In this paper, effectiveness of a new base isolation system i. e. elliptical rolling rods between the base and the foundation of structure is investigated. Equations governing the motion of a multi-storey shear type building supported on the elliptical rolling rods are derived. The dynamic response of the system to both harmonic and real earthquake ground motions is obtained by integrating the incremental equations along with an iterative technique. The iterations are required due to non-linear force-deformation behaviour of the elliptical rolling rods. Effectiveness of the elliptical rolling rods is studied by comparing the response between isolated and corresponding fixed base system. In addition, a parameteic study is conducted to investigate the effects of important parameters on the effectiveness of elliptical rolling rods. The parameters considered are: the fundamental time period of the superstructure, the coefficient of rolling friction and the eccentricity of the elliptical rolling rods and the frequency content of ground motion. It is shown that the elliptical rolling rods are quite effective in reducing the dynamic response of the system without undergoing the large displacements or living the large residual base displacement.

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The equivalent linearization method (ELM) is often used to estimate the maximum displacement of isolated structures. Damping-dependent coefficients (C_D) which are a scale multiplier required to give simplified elastic acceleration design spectra (EADS) for greater damping values are proposed. The C_D is obtained from the relationship between nonlinear time history analysis (NTHA) and ELM using the standard waves from various ground types and different types of earthquakes. The proposed C_D is compared to the previous one and validated for various isolated structures under a natural earthquake and standard waves.

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Long-term fatigue behavior of plate girder specimens with four types of vertical stiffener connections is investigated through fatigue tests under constant amplitude and highway bridge variable amplitude loadings. Fatigue cracks are initiated from fillet weld toe at the top and bottom ends of each stiffener and from blow holes contained in the web-to-flange longitudinal weld. It is found that the fatigue failure life of all four connection details plotted against the maximum principal stress range satisfies JSSC fatigue category D.

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During the Great Hanishin-Awaji Earthquake, many steel bridge structures experienced brittle fractures, following the large scale deformation of their members. Hence, in this work, various material tests are performed on specimens which are made out of damaged steel bridge structures. The plastic strain, induced during the earthquake, is estimated through the change in their material properties. And then, the embrittleness of the steel due to the induced plastic strain is discussed, in order to study the mechanism of the occurrence of the brittle fracture during the earthquake.

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To investigate the dynamic soil spring characteristics in axial direction of the buried pipeline by the real scale experiment, the high velocity loading system was developed and the buried pipe of 600mm in diameter and 180cm in depth to the top, was loaded. The conclusions are as follows; 1) the slippage occurs between the pipe and the soil when the shear stress between them reaches the critical value, 2) the soil spring stiffness and the critical shear stress increases as the loading velocity increases, 3) the critical shear stress in high velocity, is the largest in the virgin loading, and it decreases 40%-50% in the second loading.

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A wing-attached pile is proposed as a new concept of liquefaction remediation to expect a tranquilized lateral resistance even in a liquefying ground due to a strong earthquake motion. Elucidation of the proposed wing-pile with a pile-top displacement reduction effect is presented by showing results of a series of shaking table tests and comparing between a wing-pile and a normal pile. A reduction factor of pile top displacement of wing pile is studied related to magnitude of an input motion, density of ground, mass of pile top and cyclic mobility appearance. Magnitude of a reduction factor is about 0.8, which is same as a pile in compacted ground.

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This paper describes an experimental study to investigate the stiffness, ultimate strength and ductility of concrete-filled steel members (composite members) with thin-walled circular cross section subjected to bending, torsion and their combinations. Torsional moment with constant distribution, bending moment with triangular distribution along the member axis, and their combinations are applied to 4 steel member specimens and 4 composite member specimens with comparatively compact circular cross section up to their ultimate state. The main conclusion is that the ultimate strength of these composite cross section can be predicted by a fully plastic interaction curve through the adoption of a practical compressive strength and shearing strength of encased concrete by considering the effect of transverse compression due to the hoop action of the outer steel tubes.

