We developed a multi agent simulation code, enhanced with high performance computing (HPC), for simulating mass evacuations triggered by catastrophic events like a tsunami. Prediction of mass evacuations is of great importance to ensure public safety, in which the complex human behaviour is a key issue. A parallel multi agent simulation code is developed with the aim studying the problems associated with large urban area evacuation; no real experiment is feasible for large area evacuation involving millions of people. The HPC enhanced code scales linearly up to 256 CPU cores. A preliminary study is conducted to identify the effectiveness of reducing the evacuation time with official agents with different responsibilities. It was found that using 3% officials produces similar results when all the agents evacuate immediately, without any preparation time.

抄録全体を表示

A new methodology using spatial moment analysis linked with image processing of a dye tracer behavior in porous media was developed to estimate dispersivities not only in longitudinal but in transverse directions. Laboratory tracer experiments using a relatively mobile dye tracer Brilliant Blue FCF were conducted under saturated and unsaturated flow conditions. Uniformly packed homogeneous fields, which were comprised by silica sand or andisol taken from a maize field, were of concern under four different infiltration rates as well as under saturated flow conditions. An image processing technique based on digitalized spatial distributions of dye tracer allowed to link with a spatial moment approach to identify the transverse and longitudinal dispersivities. Dispersivities exhibited an increasing and decreasing tendency associated with infiltration rates and showed a marked difference between estimates under saturated and unsaturated conditions. Laboratory study was extended by a comprehensive literature search to compare the new results with earlier work, demonstrating a good agreement between the experimental and published results. Developed methodology was applied to a field with approximately 100 cm depth from the ground surface under unsaturated conditions. Dye tracer moved through the soils in a preferential path pattern, which induced higher dispersivities in more irregular pore patterns as compared with estimates obtained in laboratory tracer experiments. Experimental results demonstrated the effectiveness of the developed methodology for simultaneous assessment of transverse and longitudinal dispersion in unsaturated soils.

抄録全体を表示

This paper describes the basic characteristics of the development of supercritical flows in the downstream of an abrupt expansion in a steep open channel. Although Rouse and Bhoot (1951) showed the method of analysis to calculate supercritical flows in the downstream of an abrupt expansion based on Method of Characteristics (MOC) with a graphical method, and the authors developed MOC based computational method using the fixed grid system, the basic characteristics of flow development have not been clarified. In this paper, it is shown that the flow characteristics can be classified into two regions. One flow region called the pressure-inertia region is located in just downstream of an expansion and the flow characteristics can be reproduced by the approximate solution based on MOC to the shallow flow equations. The other flow region extends in the downstream of an expansion, and the flow developments can be formulated by applying the self-similarity distribution analysis.

抄録全体を表示

Turbulent flows over rough walls have considerable engineering interest. In spatial inhomogeneous flow such as wall roughness flowcan be rendered globally homogeneous by using time- and space-averaging (double-averaging) method. There are a lot of experimental and numerical studies on wall roughness flow. However, spatial developing characteristics of rough wall has received less attention. Therefore, in the present study, turbulence measurements are conducted in open-channel flows with two-dimensional regular transverse square bar roughness by PIV. Spatial variability of flow field and dispersive effects in rough wall floware examined in detail.

抄録全体を表示

It is well known that groynes navigate mainstream effectively to protect a river basin. An associated dead water zone can be a valuable space for various aquatic eco-system. In contrast, such a closed water environment reduces water quality rapidly, and it is therefore of vital importance to consider not only hydrodynamic properties but also mass transfer mechanism beneath the mainstream and the dead water zone. We conducted turbulence and dye concentration measurements in a laboratory flume by using PIV and LIF techniques, respectively, and based on the present results, a phenomenological flow model was developed which describes comparison of large-scale gyre structure and mass transfer coefficient among the different rank number.

抄録全体を表示

There is a lot of knowledge about head of the groin and between the groins. The influence of a groin reaches to the distant downstream. However there are many unknown things that flow condition and downstream of the groin is influenced by layout of the groin. Purpose of this study analyze flow characteristic of downstream on the single groin and the groins by experiment of different layout. As a result, the form of the separation vortex under the groin has affected structure. For example, since a single groin has the strong flow which goes to the center of a channel, its separated flow region is larger than groins. Therefore, since the momentum transport on boundary of groin region is small, the position which returns to steady flow becomes distant downstream.

