to estimate the probability of failure during the live loads and investigate the difference in the probability of failure due to the observation error size and number of loading phases.

An application of data assimilation to the estimation of the permittivity distribution inside concrete in FDTD simulations is attempted. Specifically, the applicability of the method to the estimation of permittivity distribution is examined by using an ensemble Kalman filter as a data assimilation method for a two-dimensional electromagnetic wave propagation problem in a multi-layered material model that simply models concrete. As a result of the fundamental investigation, although the number of observed data is only one as a characteristic of radar tests, the relative permittivity of multiple internal regions could be estimated by targeting a series of radar movement processes.

SPH methods discretize a continuum with particles and update their position based on the Lagrangian description. Therefore, deformation of the domain can be represented by the movement of the particles. Besides, SPH methods generally use interpolation approximations with a fixed kernel depending on the distance from the target particle to the neighboring particles. Hence, its computational accuracy is guaranteed only when the particles are distributed regularly. Several methods to support its accuracy are proposed such as particle shifting methods, which re-arrange the particle configuration to a regular state, and the correction of differential models in response to particle disorder. In this context, we present a high accuracy second-order derivative model and demonstrate the performance improvement with several examples. In addition, we find that particle shifting methods provides higher-order approximation and simulation stability.

This paper presents a semi-analytical method for bogie-track-tunnel-soil dynamic interaction problems. The railhead roughness is considered as a random process. To evaluate the mathematical expectation of dynamic response, the relation between the railhead roughness and the expected value of energy spectrum density of acceleration at observation points inside the tunnel is derived explicitly. Based on the developed method, influence of the track-tunnel coupling structure on the frequency spectra is investigated.

Isogeometric Analysis (IGA) is effective for the structural analysis of curved members because it can maintain their exact geometry. Therefore, we developed a curved Bernoulli-Euler beam element using the NURBS basis function based on the concept of IGA. The traditional Bernoulli-Euler beam element includes the deflection angle as an unknown variable to maintain the continuity of the deflection angle between elements. On the contrary, our beam element has only displacement as unknown variables. In this study, we analyzed several types of beams. As a result, we confirmed that our IGA beam element is effective for the analysis of curved members. Especially, the beam element could be obtained equivalent performance to FEM when the cubic basis functions were used in straight beams. Moreover, it had high convergence rates of relative error compared to the traditional beam element in a quarter curved beam.

A multiphase computation method based on the phase-averaging method was applied to water-ice phasechange problems accompanied by the natural convections including density inversion regions in water. The computation method for the Stefan condition was improved in this study to calculate the freezing thickness considering the position of the water-ice interface in the computational cells. After the basic verification of the proposed method using the one-dimensional freezing problem, the experimental results of the unsteady freezing problems and those of the unsteady melting problems in rectangular cavities were calculated with the present method. As a result, it was shown that the changes in the calculated water-ice interfaces are in good agreement with the experimental results and that the natural convections with density inversion are reasonably calculated.

In recent years, a number of bridges have been washed out due to torrential rains. When analyzing scour around piers, one of the causes of damage to bridges, using particle methods such as the SPH(Smoothed Particle Hydrodynamics) methods, the non-uniform distribution of particles and tensile instability caused by negative pressure occur. We especially focus on the pressure gradient model, which has been conventionally and frequently used for stable analysis, and discuss pressure gradient calculations suitable for negative pressure regions. Moreover we introduce a modified gradient model that satisfies first-order consistency as well as PS (Particle Shifting) scheme to maintain the particle distribution regularity. The modified SPH method reproduces von Karman vortex, and its validity is quantitatively examined by comparing the twin vortex size, drag coefficient, lift coefficient and Strouhal number with experimental data.

