Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM))
Online ISSN : 2185-4661
ISSN-L : 2185-4661
Volume 67, Issue 2
Displaying 51-98 of 98 articles from this issue
Journal of Applied Mechanics Vol.14 (Special Feature)
  • Yoshihiro TAKEI, Norihiro IZUMI
    2011 Volume 67 Issue 2 Pages I_511-I_519
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Overland and seepage flows have been hypothesized as dominant factors in the initiation and evolution of gullies and channels. Many studies on channelization due to erosion by overland flow have been carried out whereas only few studies have focused on seepage erosion. This study aims to acquire fundamental knowledge on the seepage erosion from experiments and a linear stability analysis. We use the Dupuit-Forchheimer equation and a description of the retreat of the seepage front. The retreat speed consists of two terms: the first is assumed to be a power law function of a specific discharge at the front exceeding a critical discharge, and the second is assumed to be a diffusion-like function of front shapes, in which the retreat speed is enhanced and retarted by the convexity and concavity of fronts, respectively. We find that the characteristic channel spacing becomes infinitely small when the effect of the front shapes is excluded. We conduct a series of experiments with various depth of sediment layers and chamber slopes in order to estimate the diffusion-like coefficient. We find that the width of gullies increases with increasing grain size and bed gradient, while channel spacing decreases. We propose a relationship between the diffusion-like coefficient and the combination of the two functions, water level at the seepage front and weight of a failure block.
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  • Kazuya INOUE, Haruka SHIMADA, Tsutomu TANAKA
    2011 Volume 67 Issue 2 Pages I_521-I_532
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    This paper presents advective-dispersive solute transport processes using a random walk particle tracking approach in upscaled stratified aquifers. An upscaling of hydraulic conductivity distributions is conducted not only for the idealized stratified aquifers but also for an aquifer in a field where the profile of hydraulic conductivity distributions in a vertical direction was measured. The macrodispersivities in corresponding aquifers are estimated using temporal and spatial moments based on breakthrough curves at control planes and spatial distributions of particle crowd, respectively. It is shown that the difference of macrodispersivity attributes to the nature of temporal and spatial moments in the evaluation of a travel distance of particle swarm. The results indicate that the tailing of particle traveltimes depends on the degree of upscaling, although upscaling has a substantially low impact on the macrodispersivity estimates and median traveltimes of particles reaching a control plane. Moreover, particle transfer between layers and its stochastic modeling employed in random walk particle tracking have an effect on the increase of transverse macrodispersivity with the increase of travel distance.
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  • Keisuke Yoshida
    2011 Volume 67 Issue 2 Pages I_533-I_540
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    It is well known that the Manning roughness coefficient possibly varies during floods, depending on the bed conditions with or without sand waves and vegetations, and it is then difficult to identify the effective value of the coefficient by means of the on-site observation of the bed materials during normal stages. This paper proposed a practical method of an inverse estimation of the time-variant coefficient by using the flow data. The method is based on the optimal control with an adjoint shallow-water model. The fundamental twin experiments were carried out with the synthetic observation data of water level and depth-averaged velocity, in order to verify the method. The results showed that the time-variation can be accurately identified by using more observation data than the number of the unknown variables.
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  • Yoshiyuki SHIBAYAMA, Shinichiro ONDA, Takashi HOSODA
    2011 Volume 67 Issue 2 Pages I_541-I_548
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Flow resistance is increased with vegetation and prediction of resistance is of great importance in river engineering. In this study, numerical simulation of open channel flows with rigid vegetation is carried out using a detailed two-dimensional depth averaged flow model with fine meshes and a spatially-averaged flow model with coarse meshes. Then, comparing the numerical results, the effects of the vortexes du e to shear instability and the vegetation density on flow structure is investigated. It is shown that the flow resistance due to vortexes can be reproduced by both a detailed two-dimensional model and a spatially-averaged model.
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  • Fumiaki HASEGAWA, Takuya YAMAMOTO, Fatima JAHRA, Yoshihisa KAWAHARA
    2011 Volume 67 Issue 2 Pages I_549-I_557
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    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 structure and lateral momentum transfer process in vegetated compound channels through experiments and numerical simulations. Two types of vegetation zone on a floodplain are discussed. In the first case a floodplain is fully covered by vegetation. In the other case a floodplain has a belt of vegetation zone along the interface between main channel and floodplain. The measured data are compared with the numerical results that are obtained using a non-linear k-ε model and a vegetation model. It is found that the numerical model can reproduce the main characteristics of the flow and that the convection and the turbulent diffusion play important roles in the lateral momentum transfer across the interface between vegetated floodplain and main channel.
