In this study, we conducted a series of numerical simulations for caisson type breakwater that is subjected to an external wave loading. In order to investigate the overall behavior of the breakwater and the load support mechanism of a rubble rock foundation, we employed a two-dimensional distinct element method. In this paper, we show the modeling method of this system and the parameter determination procedure for the simulations. Based on the simulation results, we report some preliminary results on the load support mechanism and the breakwater behavior.

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In order to clarify mechanical behavior of sand ground-structure system under cyclic loading condition, a series of FEM analysis and model test were carried out. In the model test, it is found that the rigidity of sand ground changes with increasing of the settlement of structure. Softening behavior of sand deposits suddenly occurs if the lateral flow deformation due to cyclic loading exceeds a limit. Based on the results of model tests, a technique of analysis for lateral flow deformation of sand ground is proposed. By using the proposed technique, the settlement and lateral flow deformation of sand ground subjected to cyclic load such as wave force can be well simulated.

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The heat transfer and seepage behavior in unsaturated soil should be investigated to analyze the mechanism of slope failures and predict their occurrence due to heavy rainfall. From this view point the numerical model taken account of evaporation was proposed in this paper. The numerical experiments were carried out to prove the validity of proposed model, i. e., the amount of rainfall and temperature in soil were used as input data and the calculated suction was compared with that obtained by field measurement. It was found that the proposed model may be promising for the investigation of heat transfer and seepage behavior in unsaturated soil.

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This paper presents the simple method of generating 1-D fractal permeability field based on theoretical consideration of spatial variations of hydraulic conductivity. Then, we examine the statistical properties (e. g., probability density function, spectral density, variogram) of this random fractal field. Moreover, the propriety of this model is inspected by permeability distribution collected from several boreholes. The results show that the spectral density of the field data resulted in ƒ^-ζ? type same as this model.

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This paper presents a one-dimentional dynamic response analysis method to evaluate the dynamic response of the embankment and support ground system considering multi-reflection theory based on layer matrix method. Hence, the shape of embankment is modeled as an arbitrary trapezoid. Furthermore, by dividing the embankment into some horizontally layered thin elements, a variation of the material properties with depth is possible to take into account. It is found that the shape of embankment and the dynamic interaction with a support ground affect the vibration characteristics and that the damping characteristics of ground around the predominant frequency of embankment has the important role for the dynamic response.

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Resisting capacity of reinforced concrete (RC) column, which is subjected to 2-directional horizontal forces, degrades in comparison with the case of single horizontal force. In this paper, the influences of the analytical model on the behavior of RC piers subjected to bi-axial bending are discussed.

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When the strong earthquake occurs and a bridge suffers the longitudinal impact, a superstructure and abutments of a bridge will collide. There is a spatial gap between superstructure and wall of abutment and this gap may effect to accelerate collision speed between them. Then, in this paper, effect of shock-absorbing device to softening the collision is investigated in the cases of simple and continuous girder bridges. And the effect of stiffness of shock-absorbing device, laying-gap length and back-fill ground of a abutment to soften the collision response, is analyzed.
Moreover, influence by laying-gap length and an abutments of back-fill ground when colliding was examined.

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Realistic simulation of a possible earthquake is important for making rational plan against earthquake disasters. This paper proposes such a simulation method using a high resolution strong motion simulator and constructing a computer model of a whole city. The data for the model are provided by certain Geographic Information System, and underground structures and each building are modeled. The methodology of constructing these models is studied, since available data are usually limited. An example of a city model is constructed and earthquake simulation is made to examine the basic usefulness of the simulation.

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A new analysis method is developed for predicting dynamic structural responses with high accuracy and spatial resolution. Estimation of dynamic behavior of complicated structure requires a huge amount of computation. Our method takes advantage of multi-scale analysis for reducing such a computation. In this paper, we present the formulation of this new analysis method, the application of it into a simulation of simple structure and the comparison between this method and conventional methods are presented to verify the performance of our method.