This paper presents the method of fundamental solutions (MFS) for anti-plane wave problems of anisotropic materials. MFS is a numerical simulation method of mesh-free type and expresses an approximate solution using the fundamental solution of the target problem. In the MFS, the approximation coefficients are determined by solving the system of equations based on the prescribed boundary conditions. In this paper, we have applied three types of MFS (Standard MFS, LS-MFS, and OMP-MFS) to wave scattering problems. We discussed the performance of the MFS by comparing with a reference solution obtained by the boundary element method. From the analysis results, we confirmed that the MFS is superior in convergence for materials whose anisotropic effect is not so strong. On the other hand, for materials with strong anisotropy, the MFS shows poor convergence.

Thanks to the development of additive manufacturing technology, it is becoming possible to produce materials with desired mechanical properties defined by their periodic microstructures. To design optimal microstructures, multi-scale topology optimization has been paid attention to in many engineering fields. However, its high computational cost prevents practical use, such as high-resolution 3D analysis for precision modeling and non-linear analysis assuming actual materials. In this study, to solve this problem, we focus on the homogenization approach using fast Fourier transform and develop a new optimization method with fast computing speed and low memory requirement. By performing stiffness maximization analyses with linear elastic materials, we demonstrate the validity and efficiency of the proposed method.

The variation of sleeper reaction force and wheel-rail contact force induced by the spatial variation of geometric dimensions, material parameters and surface profile of rails are simulated with the stochastic FEM (SFEM) and the stochastic collocation method. The spatial varitation of the dimensions or parameters is prescribed with Karhunen-Loeve expansion. The influence of the spatial variation of moment of inertia, area, Young’s modulus, density and surface pofile on the simulated force is investigated through numerical tests with a certain setting of wheel running speed. The simulated sleeper reaction and wheel-rail contact force for high running speed tend to have larger standard deviations than those for low running speed.

A structure with high strength and toughness is an ideal structure for engineering. Some existing composite structures demonstrate these performances with the proper combination of ductile and brittle materials. In this study, we propose a topology optimization method to maximize the strength and toughness of such composite structures by assuming a two-phase structure consisting of a brittle damage material for strength and a von-Mises elastoplastic material for toughness. It uses a unique material representation method, which partially combines two material constitutive laws with different mathematical structures. In this paper, a series of formulations of the method are described, and some numerical results are presented.

When performing numerical calculations of incompressible density currents, it is important to use effective preconditioning for the pressure Poisson equation in order to reduce computation time. In the C-HSMAC method, which is a fluid calculation method, the incompressibility condition, which is important for obtaining valid calculation results, can be satisfied with high accuracy by iteratively solving the pressure Poisson equation at each time step. In this paper, the effect of using preconditioned Bi-CGSTAB methods for solving the pressure Poisson equation in the C-HSMAC method is discussed. As a result, it was confirmed that the preconditioning can reduce the computation time. In some cases, the number of iterations of the C-HSMAC method was smaller than that of other methods when the Multigrid method was used as a preconditioner. It is possible to expect not only a reduction in the computation time for a single iteration of the pressure Poisson equation, but also a reduction in the computation time due to the reduced number of iterations of the C-HSMAC method.

The contribution of this study is to examine the computational efficiency of Stochastic Collocation method (SC method) for evaluating dispersion in crack propagation problems. One of the advantages of the SC method is the independence between stochastic and mechanical calculations like the Monte Carlo method (MC method). The other is that the orthogonality of the Lagrangian polynomial and Gaussian quadrature rule makes it computationally efficient enough to evaluate the dispersion in a few samples. To represent brittle fracture, we employ the cohesive traction force embedded damage-like constitutive law, which incorporates a cohesive zone model with an arbittrary material constitutive law in finite element analysis (FEA). The cohesive zone model is able to represent the stress release process associated with brittle crack propagation after the maximum principal stress reaches local tensile strength. Thus, the combination between the FEA and the SC method enables us to predict the variation in brittle crack propagation due to the uncertainty in the local tensile strength and critical energy release rate. In addition, Radial Basis Function interpolation (RBF interpolation) is employed to reproduce the spatial distribution of material constants due to its dispersion in a specimen. The capability of the SC method is demonstrated throughout assessment of brittle crack propagation in comparison with the result of MC method. The statistics of brittle crack propagation, which are caused from spatial dispersion of material constants in the specimen, is evaluated by the proposed method combined with RBF interpolation.