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  • Takuya Maegawa, Iehisa Nezu, Aki Katayama
    2011 Volume 67 Issue 2 Pages I_559-I_568
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    A lot of aquatic plants are observed in actual rivers, and they are responsible for water quality, nutrient and particle removal, and can reduce turbidity and sediment transport. Recently, the importance of flow and turbulence to the ecology of aquatic benthic organism has been widely reported. For submerged vegetation, a shear-layer is generated near the vegetation edge, and it generates coherent vortices by Kelvin-Helmholtz (KH) instability. These large-scale eddies control mass and momentum exchange between the vegetated and non-vegetated zone, influencing the mean velocity profile, as well as the turbulent diffusivity. Therefore, it is very important to reveal the coherent eddies in vegetated flows.
    However, the transition from boundary-layer flow upstream of the vegetation canopy region to a mixing-layer-type flow within the vegetation canopy has not been fully investigated. So, in this study, turbulence measurements were conducted intensively in vegetated open-channel flows by using PIV. The present data provide insight into spatial growth of coherent structure.
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  • kenjirou Hayashi, masakazu Tatuno, Hisao Nagabayashi, Haruyuki Hasimot ...
    2011 Volume 67 Issue 2 Pages I_569-I_580
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Flow and fluid forces acting on several kind of trees in large scale wind tunnel were measured by using wind flow velocity meter and load cell. Drag coefficient of drag forces acting on a tree decreased with increase of Reynolds number because projected frontal area of tree canopy in still air decreased with increase of incident flow velocity. The reverse flow was not found at down stream region of tree under the influence of the flow passing through the tree canopy. The recovery of flow velocity in the wake of tree was more slow compare to that of circular cylinder in uniform flow. The impulsive forces acting on a pine tree were also measured.
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  • Takaaki Okamoto, Iehisa Nezu, Hirokazu Ikeda
    2011 Volume 67 Issue 2 Pages I_581-I_588
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Aquatic plants reduce suspended sediment transport because of the local reduction in bed shear stress. Therefore, it is very important for river environment to reveal the mass and momentum exchange near the vegetation zone. Turbulent diffusion mechanisms in emergent vegetated flows have recently been investigated by many researchers. However, the effect of the submerged vegetation on the turbulent mixing process has not been fully investigated. So, in the present study, the combination of PIV and planar laser-induced fluorescence (LIF) technique is applied to the vegetated open-channel flows. Two-dimensional data allow the identification of coherent structures and quantification of the vertical mass transport.
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  • Michio Sanjou, Takaya Komatsu, Iehisa Nezu
    2011 Volume 67 Issue 2 Pages I_589-I_598
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    It is well known that wind-induced water waves generate formations of Langmuir circulation. This phenomenon is observed together with the high-speed and low-speed streaks, i.e., the convergence and divergence zones, respectively. Mass and momentum are transported significantly from the divergence zone toward the convergence zone, and consequently, strong downflows appear in the convergence zone. So, it is very important to study hydrodynamic properties of Langmuir circulation in natural lakes and ocean. In this study, stereoscopic PIV measurements were conducted in order to reveal the distributions of all thee components of velocity vectors. These experiments allowed us to investigate 3-D turbulent structure under the water waves and generation mechanism of large-scale circulations.
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  • Mohammad Bagus ADITYAWAN, Hitoshi TANAKA
    2011 Volume 67 Issue 2 Pages I_599-I_606
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    Numerical experiment is conducted based on canonical problem for breaking solitary wave run up on sloping beach. The model in this study was developed using simultaneous coupling method of shallow water equation (SWE) with k-ω model for assessing boundary layer under solitary wave run up. Free stream, bed stress, velocity profile, and k value are recorded in three measurement points. The locations are, at the start of bed slope, near shore, and another one between them. Free stream velocities measurements show that the wave deformation due ti wave breaking causes a longer period of deceleration as the wave travel to shoreline. The effect is observed in the bed stress profile, vertical velocity distribution and k value. It is found that k value increases as the wave approaches the shoreline and its generation is highly effected by the wave breaking.
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  • Min Roh, Xuan Tinh Nguyen, Hitoshi Tanaka
    2011 Volume 67 Issue 2 Pages I_607-I_614
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    The tsunami wave, approaching to river entrance, is related with various river characteristics. In wave propagation process, river mouth morphology is one of the dominant factors because it is first the feature of the river when the tsunami wave arrived near rivers. At the tsunami wave generated by the 2010 Chilean Earthquake, the field observation data indicated a different aspect of wave propagation according to the river entrance structure. In this study, in order to evaluate the influence of tsunami wave due to river mouth morphology, a numerical experiment was conducted for hypothetical cases are based on the representative river mouth type. The results of numerical simulation and analysis of measurement applied to the effect of tsunami wave by the change of the river mouth.