抄録全体を表示

Better management of riparian vegetation for flood control and environmental preservation requires in-depth understanding of flow characteristics in the presence of vegetation. This study aims at clarifying the flow resistance due to floodplain vegetation in compound channels through experiments with the help of numerical simulation. The effects of the size and the location of vegetation zone on the stage-discharge relationship and vegetation distributions are discussed. It is found that separated vegetation belts near the edge of the floodplain give higher conveyance than the continuous vegetation belt. A spectrum analysis of the instantaneous velocity components indicates that the streamwise scale of the large vortex near the interface is correlated with the carrying capacity of flow.

抄録全体を表示

Channel network configurations are changed by hydraulic conditions. The characteristic of a river channel network configuration is directly connected with river channel disasters and a river ecosystem. For this reason, the relation between the form characteristic and the hydraulic conditions needs to be grasped. In this study, hydraulic experiments on channel network configurations were conducted. Sufficiently wide flume was used for the experiments so that the influence of side walls might not appear in the channel network formation. Although few channels were formed in the hydraulic condition that the bed shear stress was near the critical bed shear stress, multi-row bars were formed in the condition that the bed shear stress is to some extent large. As a result of conducting linear stability analysis, it was shown that a phenomenon which is different when hydraulic conditions differ arises.

抄録全体を表示

This paper presents an experimental study on the upstream channel responses due to partial removal of a weir, focusing on the impacts of the removal shape of the weir on the hydro-morphological features. It is found that the shape of the removal significantly affects the 3D flow structure and the local scour around the weir and poses influences on the propagation process of upstream sandbars. However, the characteristics of the sandbar system at the quasi-equilibrium stage are governed by the removal area rather than the removal shape. Governing parameters characterizing the removal shape is proposed as well. Desirable morphological features could be achieved by a careful selection of those parameters.

抄録全体を表示

In this paper, the numerical simulations of flow and bed deformation under the experimental conditions are carried out to verify the applicability of numerical models and to clarify the mechanism of the sandbar formation at the downstream of the back-step. In order to simulate the bed deformation, two conditions common equilibrium sediment transport model and the non-equilibrium model for bed-load transport are tested. It is shown that the result of non-equilibrium sediment transport model is in good agreement with the experimental results, in which sediments were deposited in the middle of the channel and along the sides where shockwaves are generated. However equilibrium sediment transport model was not able to capture the well features of sandbar formation. Furthermore, we clarified the mechanism of sandbar formation at the downstream of back-step by the results of non-equilibrium model.

抄録全体を表示

It is commonly observed that river channels become unstable to shift their courses repeatedly particularly when bed aggradation is taking place. On the contrary, river channels are stable and maintain their courses under bed degradation. We study the effect of bed aggradation and degradation on stability of river channels. We perform linear stability analysis of channel meander taking account of gradual bed aggradation and degradation. It is found from the analysis that bed aggradation decreases stability of channels and induce channel meandering while bed degradation stabilize channels and inhibit channel meandering.

抄録全体を表示

The sand-bar in the Kawasaka district of the Kita River was excavated with vegetation in 2001 through the special emergency project after the sever disaster due to flooding by Typhoon No.19 in 1997. A flood on Oct. 2004 destroyed again almost all vegetation in a recovery process on the sand-bar. Nowadays, herbaceous vegetation is restored over all the sand-bar because of no flooding since 2008. In the paper, the destruction of herbaceous vegetation by the topographical changes of sand-bar was described from field survey and simulated through the 2-D analysis of the riverbed evolution. It was considered from the field survey that almost all vegetation were lean in 1/3 the height. Moreover, destruction of herbaceous vegetation has been reproduced by the built model.

抄録全体を表示

To improve the reliability and the prediction precision of the inundation analysis, the adjoint method is expected to be an effective method. The method can assimilate observation data to a analysis model, consistent with dynamics equations strictly. However, the method is not capable of functioning in some cases, such as non-linear numerical models. In this study, non-linear inundation model is derived from PBM in considering groups of houses, and the applicability of the adjoint method to the inundation analysis is evaluated on some simple conditions, composed of topography, the observation positions, by inverse analysis of inflow conditions. As a result, the method is verified to be effective enough, on appropriate conditions.

