There is already presented a quantitative method to estimate the stablitity states of frame members in a global buckling. In that analysis applied to a rectangular rigid frame for the individual members, however, the resulting effective lengths of columns are different from those required in the design scheme. In this study, a rectangular frame is decomposed into those structural units which represent the axial strengths of columns stiffened with their adjacent beams. The effective column lengths are estimated upon the critical axial forces in those respective units. At the same time, to observe their interactions in a global buckling, the preceding analysis for members is generalized to deal with the stability of structural units.

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This paper presents inter-comparison among four hysteretic models for inelastic seismic response analysis of cantilever-type steel bridge piers: the bilinear model, the trilinear model, the integrated 2 parameter model and the damage-based hysteretic model. It is shown that the commonly used bilinear model is not suitable to predict residual displacement in analysis. The trilinear model is a better choice than the bilinear model, but cautions should be taken in its application due to its non-degrading, kinematic hardening formulation. Except for residual displacement under Level 2·Type·I Ground Type III accelerograms, very good agreement is found between the damage-based hysteretic model and the integrated 2 parameter model within the range of H_r≥H_y (H_r is the predicted horizontal strength).

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A method is introduced for extracting tensorial stress measures from rigid-body-spring networks with random geometry. Stress analysis of a uniformly stretched material indicates that rigid-body-spring networks can be made elastically homogeneous provided two basic conditions are met: 1) network geometry is defined by a Voronoi diagram, and 2) the network degrees of freedom are defined at the Voronoi cell nuclei. For more general loadings, accuracy of the stress retrieval algorithm is demonstrated through comparisons with finite element analysis results, where the finite element mesh is based on the corresponding Delaunay triangulation of the domain.

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At first, an analytical procedure to determine the linear buckling loads of the cylindrical sandwich shells subjected to the external pressures is derived based on the variational method. The method is compared with other analytical method, and the effects of the mode in circumferential direction to the linear buckling loads and the components of the energy of the members are examined. Furthermore, the elastic buckling strength of the members in considering the scatter of the initial imperfection is proposed based on the reduced stiffness method, and these strength are compared with those obtained by the finite element method.

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In a conditional lognormal stochastic field, Kriging method produces the optimum estimator and error covariance, whereas the conditional mean and conditional covariance are obtained from the conditional probability density function (CPDF) method. What is the inherent difference between these two methods? It is found that: 1) the optimum estimator is equal to the conditional mean; 2) the estimated error covariance is dependent on the locations of sample observation, but independent of the values of observed data; and 3) the conditional covariance does not coincide with the estimated error covariance. The optimum estimator and conditional mean prove to be completely equivalent. Conditional simulation can be carried out by use of not the Kriging method but the CPDF method.

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This paper proposes a theory for evaluating the maximum entropy estimators and their associated entropy indices for conditional non-Gaussian translation stochastic fields when observation is made at some discrete points. Through analytical development and numerical examples of stochastic fields with the six types of distribution, kriging and maximum entropy techniques for spatial estimation are also compared. It was found that: 1) the maximum entropy estimate and conditional entropy are dependent on the values of observed data; and 2) the average conditional entropy has an independence on the observations, and is not larger than the average unconditional entropy.

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In order to study the earthquake resistant characteristics of anchor bars of seismic stopper, model tests were performed. The main findings were as follows: 1) the failure mode of anchor bars was not the shear failure of steel bars, but the tensile failure together with the bending failure; 2) the capacity of anchor bars decreased if the ratio between the superstructure-substructure-gap and the diameter of bars increased; 3) the size of gap inside sleeve pipe had little effects on the capacity; and 4) the tensile strength, not the yield strength, was the main factor affecting the capacity. Based on the above findings, the capacity evaluation method of anchor bars was proposed.

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The phenomenon of beats has been observed on vibration tests of the hanging type shuctures such as the stress ribbon bridges with very closely spaced natural frequencies. In order to estimate the dynamic characteristics of the structures, the two curve fitting methods which are direct applied to the frequency response and impulse response by the nonlinear least square method are proposed. Effectiveness of the methods are discussed by the numerical simulation and field vibration test for the stress ribbon bridge. Result shows that dynamic characteristics can be estimated highly accurately by the both methods. However, the time domain method have higher accuracy compare with the frequency domain method.

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Vortex-induced vibration was observed in a 10-spans continuous steel box girder; total length of the bridge is 1, 630m including two spans of 240m length. Measurement of vibration showed that the maximum amplitude of the first bending mode which occured at wind of 16-17m/sec, was approximately 54cm. This is consistent with the result of wind tunnel test. Second mode vibration was also observed at the wind speed nearly 23m/sec. The wind direction when the vortex-induced vibration occurred is limited to a range of about ±20° from perpendicular to the bridge axis.

