The Hyogo-ken Nanbu Earthquake, 17 January 1995 caused by inland active faults resulted in a disaster belt zone of JMA intensity VII in Kobe city. In this paper, addressing attention to the geological features, the authors conducted computer simulation in order to interpret the above consequence. The gradually increasing surface alluvium toward the coast and the deep Osaka Group soils bounded by abrupt dipping of the rock formation at the foot of Rokko range are focused. The results shows that the former is related to the localized amplification of the short period motions (0.5-1s) while the latter to the long period motions (1-2s) and that the seismic amplification in alluvium might be more concerned with the heavy damage.

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A deterministic seismic hazard map of Japan using the concept of maximum credible earthquakes (MCE's) is developed for engineering. Seismogenic mapped faults on land in Japan, which may produce a significant earthquake, are used for seismic sources. An appropriate attenuation relationship of peak rock accelerations (PRA's) for this analysis is selected after comparing five published attenuation studies. The horizontal PRA's are obtained by applying the estimated MCE magnitude to the attenuation relationship. The median PRA contours for 0.7g, 0.5g, 0.3g, and 0.1g (g: acceleration due to gravity) levels are shown in the seismic hazard map.

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A circular rigid punch is located on a semi-infinite plane with an oblique edge crack. The punch is acted by an eccentric load to keep the punch vertical, and frictional force is assumed to exist on the contact region. A pair of concentrated forces or point dislocations is assumed to act at arbitrary points in the semi-infinite plane. The analytical solution (Green function) is obtained by a rational mapping function and a complex variable method. To solve the problem, the complex stress functions are divided into two parts; one is the principal part, which corresponds to the fundamental solution of the semi-infinite plane with an oblique edge crack; the other is the holomorphic part of the problem, which can be derived explicitly. The stress intensity factors and resultant moment on the contact region to decide the position of the vertical load on the punch are shown.

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This paper presents the force transfer mechanism and the fatigue performance of a pin-connection anchor of hanger for a box-type suspension bridge. Static loading tests were conducted using a full scale specimen, and contact pressure distribution and pin bending stress were measured under the design ordinary and wind loading conditions. In the subsequent cyclic loading tests, it was found that fatigue cracks occurred from seal weld at pinhole. Finite element analysis showed contact pressure distribution and the stress at welds of anchor plate and doubling plates.

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This paper presents an efficient optimal earthquake-resistant design method for truss structures. The optimum design method is developed by using convex and separable approximation concept, dual method, discrete-sensitivity analysis and suboptimization techniques. The coordinates of panel points, cross-sectional dimensions and discrete material kinds of all member elements are dealt with as the design variables. Constraints on stresses and displacements caused by static and earthquake loads and constraints on slenderness ratio are considered, respectively, as behavior and side constraints. The behaviors and their sensitivities due to earthquake motions are calculated, respectively, by the response spectrum analysis method and the Nelson's method. As the design examples the cost minimization problems of 193-bar transmission tower are shown for the three design conditions with different unit costs of land of construction sites. By comparing the optimum solutions, the rigorousness, efficiency and reliability of the optimum design method are demonstrated.

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This study develops a method of conditional stochastic discrete limit analysis (CSDLA) for a rigid bodies-spring models (RBSM) which is based on Bayesian probability. The CSDLA is a method of reliability analysis of a stochastic Gaussian field, when observation is made at discrete points. Furthermore in this paper, the CSDLA is applied to the stability analysis of embankment.

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Fragility curves for the slope failure probabilities conditional to the ground motion level were evaluated based on statistical method. For the evaluation of fragility curves, resisting capacity of slope in earthquake was assumed to a log-nomal distribution with random variable as ground acceleration, and the parameters of the distribution were estimated using the maximum likelifood method. A risk of slope failure was categorized into three levels considering to topographical factors as the inclination and condition of water erosion which were extracted from the topographical map. The obseved data from Izu peninsula earthquake (1974) and Izu-Oshima-kinnkai earthquake (1978) were used as statistical sample data, and contribution of factors to risk of slope failure were studied.

