The serious damage of coastal dikes occurred in the tsunami caused by the 2011 off the Pacific coast of Tohoku earthquake. It is important to reinforce these coastal structures with the concrete blocks and to give the function of tenacious structures. In case of coastal dikes, the stability of concrete blocks and the damage of coastal dikes are affected by the strength of foundation in spillway and the fluid forces acting on concrete blocks armoring on slope just near the crest of dikes in the side of land for the over flow in tsunami. The relationship between the velocity distributions on concrete blocs and pressure distributions on the mound of slope, and the fluid forces and overturning moment acting on a concrete block adjacent to the crest of dike in the side of land. The forces and moment are measured by using a load cell.

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Spur dikes are sometimes used to control main flow and they may affect opposite-side flow structures. In this study, effects of spur dike on flow structures in a side concavity zone on opposite side were investigated. The velocity was measured by using PIV method in a laboratory flume. Location of the spur dike relative to concavity zone was changed and its effects were considered. The magnitude of recirculation velocity and water exchange velocity in the concavity zone was enhanced by setting a spur dike on opposite side. This is mainly caused by acceleration of interfacial main flow due to contraction effect of spur dike. This acceleration process is changed with emerged or submerged condition of spur dike. Whereas separation zone behind emerged spur dike is elongated far downstream, that is shortened behind submerged spur dike. Other effects of spur dike such as flow deflection and three-dimensionality also have some effects on water exchange process between concavity zone and main flow.

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This paper presents results from numerical investigations into mass transport driven by periodic internal waves in a two-layer fluid system. The experiments concentrate on particle transport inside the interface and its adjacent regions. A series of numerical experiments were carried out for different interfacial thicknesses. We found that the mass transport velocity does not reach a maximum at the center of the interface but at the two boundaries between the interface and the layers. For a thin interface, particles near the interface travel in the direction of propagating waves. However, as the interfacial thickness increases, particles in the interfacial layer might remain stationary or they may move back offshore, against propagating waves.

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Gas-solid-two-phase flows consisting of fine particles suspended flow is observed in various phenomena, for example powder snow avalanches, in nature. One of these features is that the movement form is affected by mass change due to a sedimentation or entrainment of suspended particulate. In this study, powder snow avalanches are analyzed by numerical simulation model using k-ipusiron turbulence model. Due to introducing the concept of entrainment coefficient, the erosion and deposition of snow particles are taken into account in this model. The travel distance and the stopping place of powder snow avalanche occurring in Hidarimatatani are compared with numerical results.

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When rain pours over porous media, rain water tends to infiltrate their inside. In order to enable further infiltration, the air in the void of porous media has to be replaced with water. If the replacement between water and air is not smoothly implemented, water cannot seep into porous media as observed on river levees during heavy rainfall. This might be caused by the fact that the equilibrium of water with a relatively high density on top of air with a far lower density may be stable or weakly unstable in porous media. We have performed a linear stability analysis to study the Rayleigh-Taylor instability in porous media.

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This work presents a detailed morphodynamic modelling of bed forms under unsteady discharge, using large eddy simulation (LES). This model reproduces the temporal development of river dunes and accurately replicates the physical properties associated with bed form evolution. Several numerical experiments with different grain sizes and different discharges are performed to analyse the hysteresis of drag under variable discharges. It is shown that the hysteresis is more significant for gradually varying discharges, because the bed can adapt itself to the discharge. In a rapid change of discharge, the bed has not enough time to adapt. Furthermore, we observed that the size of sediment has a significant effect on the hysteresis. Sediment with large diameter affects the hysteresis significantly. If difference between the relaxation time of a particle and Kolmogorov time scale increases, it leads to a large time lag between discharge variability and morphodynamics, which leads to a significant hysteresis effect.

