Time-domain modeling of bridge deck flutter is examined. The frequency dependent aerodynamic self-excited forces acting on a bridge deck are approximated in the Laplace domain by rational functions. Two matrix formulations of the rational function approximation, namely least-squares and minimum-state, are applied to aerodynamic data experimentally or theoretically obtained for various bridge decks. The precision of the approximations and the comparison of the critical wind speed computation by the conventional method and the proposed method are presented.

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This paper presents a detailed re-examination of the coupled local and overall buckling strength formula, which is based on the Q-factor method, of a thin-walled column. For delicate comparison with experimental results, the strength formula expressed as function of initial imperfections is developed. Using this formula which takes into account the difference of initial imperfections in each specimen, experimental ultimate strengths are predicted. The results lead to the conclusion that Q-factor method has good accuracy, indicating that the error of prediction is less than 10%.

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The localization of axisymmetric plastic buckling patterns of cylindrical shells is investigated in terms of its influence on the strength deterioration under cyclic loading. Since the localization phenomenon is caused by the plastic bifurcation in the post-peak range, we first showed a rigorous method to analyze the plastic bifurcation under two-axial stresses. Then, using the proposed method, we examined the effects of structural parameters as well as constitutive models on the localization behavior. As a result, it was observed that the strength deterioration under cyclic loading is significant when the radius-thickness ratio (R/t) and length-radius ratio (L/R) are large.

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A rigorous method for the analysis of plastic bifurcation under in-plane stress was presented in order to precisely assess the localization of plastic buckling patterns of plates structures. In this analysis, two kinds of constitutive models, i. e. bi-linear model and two-surface model, respectively, within the framework of J2 flow theory, were considered to investigate the effect of constitutive relations. By using this method, it was examined how the localization behavior is influenced by the localized initial deflections. Based on this result, we discussed the validity of the approximate method proposed by Tvergaard and Needleman where a small localized initial deflection was given to analyze the localization phenomenon without carrying out the plastic bifurcation analysis.

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A method of analysis for the solutions of transient wave propagation in an infinite thick plate on elastic foundation is developed in terms of eigenfunctions depending on the Fourier integral transforms. The Winkler assumption that the reaction forces of the foundation are proportional at every point to the bottom bounding displacements of the plate touching the foundation is taken here. The time history of displacements and stresses representing the head of the disturbance are evaluated as transient wave propagation corresponding to different speeds of concentrated moving loads that are suddenly applied at the free surface of the plate standing still initially.

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The relationship between spring constants of distinct element and macroscopic elastic constants (shear modulus; G and Poisson's ratio; ν) of the element assembly is derived theoretically. As the distinct element, circular disc with the normal and tangential springs at the interelement contact points is considered for two-dimensional model. The theoretical investigation is carried out through the derivation of equilibrium equation of the elastic body from the equilibrium conditions of distinct element, based on the assumption that the displacement field of the assembly is smooth enough to be introduced the Taylor expansion. It is found that elastic body with ν≤1/4 can be approximated by the distinct element method.

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This paper presents both experimental and analytical approaches for the local dissipated energy and rheology model at impact point of concrete specimen. At first, the local dissipated energy of concrete specimen is measured by the pendulum impact test. Secondary, the three rheology models are proposed by using the parameters of local spring constant, local damping constant and dummy mass in which the dissipated energies of sound and vibration are considered. Finally, the proposed models are applied to the concrete check dam wing. It is found that the rheology model 3 considered the dynamic spring constant as well as local damping constant and dummy mass can simulate well the impact model test results of the concrete check dam wing.

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Studied herein is the 3 dimensional contact/separation behavior of high strength bolted flange joints considered to have many advantages over the other types of joints from the viewpoint of mechanical behavior, erection and aesthetic design. The tensile loading tests for the split tee flange joints are carried out and the parametric analysis by 3 dimensional finite element method considering material and boundary non-linearity is made. It is concluded that a contact/separation behavior of split tee flange joints significantly depends on the thickness of the flange plate, particularly the ratio of bending strength of the flange plate to the strength of bolts. It is also found that the increase of the bolt force may be affected more significantly by the local deformation of the flange plate than the prying action.