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A numerical approach to analyse pounding responses of adjacent buildings on subsoil to earthquakes is presented. The nonlinear calculation of the soil-structure system is performed subsequently in the Laplace and the time domain. The adjacent buildings and the subsoil are described by finite elements and boundary elements, respectively. In the numerical investigation the effect of Kobe, Northridge and Chi-Chi near-source earthquakes is considered. The result reveals that both the subsoil and long-period pulses in the ground motions can increase the pounding potential of buildings. In addition, poundings can amplify the induced floor vibrations. In contrast, soil-structure interaction has reduction effect on the induced vibrations. In order to estimate the distance required to prevent pounding the influence of the soil-structure interaction is significant.

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Structural response to the ground excitations and the ground response to a moving load on the soil surface are considered. The reduction of the structural response is achieved by reducing the ground vibrations using a trench and a wave-impeding barrier (wib). The numerical investigation is performed by using a boundary element and finite element method. The response of the structure increases with the moving speed of the load, independent of the reduction approach. The investigation reveals that both trench and wave barrier can be used as a reduction measure.

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When a strike-slip occurs, the base bedrock itself slides uniformly, but on the ground surface so-called echelon faults, which are periodical oblique faults, emerge. In order to examine such characteristics of propagation of localized deformation in foundation, 3D-FEM analysis is carried out. Constitutive law of the soil in the foundation is expressed by the void damage theory. Various finite elements are analyzed in order to investigate change of the echelon pattern influenced by the scale of analyzed region and the material property.

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For the safety of civil structures, it is required to predict the possibility of ground surfce deformation caused by a surface earthquake fault. In order to provide quantitative estimate of hazards due to surface earthquake fault, the authors have been developing a numerical simulator based on the spectral stochastic finite element method. In this paper, we report the current state of the simulator. We calculated the ground surface deformation caused by lateral sliding of numerical model of earthqauke surface fault and examined numerical results qualitatively and quantitatively in the meaning of character and probability by comparing with the result of model experiments for lateral sliding of a sand box. The numerical result is consistent with the result of the model experiment in the meaning of character of configuration of Riedel shears and amount of the base slip at which the Riedel shears appear on the surface. But the experiment result couldn't be reproduced in the meaning of probabilistic character like a standrad deviation.

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Though several mechanisms are proposed, why earthquakes stop is a longstanding dilemma. We propose a new mechanism which explains arrest of fracture in earthquakes taking into account the fact that density around the faults is smaller because of the existence of fracture zones. The present analysis using the boundary integral equation method in 2-D shows that a small difference of density or rigidity causes arrest even without barriers. In addition, it also become clear in this study in 2-D that ruptures propagate in pulse-like mode and rise times become very short compared to the overall duration of ruptures.

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In Japan, deep brine aquifers in sedimentary basins have a huge sequestration capacity and extensive distnbution, therefore, sequestration of carbon dioxide (CO₂) in deep aquifers is one of the variable and feasible options for CO₂ emission cutting.(Tanaka et al., 1995; Koide, 1999). However, the injection of CO₂ may considerably modify the stress state in the subsurface and result in the deformation and even failure along the previously existing soft bands, especially the fault, in the strata. Although most researches have been carried out abouthe process of CO₂ injection, the interaction between CO₂ and water, and the seepage of CO₂ in the formations, the research is rarely touched on the reaction of the fault around the storage site after the CO₂ injection. Our research in this area is focused on the stress variation and deformation around the storage strata after the CO₂ injection, especially its effects on the fault An FEM simulator was constructed with considerations of the initial stress, pore pressure, and fault. This paper reports our recent efforts in developing such a simulator and some preliminary simulation results. These preliminary simulations have been conducted to investigate the CO₂-driven buoyancy stress distribution, injection force and the influence process of CO₂ injection on the fault under different positions and different dip angles. At last some interesting results are concluded.

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This paper describes the development of soil/water coupled dynamic finite element computation technique considering irreversible deformation characteristics of porous media such as soils. Incremental governing equations taking into account of the effect of acceleration, first, are summarized and discretized in spatial and time domain. Thus obtained discretized equations are formulated based on the finite element technique so that the acceleration and the total pore water head are unknown values that should be solved under imposed boundary and initial conditions. The finite element code newly developed in this paper is verified by comparing some strict solutions for solid/water coupled problems and is examined whether the seismic responses of soil/water coupled media can be explained. Fina ly, the vertical settlement due to the horizontal seismic external force is successfully simulated.

