[in Japanese]

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Comparing an estimated death toll in the reconstructed environment of Tangshan in 1991 with the actual deaths in the 1976 earthquake, we evaluated the enhancements in seismic safety attained during the reconstruction. It was found that while the most severely affected area was remarkably improved, the less severely affected area was not rebuilt to the standards of the most severely affected area. The increased safety of the most severely affected area can be attributed to the reinforced concrete elements of the buildings. The hazardous situation in the less severely affected area is due to the collapsible nature of the unreinforced masonry construction.

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We compute the energy release rate at the onset of crack kinking in an anisotropic elastic body by using the E-integral, which is path-independent even for such cases. The model is an infinite plate with a center crack under the mode I loading in three types of transversely isotropic body.
As a result, we find that, in the anisotropic elastic bodies, the kinking angle for the maximum energy release rate is nearly equal to zero as in an isotropic body; however, the magnitude of the energy release rate is much dependent on the derection of anisotropic axes.

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It is important to grasp plastic behavior of steel structures and a constitutive equation which can represent stress-strain relationship for structural steels under cyclic loading is required. In this paper, a constitutive equation based on a monotonic loading curve is developed. The feature of this model is that plastic strain-true stress relationship of a structural steel consists of two domains which are a part of a monotomc loading curve and a transition domain. And three types of experiments for resolving the material properties were shown. The proposed uniaxial constitutive equation is extended to the mutlidimentional stress state. It is confirmed that this proposed constitutive equation can represent experimental data adequately.

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In case of plated structures under compressive loading, their final buckled pattern involves a localized deformation in contrast to the periodic deformation pattern associated with the critical buckling mode. The experiment under cyclic loading showed that the strength as well as the ductility of plated structures deteriorate considerably due to this localized deformations of structural components. This implies that the localization of buckling patterns has an unfavorable effect on the earthquake resistance. Herein, we investigate the localization behavior of rectangular plates under uniaxial in-plane load, including that under cyclic loading. In addition to the perfect plates without initial imperfections, plates with initial deflections and residual stresses are analyzed to examine their effect on the localization behavior.

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Recently, numerous horizontally curved box girder bridges have been constructed in Japan. This paper presents a few numerical results of the elasto-plastic analyses for such a typical curved box girder bridge. Those results are compared with the numerical results of elastic linear analysis. It has been concluded from the numerical results that the ultimate strength for horizontally curved box girder bridges can be estimated by the elastic linear analysis. Furthermore, the ultimate strength with local buckling for another curved box girder bridge has been shown by using the transfer matrix method.

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The application of prestressing technique to steel structures makes it possible to increase the load-carrying capacity as well as to stretch the elastic region of existing steel bridge system. The aims of this paper are not only to develop a method of nonlinear analysis of prestressed composite plate girders based on the incremental deformation method but also to demonstrate the feasibility of the prestressng technique to strengthening of steel bridges. The accuracy of the proposed analysis is verified by comparisons with test results on full scale prestressed composite plate girders which varied of prestressing force level, eccentricity of draped tendons and material properties of tendons. This method is found to be capable of predicting the ultimate response and also failure modes of the various prestressed composite plate girders. Then the performance of different types of prestressed composite plate girders under static loading is analytically evaluated in the strengthening of existing steel bridge system. Furthermore, a method of the performance evaluations related to the load-carrying capacity and the deflection control of the prestressed composite plate girders with external tendons is proposed based on the analytical results considered with some optimum parameters which are geometric parameters and material parameters. Finally, a design concept of the prestressed composite plate girders with external tendons is discussed in the construction of new bridges as well as in the bridge strengthening.

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In many instances, the determination of the maximum loads and displacements of structural members is of greater practical importance. The development of efficient methods for computing the load-carrying and deformation capacities in a more simple way, therefore, is of great practical interest to engineers. This study is concerned with the development of such a method. To obtain the complete load-deformation behavior of the columns, the M-P-Φ relations proposed by writers are integrated along the member axis with the use of the finite element technique. This procedure is first described in detail, and is followed by a comparison of the numerical results with the experiments. Next, design charts for determining the ultimate strengths and corresponding deformations of the concrete-filled steel box columns under constant axial force and lateral load are presented. Finally, a design recommendation for determining the optimum length of the filled-in concrete is proposed.

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The behavior of steel structures subjected to seismic load depends on the mass, material and dimensions of the structures, and the applied seismic movement. The quantitative evalution of the ultimate strength and ductility of the structures against earthquake is, therefore, very difficult. For this purpose, a simple experimental method is proposed in this study. Then, the ultimate strength and ductility of steel piers and composite piers partially filled with concrete in bottom part of them are investigated by using the experimental method.

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This paper presents experimental and analytical approaches for the impact response displacement of steel pipe beam considering both local deformation and strain rate effect. First of all, the static and dynamic (high-speed) tests are performed in order to obtain the formula of the local deformation considering the strain rate effect. Secondary, an analytical approach for the beam displacement is proposed by assuming the local deformation as the shapes of a gourd, a cup, a half moon and an ellipse. Finally, it is confirmed that the impact response displacements by this method are good agreements with the experimental results and this method can provide the useful data for the impact resistant design of steel Sabo dams.

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This paper presents an experimental approach for the energy absorption capacity of the concrete-filled tubular steel beams subjected to the static and impulsive loads. Twenty-eight test beams of the concrete-filled steel tube reinforced with several types of tendons, that is, reinforced bars, bonded PC bars and unbonded PC bars, are tested under staic and impulsive loads. It was confinned from the test results that both the filling up a steel tube with concrete and the well-disposing tendons were effective for increasing the strength and ductility, and thus the energy absorption capacity of the tubular steel beams.