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Stress analyses by using three dimensional fmite element method and stress measuring tests are performed in order to make clear the reduction of stress concentration by bolting the stop hole which is a circular hole drilled at the tip of fatigue crack. On the basis of the results of above examinations, evaluating procedure for fatigue strength of fatigue damaged steel members repaired by drilling and bolting the stop holes is proposed, and validity of this procedure is verified by comparing predicted results to experimental results.

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In order to develop a method to improve fatigue strength of fillet welded joints made from high strength steel, specimens with special considerations in electrode materials or post welding treatments were made and tested. Fatigue test results showed that weld toe re-melting method or TIG dressing could obviously improved fatigue strength, while applying under matching welds or special electrode with high fluidity had little advantage. These results were discussed in relation to welded toe profile, residual stress and hardness.

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The superconducting magnetic levitation vehicle system (Maglev) is being developed. In the guideway steel structures, the energy loss and the resistance to the movement of vehicle, called a magnetic drag force, are induced by the passage of vehicle. It is very important to evaluate the magnitude of the drag force quantitatively and to make it small below the limit value when we use the steel as a member of guideway structure. In the accordance with magnetic drag force, the approximate analysis method is proposed, and also the characteristics and the reducing measures are investigated by our experiments and the analysis.

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This paper aims to investigate the vibration mechanism of the rain-wind induced vibration of the cables in cable-stayed bridges, and to describe the important role of three dimensional flow field around inclined cables on cable aerodynamics, in particular subject to so-called “High speed vortex-induced excitation”. The cable with “Elliptical plates” is proposed. This control means guarantee its stability against the wind. And the relationship between the Karman-vortex shedding and the axial flow behind the cable is surveyed. On the other hand, unsteady pressure around the cable is measured in order to clarify the characteristics of the heaving vibration and rolling vibration.

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In wind resistant design of long-span bridges, their behavior against the wind are evaluated through wind tunnel tests or analytical approaches. A little evidence has been reported so far whether or not wind properties acting on bridges are the same ones as assumed in the design code and they behave in the same way as assumed in it. This paper presents the result of the study on the validity of wind resistant design for long-span bridges based on the field observation results of the Ohnaruto Bridge and the Minami Bisan-Seto Bridge. The possibility that the wind load for long-span bridges could be reduced is suggested by reconsidering the spatial correlation of the wind.

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This paper discusses a time-domain representation of wind-induced gust response analysis based on state space equations. Wind fluctuation, aerodynamic admittance and structures can be considered as linear filters, respectively, and these filters are described by state space equations. These three sets of equations are combined to obtain one set of equations with the white noise as input and the gust response as output. Frequency-dependent self-excited aerodynamic forces are included in this formulation by introducing frequency-independent finite state approximate model. Aerodynamic coupling and correlation between vibration modes of structure can be systematically considered by this time-domain method.

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Analytical prediction of vortex-induced oscillation of bridges is treated based on the Scanlan's semi-empirical nonlinear model. The effects of self-excited forces which produce aerodynamic damping and the effects of imperfect spanwise correlation of vortex-induced forces are incorporated in the analysis. A wind-tunnel test of 3-dimensional model of cable-stayed bridge produced responses consistent with the proposed analysis using aerodynamic parameters identified by 2-dimensional model tests in both laminar and turbulent flows.

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A wind tunnel experiment using a SDOF circular cylinder tower model was conducted to study the characteristics of the vortex-induced vibration which occurs at a wind speed higher than the occurrence wind speed of the ordinary vortex-induced vibration. Across-wind model response and the fluctuating wind velocity behind the model at various heights were measured. Wavelet analysis was applied to the data of the fluctuating wind velocity behind the model. The wavelet analysis clarified that the tip-associated vortex is formed rather intermittently around the model top and this causes that vibration. The amplitude of that vibration possesses a slight modulation due to the intermission of the tip-associated vortex.