Various damages to SUS panel tanks have been reported due to the earthquakes. These causes are due to the bulging vibration. The bulging vibration is a coupled vibration interacted the wall structure and fluid by short-period seismic motion. However, there are no design standards for bulging vibration, and it is necessary to establish those standards. In this paper, we carried out the time history response analysis of the fluid structure interaction with changing attack angles. This analysis clarifies the weak points of SUS panel tanks when the bulging vibration occurs. As a result, it was found to be maximum of the displacement at the attack angle 0°. As for the von Mises stress, the corner members are the weak points regardless of the attack angles.

The internal fluidization and the failure of a saturated granular bed due to the vertically-upward water flow entering from the bottom surface were investigated with the experiments and the computations taking account of the particle-scale fluid-solid interactions. Two types of gravel particles (average diameters are about 7 mm and 4 mm) and glass particles (diameter is about 7 mm) were used in the experiments, in which the particle movements were captured with a high-speed camera and the pore-water pressure was measured with four ultra-compact pore pressure gauges. In the computations, the fluid forces acting on up to about 21,936 particle models, each of which is represented with multiple tetrahedron elements, were calculated from the pressure and viscous terms. The number of the fluid cells was up to 117,504,000 and the maximum number of the cores in parallel computations was 2,176 to decrease the elapsed time. As a result, in the fluidized area of the granular layer, it was shown that the computation method enables us to obtain adequately the distributions of the excess pore-water pressure and the typical flow patterns of particles, which are important to understand the mechanisms on the behaviors of the particles driven by the water flows entering from the bottom.

The bentonite extrusion of crack in rock fracture must be predicted to evaluate the performance of the natural barrier system for high-level radioactive waste disposal. This paper presents a simple analytical model for predicting the bentonite extrusion of closed-end crack by considering the swelling behavior of bentonite. The swelling behavior of bentonite is assumed to be caused by volume expansion due to the absorption and diffusion of trapped fluid in closed-end crack into bentonite. A governing equation is derived based on the balance of forces exerting on bentonite, and numerical solutions are derived by solving ordinary differential equations simultaneously. The analytical results obtained suggest that bentonite extrusion depends on the external swelling pressure and viscous resistance force in the initial stage of the extrusion process, and that bentonite fills the crack over a long period owing to the absorption and diffusion of trapped fluid.

This paper investigates on the four-point flexural deformation behaviors of helicoidally laminated CFRP by the use of Digital Image Correlation method. It is found that the helicoidal laminate shows very unique deformation behaviors. Namely, in the flexural span, the helicoidal laminate exhibits large shear strain values and equivalently inclined principal strain vectors on the tension and compression side. These behaviors clearly show that the helicoidal laminate does not follow beam theory.

This paper develops meso-scale concrete models with realistically shaped coarse aggregates in three-dimension. The discrete Voronoi diagram produces coarse aggregates, each of which is then arranged randomly without overlapping in accordance with the grading curve. The volume fraction, distribution, size, and shape of coarse aggregates obtained from the proposed model are compared quantitatively with those of actual concretes. Good agreements are found between the numerical and real concretes, but the result shows that the coarse aggregate shape obtained from the proposed model is somewhat more isotropic than real aggregates.

A surrogate model for non-linear finite element analysis of reinforced concrete beams is proposed. The model is formulated based on the response surface methodology and can approximate the results of non-linear finite element analysis with second-order accuracy. The explanatory variables are determined by the sensitivity analysis of the material parameters of concrete. After verifying the accuracy of the surrogate model, we demonstrate that Monte Carlo simulation can be performed with a low computational cost by using the surrogate model instead of the non-linear finite element analysis. The proposed approach is also helpful for uncertainty quantification in the verification and validation.