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A simulation method which can solve the dynamic interaction problem between high speed railway vehicles and railway structures was develped using a three dimentional mass-spring-damper linked vehicle model and a finite element structure model. In this method, a simplified model of the creep phenomenon between wheel and rail is adopted, and the lateral elasticity of rail is also taken into account to simulate rolling action of wheelsets. A modal superposition method is adopted to solve this problem efficiently. The formulation and numerical techniques are described in this paper.

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Serviceability assessment of existing bridges relies heavily on subjective judgements based on heuristics to be made by the experts. So, it is important to consider how to extract and express heuristics that has a certain level of intrinsic fuzziness due to subjectivity. In this paper, an empirical knowledge acquisition method is proposed by relating the knowledge, acquired from questionnaires, with a basic probability based on Dempster & Shafer theory, and quantifying the subjective uncertainty included in the knowledge using the concept of Yager's measure and Dempster & Shafer theory. Furthermore the proposed method has been applied to a questionnaire conducted to evaluate the serviceability of an existing bridge. And the validity of the method is verified through the comparison between the subjective rating results acquired from the application of the method and the objective rating results obtained from various field tests conducted to a same bridge.

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This paper shows an approach to optimum repair planning of existing bridges within the budget. The planning process is formulated as the knapsack problem and the genetic algorithm is adopted. The evaluation of repaired bridge is made, based on the results of analysis by Quantification Analysis Type II for damage check lists of the bridges.

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In this paper, a closed-form solution for the Green functions of saturated porous media is derived by using thin layered elements based on Biot's theory. The validity of this solution is checked by comparison with the results computed by the boundary element method. The effect of the numbers of thin layers on the accuracy of the solution is also investigated. The solution is applied to examine the dynamic behavior of layered strata which have different permeabilities. It is found that the difference of permeability of layers affects the increase of pore fluid pressure in the submerged soil.

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The block-diagonalization method has come to be utilized to exploit the symmetry of structures. This paper applies this method to dynamic problems of damped symmetric structures. By means of a suitable transformation, we can simultaneously put the stiffness, the damping, the mass matrix, and the matrix of control system into block-diagonal forms. The equations of motion, accordingly, can be decomposed into a number of independent equations. This method, which is compatible with arbitrary damping matrix, is applied to a number of axisymmetric structures to show its numerical efficiency.

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Seismic ground motions on layered media with irregular interface are not uniform because of the effects of focusing and scattering effects. In Aki-Larner method, the scattered wave field is represented by the combination of the plane wave, and the coefficients that satisfy the boundary condition approximately are determined. Subsurface conditions embrace many uncertain factors such as the assessment of irregularities in interfaces and properties of the layered media. In this paper, we developed stochastic Aki-Larner method with which to investigate the effects of the variation of subsurface soil profile. The first order approximation method and perturbation technique are incorporated in Aki-Lamer method, and estimate the seismic ground responses taking into account the uncertain modeling of irregular interfaces.

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The dynamic behavior of the base isolated bridge with the sliding system composed of the sliding bearings and the restoring force devices is studied by using the dynamic response analysis. For the simple supported bridge model, the influences of the friction coefficient, the stiffness during sliding of the isolation system and the predominant period of the bridge are analyzed. Artificial motions for the design of bridges are used in the analysis. As the results of the analyses, the effect of these parameters on the response have been clarified. The sufficient isolation capability as well as the suppression of the excessive displacement can be achieved by selecting appropriate design parameters. One example of the analysis for the continuous bridge with the sliding isolation system is carried out. The effectiveness of the sliding type isolation system for the continuous bridges is confirmed.

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Instead of traditional welding splicer, a High Ductility Aseismic Joint (H. D. A. J.) was newly developed for the pile splicing. In order to examine the energy dissipating effect of H. D. A. J., following procedures were performed. First, a series of experiments was conducted to clarify the characteristics of the splicing by the bending test. Meanwhile, a nonlinear FEM which takes into account both geometric and material nonlinearities was proposed. After checking the validity of the numerical method by simulating the bending test results, numerical analyses were performed to investigate the effectiveness of H. D. A. J. spliced piles subjected to liquefaction-induced large lateral ground displacements.

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An importance factor evaluation procedure is presented for existing road bridges in a metropolitan area in order to establish their disaster mitigation plan against earthquakes. Priority for retrofitting bridgess and for emergency response after an earthquake occurrence can be decided according to the importance factor of the bridge as a vital transportation link.
Importance or criticality in relation to a road network is evaluated in terms of the importance of the route the bridge located in the road network as well as the direct effects when the bridge is destroyed. The importance of the route is evaluated by considering daily traffic, regional land use along the route, results of network analyses including traffic demand, route assignment, trip time or distance calculations. The direct effect of the bridge failure in relasionship to utilities must be evaluated and the use of an underpass should also be considered.
This procedure has been applied to the road network and bridges in the Tokyo Metropolitan area and its usefulness has been examined.

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A new computer simulation method based on potential model is proposed to analyze human behavior during evacuation in large and populous underground facilities. Previous models cannot efficiently handle obstacles in the path. To check the adequacy of the method for human behavior analysis, this method is applied to simple corridor models. By comparing the results of the computer simulation to the results of past researches on human behavior, the proposed method is found to be a good and practical method to simulate human behavior in populous underground facilities.

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