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A theoretical formulation is presented to estimate conditional non-Gaussian field when observation is made at some discrete points. The formulation is based on conditional probability function incorporated with mapping of non-Gaussian variable into Gaussian variable. A method of conditional simulation of a sample field at an unobserved point is proposed. Numerical examples are evaluated to illustrate accuracy and efficiency of the proposed method. The best estimator at an unobserved point is derived using least mean square estimation and discussions are made on error variance and conditional properties of the estimator.

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In oreder to examine the effect of some improving methods on the fatigue strength of high strength steel welded joints, fatigue tests of large-sized girders with flange-web joints, vertical stiffener joints, web-gusset joints and flangegusset joints are performed. The objective methods are grinding and TIG dressing to the weld toes, whose effects have been ascertained by many fatigue tests of small specimens, and applying the undermatching weld materials.

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This report presents a experimental study for structural details of the connection of diaphragm which is used in the first two girder steel bridge “Horonai River Bridge” to serve as a expressway bridge in Japan. These details are required adequate safety for construction load or fatigue action, As for these details of the connection, the following 4 types are considered, the connection with triangular rib plate or connection plate, split-tee connection and endplate connection. The loading tests are conducted using real-size bridge part models to investigate the applicability of these connection details to this two girder bridge.

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Contact pressure between pin and pin plate is discussed by FEM and UT from the point of view of the connection detail of hanger lope of long span suspension bridge. Application of the UT to the 25S surface specimen (and smoother surface) is effective. The results of UT and FEM distribution of contact pressure near the center of plate almost agree with the Hertz law. However near the surface of pin plate the contact pressure and plate width of large contact pressure region increase larger than those near contact pressure and plate width of large contact pressure region increase larger than those near center of pin plate.

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7 kinds of accelerated corrosion tests have been investigated in order to find out the test method of steel bridge painting which can reproduce the result of actual exposure test for 10 years accurately by short term. In addition, actual exposure test of painted specimens has been carried out at 3 different corrosive regions since 1988. Each method was distinguisuished by its unique cyclic patterns, the temperature and period of salt water cycle, humid cycle and dry cycle. As a result, combined cycle condition deeply correlative with actual exposure test was found out. In this cycle, the result of exposure test for 4 to 15 years can be presumed by 6-months accelerated corrosion test.

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Fatigue cracks have been found at the connection between floor beams and upper chord members of highway steel truss bridges. The major cause of these cracks was considered to be the bending moment at the fixed end of the beam, induced by the heavy traffic load. Retrofitting method for this problem was proposed in which the upper flange of the floor beam was directly connected to the upper flange of upper chord by welding. Test execution was conducted to obtain rational work procedure and good quality of welding. Water jet excavation was adopted in concrete removal work over the upper flange for welding. Improvement of stress condition was confirmed by stress measurements before and after this retrofitting work.

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In this paper, the strain aging of cold worked structural steel is studied to determine allowable cold working radius of steel bridges. In Japanese bridge design code, the allowable cold working radius of steel plate used in bridges is specified to be more than 15 times of thickness of steel plate (This corressponds to the plastic strain of 3%). The effects of strain aging on modern steels are discussed based on the experimental data of Charpy absorbed energy. It was found that the plastic strain of 7.5%-10% is acceptable to ensure the required toughness of structural steels. As a result, the change of allowable cold working radius is proposed with regards to the level of Charpy absorbed energy.