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In this paper, basic characteristics of tsunami invasion processes are discussed. The authors had applied self-similarity distribution analysis to shallow flow equations in order to clarify the characteristics of tsunami invasion processes in previous study. In the study, inertia-pressure regime and pressure-friction regime had been considered separately and the self-similarity solution in pressure-friction regime had been derived, assuming the water rising. In this paper, inertia-pressure regime in increasing the water depth were discussed to throw further light on the features of tsunami invasion processes. In addition, in order to study the characteristics in decreasing the water depth, the self-similarity solution in this process was derived. Numerical simulations were also carried out to verify the theoretical findings. Finally, the tsunami invasion processes were classified from these characteristics based on self similarity distribution analysis and were verified by numerical simulations.

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Grid structures of the general curvilinear coordinate system with gross distortions have never given solutions of the hydraulic equation even under accurately computations. A relationship between a quality of the grid structure and a stability of computations has not quantitatively investigated. This study shows that a estimation method for truncation error of metrics of the grid structure and the method can detect instability of solution without numerical computation. An optimization method for the grid structures with the elliptic partial differential equation can effectively reduce the truncation error and derive physical solution.

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Tsunami source of the 2011 off the Pacific coast of Tohoku Earthquake reached into head of Tokyo Bay. The observed wave height at head of Tokyo Bay was greater than at mouth of it. The increase of wave height couldn't elucidated by the oscillation characteristics of long wave in the bay has been already clarified. We investigate behavior of long waves at head of the bay by 2D nonlinear shallow-water equation with the quadtree grid system to describe geometry of ports. This study reveals that local scale topography plays an important role in the oscillation characteristics of long waves at head of a bay. Since there are so many population, property and many connecting rivers at head of the bay, this study is an important knowledge for disaster mitigation.

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This paper presents the effect of rehabilitation of thickness-reduced steel plate repaired by bonding or bolting patch plates. Generally, the thickness of patch plate is designed by using composite section of thickness-reduced plate and patch plates. However, it has been reported that the stress introduced in thickness-reduced region becomes larger than that calculated by composite theory when the patch plates are adhered onto the thickness-reduced plate. This is because the assignments of cross-section forces in thickness-reduced plate and patch plate are different from those calculated by composite theory. Thereby, this phenomenon will also be seen in the thickness-reduced plate repaired by bolting the patch plates. In this research, the tensile tests of thickness-reduced steel plate repaired by bonding or bolting patch plates were carried out. As the results, the strain in thickness-reduced region became larger than that given by the composite theory in both cases, and became the yield strain earliest.

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In this study, wireless monitoring systems were developed as an element technology of next-generation asset management. Prototypes which have features of processed data collection using road-to-vehicle communications, original data collection using wireless communications, easily-exchangeable sensor and autonomous driving based on battery, etc. were produced. By applying prototypes to long-term monitoring of actual civil structures, the following results were obtained. In long-term monitoring for approximately 10 months, prototypes have some troubles however measurement of acceleration response and collection of original data based on wireless communications are possible. Reductions of the battery voltage in the actual environment are larger than the predicted value, and it requires attention to the battery capacity.

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Steel structures may suffer cracks during hot dip galvanizing due to abrupt changes in temperature. Steel structures with draining holes to be galvanized are prepared. Then, authors measure what stresses are generated around those holes when galvanizing the steel structure. Moreover, authors presume thermal stresses arising in steel members during its hot dipping process by the coupled analysis of thermal conductivity and thermal stresses to compare with actually measured values. From the analysis result of four different scallop-added steel structures, proper structural details of scallops to avoid galvanizing cracks are decided.

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This paper describes the results of a simple beam vibration test and the corresponding numerical simulation. We have been developing a structural sensing method using the wireless sensor network and the accurate small vibrator. This vibrator is able to excite very accurate harmonic vibrations to a structure with a known force function. In this study, vibration test of a simple beam was conducted and the frequency transfer function was estimated with the use of ARX model. The obtained frequency transfer function is compared with a frequency transfer function calculated by a FEM analysis. The results show that the frequency transfer function measured by the structural sensing method is successfully simulated by the FEM analysis.