抄録全体を表示

The sloshing phenomenon caused by long-period earthquake ground motions has been observed repeatedly in recent years. Overflow of liquid in water tanks often takes place. Damages of water tanks by the East Japan Earthquake of 2011 are the most recent example. In contrast to circular tanks, rectangular tanks show direction-dependent response behavior. In this paper, shaking experiment was conducted to make this effect clear by changing vibration direction. Experimental results suggest interaction of vibration modes.

抄録全体を表示

In this paper, computational fluid dynamics for flow around a circular cylinder is carried out by means of solving the incompressible Navier-Stokes equations with the turbulence model by the finite element method. The Reynolds number is from Re=2.8×10⁵∼3.5×10⁵. By using results of calculations, the flow patterns, drag and lift coefficients and Strouhal number depend on the Reynolds number are investigated. There are differences between the computational data and the experimental data, however the dependence of the Reynolds number and the drag crisis in the Critical Reynolds Number regime can be simulated near wake.

抄録全体を表示

This paper presents experimental and theoretical investigations of water particle trajectory and mass transport of internal waves propagating over a sloping bottom in a two-layer density-stratified water. The water particle trajectory has been obtained by experimental, numerical, and analytical methods for two different thickness ratios as well as two wave periods. In addition, the mass transport velocity was estimated. The trajectory of individual particle is not closed but shows a quasi-elliptic pattern. It was confirmed from the measured and computed results that the particle near the density interface yields a maximum forward drift while one away from interface tends to move backward to conserve the mass in the closed wave tank. The theoretical solution gives reasonable results for the drift of the water particle near the density interface.

抄録全体を表示

In this study, damage evaluation of RC column subjected to cyclic loading and evaluation of retrofitting effect were conducted by means of 3 dimensional finite element analysis. Damage area of RC column was evaluated by using averaged compressive strain which was calculated by average of strain within certain area. Bond deteriorated area, in which concrete and rebar behave independently, could also be considered as the damage index of RC column. By comparing with the test result, both averaged compressive strain and bond deteriorated area corresponded to repaired area. Structural behavior of repaired RC column was simulated. As the results, it was confirmed that the damage evaluation method and repairing procedure in this study were suitable to simulate the repaired RC column.

抄録全体を表示

For examining the characteristics of residual stress generated in slit welded joints under restraint or loading, a series of numerical simulation was carried out. The residual stress in weld metal in the cross direction to the weld line under the condition that the in-plane displacement at the plate edge was fixed (i.e., the external restraint condition) was larger than that when the displacement was not fixed. However, the residual stress under the constant tensile loading on the plate edge was almost the same as that under the external restraint condition. The degree of the restraint in the slit under the various boundary conditions could be relatively evaluated by the restraint intensity. Although the slit length was the same, the welding residual stress varied from 20 to 80% of the yield stress due to the difference of the degree of the restraint.

抄録全体を表示

Recently, the optical full field measurement is researched. There is digital image correlation method (DICM) in that. DICM calculates the digital image of which it takes a picture with CCD camera and displacement and the strain distribution can be calculated easily by analyzing the value. In this study examined the strain highly accurate measurement in several 100μ or less minute strain area. The analysis that changed the analysis condition and the improvement of the strain measurement accuracy by the multi-rosette analysis method that used DICM were tried.

抄録全体を表示

This paper presents an image analysis on the flexural behaviors of CFRP box beams with two different CFRP laminate structures: quasi isotropic (QI) and cross ply (CP) laminate. Image analysis is conducted in order to measure the deformation field around the center span of CFRP box beams, and strains, principal strains, principal stresses, and Tsai-Wu index are calculated consequently. QI and CP showed a different flexural response due to their laminate structures, but both showed a final brittle failure in upper flange and web. Strains, principal strains, and principal stresses clearly show characteristic distributions around the center span, and some of them indicate local concentrations near loading points. Tsai-Wu index explains fracture origin location possibly for QI, but it does not for CP.