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We describe herein the frequency wavenumber domain's solutions of seismic waves radiated from the kinematic source model with 4 types slip directions in a three-space Cartesian coordinate system, and also the closed form solutions of the soil layered stiffness matrices necessary to calculate the seismic waves in the layered soils. To demonstrate an applicability of the presented solutions, we synthesize the near-field ground accceleration motions recorded during the 1966 Parkfield earthquake, by using the presented solutions for the frequency range of 0-1.25Hz and adding the stochastic waves simulated by a stochastic method for the frequency range of 1.25-10Hz.

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Instead of traditional welding splicer, a High Ductility Aseismic Joint (H. D. A. J.) was newly developed for the pile splicing. In order to gain the elementary characteristics of the H. D. A. J. spliced pile, which is necessary for the dynamic response study, authors performed a series of cyclic load experiments. Based on the experiment result, comparison and examination are performed on behavior subjected to cyclic loads between the traditional pile and the H. D. A. J. spliced piles. The nonlinear characteristics of the H. D. A. J. were assumed to be hyperbolic curves based on these cyclic load experiments. The bending moment induced in piles will be remarkably reduced by introducing the H. D. A. J. which implied that the H. D. A. J. increased the safety on pile foundation system during the strong ground motion by far.

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This paper describes a numerical result to clarify the effectiveness of the rubber type restrainer to mitigate pounding effect between adjacent decks. A series of nonlinear dynamic analysis was conducted for two structural system consisting of 5 spans continuous bridge subjected to an extreme ground motion. It is found from the analysis that effect of the restrainers is significant in deck response and plastic curvature at pier bottoms. It is also found that effect of the energy dissipation in the restrainer is limited because of the small contribution to the total energy dissipation. The effect of the skeleton curve of the restrainer between the strain hardening and strain softening is also studied. It is found that the strain hardening type restrainer is favorable in limiting deck response in both bridges.

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In this paper, an attempt to develop the JMA (Japan Meteorological Agency) instrumental seismic intensity and its algorithm was made so as to be responsive to the seismic phenomena and earthquake damage features in wider period range. The range of natural period of man-made structure has, however, been spreading rapidly in both shorter and longer directions and new structures have been increasing in number as well. In this new situation, an advanced seismic intensity available for wider period range, say, from 0.05sec to 20sec, is expected to develop.
In this recognition, an attempt was made for a new instrumental seismic intensity that combines a set of three index values for short, medium and long periods respectively. The algorithm to evaluate the index values for medium and long periods are developed in parallel with a slight modification. Examples of evaluation for the Kobe earthquake and other recent major earthquakes in Japan revealed the importance of introducing such combined seismic intensity and the effectiveness for application to seismology as well as earthquake engineering.

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The simple supported steel-concrete composite slab bridge has many advantages such as light weight, high structural performance and time reduction at the construction site. The application of this composite slab bridge to the continuous bridge should be associated with the control of concrete cracks at the intermediate support. This study focuses at the crack behavior in the negative moment region. The optimum ratio of the additional reinforcement as well as the concept of intermittent composition in the negative bending region are verified by load-caning test of several simple and two continuous beams.

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A questionnaire survey is carried out to investigate the distribution of seismic intensity in Osaka prefecture during the 1995 Hyogo-ken Nanbu Earthquake. The results are compared with the measured seismic intensity calculated from the observed records and the questionnaire seismic intensity resulted by other surveys in the overlapped regions. It is concluded that the questionnaire seismic intensity needs to be corrected using the observed strong motions. The reliable distribution of the seismic intensity is obtained by adding 0.8 to the questionnaire seismic intensity. The effects of source, path, and site characteristics on the seismic intensity distribution are also examined.

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Damage to Hanshin Expressway ‘Kobe Route’ (P1 to P718) is described in conjunction with the structural characteristics. Although the damage level of many piers was generally very high in the Kobe Route, it is also true that the visually-judged damage of many piers is moderate or mild. The visually-judged damage level is scattered along the route; no consistent trend can be found. On the other hand, there were many piers which have large residual inclination without severe damage in appearance. In the latter part of this paper, damage to the piers from P1 to P350 is investigated in detail. Considering that large residual inclination (>0.5°) of piers is earthquake-induced severe damage, it is shown that almost all the RC single piers from P35 to P350 received severe damage consistently. The ratio, r of flexure to shear capacity of the RC single piers from P1 to P350 was calculated from the design drawings; it is found that, for severely damaged piers, the damage mode (flexure or shear) in the piers is fairly consistent with the value of r, either >1.0 or <1.0.