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To make the super long span bridge projects more feasible from a viewpoint of the wind resistant design, new significant progress in the aeroelastic numerical analysis as well as the detailed measurement of the full-dimensional unsteady aerodynamic force measurement must be required in the investigation of the bridge behavior against the wind action. In this paper a new method of the full dimensional aerodynamic force measurement is introduced for the three dimensional input of the response analysis as the Modal Decomposition and Reassemblage Method.

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An energy-based evaluation method of vibration damping in cable-stayed bridges is proposed and discussed in this paper. The damping values of five modes of the Tsurumi Tsubasa Bridge, which were obtained by the field vibration test, are analyzed by using the energy method. It was found that the contribution of dissipation energy from shoe friction, aerodynamic damping, and oil dampers and high damping rubbers for suppressing cable vibrations, can be large in the Tsurumi Tsubasa Bridge. In addition, damping characteristics of this bridge, such as high damping value and mode dependency of damping were reasonably explained by the results of energy analysis.

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Suppression of 1 degree of freedom flutter by gyroscopic damper is studied. The stability of the system equipped with the damper is examined using Routh's criterion, and the optimal design parameters are proposed. The comparison of the response of the gyroscopic damper with that of tuned mass damper reveals that the gyroscopic damper requires smaller added mass because of the effect of gyro-moment. The overall response of the system equipped with the damper is also presented from the view point of the responsive amplitude and frequency, which are important in practical design.

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In the present paper creep analysis and torsional vibration analysis of cable-stayed bridges with two edge composite girders are discussed. For this type of the bridges there occurs stress redistribution not only within the composite girder but also between the girder, the cables and the pylons due to creep of concrete slab. Two creep analysis methods are presented, applied to an assumed bridge and compared.
To conduct torsional vibration analysis precisely is very important for this type of bridges with regard to aerodynamic stability because of relatively low natural frequency caused by low torsionaly rigidity of the open girder section. Also two analysis methods are presented, applied to the bridge and discussed.

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Field vibration test of Tsurumi Tsubasa Bridge, whose main span is the longest in the world among the single plane supported cable stayed bridges, was executed. Identification of the dynamic characteristics such as natural frequency, vibrational mode, modal damping, was done by different methods and the accuracy of identified values was first discussed. Then the dynamic characteristics of Tsurumi Tsubasa Bridge were investigated in comparison with those of other cable stayed bridges. It was found that the modal damping is higher and the natural frequency is lower compared with other cable stayed bridges whose main span is close to this bridge's.

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This paper describes the impact of the 1993 Hokkaido Nansei-oki Earthquake on the travel demand in the region affected by the earthquake. Such data is essential for post-earthquake road planning. Questionnaire survey was made to residents who suffered damage at Hiyama district. It was found from the analyses that travel volume for evacuation one hour after the earthquake reached 45.5% of the averaged daily travel volume, and that about 56% of that volume used automobiles. It was also found that travel volume for school and work deceased, while that for business and shopping increased after the earthquake. Multiple classification analyses showed that type of job and age are major factor for causing the variation of travel demand. In particular, variation of travel demand reached more than 80% of the average value in sales, transportation, educational business, and in the ages of 20's and 30's.

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The covariance matrix of unknown parameters has important roles to perform back analysis. In this study, we discuss two topics related to the covariance matrix. When we perform the back analysis with several construction or observation steps, the unknown parameters can be estimated totally from observation data of all steps if the result of back analysis of every step is succeeded to the next step as the prior information. The first topic is the methodology of the back analysis with time update. We discuss the effect of process noise, which is added to the covariance matrix in the update procedure. The second topics is the performance index for senser locations, based on the covariance matrix of unknown parameters or conditional responses. The usefulness of the index is demonstrated for a sensor locations of an embankment model.

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