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Recently, assessing the integrity of the civil or mechanical structures has been extremely important in order to ensure safety. In general, damage localization is performed through comparisons of some feature which robustly quantifies damage-induced changes, which implies that some baseline data needs to be possessed under the intact condition of the structure in advance.However, there aremany existing structureswhich have no such baseline data. In this study, an attempt is made to develop a baseline-free damage detection system using digital image correlation method and fractal dimension analysis. The numerical and experimental results demonstrate that the proposed system can make it possible to detect damage location without using any baseline data by evaluating breakpoints of fundamental vibrationmode.

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For examining the characteristics of residual stress generated by fillet welding of a stiffener to a steel plate under tensile or compressive loading, a series of numerical simulation was carried out. In both cases of welding under constant tensile and compressive loading in the welding direction, the residual stress around the weld metal was almost the same as that by welding without external loading. On the other hand, the residual stress in the base metal was variously changed by the difference of the tensile and compressive loading and those magnitudes. It was proposed that the average residual stress in the base metal under the external loading could be predicted by superposing the welding residual stress without loading and the nominal stress due to the external loading.

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This paper presents a study on the failure load and deformation of CFRP box beams based on the fracture of individual laminas. Two different CFRP laminate structures are tested and analyzed: quasi isotropic (QI) and cross ply (CP) laminate. Nonlinear constitutive law is obtained by considering the fracture of individual laminas, and the law is implemented into a fiber model to obtain the failure load of the beams. The fiber model is also used to obtain the flexural deformation of the beams, while Timoshenko beam is referred to obtain the shear deformation. Analysis shows a good agreement on the failure load and load-displacement relation of the two kinds of beams which show a different flexural response.

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The interest in the mechanical behavior of corroded steel members has been stimulated by the increase of aged steel structures including steel bridges. Some researchers have developed formulas to estimate the residual tensile strength from an average thickness of minimum cross section. However, it is found from the tensile tests and finite element analysis conducted in this research that the conventional methods do not necessarily predict the strength with high accuracy. Therefore, more accurate formulas are developed to estimate the strength which considers not only the average thickness of minimum cross section but also standard deviation of the thickness by reference to the nonlinear behavior observed experimentally and numerically. In addition, we have developed yet other formulas with acceptable accuracy, but required measurement efforts are much less. This allows the owner of steel structures to understand the residual strength of their structures with realistic efforts and costs.

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Recently, the polarization resistance method is highly noticed as a non-destructive test method to evaluate the corrosion rate of rebar in concrete structures. The corrosion rate can be estimated from the apparent polarization resistance and the polarized area. It is necessary to know the polarized area so as to estimate the accurate corrosion rate. The polarized area is affected by many factors, such as the polarization resistance, the electrical resistance of concrete, the covering depth and the diameter of a rebar. In this study, to examine the influence of these factors on the polarized area, the current distribution in concrete is analyzed by a finite element method. From the analysis, it is clarified that the distribution is strongly affected by the factors, and that the distribution depends on only the ratio of the polarization resistance to the electrical resistance of concrete.

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The method for rationalizing design and construction of welded steel structures, which join different materials and fabricate their members, is developed. In this case, it is important to clarify the mechanical behavior of members in the joining boundary. To prevent the failure of members with defects in the joining boundary, it is necessary to establish the technique evaluating the mechanical performances of their members, simply and quantitatively. In this study, taking up interface-notched tensile plates as a model of members with defects in the joining boundary, the simple method for evaluating the elasto-plastic strain of them are proposed, and the validity is verified throughout numerical tests of J-integral analyses by using the finite element method.

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Recently, a rehabilitation of existing damaged steel members by bonding patch plates has been reported. The rehabilitation by bonding patch plates has essentially concern about the debonding from the steel members. To assist the verification of debonding prevention, the shear and normal stress in adhesive layer have been theoretically clarified. For debonding verification of patch plate, principal stress in adhesive has been adopted in some guidelines for strengthening of steel member with CFRP (Carbon Fiber Reinforced Polymer) plate. On the other hand, an energy release rate (ERR) for verification of debonding patch plates has also been employed in the guidelines. However, the ERR equation in the guidelines is not divided into debonding modes I and II, which are the opening debonding mode and the in-plane shear debonding. Depending on the loading conditions, the ERR of each mode might be required for verification of debonding prevention. In this study, the ERRs equations of modes I and II were derived from the shear and normal stresses in adhesive. Furthermore, Finite Element (FE) analysis was conducted to verify the ERR of each mode. As the result, the ERRs of mode I and II were close agreement with the FE results.

