This paper highlights recent developments of earthquake monitoring systems and early damage assessment systems in Japan. UrEDAS of the Japan Railway group and SIGNAL of Tokyo Gas Company are the pioneers of such systems. A few other early damage assessment systems were also developed by local governments. After the 1995 Hyogoken-Nanbu (Kobe) Earthquake, installation of seismometer networks and development of early damage assessment systems boomed Although some networks and systems are still under construction, this paper provides an overview of recent vintage and future directions of real-time earthquake hazard assessment are discussed. Recent developments in the United States were also reviewed.

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In the global buckling of a framed structure, members are examined for their own stabilities. It is shown that, besides the actual member forces exerted, there can be considered a critical axial force of each member determined by its displacement mode in the global buckling. The effective lengths of members are defined for those critical forces. The stability state of each member is qualified by the actual axial force acting on that effective length. The global buckling is explained as an assembly of those stability states of members.

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This paper deals with the characteristic of non-parametric planes caused by the dynamic responses with the hysteretic restoring forces (HRF). In the first place, this method evaluates the plane represented by the 2D wavelet coefficient. In addition, the plane is investigated by the equivalent values (ω_eq, β_eq) on the dynamic properties of the HRF system. This 2D wavelet transformations is very effective to understand the characteristic of the non-parametric plane. In the second place, the equi-response spectrum is the absolute accelerations with a linear system under the uniformity power of response or input. The equi-response spectrum is defined by the wavelet function and is considered the property by the comparison with the response spectrum of hysteretic systems.

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A mechanism of propagation for elastic SH wave which is composed of Love wave and leaking mode is investigated. We proposed a formulation for impulsive response in an elastic half space using Love wave and leaking mode in the last paper. Calculating the impulsive response following the formulation, behavior of the motion in the ground surface is explained by ray theory, because, the dispersion for Love wave and leaking mode is connected with the property of propagation derived from the ray theory. It is found that there is a relationship between phase velocity and group velocity, investigating the property of dispersion of the modes. Following the relationship, the mechanism of propagation of dispersed wave composed of Love wave and leaking mode can be explained from a point of view for the ray theory.

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The incident seismic wave on the base layer is generally calculated on frequency domain using multiple reflection theory from the observed records on the ground surface or in the borehole. In this case, the equivalent linear model is employed to approximate the non-linear behavior of soil. However, the equivalent linear model is not suitable for simulations under strong shaking. In this paper, a backward calculation method to identify the incident wave in time domain is proposed for applying non-linear analysis. Numerical examples are conducted to examine the accuracy and stability of this method.

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The use of the recursive prediction error method (RPEM) is often effective to identify the linear sytems. However the RPEM algorithm applicable to the structural systems even with linear dynamic charactristics has not been clearly developed because the observation equation becames a nonlinear function of dynamic structural parameters. The first purpose of this paper is to develop a non-linear recursive prediction error algorithm and apply it to identify the non-stational dynamic characteristics of a structural system. The second is to develop a method to determine the value of forgetting factor in RPEM algorithm. The numerical examples give satisfactory results to identify dynamic properties of structural systems with time-varying dynamic characteristics.

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An idea of probabilistic scenario earthquakes (PSE) is proposed and its engineering applications are described. PSE is developed by establishing a link between probabilistic seismic hazard analysis and scenario earthquakes, and makes it possible to objectively determine the scenario earthquakes corresponding to the specific risk level. The procedure of determining PSE and several case studies of PSE, which include the examples for major cities in Japan and the seismic hazard maps in terms of PSE, are shown in this study. In particular, the case study for Kobe demonstrates that the PSE can be applied to the evaluation of the “low frequency-high impact seismic event” such as Great Hanshin earthquake of 1995.

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An estimating method for a phase velocity of fundamental-mode Rayleigh waves on multi-layered media is proposed. This method needs only S wave velocity and thickness of each layer. The applicability of this method is examined with a series of numerical simulation. As a result, the phase velocity estimated by this method is fairly close to the exact value. Based on this method, then we apply this method to estimate Vs-profile of ground.

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The objective of the present paper is to propose a simple method for bending analysis of composite girders with corrugated steel webs.
In this analysis, it is assumed that a composite girder with I-section consists of three parallel beams bonded together; each beam is divided into thin laminas; displacements and stresses within each lamina are linearly changed. Nonlinear analysis is performed by using the initial stress method. Results of the present analysis were compared with experimental results.

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In case of field welding for I-section girders, cope hole details are applied at web plate. Local stress concentration is caused by shear deformation due to the existence of cope hole. This kind of joints has low fatigue strength. FATIGUE DESIGN RECOMMENDATIONS of JSSC regulates this details as class G. In this study, fatigue strength of cope hole details with thick flange plates was examined for the model of fewer main girders brige with cope hole, especially taking the influence of shear into account. Besides, in order to improve fatigue strength, the effect of grinder finishing of boxing weld was investigated. Based on the results of theses investigations, some conclusions were obtained for design and fabrication of structure details to apply to field welding to I-section girders with cope holes.

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The dynamic instability of local vibration of the simple supported thin-walled members under periodic axial loads is investigated by applying the finite strip method. At first, the analyses of the local buckling and the free vibration of the members are carried out and the characteristics of them are discussed. Secondly, the unstable regions of local vibration of the members under various geometrical parameters are calculated and the effects of the some factors which control the dynamic instability phenomena are clarified. Based on these results, the most efficient dispositions of diaphragm or stiffener are mentioned.