抄録全体を表示

In steel members strengthening with CFRP plate, thermal stress is introduced in steel members by temperature change, due to difference in coefficients of thermal expansion between steel and CFRP. In the previous study, reduction technique of thermal stress in steel members, which is additional bonding of aluminum alloy plates with CFRP plates, was proposed. However, by bonding laminated plate consisting of CFRP and aluminum plates on one side of thin steel plate, thermal stress is not completely reduced. Therefore, to confirm the effect of proposed method for one side bonding, heat tests of steel plates or steel member with bonding laminated plate on one side were carried out in this research. Additionally, to verify the test results, numerical analysis of proposed method was also carried out. As a result, it is found that the three-layered laminated plate consisting of one CFRP plate and two aluminum plates was required for reduction of thermal stress in thin steel plate. However, two-layered laminated plate could fully reduce the thermal stress in steel girders.

抄録全体を表示

Recently, repair or strengthening of steel members by bonding CFRP plates has been widely reported, and the design method to prevent the debonding of CFRP plates were proposed in overseas. In Japan, however, debonding-prevention-design for CFRP plate bonded steel members have not been specified. In this research, to clarify the effect of loading conditions on the adhesive stresses of steel members strengthened by bonding CFRP plates, shear and normal stresses in adhesive at CFRP plate ends were derived under the conditions of pure bending moment, concentrated load and uniformly distributed load. Furthermore, estimation equations of shear and normal stresses in adhesive at the end of CFRP plate under several loading conditions were given.

抄録全体を表示

For the effective evaluation of hydraulic conditions of pipeline system, it is necessary to evaluate not only the material properties but also unsteady flow conditions, such as pressure wave. In this study, quantitative evaluation of pressure wave is going to be performed, applying acoustic emission (AE) and digital image correlation methods in pipeline. The pressure waves were detected in pipeline, based on control of valve closing time (0.40-10.48s). Thus, the maximum pressure could be detected by comparing maximum pressure level with a rate of AE generation, which is analyzed by AE parameters. Using digital image correlation method, a relationship between maximum pressure level and displacement is correlated. By monitoring the pressure waves in service pipeline based on these results, the generated pressure waves in pumping flow conditions is successfully detected by AE.

抄録全体を表示

As a detail inspection of damage of pipe materials in service, elastic waves in fracture process are usually detected and then material damage is estimated. The acoustic emission (AE) method is useful method for detection of elastic waves. In this study, asbestos-cement pipe samples are examined based on fracturing behavior under unconfined compression with AE. AE behavior of pipe materials under compression is dependent on the degree of damage, and could be approximated, applying the AE rate process analysis and the Weibull analysis. A relation between AE rate and Weibull parameter is correlated. By calculating C value from AE rate process analysis based on this relation, the material damage of pipe samples is successfully estimated.

抄録全体を表示

This research evaluates the effect of simultaneous high speed train loadings on double-track for the fatigue design of railway concrete bridges by using a numerical analysis. Concretely, this research examines the tensile fatigue strength by defining the probability density curve of the shift time from train schedule diagram, and by using section force-time relation of simultaneous train loadings. This research clarifies the following items: firstly, regarding tensile fatigue strength, the effect of increase of the section force by uplift is more dominant than the effect of simultaneous train loadings. Secondary, the simultaneous train loadings coefficient b which expresses the effect of simultaneous train loadings in the current fatigue design doesn't become the determination factor for the fatigue design. Thirdly, the simultaneous train loadings coefficient b may be considered zero in general.

抄録全体を表示

This paper reports on the accuracy improvement in damage detection of bridge joints based on the passing sound of a vehicle using Chaos prediction analysis and frequency analysis. Herein, the factors such as sampling rate, frequency band, supervised data and criteria for judgment were examined. It was found that sampling rate is not significant for POA (partial overall value based on frequency analysis) but slightly affects the accuracy of error prediction. It was also clarified that the index of max by deviation for threshold shows better accuracy than that of Kurtosis for both evaluation methods. As for the frequency band in POA, the band of 210-230Hz and 450-650Hz exhibits the most accurate recognition. Finally it was found that detection performance by POA slightly exceeds that by prediction error.

抄録全体を表示

This paper describes the results of accuracy tests of the structural sensing method proposed by the authors. We have been developing the structural sensing method using the wireless sensor network and the artificial vibrator which is able to excite very accurate harmonic vibrations to a structure with a known force function. We conduct some laboratory experiments using a simple beam to investigate the measurement accuracy of the prototype system. The results show that the prototype is able to measure the frequency response function accurately. The results also show that the response of the simple beam clearly depends on the surrounding thermal condition.