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Singularity of the horizontal wavefunction as well as properties of the complex Rayleigh wave modes are investigated for the spectral form of the Green's function for an elastic layered half space. First, the spectral representation of the Green's function is extended into the form for which the field and source points are separated completely to generalize the investigations. The effects of the singularity at k = 0 of the horizontal wavefunction are studied next, where k is the wavenumber. A close investigation reveals that the singularity has no effects on the Green's function, that is summerized by Theorem 1. The properties of the complex Rayleigh wave modes are also examined based on the present Green's function. Here, a comprehensive explanation for that the complex Rayleigh waves show standing waves is given, that is summerized by Theorem 2. Finally, a practical method for obtaining the derivative of the spectral form of the Green's function is discussed based on numerical calculations.

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Green's function in the time domain for 3-D layered acoustic half space is derived here. The Green's function is composed by the time-wavenumber domain solution based on discrete wavenumber method. The time-wavenumber domain solution is obtained from the Fourier inverse transform for the frequency-wavenumber domain solution with respect to the time, so that the time-wavenumber domain solutions satisfies the causality condition. The frequencywavenumber domain solution is expressed in terms of the eigenfunctions for the discrete and continuous spectra. As a result, the present Green's function is completely expressed in terms of the eigenfunctions for the discrete and continuous spectra. Several numerical calculations are carried out to verify the accuracy of the present Green's function.

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Numerical simulations are performed to investigate the characteristics of the formation of alternate and multiple bars with the use of the NHSED2D model. The results of the simulations show reasonably good agreement with the results of the theoretical analysis and the experiments. It is found that periodic boundary conditions with an insufficiently small calculation domain tend to stabilize multiple bars. It is also found that there is possibility that different initial configurations lead to different equilibrium states. The reduction of the bar mode can be well explained by the theoretical results that the difference between the dominant modes associated with the maximum growth rate and the maximum equilibrium amplitude. The irregularity appeared in the reduction process of the bar mode is suggested to be caused by the nonlinear interaction between multiple modes of bars.

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It has been known that a series of steps often develop on an erosional bed. In this study, a weakly nonlinear stability analsys is perfomed with the use of the two-dimensional Reynolds equations. The anlysis leads the value of the first Landau coefficient in a nonlinear amplitude equation with the use of the amplitude expansion method. The results show that when the wavenumber is larger than the chracteristic wavenumber obtained in the linear stability analysis, the perturbation keeps growing in the process of the nonlinear development_ This result corresponds to the fact that steps on erosional beds develop to form a series of waterfall-like steps or overhanging cliffs in channels. This does not mean the steps can actually grow infinitely. Fully-developed steps, which cannot be described by this formulation, can be illustrated by Parker et al's theory to have an equilibrium amplitude.

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Sediment bypass system has been proposed as a countermeasure against sedimentation and turbid effluence that occur in reservoirs over long period of operation. The system allows both bed load and suspended sediment to bypass the reservoir via a steep-sloped tunnel connecting the upstream of reservoir and the downstream river. In order to provide a guide for rational design of such bypass system, the sediment transport mechanism in a steep tunnel has been studied both experimentally and numerically. The phenomenon observed in the experiment indicates highly unsteady flow, but the analysis method for flows in open-channel with movable bed is found to reproduce overall phenomenon. Better representation of the rapidly changing parts of the flow will further improve results.

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Nature-friendly hydraulic structures made of natural material are attracting attention in recent years. In this point of view, the authors have investigated basic characteristics of a rubble mound weir and clarified the discharge-water-level characteristics and so on. This study was carried out to investigate basic hydraulic characteristics in a failure stage of the rubble mound weir. As a result, it is clarified that the velocity at downstream weir slope and the seepage force in the rubble mound weir have an effect on the failure of the weir.

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Spur dikes have been used to realign a channel or redirect main flow away from a streambank to protect it from erosive tractive forces. They are also used to increase channel roughness at locations that lack roughness elements. In certain cases, spur dikes can be used to narrow the channel in low-gradient, aggrading reaches causing flow velocities and sediment transport rates to increase. Water surface oscillation was produced in dikes fields when non-submerged spur dikes were set up in a case of their arrangements. The water surface oscillation was attributed to the interaction of large scale eddies formed in the spur dike fields along both banks, and was probably triggered by the separation eddies behind the first spur dike. This study focused on the interaction between water surface oscillation and large eddies in both cases of spur dike set up along both banks and one bank. The result showed that when a remarkable water surface oscillation was observed, the interaction of the large eddies in both banks was strong.