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  • Makoto UMEDA, Yusuke BETTO, Kentaro SHINDO
    2011 Volume 67 Issue 2 Pages I_615-I_623
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    Lake Izunuma is a shallow lake located in the north part of Miyagi prefecture, whose water quality has been extremely deteriorated. One of the phenomena that influence the water quality is behavior of sediment that has accumulated on the bottom of the lake. In this study, field measurements were conducted during the windy season of winter, when resuspension of sediment is most active. Turbidity, water velocity, wave height were continuously measured in the lake for about three weeks. From the observed data, wave height and velocity oscillation had much to do with increase in turbidity. This fact indicated that resuspension of sediment was mostly caused by wind wave turbulence, which was affected by not only wind speed but also fetch determined from the planar shape of the lake and wind direction. Considering this effect, history and distribution of turbidity during the strong wind event was reproduced with a hydrodynamic numerical modeling.
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  • Hao Zhang, Yasunori Muto, Shiro Nakanishi, Hajime Nakagawa
    2011 Volume 67 Issue 2 Pages I_625-I_634
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    This paper presents an experimental study on the impacts of weir removal on the upstream channel dynamics in non-uniform sediment beds. It is found that weir removal promotes local scour and sandbar development in upstream channels, which are two dominant processes to be considered prior to any removal action. On the other hand, the mean sediment size and the geometric standard deviation of sediment mixtures are two governing and practical parameters in characterizing the sediment bed non-uniformity when local scour and bar development are concerned. Sand ribbons are observed in non-uniform beds due to sediment sorting and exert great influences on the bar system and the channel morphology.
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  • Ryuichi HIRAKAWA, Kunitoshi WATANABE, Terunori OHMOTO, Shohei MATSUMOT ...
    2011 Volume 67 Issue 2 Pages I_635-I_644
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    The groin changes from non-overflow condition to overflow condition in the actual river according to the flow discharge. In that case, it is thought that the riverbed and flow structure around the groin always changes. The flow characteristics and morphological responses around single groin has been clarified. In the present study, it aims to clarify the characteristic of the bed form and flow characteristics around six groines for changing relative water depth by the laboratory experiment under the condition to assume the Froude number to be 0.2. The bed form in the larger relative water depth has large scale of the scour. Accretion point in main flow region moved to groin region and downstream. The flow velocity of the main flow region become slower in the downstream.
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  • Mohammed ALAUDDIN, Takashi TASHIRO, Tetsuro TSUJIMOTO
    2011 Volume 67 Issue 2 Pages I_645-I_652
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    A groyne is an important river restoration structure. Although its history is for long and widespread use, optimized design of new groynes is not attempted much, which is very important to treat the highly unstable lowland river channels. A completely blocked impermeable groyne suffers from instability of the structure itself; whereas, fully permeable structure can not divert the flow rightly. Considering the present demands, four different groyne structures including modified combined and bandal-structures are examined in the laboratory channel to recognize their fluvial responses, incorporation with some field information. The performance of a groyne is confirmed through three key features: scour near groynes (structure stability), deposition in the groyne field (bank stability) and erosion in channel bed (navigability). Analyses of data show that the combined groynes cause gradual deceleration of flow towards the land and minimize local scour compared with the conventional impermeable ones. Also two other important features: deposition near bank and channel erosion, are better responded from modified bandal-structures and modified combined groyne.
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  • Gen Takahashi, Hiroyasu Yasuda
    2011 Volume 67 Issue 2 Pages I_653-I_660
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    Almost no explanation is given about development process of sand bar in non-straighten channel because the phenomenon of sand bar has been investigated using straighten channel. This study conducted a numerical experiment of development process of sand bar in a meandering channel and a figure-of-eight(gourd) as fixed wall. The results shows that the development process clearly differs in channel of straighten, meandering and figure-of-eight(gourd). The result of figure-of-eight(gourd) doesn't occur mode degradation and keep multiple bars.
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  • Tomoaki TAKAHATA, Norihiro IZUMI
    2011 Volume 67 Issue 2 Pages I_661-I_669
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Bed slope changes due to bed aggradation/degradation caused by an increase/decrease of sediment supply. Though we have performed a linear stability analysis of sand bars incorporating effects of bed aggradation/degradation, the analysis has assumed bed elevation changes without changing its shape, and temporal variation of bed slope has not been taken into account. In order to study bar instability with temporal variation of bed slope, the WKB method is applied with the use of the rate of bed slope changes as a small parameter. The analysis shows that, unstable regions in the instability diagram is expanded to the range of large wavenumbers when bed slope decreases while unstable regions are reduced when bed slope increases.