It is important to establish computational methods for quantitatively predicting the montmorillonite swelling to understand the long-term mass transport behavior in geological disposal sites for high-level radioactive wastes. To this end, it is necessary to understand the hydration interaction between water and cation in the montmorillonite interlayer at the molecular scale. In this study, the distribution of interlayer water molecules and cations in Na- and Ca-montmorillonite were analyzed by molecular dynamics simulation to investigate the swelling characteristics of montmorillonite from the viewpoint of hydration structure. As a result, it was clarified that the water molecule coordination number of cations differs depending on the interlayer water content and cation species and that cations have hydration structures specific to the species and coordination number.

In this study, the effect of the enclosed air contained in unsaturaed soil on the cyclic shear was investigated numerically. First, the govering equation of unsaturated cyclic triaxial test was developed based on the mass balance equations and constitutive equations with consideration of the enclosed air. Then, the series of numerical simulations were performed to clarify the effect of the change of mass between enclosed air and continue air, and the existance of enclosed air before starting cyclic loading. The simulated results showed that the consideration of the enclosed air affected the behavior of the suction, the pore water and the air. Finally, the simulations aimed to the unsaturated cyclic triaxial test showed the good agreement with the experiment in the point of view of reproducing the tendency of decrease of the suction.

The authors have proposed a similarity law that can be applied to scaled model tests using the same materials as full-scale structures in a gravitational field by setting different dimensions for displacements and geometric lengths. The validity of the proposed similarity law was verified through experimental and numerical investigations on cantilever beams, but the theoretical basis of the proposed similarity law remained unclear. This study theoretically derived the proposed similarity law from the governing equations for beam deflection. As the load-displacement relationship of the scaled model and the full-scale structure coincide in the elastic range, the equal-energy rule relating the elastic response to the elasto-plastic response is applied to estimate the elasto-plastic deformation of the full-scale structure.

This study investigated the local failure assessment of RC slabs subjected to projectile impact. The inertia and shear force responses of RC slabs subjected to impact loads were obtained from experimental and numerical analysis. Numerical analysis showed that the analytical values underestimated the experimental values for the acceleration and velocity responses of the RC slabs. The occurrence of the scabbing by comparing the shear force and modified punching shear capacity was evaluated by proposed method in this study.

In order to investigate the dynamic response characteristics and failure behavior of the RC beams strengthened in flexure with Aramid FRP sheet when the cushion rubber is set on the impacted area, energy gradually-increased consecutive impact loading tests of the beams were conducted varying the sheet volume. The results obtained from this study are as follows: the primary peak impact force can be decreased by less than approximately one-fourth that without the rubber; however, the dynamic response behavior and failure mode of the beams may be similar irrespective of with/without the rubber and sheet volume.

Spiral piles are made by twisting flat steel plates and can be driven by rotary penetration only by human power, so they are expected to be used in construction sites that are so narrow that heavy machinery cannot enter. However, many points are unclear regarding the bearing capacity characteristics of spiral piles, especially regarding vertical pull-out resistance. In addition, the principle of pull-out behavior assumed at actual construction sites has not been fully clarified. Therefore, in this study, a pull-out test of a model pile was conducted using Toyoura dry sand, and the effects of the degree of construction accuracy, such as over-rotation, pushing, and pile shaking during driving, were examined. The effects of the decrease in construction accuracy for pull-out resistance tended to differ depending on the distance between two piles. These are thought to be caused by changes in the ground density around the piles owing to the placement of the piles.

Recently investigation reports of collapse incident concerning steel pipe open sabo dam have been reported due to large-scale debris flow. These were disaster incident caused by the impact of debris flow that exceeds the design load. It is required to estimate the design load of structures that can withstand large scale debris flow, in order to study the limit states and failure mechanism of steel pipe open sabo dam. The study validated the failure mechanism to analyze the reproduction of the damage case in distinct element method. Then, the constitutive law of the steel pipe is determined by the section division method. In addition, analysis is conducted using the modified flow velocity distribution model that applied the infiltration flowrate between the sediment gravel. This result show that the top of a steel pipe open sabo dam is affected by the steel pipe connections and especially the compressed deformation steel pipes are the main cause.