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Modeling phase characteristics of earthquake ground motion is important to synthesis a design earthquake motion consistent with the given response spectra. We assume that an earthquake ground motion can be expressed by the convolution of the two time functions; 1) the time delay caused by rupture propagation on the fault plane which is assumed to be expressed by a train of impulses, 2) the effect of path of transmission. This paper presents a simple method to model phase characteristics of earthquake motion using the concept of group delay time. A method to model the group delay time of a train of impulses is proposed. The phase shift due to the transmitting path of seismic wave motion is also expressed by the minimum phase transfer function of its amplitude spectrum.

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This study is to investigate local stress and fatigue behavior of a pinned anchor to deck welded joint and the reinforcement structure underneath for a box-type suspension bridge. Concentrated loads are transmitted from the pinned anchor to members consisting box girder. In order to avoid the weld lines crossing, scallops are made at the intersection where stress concentration occurs. For verifying the fatigue strength and to find better structured details, fatigue tests and static loading tests were conducted for a pin connection detail on full-scale specimens of a anchor structure in order to verify the weak point and the fatigue strength under the ordinary load condition and the wind load condition.

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Wind tunnel experiments using a circular cylinder rocking model were conducted to investigate the characteristics of the vortex-induced vibration at a high wind speed. Attaching a thin circular disk on the model top to modify the flow passing the free-end, the response of that vibration was diminished and the occurrence wind speed tended to be rather low as increase of the disk diameter. This reason was clarified by measurement of the wake fluctuation around the free-end: as the disk diamter increased, the generation of the tip-associated vortex which had been considered as the cause of that vibration weakened and its frequency gradually increased.

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We have proposed a slit-type bridge restrainer as a possible method to retrofit a steel highway bridge to prevent the fall-off of girders. The slit type restrainer provides enough moving distance and energy absorption capability to comply with the revised specification of highway bridges. These characteristics critically depend on the large plastic deformation of the restrainer plate. In this work, we examine the mechanical behaviors of the slit type restrainer by parametric FEM analyses with the establishment of practical design method in mind. The numerical analysis also covers the possible application of new type material (low yield point steel) and the estimation of ductile fracture.

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In this paper, we analyze the energy release rate for a frictional crack subjected to remote proportional compressive loads using the finite element method. The energy release rate is calculated by using the path-independent E-integral of the complementary strain energy type, which is path independent even at the onset of crack kinking. We find that the E-integral gives the energy release rate under the compressive loads with a high accuracy.

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Strong-motion and microtremor observations are carried out in loam plateaus and Holocene lowlands in the Hassaku area, Yokohama, to investigate site-amplification characteristics in the area. Strong-motion observations show that a plateau site has larger site-amplification characteristics in comparison to lowland sites by a factor of about 1.5 in peak horizontal ground velocity and about 2 in spectral peak amplitude of Fourier acceleration spectra. The amplification is due to subsurface soils which are accumulated on soft rocks. Microtremor observations demonstrate that resonance periods on plateaus are related to elevation; high site amplification areas distribute along rivers in the lowlands and on the Shimosueyoshi plateau.

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The spatial estimation method of the average of the process over a block whose location and geometry are known is proposed in this paper. A theoretical formulation is presented to estimate conditional lognormal stochastic field when observation is made at some discrete points. The optimum estimator and minimized mean-squared estimation error of a block average value are then compared with the results obtained by Point Kriging when an unknown value at a known location is estimated. Numerical examples were carried out to examine the influence of block size on the optimum estimator and estimated error variance. Except for very small block sizes, the results indicate that the Block Kriging is critical method.

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In this paper, the safety to overall lateral-torsional buckling and the lateral-torsional buckling of the main girders between the cross girders is examined for the erection of the steel twin girder bridges before the concrete slab is harden. Using the elasto-plastic finite displacement analysis to the structural system under erection, which have changed distance of main girders, or cross girders. To the lateral-torsional buckling, the proper parameters are established and the relation between the buckling strength and parameters are considered. And, the safety to initial deflection, the lateral-torsional buckling and the reaction force is examined in the case of the incremental launching method.

