Concrete tunnels subjected to the ground pressure usually show a compressive failure mode. Moreover, due to an unbalanced soil constraint, deformed tunnels under an additional concentrated load will show more complicated compressive failure behavior with the propagation of multiple concrete cracks. Therefore for a better understanding of compressive failure mechanism of deformed tunnels, a parabolic compressive softening model and the concept of compressive fracture energy are introduced and discussed in this paper. It is found that the final failure, load-carrying capacity and structural deformation behavior of deformed concrete tunnels depend on the compressive behavior of concrete significantly.

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An M_J6.4 earthquake occurred on July 1, 2000 offshore of Kohzushima Island in the Tokyo municipal jurisdiction. Large tremors also were felt on Kohzushima on July 9 and on Niijima on July 15. This is the damage investigation report on the 2000 Kohzushima Kinkai earthquake made by a JSCE reconnaissance team. Earthquake swarms continued near Kohzushima, Niijima, and Shikinejima islands for about three months. A JMA seismic intensity of lower 6 was recorded twice on Kohzushima during July, 2000. An outline of the earthquake and aftershocks and the damage done to civil structures is given. Slope failures, damage to retaining walls and disaster responses, in particular, are focused on.

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In our previous paper, we described vibrations with circumferential mode number n = 2 when a frequency of a pressure pulsation in a turbine coincides with the natural frequency of a steel penstock. We proposed the use of natural frequency calculation formulae based on numerical analyses that target n = 2, 3 vibrations. Because a limited number of papers are available describing experimental or analytical vibration studies, we performed 1/4 scale model experiments on pressure pulsations with the parameters of plate thickness and the presence of stiffeners. Based on a comparative study of experiments and numerical analyses, we proposed modification of the vibration prevention specifications stipulated in the current technical standard.

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The behavior of sliding isolation bearings with respect to vertical movement due to earthquake excitation is investigated through experiments and simulations. Bridge girders may undergo vertical motion during severe earthquake events, and since the friction damping provided by sliding isolation bearings is dependent on maintaining contact between the bearing and the girder, there remains an issue as to whether sliding isolation bearings are appropriate for this application. It was shown in this study that multi-layer rubber horizontal load distribution (HLD) devices with steel plate reinforcement are essential for bridge applications, as non-reinforced HLD devices are likely to fail under severe vertical tensile loads. The bearing surface, however, is found to be resilient to impact with an uplifted girder, and simulations demonstrate that contact is maintained with at least one bearing during severe ground motion due to lateral rocking of the girder. The results therefore suggest that appropriately designed sliding isolation bearings are suitable for bridge applications.

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As a method of connecting two concrete-filled circular steel tubular constructions, a simple socket joint in which a small diameter tube is inserted with the specific length to a large diameter tube with concrete filling the gap between two tubes has been proposed as an economical and effective joint connection. The T-shaped joint specimens which differed in parameters such as the path of the shear connector on tube faces and the plate welded to the small diameter tube, thickness of a large diameter tube, length of a large diameter tube, etc. were tested in order to investigate the failure mechanism and the ultimate strength of the joint connection. In this paper, we propose the equation for calculating the ultimate strength.

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The authors have proposed an equation for estimating the ultimate strength of T-shaped socket joints. However, the effect of cyclic loading and external diagphragms, applicability to the cross-shaped joint and other issues must be verified. Therefore, the static loading tests by using the T-shaped joint specimens were carried out in order to investigate the effects of loading method and the diaphragm. Monotonic static loading tests by using the cross-shaped joint specimens were also carried out. The test results indicate that the loading method and the diaphragm affect the ultimate strength, and that the application of the proposed method to the cross-shaped joint is promising.

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A simple mechanism for a vibration sensor based on fiber Bragg grating (FBG) is proposed. The mechanism utilizes the gravity force to allow the maximum sensitivity of the sensor into vertical direction while the minimum sensitivity for other two transverse directions. The sensor consists of a FBG cable and several masses to form a vibration system. The cable is extended to introduce a certain tensile force and acts as a spring. The sensitivity of the sensor is more than 1 μstrain/gal for vertical direction. This simple sensor has been developed for damage detection of large structures. Several prototypes were fabricated. And extensive shaking table tests were conducted to examine the performance.

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A FBG-based strain sensor equipped with a mechanical temperature compensation system is proposed. Direct bonding of a FBG element may cause broadening of the reflected optical spectrum due to fluctuation of strain distribution of the material under the FBG element. The proposed sensor avoids this difficulty by introducing a mechanism to induce uniform strain distribution to the FBG element. In addition, a simple mechanical system that can cancel the effect of temperature on the strain measurement eliminate the need for another FBG sensor for temperature compensation. Extensive tests have been conducted using prototype sensors. The results showed their excellent performance.