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In the 10-spans continuous steel box girders (max. span: 240m) of the Trans-Tokyo Bay Highway vortex-induced vertical vibration of the girder at wind velocities around 16m/sec was observed. New type of TMD was developed and 16 TMDs were installed to suppress the first and second mode vibrations of the bridge. The amplitude 40.7cm of the first mode vibration of the girder was reduced to only 5.4cm after the installation. Vibrations of higher modes of the bridge were controlled by vertical plates installed on the bridge guard rail.

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At first, surveyed in this paper are the initial imperfections which greatly affect the ultimate strength of stiffened plates with opening subjected to compression. For the initial deflections of stiffened plates with opening. Twenty existing steel bridge piers were measured to investigate the shape of distribution and the magnitude of them. Also, the residual stresses in small models were measured. Secondly, uni-axial compression tests were carried out by using four types of test specimens and then the elastoplastic and finite displacement analyses of the analytical models corresponding to the test specimens were executed. Thirdly, the parameters, which affect the ultimate strength of stiffened plates with opening, are examined. Finally, the effective methods for strengthening stiffened plates with opening and a practical method for predicting their ultimate strength are proposed.

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This paper presents instability analyses, such as elasto-plastic finite displacement analysis under in-plane load, finite displacement analysis under displacement-dependent wind load and flutter analysis based on modal coordinate, which identify static and dynamic instabilities of long-span cable-stayed bridges. Using 1400-meter cable-stayed bridge models with four types of cross sectional shapes of the girder, whose span-to-width and span-to-depth ratios are considerably large compared with those used in past long-span conventional cable-stayed bridges, instability analyses are carried out. From these calculations, a minimum cross sectional shape ensuring safety against static and dynamic instabilities was presented. It was found that instability under static wind load is the most critical, but that the span-to-girder width ratio can be greater than the widely-believed value of 40.

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This study presents the interactive response between adjacent bridges; especially for the case of a long-span bridge and a small bridge. Different natural periods between two bridges cause the large relative displacement at their joints. The three dimensional earthquake response analysis was carried out considering the effect of the displacement limitation of the shoes and the aseismatic connector. The results showed that the limited device of the long-span bridge affected the response of the adjacent small bridge. The relative displacement response between the long-span bridge and the small bridge increased, when the shoes of the small bridge had been broken.

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This paper presents ultimate compressive strength of hot-rolled stainless clad steel plates and their residual stress distribution in the direction of thickness. Distribution of the residual stress is analytically given by simulating the cladding process, and modeled based on the analytical results as well as experimental results. Lastly, the ultimate compressive strength of clad plates simply supported around is obtained by elastoplastic nonlinear analyses, considering with the residual stresses model. Results show that the residual stresses induced through the producing could be predicted analytically, and the direction of initial deflection remarkably affects the ultimate strength, though clad ratio does not affect so much when it is less than 0.2.

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A perfobond rib is a steel plate with openings and acts as a shear connector in the concrete by a concrete dowel effect. It is realized that the perfobond rib shear connector would reach split failure at ultimate under low confinement and low shear strength, but the shear strength will be improved by enough confinement against split failure. In this paper, the shear strength of perfobond rib is examined by two series of experiments which are active confinement tests using hydraulic actuator and passive confinement tests using reinforcing bars. The test results indicate that the shear strength would be able to improved by giving confinement stress and the evaluation of shear strength under confinement is proposed.

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Elastoplastic analysis method is developed for wire mesh of box gabions. The wire mesh is modeled as a macrocontinuum. Constitutive relation of the continuum model is derived using the principle of virtual work, in which the equivalency of energy stored in the wire mesh to that in the continuum is taken into account. The derived expression of stress-strain relationship containes the term of forces which take place at the wire ends in a unit cell of the mesh. In order to save the computational effort, evaluation of the forces is carried out by using neural network. The nonlinear behavior of the wire is then described by the neural network. The analysis method is developed base on finite element method. Numerical analyses are compared with experimental results and good agreement is obtained.

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A new class of computational algorithms for multi-scale analyses of heterogeneous elastic-plastic bodies is developed in this paper. Based on the two-scale convergence theories in the mathematical homogenization, the variational formulation with micro-macro representation of the field variables is newly proposed in the context of computational plasticity. The formulation does not involve the method of two-scale asymptotic expansions and therefore naturally leads to a computational strategy for fully global-local structural analyses. The consistent linearization of the discrete nonlinear equations enables us to evaluate the elastic-plastic behaviors accurately and effectively. We also present several numerical examples in order to show the possibilities of actual computations.

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