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  • Tomofumi HIRATSUKA, Norihiro IZUMI
    2011 Volume 67 Issue 2 Pages I_671-I_682
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    There have been a large number of studies on bed waves in rivers. It has been known that bed waves are strongly related to the Froude number. Meanwhile, there are only few studies on waves formed at the boundary between flowing water and erodible beds in closed conduits without free water surfaces. In order to predict the flow resistance of closed conduits such as sediment bypass tunnels and ice-covered rivers, it is important to obtain detailed information on the formation of boundary waves. Seki and Izumi2) have proposed a linear stability analysis to explain the formation of small scale boundary waves in closed conduits. They have also reproduced small scale boundary waves in flume experiments, and compared with their analysis. According to their analysis, the Shields and Euler numbers are the dominant parameters, and the flat bed becomes unstable when the Euler number becomes larger than the critical Euler number, which increases with the Shields number. However, the agreement between the prediction and their observation is not sufficiently good. In this study, we introduce the ratio of the shear velocities between the lower and upper walls as a new parameter, and improve the agreement. In addition, we perform a weakly nonlinear stability analysis to obtain more detailed information on behavior of boundary waves in the vicinity of the critical Euler number. We find that the transition between flat bed and boundary wave regimes in closed conduits is characterized by subcritical bifurcation.
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  • Hiroki Yoshitake, Ryota Tsubaki, Yoshihisa Kawahara
    2011 Volume 67 Issue 2 Pages I_683-I_691
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Floods accompanied by bed elevation change were observed in a steep reach of the Minochi River in 2009 and 2010. The flood discharge hydrograph in 2009 is estimated by three methods, namely the conventional float measurement, Large-scale PIV method and 2-D unsteady flow simulation. The 2-D flow simulation considers vegetation toppling during flood and bed elevation change due to bed load transport. In the numerical simulation, water level hydrographs observed at various points are used for boundary conditions at upstream and downstream ends and the evaluation of the vegetation drag parameter. The flood discharges obtained by three methods are compared to find that the 2-D unsteady flow model yields good agreement with the discharge by Large-scale PIV method. The selection method of the location of suitable upstream boundary in a step reach is also discussed
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  • Hiroyasu YASUDA, Tsuyoshi HOSHINO
    2011 Volume 67 Issue 2 Pages I_693-I_702
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    Numerical computation of river flows have been employed the general coordinate system to adjust a river plane form. An adjustment flexibility of the coordinate system is better but it is difficult to generate a grid system in order to compute stably because grid system is not determined uniquely. This study develops a new boundary fitting method introducing the hierarchical quad-tree grid system in computation of shallow water equation. The numerical model with the quad-tree grid system apply to compute flow pattern in meandering channel, the result agree with experiments result well.
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  • Ryuichi SHIMADA, Ichiro KIMURA, Yasuyuki SHIMIZU
    2011 Volume 67 Issue 2 Pages I_703-I_712
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    Bed deformations in river bends are crucial for river management. However, due to the complex flow structures, the prediction of bed deformations in river bends is difficult. In this study, flow structures and bed deformations in curved open channels are discussed through laboratory experiments and 3D numerical simulations. In the 3D model, RANS approach was adopted. The numerical results were compared with experimental data performed by Hinokidani (1998). It is indicated that the fundamental properties of both flow and bed deformation can be captured well by present computations. In addition, numerical and laboratory experiments were conducted for verifying the difference of bed deformation patterns depending on different channel and hydraulic conditions. The experimental results showed that bed deformation patterns in river bends closely depend on two dimensionless parameters; the Dean number and the depth over the curvature radius.
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  • Takao KURIYAMA, Hiroshi INOKUMA, Akihiko NAKAYAMA
    2011 Volume 67 Issue 2 Pages I_713-I_720
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    In order to develop a Large-eddy Simulation (LES) method that will be applicable to real river flows, a numerical method based on the moving curvilinear coordinates has been developed and applied to a flow in a channel bend. The flow in a channel bend is a good benchmark test case for numerical simulation method since it has many important elements essential to real river flows. There are experimental data and calculation using more conventional Reynolds-averaged Navier-Stokes (RANS) methods. By directly simulating the large-scale flows with about 50 percent of the fluctuating velocities resolved, the present method is found to reproduce the mean streamwise velocity and the secondary flow very well and the turbulent stresses and the free-surface fluctuation are reproduced reasonably well.
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  • Yuichi Kouchi, Takasi Hosoda, Ichiro Kimura, Toshiaki Kimura
    2011 Volume 67 Issue 2 Pages I_721-I_730
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Turbulent flow structures in open channels with various roughnesses are important topics in hydropower engineering. In this study, applicability of numerical mode with URANS type turbulence models and LES for simulating the channel flows with triangular roughness on side walls..We carried out the experiments and showed the comparisons with experimental data and calculated results were generally adequate. The numerical result showed that non-linear k-ε models and LES could reproduce the velocity profile, formation of cross - sectional secondary currents in the channel and the maximum-velocity-dip phenomena. Furthermore, we visualized vortex pipe from the calculated result and investigated the three-dimensional unsteady flow structures around side walls such as waver of secondary flow.