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This paper proposes a reliable method identifying both a location and a history of an impact force acting on a plate using multiple sensor responses. First, a fundamental relationship between an impact force and the strain responses is formulated based on the finite element method. The impact force history is precisely identified by the least-squares method containing a penalty term on derivative of force history. The location of impact force is determined by minimizing an error vector between measured strain responses and analytically evaluated ones. An application of proposed method to aluminum plates equipped with sensors is developed to discuss the validity of the present method.

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For the rigid body simulation, robust and efficient rigid body dynamic simulation algorithm is developed. The rotation of rigid body is represented using quaternion and volume based collision detection algorithm is developed. The rigid body is subdivided into voxels, and collision detection is carried out with spheres that include voxels. The strategy for determining time step is described. Several examples are shown to demonstrate the efficiency, robustness and applicability to the non-convex objects of the method, and compared with polygon-based method. It is shown that by changing the level of sphere subdivision, it is possible to control the accuracy and computational efficiency.

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A modified three-dimensional inverse scattering method is applied to reconstruct the shape of a three-dimensional flaw in a cylindrical specimen. In this modified method, a measurement plane is restricted to the plane perpendicular to the axis of the cylindrical specimen. Thus the crosssectional image of the flaw can be obtained. By moving the measurement plane along the axis of the cylindrical specimen, the cross-sectional image is obtained for each measurement plane. The three-dimensional flaw image is reconstructed by piling up the obtained cross-sectional images. Cylindrical specimens with a cylindrical cavity model and with a hemi- spheroidal cavity model are prepared. The performance of the modified method to reconstruct the three-dimensional flaw is verified by using the experimentally measured waveforms.

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This paper presents a 3D linearized inverse scattering method for shape reconstruction of obstacles in a two layered medium. The problem here is to estimate the shape of an obstacle embedded in the bottom layer, using scattered waves observed at points in the top layer. Wave sources are assumed to be acoustic monopoles settled in the top layer. For this situation, two inversion formulas based on the Born and the Kirchhoff approximations are proposed with the help of the Green's function for the layered medium. In numerical examples, the two inversion formulae are tested for reconstruction of spherical and spheroidal rigid scatterers from simulated wave data. It is shown that an illuminated side of the scatterers is well reconstructed by the proposed methods.

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By virtue of the development of metallurgy and the theory of dislocation, one can qualitatively anticipate the mechanical properties of a material from its microstructure. Moreover, not quali- tative but quantitative and precise anticipation is more beneficial for ecient development of new materials. In this context, we utilize a multi-scale method with atomic model, which is a particle system that has potential, and discuss the possibility of quantitative anticipation of material properties including plastic deformation through several representative numerical examples.

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In the present paper, we investigate theoretically and experimentally the number of non-zero matrix entries generated by the wavelet BEM with the Beylkin-type compression algorithm. The Beylkin-type algorithm, which is based on a prescribed level-independent threshold, retains the asymptotic convergence rate of BE solutions, like widely-used level-independent compression schemes. The coecient matrix compressed by the Beylkin-type scheme has O(N^1+γ) (0 <γ< 1, N: degree of freedom (DOF)) non-zero entries; level-dependent schemes enable us to reduce the matrix entries up to O(N(logN)^α) (α≥1). However, for matrix compression using the Beylkin-type scheme the compression rate is greater than or comparable to that of the Schneider's level-dependent scheme, in the moderate DOF range.

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More realistic simulation of a possible earthquake is crucial for making a rational counter plan against earthquake disaster. This paper proposes such a simulation system, called Integrated Earthquake Simulator (IES), which combines various numerical simulations of earthquake and structure behaviors with data stored in geographical information system (GIS). The key simulation of IES is to achieve high resolution of strong ground motion (SGM), even though some ambiguity remains in modeling the ground structures due to lack of available data. Examined is the validity of numerical simulation of SGM, which takes advantages of stochastic modeling of the ambiguity. Once high resolution of SGM is achieved, all structures within a target area are modeled by using the GIS data, such that a digital city is constructed in computer. Examples of such a digital city and its earthquake disasters are computed by using a prototype of IES.

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This paper discusses the effects of sleeper size on cyclic deformation properties of railway ballast under the cyclic loading. Two-dimensional FE linear elastic analyses were performed in order to investigate the effects of sleeper size on the stress distribution in the ballasted track. Based on the results of FE analyses, a series of full-scale cyclic loading tests were performed by using various sleepers of different lengths and heights. It is found that the track settlement in the state where a clearance gap exists between sleeper and ballast can be estimated by amount of displacement amplitude up to a full contact and a maximum displacement rate of sleeper.

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