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Characteristics of separated shear layer due to a backward facing step, newly developed boundary-layer after the reattachment point and an undular hydraulic jump have been investigated experimentally to clarify the turbulent flow structure and energy dissipation mechanism of stepped steep open chan el. Flow measurements were conducted byusing particle image velocimetry (PIV), a high-resolution camera with 15fps (frame per second) and hot film anemometry. In this paper, authors discussed the three-dimensional turbulent flow structure, dynamic pressure distribution and bed shear stress in the stepped open channel with the undular hydraulic jump, which was generated by interaction between lateral shock waves propagating from sidewall. The upstream Froude numbers were 1.42, the Reynolds number based on step height were about 12500.

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Tuthulent open-channel flows over a backward step with smooth walls and rough walls have been investigated both experimentally and numerically. Measurements were conducted using a PIV system mainly composed of a high-speed video camera. Experimental results show that the roughness increases the turbulence and mixing downstream of thestep and shortens the recirculation region. The low-Reynolds number k-?O turbulence model does reproduce these trends fairly well by incorporating the roughness effects in the boundary value of the specific energy dissipation.

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Aerodynamic characteristics acting on rectangular prisms remarkably vary with the side ratio of the prisms. The variation of wind forces with the side ratio is caused by the aerodynamic interaction between the separated shear layer and the after-body of the prism. Especially, the re-attachment of the separated shear layer on the after-body of the prism yields the remarkable variation of wind forces. When wind attacks obliquely to a prism, the re-attachment of the flow obviously occurs on one side surface of the prism. In this condition, fluctuations of wind forces decrease and Strouhal numbers increase. The phenomenon is similar to the variation of wind forces by the side ratio of prisms of which the front face is normal to a wind.

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In late years, Computational Fluid Dynamics has been advanced by improvement of computational technology. Almost all of the numerical studies for fluid flows are done just for around the body at rest. It is very difficulto calculate flows around a moving body even if the curvilinear coordinate is adopted. In the field of civil engineering, examples of the motion of obstacles affected by flow field surrounding the body are 1) moving body in a field such as human body or woods, 2) a bridge affected by the aerodynamic drag. Numerical scheme that can treats interaction between a moving body and flows are of great use for civil engineers who concern such problems. In this study, numerical codes that can calculate interaction between body and flow fields are suggested newly. A series of numerical experiments which are 1) body at rest, 2) rotating body, 3) moving body affected by hydrodynamic force, are carried out. The calculated flow field for a body at rest shows flow pattern at low Reynolds number, which agree well with the previous study. Flow fields around a moving body and moving body affected by flows are quite reasonable

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Vegetation in a curved river influences the secondary and primary flow structures by providing form resistance to flow and by changing a pressure field. In this study, three-dimensional numerical calculations were conducted and compared with the experimental results for curved open channels with submerged and no submerged tree models located along the outer bank. A simple numerical model was employed to reproduce the effects of vegetation on the generation of the secondary flow. The characteristic patterns of secondary flow are well predicted by this model even in curved open channels with vegetation, though the outer-bank vortex cannot be reproduced. The calculated primary-velocity structures also agree with the experimental results in reasonable accuracy.

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3D flow structures around sub-merged skewed spur dikes are numerically investigated. The basic equations of the numerical model are derived on a generalized curvilinear movable coordinate system with full-staggered arrangement of hydraulic variables. A 2nd order non-linear k-c model with effects of the strain parameter and the rotation parameter is adopted as a turbulence model to simulate the complex turbulent flows with separation and vortex shedding from the edge of the spur dikes. Numerical results are compared with the PIV measurements by Tominaga et al (2001) and the model performance is examined. The present numerical model could reproduce the fundamental aspect of the 3D turbulent flow features affected by the inclination angle of spur dikes.