The installation of a spiral coil in vertical pipe has a potential to create effective drainage function for clarification of hydraulics in vertical pipe flow during rainfall. As a first stage, experimental investigation on drainage function of vertical flow was conducted by using an adjusting tank connected to a vertical pipe. In vertical pipe with a spiral coil, covering the upper part of the suction vortex will work suction on the cover and greatly improve the drainage function. The discharge coefficients evaluated from Bernoulli’s theorem applied at the horizontal pipe inlet connected to the manhole differ by about 1.5 times from the case where the spiral coil is installed in vertical pipe and the manhole space is occluded or open.

To evaluate the impact of barometric pressure variation caused by the upcoming super typhoon on the formation of flood flow is important to flood control planning. Thus, the physical phenomena based hydrologic model that combines barometric pressure variation, surface-water flow, ground-water flow is developed. Using this model, numerical experiment is conducted in which barometric pressure variation. The result shows that barometric pressure variation of 100hPa make the runoff height increase 1.3 times. The spatial distribution of barometric pressure variation led to two modes of river basin rain-runoff situation.

We performed large-eddy simulations for turbulence flows with particles around a cylinder under high-Reynolds number conditions. After validation and verification through comparison with existing studies under ideal flows, we examined changes in particle impaction efficiencies on the cylinder surface with Reynolds and Stokes numbers. The Reynolds number effects on the impaction efficiencies at the front side is negligible, while the efficiencies essentially increase with the Stokes number. On the other hand, the impaction efficiency at the back side takes a maximum with respect to the Stokes number and depends as well on the Reynolds number to some extent; this is due to the formation of three-dimensional wake structures under high Reynolds number conditions near the cylinder surface in the wake region under high Reynolds number conditions.

One of the vertical axis wind turbines that utilize drag force is the Savonius wind turbine. Savonius wind turbines are characterized by low speed rotation and high torque, so they are rarely used for wind power generation but have possibility to apply to ocean current power generation, which has been attracting attention recently. In this report, we actually performed a numerical simulation of the flow using suitable grid system, focusing mainly on the case where two wind turbines are rotating in reverse at a constant speed, and investigated the state of the flow field. Two-dimensional incompressible Navier-Stokes equations are adopted as the basic equation and solved numerically using the finite difference method. In addition, in order to enable calculation even in a high Reynolds number flow, the nonlinear term of the equations are approximated by using the third-order accuracy upstream difference method. In general, when analyzing the flow around a rotating object, a rotational coordinate system is often used. However, it is difficult to calculate with such coordinate system when two objects rotate independently. Therefore, we used the overset grid that consists of two rotational coordinates for each turbine immersed in a steady coordinate to calculate this turbines’ system. The simulation was performed under the condition that the flow corresponds to five types of angles of 0, 45, 90, 135, 180 degrees with respect to the line connecting the centers of the two wind turbines. The flow field differs greatly depending on each angle, and the interaction between the two wind turbines has been clarified. Furthermore, a calculation was performed with a phase difference added to the rotation of the two devices, and it was found that the efficiency was the highest when the phase difference was approximately 45 degrees.

In order to accurately estimate the deflection and impact coefficients, it is necessary to quantitatively consider the the influence of non-structural members on the main structural rigidity of the bridge. This study simulated railway steel or composite bridges based on the 3D finite element analyses for the purpose of clarifying the effect of non-structural members such as track members on the flexural rigidity of the main structure. It was clarified that the effect of the main structural rigidity of the open-floor steel bridge on the secondary members such as the horizontal structure and the anti-tilt structure is small, although the effect of the rail is relatively large, and the rigidity contribution greatly depends on the constraint condition of fastening devices. In the case of simply supported composite girders, vibration-reducing concrete and road-bed concrete have a relatively large effect on the main structural rigidity among non-structural members. In the case of continuous composite girders, the influence of rails was smaller than that of simply supported girders since the influence of rotation-al constraints at the long continuous bridge boundary gets small.