抄録全体を表示

This manuscript presents a new bridge deterioration prediction method with stochastic Markov Chain model, which uses the transition probability matrix whose elements are described as random variables. The model is able to develop a prediction interval of bridge deterioration while the conventional model is not able to. In addition, we have developed the method to consider the individual deterioration characteristic expressed as the inspection results by Bayesian theory. The prediction interval developed by the proposed model allows bridge owners to understand the deterioration in several ways, including safe-side prediction and average prediction. It is expected to provide a better insight into the estimation of maximum, average, and minimum maintenance cost to the bridge owners, which makes their decision making process more productive.

抄録全体を表示

The damages of water tank, which gives rise to sloshing motions during an earthquake with long-period, have been reported in the present study. Herein, experimental studies have been performed to investigate the sloshing behavior of rectangular tank with the different dimensional aspect ratios, under the different excitation angles. In addition, the behavior of tank with a special aspect ratio (i.e., near to 1) has been examined in detail. Also, the sloshing suppression methods using plastic filters have been developed based on the present experimental results. Finally, the effective variables, such as position of filter installation, depth, length and area for the wall of tank, have been proposed.

抄録全体を表示

The conventional seismic design standard specifies a modeling way of train action on insufficient grounds. The aim of this paper is to clarify the mechanism of dynamic interaction between a train vehicle and a structure and to develop a reasonable modeling way of train action for seismic design of structure. The conclusions are as follows: 1) dynamic interaction is dominated by creep force between wheel flange and rail in the case of small vehicle response and by contact force between them in the case of large vehicle response; 2) the way in which train is modeled by assuming a train as a rigid mass gives most reasonable results for seismic design; 3) more accurate modeling of train action requires to consider the creep force and high-order vibration modes as well as the stiffness of vehicle.

抄録全体を表示

This paper presents the dynamic Green's functions by the use of the stiffness matrix method for layered elastic half space in Cartesian coordinates. The presented Green's functions in Cartesian coordinates are represented by the two fold Fourier integral, and then the 2 Dimensional Fast Fourier Transform (2DFFT) can be effectively used to calculate the dynamic Green's functions. To verify numerically the validity of the presented Green's functions in Cartesian coordinates, the numerical examples of comparison with the results of the method of Luco and Apsel, and those of the numerical method using the FEM for a layered elastic half space are shown.

抄録全体を表示

A floating offshore wind tubine using spar platform as the floating foundation is considered here. It is known that a spar platform may show Mathiew instability in its dynamic motions. This is because the equations of motions in heave and pitch directions couple each other, and the equation of motion in pitch direction reduces to Mathiew equation in its approximated form.
In this paper, we propose a stability diagram of the parametric excitation for a spar platform, where the effects of damping and wave elevation are both considered. Then, the applicability of the derived stability diagram is validated by numerical examples using a spar platform model, where the upper part of the spar has a reduced diameter. Some design guidelines concerning the ratio of pitch/heave natural periods are also given.

抄録全体を表示

This paper presents a numerical method for two-dimensional solid phononic crystals having a defect. This problem is divided into two domains of the finite defective region and the surrounding periodic medium. The analysis method is then constructed by combining the finite element equation of the irregular region with the impedance matrix representing the external field. The impedance matrix is derived by analyzing a series of harmonic excitation problems of a periodic field given by the surrounding array. These solutions are obtained by the aid of Floquet transform. The developed method is applied to wave propagations through a defective field imbedded in a square lattice of circular holes. Modes trapped in the disturbed region are also analyzed for a composite material possessing a dispersion structure with a wide bandgap.

抄録全体を表示

Mixed formulation of FEM is frequently used for the modeling of incompressible or nearly incompressible material such as liquid, to avoid volumetric locking. In this paper, Convolutional PML is developed, which is consistent with mixed formulation of FEM for liquid. Resulting coefficient matrices are symmetric just as corresponding FE. Boundary conditions considering surface waves and solid-liquid interfaces are also formulated for convolution PML. The performance of developed Convolutional PML is demonstrated by the comparison with other boundary conditions and with a rigorous solution using reservoir models. The performance of the proposed method including solid-liquid interface elements is demonstrated using dam-reservoir-foundation rock models.

抄録全体を表示