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  • Ryohei Matsuda, Kazuyuki Izuno, Akihide Hatanaka, Hiroshi Kobayashi
    2011 Volume 67 Issue 2 Pages I_731-I_742
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    This paper focused on reduction mechanism of vortex induced vibration by installing a vertical plate attached at a bottom plate. In this study, discrete vortex method was employed for the analysis. The results were as follows. The vertical plate has influences on flows and pressure distributions around a girder. Non-dimensional parameter h/H was important on the stabilization of heaving responses. Parameter h is the height of the plate and H is a height of time-integrated share layer from bottom plate which was given as the result of the static analysis of the basic section. In order to suppress the vibrations more effectively with the interference of the separation flow from a leading edge, the value h/H of 1.0 was recommended.
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  • Shota ISHII, Akihiko NAKAYAMA
    2011 Volume 67 Issue 2 Pages I_743-I_749
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    In order to make a numerical simulation method that is applicable to fluid motion in a fuel storage tank due to such external disturbance like seismic vibration, a more conventional Large Eddy Simulation (LES) method for simulating turbulent flows has been reexamined and adapted to deal with smoother flows with large body forces such as gravity and inertial acceleration, characterized by mostly irrotational motion. With some modification to the numerical scheme and the method of representing residual unresolved stresses, sloshing phenomena in rectangular and cylindrical storage tanks have been analyzed. The resonating sloshing frequency and the viscous damping are found to be reproduced well. Along with slow first-mode oscillations, higher-order modes of motion are also reproduced.
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  • Keisuke ASAKURA, Akihiko NAKAYAMA
    2011 Volume 67 Issue 2 Pages I_751-I_756
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    The concentration field of passive contaminant in a turbulent boundary layer with and without temperature stratification has been computed by large-eddy simulation (LES) method. With application to atmospheric flow over topography in mind, the numerical method has been constructed in curvilinear coordinates and the inflow boundary layer was generated by recycling velocity and temperature fluctuations in a driver section placed upstream of main calculation region. Different combinations of sub-grid scale (SGS) models for the momentum transfer and the heat and passive scalar fluxes were examined. The quality of prediction of the diffusion of passive scalar depends on the accuracy of turbulent fluctuations. The mixed time scale model combined with the dynamic eddy diffusion model was found to give the best results.
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  • Takanori UCHIDA, Yuji OHYA
    2011 Volume 67 Issue 2 Pages I_757-I_764
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    A detailed wind synopsis analysis was performed for the Asokurumagaeri wind farm (operation of this wind farm was initiated in October, 2005) in cooperation with the Kumamoto Prefectural Enterprise Bureau. In this simulation, high-resolution terrain elevation data which included the latest land development information were utilized. The simulation results suggested that the effects of wind risks (terrain-induced turbulence), which have been reported in the media, were successfully reproduced. An appropriate wind direction and an inappropriate wind direction for locating a wind turbine generator were shown based on the numerical results obtained
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  • Toshiyuki ISHIKAWA, Atsushi HATTORI, Hirotaka KAWANO, Takashi NAGAO, A ...
    2011 Volume 67 Issue 2 Pages I_767-I_776
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    In CFRP bonded onto steel plate, thermal stress is induced in steel plate by temperature change, due to difference in coefficients of thermal expansion between steel and CFRP. In this study, reduction technique of the thermal stress in steel plate, which is additional bonding of aluminum alloy plates, is proposed. Namely, the coefficient of thermal expansion of composite plate consisted of CFRP and aluminum plates is designed as that of steel. In this research, to verify the effectiveness of developed method, heat tests of CFRP and aluminum plates bonded onto steel plate were carried out. As a result of the tests, infinitesimal thermal stresses in steel plate with CFRP and aluminum plates were measured while large thermal stresses were measured in conventional CFRP bonded onto steel plate. Additionally, to confirm the test results, numerical analysis was also carried out.
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  • Masaru SHIMIZU, Toshiyuki ISHIKAWA, Atsushi HATTORI, Hirotaka KAWANO
    2011 Volume 67 Issue 2 Pages I_777-I_784
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    Recently, some research reports on the application of pre-stressed CFRP plate on steel members have been published. However, the shear and peeling stresses in adhesive at the end of CFRP plates are induced by releasing the pre-tension as well as bending moment. Therefore, in the strengthening of steel members with the pre-stressed CFRP plate, the CFRP plate tends to have debonding in the lower bending moment. In this study, to reduce the shear and peeling stresses in adhesive by releasing the pre-tension of CFRP plates, installation of non pre-stressed regions in CFRP plate was proposed. By installing the non pre-stressed regions in CFRP plate, dividing the locations of higher stresses in adhesive by releasing the pre-tension and bending moment were revealed. Additionally, the design equation of length of non pre-stressed regions was also presented.