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The method of evaluating the response of clustered pipelines has not yet been studied when it is subjected to uneven ground settlements. An analytical model of clustered pipelines is set up in order to explain experimental results and find out how it response. Transfer Martrix Method is used to present the calculating method of the response of the clustered pipelines subjected to uneven groung settlement. Moreover, the influence of the different types of joints of the clustered pipelines on their response under various ground conditions are taken into account. According to the results of experiments and numerical analysis, a simple and easy calculating method is proposed when the clustered pipelines is subjected to uneven ground settlements.

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In the case of cable suspended structures, the natural frequencies are distributed densely from the lower frequency. Therefore, some vibration modes within a certain frequency range are excited by the external forces. Applying the optimal regulator theory for the active vibration control of the structures using a reduced order model, the control system becomes unstable due to the spillover. In this paper presents the design method of the controller by the H^∞ control theory which controles the vibration modes with particular frequency range. The vibration control performance of the stress ribbon bridge excited by the pedestrians is clarified by carrying out by the numerical simulations. It is shown that effectively and stable vibration control is realized by the H^∞ output feedback controller.

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This paper presents an experimental approach for the appearance of circumferential crack phenomena of reinforced concrete (RC) pier model by the Hanshin-Awaji Great Earthquake. First, the new push-up apparatus was developed and the vertical motion was applied by using both push-up apparatus and high speed loading machine. Second, in order to examine the failure modes due to circumferential crack, the push-up impact test was performed for reinforced concrete columns and the experimental results were discussed on the accelerations, velocities and strains of concrete and reinforcing bar. Third, the circumferential crack of specimen was recorded by the high-speed video. Finally, the input velocity of the actual RC piers occurred circumferential crack at Hanshin area was estimated by a similar law.

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The present paper is concerned with an elasto-plastic large displacement analysis of cantilever type of steel pipe-section columns modeling the bridge piers under cyclic loading. A modified two-surface plasticity model recently developed in Nagoya University is employed for material nonlinearity. Comparisons between the analytical and experimental results show that the modified two-surface model can be used to predict the inelastic cyclic behavior of steel structures with good accuracy. A parametric study is then performed to investigate the effects of radius-thickness ratio, slenderness ratio, magnitude of axial load and cycle numbers on the ultimate strength and ductility of the columns. Finally some formulas on load carrying capacity and ductility are presented considering the effects of various parameters.

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We performed dynamic response analyses to investigate the effectiveness of the High Ductility Aseismic Joint (HDAJ) spliced pile subjected to strong earthquake motion by using nonlinear FEM. The nonlinear characteristics of the pile and HDAJ spliced pile were assumed to be hyperbolic curves based on the bending tests of the piles. We analyzed three superstructure-pile foundation-ground dynamic interaction models. From the analyses, we found that the maximum response displacements of HDAJ spliced piles were not larger than those of ordinary PHC piles. Besides, the maximum bending moment induced in piles were remarkably reduced by introducing the HDAJ which implied that the HDAJ increased the safety of pile foundation system by far.

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A methodology which can automatically arrange and choose the unknown parameters for efficient back analysis is proposed and discussed. Interpreting a back analysis as estimation of the expansion coefficients of basis vector of unknown parameter space, 1) determine the basis vector from eigen mode of a posteriors covariance matrix of unknown parameters, 2) determine the dimension of subspace to back-analyze, based on the criterion with information entropy, 3) the expansion coefficients of basis vector composing the subspace are back-analyzed, then the unknown parameters are estimated. The proposed methodology is demonstrated through numerical examples, in which the dimension and basis vectors of the subspace are determined according to the quality and quantity of given observation data.

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Recently it is widely recognized by LES and higher order upwind scheme without turbulence models that 3D calculation is needed for a flow around a square cylinder to consider a 3D structure of turbulence and its decay. However k-ε with a 2D calculation has possibility to represent turbulence energy balance because they are involved in it with a mathematical form. In this study modified production eddy viscosity model was applied to overcome difficulties of standard one for a flow around a stationary cylinder. This modified model was also applied to flows around vibrating cylinders in the along and across wind direction to clarify its effectiveness and limitation.

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Solid finite elements of low order could be used for the framed analysis, but shear locking phenomenon appears at the slender beam analysis and it is difficult to accurately express a simple stress situation. Then, in this case many elements are needed to obtain a solution of the same accuracy as the solution by beam elements. In this paper, a new solid finite element which can describe simple stress situations and avoid shear locking phenomenon is proposed. This element gives the same result as Timoshenko beam element using reduced integration technique at the same number as beam element. Moreover, the solutions corresponding to the solid mechanics theory are obtained when fine mesh division is used. Therefore, this element has both the advantages of beam and solid elements, and it excludes zero energy modes and also volumetric locking phenomenon that occurs when Poisson's ratio is equal to 1/2.

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The purpose of this research is to represent Green's function for liquid layered medium in terms of spectral theory. In general, Green's function represented by wavenurnber intagration can be separated into residue terms and branch line integrals. This reserch shows that the residue terms are related to the discrete eigenvalue problem and the branch line integrals to the continuous eigenvalue problem. This research also shows that the integrand of the branch line integral can be decomposed into the continuous eigenfunctions. By the decomposition, Green's function can be synthesized by using the continous and discrete eigenfunctions for the wave field.

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We developed a hybrid simulation system to be used for structural control analyses and experiments. There are five units in the system which are the seismic motion generator, the structural response analyzer, the control signal generator, the control force generator and digital filters. Part of the units is composed of either of a digital signal processor (DSP) or an actual model of structure and a control device. The system is highly adaptable to all types of experiments in the structural control research field because we can simulate various situations by combining proper units in the system. The application of developed simulator to a structural model with the active mass driver system reveals an efficiency of this system.

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