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Turbulent structures were measured in open channel flows with triangular strip roughness elements by using a laser Doppler anemometer (LDA) and a particle image velocimeter (PIV). The influences of the roughness spacing and the roughness cross section were investigated in comparison with the previous results of circular strip roughness. The distributions of Reynolds stress become linear in the outer region and the friction velocity can be evaluated reasonably from the vertical gradient of the Reynolds stress. The similarity of the statistical turbulence quantities is proved in the case of triangular strip roughness. The resistance of the triangular strip roughness is considerably greater than that of the circular strip roughness. From the PIV measurements, it is suggested that the organized turbulent motions near the roughness elements are different between the triangular and circular strip roughness.

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It is very important to accurately predict local wind field over a two-and three-dimensional steep topography, such as a ridge and a hill, because these results on separated flow provide some understanding of how a specified approaching airflow should be modified over complex terrain. In the present study, we have performed the three-dimensional direct numerical simulation (DNS) of a non-stratified airflow over a two-dimensional steep ridge. The numerical results are compared with those of two-dimensional DNS results. In addition, the wind tunnel experient is also conducted by using a smoke wire technique. Through a comparison between the numerical and experimental results, the unsteady vortex shedding from a two-dimensional steep ridge is investigated in detail. As a result, the difference in the unsteady vortex shedding between two- and three-dimensional calculations is clearly found.

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Fully developed turbulent flows over wavy beds such as ripples, dunes and sinusoidal curve in an open-channel were computed to investigate the large scale coherent vortex structures over wavy boundary by direct numerical simulation (DNS) using a regular grid under a generalized curvilinear coordinate system. The coherent vortex structures were also examined using invariant analysis in addition to visualization techniques (identification of cylindrical vortex tubes).“Boil of the first kind”, which was unique to the flow field over dune-type sand wave, was numerically reproduced satisfactorily. The results showed that kolk, which causes boil of the first kind, can be detected as cylindrical vortex tubes rising from the bed. In addition, the boils were generated not only from “hairpin vortices” conventionally noted, but also from “reverse hairpin vortices” newly discovered in this study with their head near the bed and cyclonic vortices at their foot.

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This paper describes the scope of mechanics for infrastructure maintenance problems. The domain of problems encompasses all the lifecycle stages of structures. Physical, chemical, or mathematical models need to be developed so that understanding, prediction, and control of deterioration mechanisms can be made possible. Those models should take advantage of feedback and interchange of existing structures' state information. The paper is organized with four subjects: fracture and delamination, life-span simulation of concrete materials and structures, structural monitoring and control under service conditions, and system integration. State of the arts and future outlook on the subjects are discussed.

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The deformation of soils is essentially dependent on the stress/deformation history in the past. The construction activity is nothing else but such a mechanical action given to foundation ground as the stress/deformation history. In this paper, considered is an imaginary construction of man-made reclamation land on soft ground foundation and examined is how difference of construction sequences effects on the final quality of the soil structure. Particularly, developments of inhomogeneous settlement, stress and pore water distribution after the completion of construction work are compared through a series of soil/water coupled elasto-viscoplastic finite element simulations. The final target of this study aims at specifying necessary maintenance works resulting in reducing the total life-cycle-cost (L. L. C.)

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The mechanical behavior of unsaturated soils strongly depends on the pore water distribution as well as the suction. The water characteristic curve (W. C. C) specifying the pore water content and the suction value plays a very important role in describing the mechanical modeling for unsaturated soils. However, the W. R. 0 shows the hysteresis loop in the wetting/drying processes. This paper emphasizes the importance of considering the hysteresis of W.C.C in the modeling. The accumulation of irreversible strains in the soil structures caused by rainfalls cannot be explained well without considering the hysteresis of W. C. C. An existing model of W. C. C is modified so as to express the accumulation of irreversible strains as the cyclic suction loading. Finally, it is shown that the modified model well explains the experimental results.

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The objective of this study is to apply mechanics of unsaturated soils to prediction of compacted soils behavior. First, we performed static compaction tests with monitoring the change of applied stress and suction of specimen during compaction. Next, we carried out compression tests for the statically compactedsoil specimen and measured consolidation yield stress of them. As a result, it was found that suction of compacted soil depends on the dry density as well as the water content. Moreover, compression lines of compacted soil retaining samesuction converged into on unique compression line. Finally, we proposed the simple method to predict consolidation yield stress of compacted soil using simplified model of unsaturated soils.