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Large scale model tests are performed to investigate the ultimate behavior of rectangular steel pier base-to-footing connections under monotonic loading. The main purpose of this research is to examine the applicability of the theoretical methods to the prediction of the ultimate behavior of pier base connections. The methods examined here are a component method and a simplified method based on the RC double reinforcement beam model. The validity and accuracy of the component method that were confirmed for the circular steel piers are also confirmed for the rectangular steel pier. This implies that the component method can be generally used to assess the ultimate behavior of pier base-to-footing connections. Regarding the RC double reinforcement beam model, an adoption of a realistic constitutive relation and an assumption of a proper RC cross sectional size lead to an acceptable result.

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A cyclic loading test was performed on a 1/3 scale model of a rectangular steel pier base-to-footing connection. From the experimental results, the maximum pier base moment and the corresponding rotational angle under cyclic loads decrease by 20% and 60%, respectively, compared with the results under monotonic loading. In the post peak range, however, the moment drop is small and the connection exhibits a stable behavior under cyclic loading. Based on the hysteretic behavior obtained by the experiment, a hysteretic model for a rectangular pier base connection was presented, following the procedure proposed by Goto et al.

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The 1995 Hyogoken-Nanbu Earthquake caused unprecedented damage in Hanshin-Awaji area. In order to evaluate the damage of structures in this area, it is important to estimate the distribution of earthquake ground motion. However, sine the number of strong ground motion records is not enough, it is necessary to estimate the distribution using other data sourees. In this study, the relationships between the building damage and the ground motion indices (PGA, PGV, SI and JMA intensity) were constructed using the building damage data compiled by the Building Research Institute and the recorded motions. The fragility curves obtained for residential buildings were then employed to estimate ground motion distributions in the 1995 Hyogoken-Nanbu Earthquake.

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In a dynamic analysis of the bridge, the damping ratio is usually set from a main material. On the other hand, the energy-based damping theory is developed in recent years. Therefore, This study concerned with energy-based estimation method of damping ratio of single span PC stress ribbon bridges. The equivalent damping ratio of the slab becomes h_G=0.0101 form the statistics analysis of the measurement damping ratio, and modal damping can be estimated form the equivalent damping ratio and the ratio of the strain energy to the vibrational energy. In addition, the influence which the damping ratio gives to the serviceability for the pedestrian-induced vibration was examined by the parameter analysis, and considered about presumption accuracy of the damping ratio technologically needed.

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The fatigue tests were connducted using full-scall welded plate girders with various cross-beam connections in order to investigate the fatigue strengths owing to the bending deformation of the main girder. The structural details that change the shape and size of coped end hole. Test results indicate that the fatigue strengths of three web penetration details were smaller than the fatigue strengths of the web gusset and they were smaller than the fatigue design curve of JSSC Category G. The fatigue strengths of web penetration details decrease with the increasing of the diameter of the hole.

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Schoolhouse of Ohnokoba Elementary School of Fukae Town was burned by pyroclastic flow of 15 September 1991. The process of preservation of schoolhouse for promotion of town is studied in this paper. The problems to be considered are discussed in detail.

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We proposed a backward calculation method to identify the incident wave in time domain for applying non-linear analysis (Proc. JSCE, No. 577, 1997). In this paper, as an application of the proposed method, the incident wave is identified at Port Island from the measured acceleration at G. L. -83m. The numerical results show the accuracy and the utility of this method. In case of the non-linear dynamic response analysis for the soil system, the proposed method is more suitable for the identification of the incident wave than the equivalent linear method.

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This paper investigated appropriate model-establishment methods for applying a bi-linear model and a two-parameter model to a circular-section steel bridge pier (steel pipe column), respectively, regarding the restoring force characteristics used for nonlinear dynamic analysis. By this investigation, we obtained a solution which approximates the results of a pseudo-dynamic test by establishing, in the case of the bi-linear model, yield point coordinates approximating the hysteresis absorption energy in a quasi-static cyclic loading test and, in the case of the two-parameter model, by applying the type of the restoring force model, which takes into account the effect of the strain hardening due to cyclic loading.

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