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  • Mikihito Hirohata, Yusuke Hageyama, You-Chul Kim
    2011 Volume 67 Issue 2 Pages I_785-I_791
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    In order to investigate whether propagation of cracks repaired with patch plates could be monitored by FSM or not, a series of experiments and analyses were carried out. A slit imitating a crack was inserted in a plate covered by patch plates and its propagation was monitored by FSM. The experiment was simulated by an electric field analysis. Although the potential difference, which was the measure of FSM-monitoring, was affected by the patch plates and the bolts, the crack propagation in the invisible area covered by the patch plates could be monitored with high accuracy by FSM.
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  • Takashi Matsumoto, Hiroki Sakuraba
    2011 Volume 67 Issue 2 Pages I_793-I_800
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    This paper presents an experimental investigation on the flexural behavior of CFRP box beams with four different CFRP laminate structures. Those four laminates have 25 laminas, and they have the proportion of longitudinal, transverse, and diagonal lamina as 1:1:0 (L1T1), 1:0:1 (L1D1), 1:0:2 (L1D2), and 1:1:2 (L1T1D2). In addition to the displacement and strain gauge measurements, image analysis was employed to observe the deformation and strain field near a failure location. Flexural tests showed that L1D1 exhibited the highest flexural strength, followed by L1D2, L1T1D2, and L1T1, where diagonal laminas clearly contributed to the flexural strength more than transverse laminas. All the beams were observed to have a premature damage near a loading plate, and finally they exhibited a brittle failure in upper flange and web. Different failure modes were observed due to the laminate structures. Among them, image analysis clarified the development of shear strain in the web of L1T1 even before the final brittle failure.
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  • Aiko FURUKAWA, Akira IGARASHI, Junji KIYONO
    2011 Volume 67 Issue 2 Pages I_801-I_812
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    In this study, estimation equations of maximum response ductility from the acceleration response of a nonlinear SDOF system during an earthquake are proposed. It is assumed that the model has a bilinear skelton curve and is subject to Masing's law. The estimation equations are the function of the equivalent natural period and damping ratio on the assumption that the nonlinear system is approximated with an equivalent linear model. The approximation is conducted in the time and frequency domains, respectively, and different estimation equations are derived for each domain. The validity of the proposed equations is confirmed through the numerical simulations. It is found that the equations derived in the frequency domain have higher accuracy if extracted acceleration records with impulsive response are used. It is also found that the equations derived in the time domain give bad accuracy when the displacement response is nonsymmetric or acceleration records contain measurement noise.
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  • Yu OTAKE, Takashi SASUGA, Yusuke HONJO, Shigeyuki MURAKAMI, Koichi KOB ...
    2011 Volume 67 Issue 2 Pages I_813-I_824
    Published: 2011
    Released on J-STAGE: April 06, 2012
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    This paper presents results of an investigation of evaluating the bridges health degree of 54 bridges managed by Gifu Prefecture in Gifu City. Bridge health degree is statistically calculated with periodic inspection data conducted by Gifu Prefecture. This inspection results consist of many items and evaluate the state of bridge details, but a currently index is insufficient as one used to maintenance. Accordingly, the index is required that can evaluate overall of each bridge elements or entire bridge. So, this study aims to express health degree of bridge elements by one or two overall index with principal component analysis, and grasped relationship to calculated health index, age, specification, design standard and environmental condition by multiple regression analysis.
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  • Hiroshi Hattori, Hitoshi Furuta, Yasutoshi Nomura, Koichiro Nakatsu, K ...
    2011 Volume 67 Issue 2 Pages I_825-I_832
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    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. In other words, it is not necessary to use the precise modeling and analysis methods before conducting the health monitoring. The proposed system learns the vibration response by using AdaBoost. By using AdaBoost technique, the network can respond to various types of external forces and the prediction accuracy increases. Previously, a health monitoring system that can adapt to the structural systems and environments through the learning ability was developed with the recognition rate of over 80% using numerical simulations. However, experimental verification is needed before real life application of the proposed system. In this paper, results laboratory experiments are presented to show the effectiveness of the methodology. It is observed that the proposed system can recognize the change of structural characteristics and condition states of a steel grid type large scale bridge model.
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  • Chul-Woo Kim, Ryo Isemoto, Mitsuo Kawatani, Kunitomo Sugiura
    2011 Volume 67 Issue 2 Pages I_833-I_842
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    This paper investigates feasibility for bridge health monitoring from output-only vibration measurements in a moving vehicle laboratory experiment. A parameter from the AR coefficient is also adopted to detect abnormality of the bridge. Consideration goes into structural diagnosis of the bridge from pattern change of identified system parameters due to damage. Observations demonstrate the feasibility of structural diagnosis of the bridge from the identified system parameters of the vehicle-bridge interactive system.