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This paper presents the Bayesian inference based model calibration strategy for constructing validated numerical models of the existing structures. There exist uncertain changes in the model parameters, such as material properties and boundary conditions, from the nominal condition due to deteriorations or possible damages in the existing structures. The target in this study was the dynamic analysis model of an existing bridge, and the model calibration procedure was applied by using measured resonant frequencies as the comparative feature. It was then shown that the meaningful posterior distributions cannot be obtained without the appropriate prior distribution setting based on the engineering judgments. The numerical modelwas then successfully calibrated by using themeaningful posterior distributions.

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In order to properly address the resonance phenomenon which is one of the most typical vibration problems of railway bridges, it is important to identify the vibration characteristics of the railway bridges at the time of train passing, and also to quantify its uncertainty. In this study, the methodology which can identify the vibration characteristics and its uncertainty by employing the SSVS (Stochastic Search Variable Selection)-VAR (Vector AutoRegressive) model and the Bayesian estimation is proposed. By applying the actual acceleration response of the bride at the time of train passing, it was found that 1) natural frequency and modal damping ratio under train passing and after train passing could be identified stably, respectively, 2) the uncertainties of natural frequency and modal damping ratio can be identified as 2% and 50%, respectively.

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In the maintenance planning, the maintenance cost is reduced by working for multiple bridges simultaneously. However, it is difficult to establish an optimal plan that reduces the maintenance cost by this work because there are a large number of bridges that requires the management. In this study, an attempt is made to propose the planning method for a large number of bridges in two stages by using Genetic Algorithm. In the first stage, the proposed method optimizes a maintenance plan for single bridge with considering the preventive maintenance. Here, this optimal plan involves the period in which the work can be postponed without losing the safety. Therefore, in the second stage, the proposed method minimizes the maintenance cost by considering the year of works in the postponable period of multiple bridges.

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In this paper, an attempt is made to develop a structural health monitoring system that can adapt to the structural systems and environments, by introducing the learning ability. This learning ability facilitates a monitoring paradigm without a need for preliminary investigation of the underlying structure and environment. The proposed system learns the vibration response by using neural network. The neural networks predicts the next state of structural behavior from the current state of structural behavior. Several numerical examples are presented to demonstrate the efficiency and applicability of the proposed system. Through the numerical examples, it is concluded that the proposed system can identify the change of structural characteristics and condition states.

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Recently, it has become difficult to keep the skill level of bridge maintenance engineers due to the retirement of experienced engineers. Hence, the daily inspection for bridges cannot be performed accurately and efficiently in order to detect damages early and take appropriate measures. This study attempts to develop a support system for decision making of the damage assessment of bridges based on the pattern recognition considering the exception extraction. In this system, the exception extraction with one-class SVM removes some data that may cause the decrease of generalization capability of pattern recognition from the database. Therefore, it is guessed that the accuracy and confidence of recognized result are improved. Numerical examples applying digital images of RC slab of bridges with cracks are presented to demonstrate the practical utility of the approach of this study.

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This study develops a calculation method of axle weights in orthotropic steel deck bridges. Curve fitting to strain due to live loads from influence lines calculates vehicle axle weights with the least square method. The curve fitting is done in a longitudinal rib and a transverse rib. The accuracy is high in the weight ratio among the axles in the vehicle in the results from the longitudinal rib and in the gross weights from the transverse rib. Hence, the results from the longitudinal rib are regarded as temporary axle weights; then, the temporary gross weight is calculated from the summation of the temporary axle weights. A correction coefficient is obtained by taking a ratio of the temporary gross weight and the gross weight calculated from the strain responses of transverse rib. The temporary axle weight is corrected to the axle weight by multiplying the correct coefficient. The standard division of the error is from 5.87% to 7.87% in the 95% confidence interval. When applied for one week dynamic strain data, axle weight over 100kN passes 1,783 times and that over 200kN does 31 times.

