We analyzed the response of elastic half space to a harmonically vibrating lateral force applied to the surface. We first derived analytic formulae which give the wave field at an arbitrary depth. These formulae provide a theoretical basis for a new method of physical prospecting which has been developed recently and is believed to be crucial for the precision investigation of underground geological structure. Next we calculated the formula for the most important lateral mode. While a large response was generated at the surface in the form of surface waves, the radiation pattern showed remarkable directivity resulting a cone shaped strongly excited area with vertical axis beneath the source.

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A series of explosion seismic experiments were conducted along the 1995 Keihoku-Seidan Profile. Most of the records acquired at the foundations of the Akashi Kaikyo Bridge had very poor S/N ratios. However, the P-waves of the explosions could be successfully delected after enhancing the records. The P-wave velocity structure was subsequently derived by fitting the travel times. The shallow crustal structure beneath the bridge is composed of four layers, with P-wave velocities ranging from 5.2 to 6.0km/s. The structure derived here is an improvement to the shallow crustal structure revealed by previous explosion experiments done about thirty years ago.

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The Hyogo-ken Nanbu Earthquake (Jan. 17, 1995) caused devastating damages in and around Kobe city. Noteworthy is the fact that the heaviest damages of JMA intensity 7 were centered in the so-called “disaster belt zone” along the coast. The authors, focusing on the geological features in a north-south section of Kobe, have performed the computer simulation for the 2-dimensional in-plane seismic (P and SV) wave propagation based on the FEM-BEM hybrid modeling. The nonlinear soil behavior was emphasized to better interpret the soft alluvium amplification that depends on the given distribution of soil properties in Kobe.

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Consideration of simple models of wave propagation helps to understand the physical characteristics of soil layers. In this paper, a new method for modeling wave propagation in multiple linear systems is developed, its application is discussed and the results are compared with those of conventional correlation, impulse response and geophysical methods. The new method reveals the arrival times of incident and reflected waves as well as their relative amplitudes. The effects of weighting coefficients on Fourier amplitude spectrum of the results are also discussed for some models and actual strong ground motion records.

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The purpose of this paper is to use the seismic response data of one 5-span continuous box-girder bridge to identify the dynamic characteristics of the system from different earthquake loading. The spectral finite element method was used by considering the flexural wave in beam to form the dynamic stiffness matrix of the substructure. Through matrix condensation the interior nodal displacement can be expressed in terms of the boundary nodal displacements. The identification was performed by using the recorded nodal displacement of the bridge to identify the EI-value and damping factor η of the substructure. Three seismic event data sets were used from the bridge strong motion instrumentation array. It is found that the identified EI-values are very stable even for different intensity of earthquake loading while the damping value may change from seismic event to event.

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In steel railway bridges, it is important to evaluate fatigue strength in long life region both for design and maintenance of bridges. There are few fatigue test data of 400-520MPa class steel with long life fatigue test and full scale specimens. Various types of welded joints in ten full scale specimens which included some details of steel railway bridges were tested. Fatigue performances of cover plate, joint of horizontal stiffener, flange gusset and longitudinal bead are discussed, and compare with those of small test specimens data and JSSC S-N curve.

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In steel railway bridges, a fillet radius of flange gusset was r=20mm and was very small radius at time when all welding bridges were adopted firstly. Fatigue strength of this flange gusset belongs to F category (65MPa) in newly design code. Moreover, there are location where the stresses which exceeds F category are measured in actual bridges. Fatigue cracks have not been reported from this corner yet. But the fatigue crack of this type propagates in lower flange and cuts lower flange, it leads to web. In this paper, experiment and analyzed are done to relieve of stress concentration and introduce compressive residual stress for improvement of fatigue strength of flange gusset corner. As a result, it was clear that relief of fillet radius and peening of fillet corner are both effect for improving of this fatigue strength.

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Dynamic response of a main structure of highway bridge under moving vehicles has been analyzed by using 2-dimensional models for a bridge and vehicles in relation to impact coefficients in design codes of bridges. In this study, 3-dimensional analytical procedure for traffic-induced vibrations of bridges is proposed for investigating the dynamic response of concrete slab and reaction force of plate girder bridge. Finite elements are used modeling girders, concrete slabs and floor systems of a bridge, and 8-degree-of-freedom system with one front and two rear axles is formulated for a heavy dump truck. Simultaneous differential equations for a coupling vibration of a bridge and moving vehicles are derived by means of modal analysis, and are solved by direct numerical integration. Numerical results of time history of dynamic response of concrete slabs and reaction force showed good agreement with field test results.