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In this paper, the deformation properties of railroad ballast under the cyclic loading revealed by full-scale model test are discussed. A series of full-scale cyclic loading tests on the various loading amplitude and the various load center were performed. It is found that the growth of track settlement is large as maximumload is small, when the load amplitude is the same. The growth of track settlement decreases as the number of cyclic loading increases. Based on test results, an estimation method for the track settlement due to the cyclic loading is proposed. In the small number of cyclic loading, the prediction based on the hyperbolic and logarithmic approximation can explain well the track settlement behavior obtained by the full-scale tests.

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The purpose of this study is to develop a new inspection method for concrete structure in the durability diagnosis. In this study, the microcrack of the concrete inside was detected using X-ray radiography with contrast medium, and the quantification of the concrete degradation was done. And, the relationship between this quantified degradation level and durability of the structure was required experimentally from the freeze/thaw test. In addition, from the structure in which the age exceeded 40 years, the core omission was carried out, and the quantification of the degradation by the X-ray imaging photographing was done using the sample.

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In recent years, the deterioration of concrete structures has become a public problem and maintenance and management techniques have been subjected to intensive research. For maintenance it is important to evaluate not only strength of concrete but also other characteristics such as degree of damage. Using acoustic emission (AE) and damage mechanics can make quantitative damage assessment of concrete. In the present study, early-age concrete, long-term cure concrete, and concrete damaged by freezing and thawing process are examined in order to assess a quantitative damage evaluation method. It is found AE behaviors of concrete differ depending on the degree of damage, and could be simulated by using the rate processanalysis. Introducing a Loland's model, a relationship between stress and strain is approximated, and the suitability of the damage parameter Ω is confirmed. By calculating the relative damage, the initial damage Ω₀ of an actual structure is successfully estimated.

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Elasto-Magnetic (EM) actual-stress measurement method by utilizing the sensitivity of incremental magnetic permeability due to stressc hangeh as been beingd eveloped Previously, it has been proved that E M measurement method enable to measure actual-stress of steel wire, PC bar and PC strand contactlessly without destroyingt heir polyethylenec overing sheath. Furthermore monitoring tensile force of PC tendon is the most important issue in PC structure maintenance management. Therefore, in this paper, in order to grasp the reliability of EM sensor for field-application purpose, a test of tensile force monitoring on PC tendon of outercable PC beam by utilizing EM sensor was conducted As the result of the test, it is conformed that EM stress measurement technology can provide adequate accuracy and reliability to monitor tensile orce of PC tendon duringa life-cycle of PC structur

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Recent years, evaluation method in maintenance inspection of infrastructures has become importantproblem in all over the world as well as Japan. The well-known method of health monitoring of structures isused by hammering sound data and so on. However, it is necessary for expert inspector or expert system tojudge and evaluate structural damage from sound data. The purpose of this study is to propose a method ofdamage identification on steel bridge structures from higher frequencies vibration component such as soundmonitoring data. The sound data is measured by hammering on bridge model with bolt-jointed lateral bracing, and analyses are performed by using Fourier spectrum, sound spectrogram, and fractal dimension. Thepossibility of application for identifying bridge damage is discussed by these results.

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This paper deals with the local excitation method of vibration test by using mutilayer piezoelectric actuators as input device to specimen for the purpose of detecting comparatively small damage of steel structural member, and measures change of an vibration characteristics. It is shown that the vibrationtest by using mutilayer piezoelectrica ctuator is effective to damage detection of steel structuralm ember. After releasing bolt supports of a steel structural member, the vibration test is carried out, and the validity of damage detection is examined. The analytical software system using genetic algorithm (GA) to evaluate the location and level of releasedb olts as a model of damage, is examined. And effectiveness of that system is verified by comparing with the experimental results.

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A non-contact and portable 3D measurement system has been developed for measuring the three dimensional profiles of membrane and shell structures. By the present system, the surface profiles of twisted thin shells are measured, and free vibrations of finite element analysis are carried out by using measured 3D data. Their resonance vibration modes are obtained by forming a hologram on photographic plate, using the time-average method of holographic interferometry. In this study, it was examined about applicable possibility to the non-destructive test of thinwalled structures of 3D-optic measurement and holographic interferometry.