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Hierarchical beam element is proposed for the matrix analysis of space framed structures. The element is formulated with C⁰ continuous polynomials based on Timoshenko beam theory and an expanded warping theory considered shear deformation, and with nodal displacements at the both ends and higherorder internal modes. The generalized displacements, i. e. translations, twist, rotations and warping are interpolated independently, so that the well-known ‘shear locking’ phenomenon appears in the analysis of Bernoulli-Euler beams. Therefore, an effective reduced integration technique is developed for the bending and warping analysis of slender beams.
It is found by the numerical calculations that the proposed hierarchical elements yield superior accuracy for warping problems, bending problems of a beam with non-uniform cross section.

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A method for identifying structural parameters of local part of a structure (substructure) is developed, in which the input motions at the boundaries of the substructure are assumed to be noise corrupted since they are observed or measured. The absolute velocities and displacements at the boundaries, that are the input motions to the substructure, are incorporated into the state equation and observation equation of extended Kalman filter from which the influence of input motion noises on identification is reduced. Numerical analysis is carried out for localized identification of structural parameters of a shear type MDOF structural model and the effectiveness of presented method is investigated.

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This paper presents an experimental and analytical approach for the estimation method of the shear resistance of the filled materials in the cellular check dam. Both the size effect of the filled material and the compaction effect on the shear resistance of the filled materials are investigated and the significant effect of the compaction is pointed out. Second, the transmitted mechanism of the shear resistance due to the compaction is clarified by using the distinct element method. Finally, the empirical prediction method of the shear resistance-shear deformation curve considering the compaction effect is proposed. Then, a design example of actual check dam by using proposed estimation method is illustrated.

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A small-size variable damper without external accumulator was developed. A series of calibration tests has been conducted to develop a mechanical model of variable damper which gives the relationship among damping force, velocity of piston and valve opening ratio. The control algorithm to generate damper force is derived from the mechanical model expressing observed damper characteristics. The feature of the control system is simple without feedback mechanism, permitting to determine valve opening ratio directly from the measured piston velocity and the targeted damping force. The efficiency of developed control system was proved by producing various types of hysteretic relationship between damping force and piston displacement.

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Normal mode superposition method for transient response analyses of layered poroelastic media was developed here. Normal modes here were complex due to the presence of the internal friction between the solid matrix and pore fluid. Orthogonality relations among the complex normal modes were established by using the symmetry of the governing equation. Transient response of layered poroelastic media is expressed by the convolution integral between Green's function and source function, and Green's function is represented in terms of normal modes which show the orthogonality relations. Numerical calculations were carried out to examine the effectiveness of the present method as well as the vibration properties of a poroelastic medium on a rigid base.

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According to experimental results of dynamic field tests, a response of external girder is considerably different from internal one's. This difference is come from influence of torsional vibration coupling with bending vibration of a bridge. In this study, simultaneous nonstationary random vibrations of a bridge and moving vehicles are theoretically analyzed by means of random vibration theory, taking account of roadway roughness and coupling vibration of bending and torsion. RMS values of random response of girder bridges are calculated and compared with those from simulation analysis.

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To enhance the flexural ductility of the prestressed high strength concrete pile, a series of full-scale cyclic loading tests were conducted, and the effect of spiral bars and infilled concrete is examined. Two ultimate stages are determined here based on the damage level and the residual lateral strength, to measure the flexural ductility of the prestressed high strength concrete pile. Test results show that the spiral bars and infilled concrete improve the flexural performance. A moment-curvature relation of the pile with enough spiral bars and infilled concrete was analyzed taking account of the confinement effect. The ultimate curvature culculated by the analysis shows good agreement with the test results.

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In order to estimate the soil spring constants for the earthquake structural design of buried pipeline structures, a method using the theory of static elasticity is presented here and the equations of the constants are derived analytically. The soil spring constant in the axial direction depends on the shear modulus of the soil deposits G and the ratio λ between the radius where the displacement is zero and the radius of buried pipeline structure. The constant for the direction perpendicular to the axis of the pipeline depends on G, Poisson's ratio of the soil deposits ν and λ.