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A simulation method is developed for the dynamic response of 3-D dam-foundation-reservoir systems. The dam is modeled with finite elements; while the foundation and reservoir are modeled with boundary elements. Interaction effects and radiation conditions can be taken into account without any geometric restrictions. Following a simple analysis, responses of a 3-D arch dam interacted with foundation and reservoir to harmonic ground motions are simulated. The dynamic interaction effects are discussed based on the computed responses of the dam and distributions of hydrodynamic pressure.

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A plate-type dynamic absorbing system having a suppressing effect on several vibration modes of plate was presented as a dynamic absorber in this paper. It consists of a plate with free boundary condition and connecting springs and dampers distributed. An approximate tuning method of the plate-type dynamic absorbing system in which application was made of the tuning method of TMD was presented and the improvement procedure of the suppressing effect of the system was proposed, in which the connecting damper distributed uniformly was concentrated on the points near the loops of higher modes of main plate. Numerical investigations have shown the approximate tuning method to be useful and have demonstrated the effectiveness of the plate-type dynamic absorbing system.

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An equivalent Tuned Mass Damper (TMD) model of circular Tuned Liquid Damper (TLD) has been developed to understand the nonlinear vibration characteristics of circular TLD based on a TMD analogy. The equivalent linearized TMD parameters of circular TLD were estimated using the experimental data of the circular TLD fluid dynamic force obtained from shaking table experiments under various excitation amplitudes. Those models were defined as the functions of dimensionless amplitude of the excitation to the TLD. The proposed model of circular TLD can make clear the relationship between the design parameters such as the radius, the depth of TLD and optimal tuning parameters as a dynamic damper.

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Pseudo-dynamic tests have been performed at Nagoya University in order to investigate the dynamic behavior of real steel bridge piers under severe earthquakes. Among the test results responses to Level 2 G. T. 1, JMA, and JR-Takatori are striking. That is, these ground motions put energy into specimens drastically in specific points. In this study, it is made clear what components of earthquake waves severely damage steel bridge piers by elasto-plastic seismic response analysis.

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This paper deals with the wavelet analysis for the records of vertical and horizontal arraies on the Southern Hyogo-ken Earthquake .The analysis is to calculate the wavelet cross correlation function (WCCF) and wavelet frequncy-wave number spectrum (WFKS) for the object earthquake waves and is to investigate the foundamental properties of the wave propagations. In addition, we carry out the numerical simulation by the rupture propagation of the fault having the earthquake source on the 3DFEM of the Osaka bay area and compare the properties of the wave propagation.

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In an analysis of elasto-plastic behaviors of steel box column piers under seismic loading, FEM shell element model is not practical because of its high cost, and a simple 3 dimensional beam model to simulate nonlinear behavior of steel box column piers has been required. Thinking it into consideration that the relation between strength of a steel box column pier against horizontal loading and its axial dimension change dose not depend on load history, the authors developed a new method for modelling performance of a pier against horizontal loads based on its behavior under monotonic loading. In this paper, the modelling method of a steel box column pier, considering buckling and yielding, and the example of calculation are shown.

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By adding a function to fade memories for past observation data to the Kalman filter which has often been used as a time marching identification algorithm we developed an adaptive Kalman filter scheme. The rate of memory fading was defined by a forgetting factor multiplying to past data at each time step. In order to track fast variation in the system parameters the value of the forgetting factor should be small. On the other hand, to remove the random noise from the signal, the number of sample points used at any time should be large enough, that is, the large value of the forgetting factor should be used. The Akaike-Base Information Criterion was applied to determine the optimal forgetting factor.

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To identify dynamic parameters of structural systems, we have to solve non-linear optimization problems because the system transfer equation of structural system is usually a non-linear function of the system parameters. The purpose of this paper is to develop a method to linearize an observation equation with respect to the structural parameters, which is derived form the system transfer equation and apply it to identify the dynamic parameters of linear and non-linear dynamic structural systems. The numerical examples give satisfactory results to identify dynamic parameters of model structures with 8 degrees of freedoms.

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Broadband strong ground motion time histories at a site above the fault plane for the 1923 Great Kanto Earthquake and future earthquakes on the Sagami trough are generated, using a hybrid method that computes the ground motions separately in the short period and long period ranges and then combines them into a single time history. Considering uncertainty in the source parameters of future large earthquakes, 960 strong motion time histories are generated. The ground motions at the site are characterized by a smooth median response spectrum and its standard error estimate, together with a subset often time histories whose average response spectrum, and whose variability approximately matches the standard error of the smoothed response spectrum.

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This study applies a standard method of the Seismic Risk Management (SRM) to a water supply system. The SRM assessment deals with seismic damages represented by an event tree, and defines a seismic risk as expected loss (a product of loss and its probability). Taking into account the properties of the network of a water supply system, its seismic risk should be classified into a physical risk and a serviceability risk. The difference between a potential risk after reduction and a present risk of a system is recognized as an effect of a measure. The SRM would offer valuable information to the decision making of seismic measures.