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A new approach to detect locations and magnitude of damage incurred in a dampedmechanical system is presented. Damage is defined as changes in system parameters such as mass, damping and stiffness. The method is derived from the equation of motion of the system before and after damage stage and importantly the method does not require any iteration procedure. It also accounts for the incomplete modal measurement and does not require estimation of stiffness matrix before damage stage. Numerical results indicate that the technique can pinpoint exact locations and magnitude of damage even though the measured modes are incomplete.

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This paper focuses on the module for strain measurement using FBG (Fiber Bragg Grating) sensor. H shaped aluminum plate is used as the base of this module, in thecenter of which FBG sensor protected by the plastic case is located. As well astemperature test, tension and bending test were carried out to evaluate the properties of this module. In addition, the light reflection spectra of Bragg Grating were evaluated by T-matrix method in order to estimate the strain distribution. As a result it is found that it may be used for the strain measurement but spectrum evaluation is needed for the accurate measurement.

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An active sensing diagnostic technique was adopted to characterize damage in aluminum beams. The technique is based on the analysis of Lamb wave signals recorded before and after damage. A series of experiments were performed using lead breaks as the simulated acoustic emission sources on the surface. The wavelet transform was applied for time-frequency analysis of the dispersive Lamb waves to estimate the wave propagation velocities. In addition, built-in PZTs working sequentially as Lambwave emitters and receivers were used to detect damage location. The basic idea of localization is from the pulse-echo method which is often used in ultrasonic inspection. An excitation control technique was developed to separate symmetric

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Since anisotropic materials have direction dependence of wave velocities, it is necessary to develop a numerical simulation tool to improve the accuracy of the ultrasonic nondestructive testing for anisotropic materials. This paper presents a simulation of angle beam ultrasonic testing for an anisotropic thick steel plate with internal cavities. Elastic wave processes in the ultrasonic testing consist of radiation, propagation and scattering, which are modeled on the basis of the integral equation approach. In the calculation, the far-field asymptotic expressions of the fundamental solutions are used. Numerical results are compared with experiment. The relationship between echo amplitudes and the probe positions is almost reproduced in the simulation.

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Fiber reinforced polymers (FRP) can be bonded to the tension face of concrete structures to enhance the structural performance via a thin layer of adhesive and this has been confirmed to be a very promising rehabilitation method worldwide. Proper understanding of effects of the adhesive properties on strengthening of RC members with FRP sheets is very essential and urgent to the FRP bonding technique. Recently, some interesting experiments have been conducted and it is found that the FRP strengthening effects can be improved by adding flexible layer or rubber modifier to the epoxy adhesive for some cases. To clarify these experimental phenomena, in this study, a finite element analysis based on nonlinear fracture mechanics is performed to investigate effects of the interfacial mechanical properties such as stiffness, local bond strength and fracture energy on the structural performance of FRP-strengthened RC beams. Through conducting parametric study on the strengthened RC beam with two possible crack patterns accompanied bydebonding failure, it is concluded that the structural load-carrying capacity is only governed by the interfacial fracture energy. This study provides a good implication for future practical application.

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In this paper, in order to keep a flexural strengthening FRP sheet for RC beam from debonding by ultimate state, an applicability of U-shaped jacketing method was experimentally discussed. Here, static loading tests for flexural strengthened RC beams with AFRP sheet were conducted taking jacketing area (height×width) and jacketing volume of AFRP sheet as variables. From this study, it was seen that jacketing the RC beams from the lower edge to half height of the neutral axis of rebar yield area in the equi-shear span using AFRP sheet with 15% volume of flexural strengthening one, the RC beams can be upgraded upto the calculated ultimate state.

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In this study, in order to investigate the bonding behavior of AFRP sheet and load-carrying capacity of flexural strengthened RC piers having stepped-rebar arrangement with AFRP sheet, monotonic-loading and constantamplitude cyclic-loading tests were conducted. The results obtained from this study are: 1) from the constantamplitude cyclic-loading test, it was made sure to keep AFRP sheet from debonding under an amplitude which is less than that of 90% of the maximum loading capacity; and 2) sheet debonding was developed due to peeling action of the concrete blocks formed in the cover concrete near stepped-rebar arrangement.

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