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This paper demonstrates an observation method of strains at ground surfaces caused by earthquakes and made clear some of the characteristics of the strains based on the observed data. Some of the important aspects of such strains are shown from the viewpoint of earthquake engineering, although the data were collected at the specific site and were limited to earthquakes of rather small intensities. The following conclusions are obtained. Strains were generated at ground surfaces in a nearly pure shear condition. The direction of the maximum principal strain almost always occured on a specific direction.

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The design spectra of Seismic Deformation Method for under ground structures have been given by the velocity response spectra defined on the seismic base layer. In this paper, a new method is proposed to define the design spectra in terms of the acceleration response spectra on ground surface. The proposed method makes possible to include the seismic and ground environment in the design spectra of under ground structures. In order to compare the proposed method with the conventional method, a conversion procedure of the spectrum defined on the ground surface into that of Seismic Deformation Method is proposed. The procedure is applied to the seismic design spectrum of Earthquake Resistant Design of Bridges of Japan and the average response spectra determined from 394 components of the strong motion records. The converted spectra are compared with the design spectra defined in various codes for underground structures.

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After the Hyogo-ken-nanbu earthquake on January 17, 1995, several design methods for restoration and new earthquake-proof standards have been proposed.
In this study, ten steel box column specimens (including seven concrete-filled steel specimens) modeling steel bridge piers were designed on the basis of the method for check of ultimate earthquake resistance proposed by the authors, and tested pseudodynamically using the accelerograms obtained during the Hyogoken-nanbu earthquake. In accordance with the test results, the varidity and usefulness of the adopted design method were made clear.

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In this paper, in order to investigate an accuracy of the equal energy assumption which is often adopted in evaluating their nonlinear maximum displacement response in seismic design, parametric studies on elasto-plastic behavior of steel bridge pier are carried out. First, the comparison between the maximum displacement response of the steel bridge pier evaluated by the equal energy assumption and the one obtained by the elasto-plastic dynamic response analysis shows that there is a quite difference between them. Secondly, an estimation procedure of the maximum displacement response of the steel pier employing an equivalent SDOF system with bilinear restoring characteristics is proposed and its efficiency is confirmed.

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It is observed often in the past earthquakes that the curved bridge tends to move to the radial direction of its curved bridge line when large seismic movement occurs and the bearings are broken. The rigid body movement of the curved girder which affects the sliding behavior is estimated. Some cases of dynamic nonlinear analysis to simulate the movement of bearing damaged curved bridge, and the parameterc study to examine the dynamic characteristics of currved bridges are carried out. Based on the relationship between the traveling of girder and the various parameters of girder shape, the equation to calculate the length of the girder on the pier for curved bridges is estimated.

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Several skewed bridges were slid and fell down from their supports by the 1995 Hyogo-Ken Nanbu Earthquake. The purpose of this paper is to study the in-plane rotational behaviour of the skewed bridges after failure of side blocks of the bearing by the horizontal ground motion. Firstly, geometric configuration of the skewed bridges in which the rotation is inevitable is investigated. Then, the rotational displacement of the skewed bridges are obtained by conducting non-linear time-history analyses in which a friction type hysteresis model is assumed to symulate the sliding of the bridge at the supports. It is found that the skewed bridges with small width-span ratios and small skew angles may have considerable sliding rotational displacements and fall down from their supports if adequate seat width is not provided. The requirement of the support length in skewed bridges is also presented.

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The observations of microtremors were carried out at 75 sites in northern area of Nishinomiya, Japan. Using frequency-wave number spectral analysis, the phase velocities and directions of wave propagation were detected from the observed data. Subsarface structures are is estimated by means of an inversion analysis of phase velocities. The deep ground structure around the Koyo Fault is surveyed from the results.

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Nonlinear dynamic response of a suspended small-sag cable driven by hannonic axial load and harmonic transverse load is presented. The effects of driving frequency ratio between the transverse load and axial load are discussed at first. Then, nonlinear transient vibration obtained by averaging method is obtained

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