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  • Kodai MATSUOKA, Kiyoyuki KAITO, Masamichi SOGABE
    2011 Volume 67 Issue 2 Pages I_843-I_854
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    In order to apply structural monitoring into practice, it is indispensable to develop a method for change-point detection of bridge vibrational properties. In this study, the authors have developed a methodology using sequential prediction, dynamic model selection, and clustering, with the purpose of evaluating vibrational properties and its change timings. In order to examine the validity, the time series that had the change in frequency was calculated, and proposal method was applied. As a results, it was found that the natural frequency is detected. As for change timings, these were evaluated as change intervals. On the other hand, when the proposed method was applied to the acceleration response of a bridge when a train passes, it was found that bridge frequency can be extracted stably, and it is difficult to detect change timings when the change is small. Based on these results, factors were studied, and some solutions to the problems were proposed.
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  • Kyosuke Yamamoto, Tatsuaki Toshinami, Yoshinobu Oshima, Chul-Woo Kim, ...
    2011 Volume 67 Issue 2 Pages I_855-I_864
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    This study focuses on the vehicle acceleration response as a source of estimating bridge's health condition, since it contains bridge profile information and a change of the bridge profile caused by bridge damage can be detected from change of statistical vehicle response. The wavelet coefficient is used as a damage index. To increase the possibility of detecting the damage, the kurtosis of the index is adopted. By observation from a laboratory experiment, it is found that kurtosis of vehicle response is a sensitive index for bridge damage.
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  • Hiroshi Hattori, Yoshinobu Ohshima, Shigeaki Tsukamoto
    2011 Volume 67 Issue 2 Pages I_865-I_873
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    This paper reports on the outlier detection in the passing sound of a vehicle over the bridge-joint using Chaos prediction analysis as well as frequency analysis. First, on the basis of frequency analysis of the passing sound, it was found that the irregular sound over the damaged joint can be identified by detecting the peaks of power in the band of 500 to 800Hz. Then, by assuming that the passing sound is Chaos series, Chaos prediction analysis was applied to the passing sound for outlier detection. Finally it was found that the irregular sound also can be detected by Chaos prediction error which is the difference between the prediction based on the intact sound and the measured one.
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  • Chiharu HIDAKA, Takuma SAITOH, Kazuki WATANABE, Masayuki SAEKI
    2011 Volume 67 Issue 2 Pages I_875-I_883
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    A structural sensing method using artificial vibrator and wireless sensor network is presented. In this method, the artificial vibrator excites very accurate harmonic vibrations to a target structure and accelerometers deployed on the structure observe the response. The observed acceleration data is collected to a central sever machine through wireless sensor network. Since the artificial vibrator is able to excite very accurate harmonic vibration and sensor nodes are time synchronized to the artificial vibrator, heavy stacking can be applied to the observed data on the sensor nodes. Besides, the response of excited vibration can be accurately estimated by means of discrete Fourier transform due to the time synchronization. These processes successfully compress the amount of data without collapsing the important information of the data that is the amplitude and phase of excited vibration. In this paper, development of the prototype system and the implementation of time synchronization between the artificial vibration source and wireless sensor node are described.
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  • Tatsunao TAKAMOTO, Masayoshi YAMAGUCHI, Kazuyuki NAKAHATA, Mitao OHGA
    2011 Volume 67 Issue 2 Pages I_885-I_893
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    The acceleration sensors which adopt the MEMS (Micro Electro Mechanical System) technology, offer high reliability and sensitivity in a small size. Using the MEMS sensor, we develop a visualization system of vibration of a civil structure at a low cost. In our system, time series of acceleration data measured at multiple points are transmitted to a computer at base-station with the wireless LAN and then converted to displacement data by the linear acceleration method. Here we make a digital filter to avoid a drift of the baseline of displacement data and to eliminate the white noise. First, our measurement setup and data conversion from acceleration to displacement using digital filters are described. Next we show an animation of vibration of a connecting bridge between two buildings by means of triaxial displacement data.
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  • Katsumi NAGAFUCHI, Kenji KAWANO
    2011 Volume 67 Issue 2 Pages I_897-I_904
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    The dynamic response evaluations of the surface ground layer play important roles on the seismic damage evaluations for the ground pavement system. A number of researches on seismic responses of the surface ground layer have been carried out to apply the seismic performance evaluation of structure. In the present study, the uncertainty effects on the seismic response evaluation of the ground pavement system are examined with the Monte Carlo Simulation (MCS). The ground pavement system is represented with the finite element method of two-dimensional plain strain situation. It is shown that the uncertainty effect on the maximum response evaluation can be effectively evaluated with the MCS to carry out the damage evaluation of the ground pavement system to the seismic motions.