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In Japan, while seismic design criteria for new substation components have been improved since 1980, many existing components have not been replaced or retrofitted because of the tremendous cost for upgrading. This paper presents a seismic retrofit method for substation components on the basis of the cost benefit analysis. The proposed method makes possible to determine an optimum number and priority of substation components to be retrofitted on the basis of the estimation for retrofit cost and company loss due to a scenario earthquake. In order to discuss practical seismic retrofit plans, the proposed method is applied to an actual secondary transmission system located in Kushiro, Hokkaido.

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This study is to investigate the rupture mechanism of compressive rupture in circular reinforced concrete bridge piers caused by the Hyogoken-Nanbu-Earthquake of 1995. Impact loading tests were done to examine the possibility of producing compressive rupture in circular reinforced concrete specimens by axial impulsive force. Four types of RC specimens with circular cross section were employed for tests. Axial impulsive load was input to a specimen by means of the horizontal impact loading machine.

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This paper deals the elasto-plastic finite element analysis of the HSFG bolted joints to classify the limit states of them. The main analytical parameters of the joints are the ratio of the design slip strength to the design yield strength of the flange. The declination of the preloaded tensile load of the high strength bolts, the stress condition, the effect of the frictional force of the joint and so on are discussed about the results. And then the kinds of the behavior of joints are classified and the limit strength of joints are investigated.

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This paper reports an experimental study on the mechanical behavior of concrete slabs at the intermediate supports of axially prestressed continuous composite girders.
Static loading tests were carried out on the concrete slab subjected to negative bending in order to grasp the mechanical behavior of the continuous composite girders. Attention is paid to the differences of mechanical behaviors in terms of manufacturing concrete slabs, prestressing and intervals of studs. It turned out from the experimental study that prestressing for concrete slabs plays a key role for reducing cracks due to negative bending.

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The purpose of this study is to apply the method of Rigid Bodies-Spring Model (RBSM) in order to explain analytically the ultimate resistance and the mechanical behavior of RC members damaged by corrosion of reinforcement. In order to investigate the modeling of the cracks due to the corrosion of reinforcement and the expression on analysis of introducing the bond-slip between concrete and steel bar, the analytical results obtained by RBSM were compared with the experimental ones of cyclic bending tests on RC beams with an accelerated galvanostatic corrosion method. As a result, it was confirmed that the analytical method of RBSM was effective for analyzing the nonlinear deformational behavior of the damaged RC beams by corrosion of reinforcement.

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Elasticity Method of folded plates structures correlate the plane stress problem and the plate problem not within the governing equations but at plate edges. This gives exact solutions in its theoretical hipotheses. This paper extended the theory for the folded plates structures from classical Kirchohoff plate to the plates with first order shear deformable ones. In this way the plate elements that we shall construct will possess, in a natural way, also the degree of freedom related to the rotation along the vertical direction. This fact permits us to use Mindlin's couple stress theory in plane elasticity. This paper suggests a way of structural analysis without refering to the exact values of scale parameter of materials.

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Finite element analyses for flow around two square cylinders in tandem arrangement were performed with two and three dimensional numerical models. The computational flow characteristics were compared with wind tunnel results in terms of drag coefficient, pressure coefficient, and flow pattern, then the applicability of the numerical simulation to the structures in tandem was studied. It has been reported that flow patterns around two rectangular columns in tandem can be classified into two modes. One of the modes, where the Kármán vortex is not formed between the cylinders, should prevail with the column spacing used in this paper, and it could be adequately represented only by the three dimensional simulation at Re=10⁴. As a result, the computed aerodynamic characteristics in this case agreed well with the experimental results, and the effectiveness of three dimensional computation and Reynolds number were confirmed.

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This method is a structural method to enhance the aerodynamic stability by adding temporarily the mass into the box girder of a suspension bridge against a storm. First of all, we researched the most effective longitudinal position of such the mass from the aerodynamic stability. And we roughly designed suspension bridges by this method. As a result, this method shows the same effect as other structural methods and reduces much structural material. It was recognized that the bridge's changed stiffness due to static wind loading makes this method more favorable. For this study, we employed the extended Bleich theory and a numerical integration method.

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Altered cope hole details for improving fatigue strength were proposed and their effects were examined by fatigue tests. It was shown that the detail in which the weld was quitted near the corner of cope hole and the end of welded bead was finished by grindings, and the detail in which cope hole was filled up with welded bead, had higher fatigue strength than conventional cope hole details.

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