The bridge deflection when passing a train, which is a typical index expressing bridge performance, requires a great deal of labor and cost to measure. In this study, a drive-by quasi-static bridge deflection estimation method based on track vertical irregularities measured on a traveling vehicle is developed, as a more efficient measurement method. The followings were clarified by theoretical analysis reflecting the actual installation position of the inertial mid-chord offset track irregularity measuring devices; the difference in track irregularities measured by the first and last vehicles is proportional to the quasi-static bridge deflection, the maximum value of the bridge deflection can be estimated by multiplying the maximum difference between the track irregularities of the first and last vehicles by the conversion coefficient, and the sensitivity changes depending on the measurement position of the track irregularities. Finally, it was demonstrated that the maximum value of the bridge deflection of the two bridges estimated by the proposed method from the track irregularities measured on the actual line is in good agreement with the result of the on-site bridge deflection measurement within an error of 10%.

The purpose of this study is to construct a dynamic response calculation method with a small computational effect that can be used for design impact factor calculation and inverse analysis of railway continuous bridges. The closed form solution of the multipoint support condition beam under moving load proposed by Johansson et al. was reformulated in this study. In addition, the modified closed form solution was implemented as a simple calculation method for the dynamic response of continuous bridges when the train passes. The accuracy and calculation efficiency of the theoretical closed form solution were verified by comparison with the results based on finite element method and the numerical time integration. As a result, it was shown that the closed form solution can calculate the dynamic response of continuous bridges 10 times faster than the numerical time integration. In addition, the practicality of the proposed method was verified by comparing it with the deflection measurement results when train passed through an actual continuous bridge.

In Bayesian structure model update, it is not possible to assume the independence in the posterior distribution of each parameter in the uncertainty estimation due to the correlation between the parameters. To overcome this, dual sampling methodology that estimates the simultaneous posterior distribution tail space separately from the expected value estimation has been proposed, however the existing second stage tail space estimation using GA has a problem in term of computational efficiency. In this study, authors introduced the replica exchange MCMC method, which is a typical wide-area spatial estimation method, as the second-stage tail space estimation method, and verified its effectiveness using the same actual bridge data as in previous study. As a result, it was clarified that the proposed method can estimate the tail space of the posterior distribution as well as the existing GA method with about 1/4 of the calculation time.

In the displacement measurement of railway bridges, optical measurement without a target is widely studied in recent years because it does not require access to bridges. However, the estimation accuracy of displacement depends on the surface condition of the structure, and there are some points where the displacement response cannot be obtained. In this study, the authors conducted displacement measurement using the digital image correlation method for a RC and a steel I girder bridges, and develop the subpixel estimation accuracy estimation method using the second-order differential value. The accuracy estimation results revealed that the horizontal errors affect to the vertical displacement estimation. Considering this finding, a practical improvement method that removes the horizontal effect is proposed, and can expand the applicable areas, which were mainly limited to the stiffener positions in the previous study.

Recent studies have considered a fatigue damage detection method using piezoelectric sensors. The authors have proposed a system that combines a MEMS (Micro Electro Mechanical Systems) accelerometer and a piezoelectric sensor. This system can utilize in actual in-service bridges where the magnitude of the load varies. However, the proposed method is complicated because it requires a combination of different measurement methods. Therefore, this study proposes a simple monitoring system using only piezoelectric sensors. To achieve this system, we attempted to determine the integration range and the acquisition of external force information with piezoelectric sensors. The measurement results on actual bridges show the possibility of monitoring fatigue damage with a simple system than the conventional method.