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  • Kazuhisa ABE, Toshihide ARAKI, Kazuhiro KORO
    2011 Volume 67 Issue 2 Pages I_905-I_913
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    This paper presents a numerical method for surface elastic waves in a half-space possessing a two-dimensional periodicity. The solution is expressed by plane waves in the vertical direction, while it is approximated by finite elements in the horizontal plane. By virtue of the Bloch's theorem, the problem is reduced to equations of motion in a unit cell. The vertical wavenumbers satisfying the equations in the unit cell are determined by solving an eigenvalue problem with respect to the wavenumbers. As numerical examples, periodic arrays of piles embedded in a ground are analyzed. In the analyses piles made of concrete and a soft material are considered with arrangements given by the square and the triangular honeycomb lattices. Under these conditions, the influences of the stiffness and the lattice pattern of piles on the band structure are investigated.
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  • Takanori Harada, Ryosuke Matsuda, Masaki Nakamura, Yushi Awada
    2011 Volume 67 Issue 2 Pages I_915-I_924
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    This paper presents the dynamic Green's functions by the use of the stiffness matrix method for layered elastic half space in Cartesian coordinates. From these Green's functions in Cartesian coordinates, the well known Green's functions in cylindrical coordinates are derived. 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 well known dynamic Green's functions of elastic half space in cylindrical coordinates are shown.
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  • Yukinobu KIMURA, Sawako ICHIKI, Kenji KAWANO, Ryota KUROSE, Taisuke KI ...
    2011 Volume 67 Issue 2 Pages I_925-I_934
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Aftershocks can increase the damage and possibility of structural collapse soon after a major earthquake. When it is considered whether the structure should be repaired or not after a major earthquake, it is necessary to estimate the influence of aftershocks on mainshock-damaged structure and the likelihood for occurrence of aftershocks shortly after the main shock. In the present study, the damage evaluations of simplified SSI system with the influence of aftershocks are examined. Besides, methodologies for evaluating the collapse probability of mainshock-damaged structure shortly after the main shock by considering the likelihood for occurrence of aftershocks are proposed. It is shown that the proposed estimation method can effectively evaluate the collapse probability of structure due to aftershocks.
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  • Tsuyoshi Ida, Ryohei Komatsu, Hirokazu Hirano, Takuho Morikawa
    2011 Volume 67 Issue 2 Pages I_935-I_943
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    The liquid sloshing of oil storage tanks caused by Tokachi-Oki earthquake in 2003 gave severe damage to oil tanks in Tomakomai area. The purpose of our study is to propose damping method against liquid sloshing so that damage and sink of floating roofs of the oil tanks can be prevented. In this paper, we propose the buffer using viscoelastic materials as for anti-liquid sloshing measure and have confirmed that the buffer damping method is appropriate to damp liquid sloshing for actual floating roof tank.
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  • Yoshihisa Okada, Yoshimi Ogawa
    2011 Volume 67 Issue 2 Pages I_945-I_953
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    There are many bridges in lowland areas in East Tokyo and soft ground in Tokyo Bay Coast. A bare possibility is that these structures might suffer disastrous damage due to liquefaction when the area is hit by a large earthquake. In this paper, interaction spring and damping model considering a process of liquefaction and relationship between natural period of ground and pier are proposed, and it is verified by using the dynamic centrifugal model test in level 2 earthquake motion. As the result, it is verified that the response of pier and footing behaviors of the test and the analysis can be well corresponded, the interaction spring and damping model considering the process of liquefaction and the relationship between natural period of ground and pier is suitable for the purpose.
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  • Hirotaka SAKAI, Fumihiro URAKAWA, Akira AIKAWA, Akira NAMURA
    2011 Volume 67 Issue 2 Pages I_955-I_964
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    The vibration of concrete sleepers is an important factor engendering track deterioration. In this paper, we created a three-dimensional finite element model to reproduce a prestressed concrete (PC) sleeper in detail, expressing influence of ballast layers with a 3D spring series and dampers to reproduce their vibration and dynamic characteristics. Determination of these parameters bases on the experimental modal analysis using an impact excitation technique for PC sleepers by adjusting the accelerance between the analytical results and experimental results. Furthermore, we compared the difference of these characteristics between normal sleepers and those with some structural modifications. Analytical results clarified that such means as sleeper width extension and increased sleeper thickness will influence the reduction of ballasted track vibration as improvements of PC sleepers.
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  • Kunihiko Uno, Hiroo Shiojiri, Pahaiti Laheman, Masaaki Mitou
    2011 Volume 67 Issue 2 Pages I_965-I_974
    Published: 2011
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    PML(Perfectly matched layer), especially Convolutional PML is known to have high capability of wave absorption. Unfortunately, it is not possible to input earthquake waves through PML, contrary to viscous damper. A method to apply seismic waves on FEM domain enclosed by Convolutional PML is described for material with damping. By comparing the numerical results by this method with those by conventional methods, the validity of the proposed method is shown. The effect of each PML parameter is also clarified. Next, Convolutional PML is applied to the model with elongated domain in numerical simulation of surface wave and its superiority over Conventional PML and viscous boundary is demonstrated by numerical results.
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