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This paper describes the evaluation of quality factor for coda wave in concrete material. The elastic waves propagating throughout concrete material can be coda waves because the waves are reflected, refracted scattered and superposed at aggregates or other factors, which are well known as coda reflection. Thus herein to evaluate the coda quality factor, Q_c, a pulse wave is given to cylinder specimens and the amplitudes of band-passed signals propagating in concrete are obtained by wavelet analysis. Finally, we found that Q_c depends on frequency and has almost linear relation, and that Q₀ (Q_c at 1kHz) varies with radius and density of aggregates, and has much influence on water-cement ratio, i.e., quality of cement matrix.

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In order to clarify the behavior of buried pipe on the non-uniform bedding, experiments and 3-dimentional finite element analyses were conducted. By removing the soil from the valves of the bottom of test pit after backfilling uniformly, loose area was made in the ground. In the analysis, different input parameters made it possible to simulate the non-uniform ground. The pipe behavior was monitored at the three cross sections. Two sections are surrounded by the loosened ground locally. Another is between former two sections. From the results, it was clear that circumferential tensile strain acted on the part of the pipe by local swelling at the sections surrounded by the loosened ground. On the other hand, even circumferential tensile strain did not act but maximum shear strain increased at the middle section because of a kind of twisting force.

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This paper presents full scale experiments of falling rock protection nets by using full scale falling rock collision test facilities. 4 types rock models, i.e. 0.35 to 2.5 ton in weight, and 6 types of collision energy parameters, i.e. 20 to 28 kJ, made by slopes set at vacant quarries are used. 4 types of real size nets, i.e. 5×15 to 15×30m are used as specimens. The dynamic deformation process of net are recorded by video and high speed camera, and the tensions of anchorage wire-ropes are measured by load cells. Experimental results are discussed from viewpoint of design code used in general.

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A dispersion analysis method is developed for surface elastic waves in a semi-infinite ground, in which a periodic array of piles with finite length is arranged. A displacement solution is given by coupling of the finite element discretization and the plane wave description. In order to consider the finite piles, a semiinfinite unit cell is decomposed into two sub-domains, i.e., the upper layer including the pile and the lower semi-infinite region. The comprehensive solution is then constructed by imposing the continuity conditions on the interface between both domains. The dispersion analysis is reduced to a search for zeros of the determinant of solving matrix in an irreducible sub-region of the first Brillouin zone. Through numerical examples, the influence of the pile length on the band structure is discussed.

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In this study, a floating crane vessel with a wind turbine rotor is analyzed using multibody dynamics theory. The analytical model is produced for simulation of the marine operation during the offshore installation of the wind turbine rotor to the nacelle. Comparison of the results of the dynamic analysis with the measured data of the floating crane vessel has shown that the analytical results can predict well the motions in roll and pitch directions but underestimate the motion in yaw direction. The complex behavior of the rotor motion is observed from the analytical results in several incident wave cases. Finally, the availability ratio of the marine operation is assessed based on the analytical results. The effect of number of mooring lines to the availability ratio is also examined.

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In order to analyse effectively the response of the members of railway reinforced concrete rigid frame viaduct to the vibration, we have developed a new analysis method. It divides the whole railway system into vehicles / track model, and the track / structure model. Using this model, we examined the influence of various parameters of the vehicle, track and structure on the structure member vibration. As a result, the following have become clear. For example, for 20Hz or more, unsprung mass has a great influence on response of structure member. For 20-100Hz and 150Hz or more, rail surface roughness, for 60Hz or more, the stiffness of the track pad, for less than 60Hz, the stiffness of the slab of structure and so on, have great influence on structure member vibration respectively.

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In the 2011 Tohoku earthquake, many water tanks were destroyed in the Tohoku region. In addition, similar damages in the Kanto region are reported, that is far from the epicenter. It is considered that the damage was caused by the sloshing phenomenon occurred by long-period ground motion. Damages by sloshing occurred a lot in the past, but will also arise in near future. This research proposes a countermeasure device against sloshing, installs it in a small model and a real water tank, and proves its performance through experiments.

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