A technique based on the principles of finite element method incorporating the contact element, called discrete finite element method (DFEM), to model masonry structures consisting of blocks of arbitrary shapes is developed and adopted in the static and dynamic analyses of masonry structures. The DFEM considers blocks as sub-domains and represents them by solid elements. Contact elements, which are far-superior to joint or interface elements, are used to model the block interactions such as sliding or separation. The applicability of the DFEM to static and dynamic analyses of structures such as towers, walls and arches of masonry type are checked and discussed.

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Local site effects of two alluvial sedimentary basins at Kuno in Ashigara valley and at Takeyama in Miura peninsula were evaluated under strong motion array seismographs observation. The horizontal spectral ratios of the gravelly soil's sediments at Kuno were constant in the component along the S wave's principal axis corresponded to the focal radiation pattern. On the soft clay's sediments at Takeyama, the spectral ratios to a reference point at the outcrop of bedrock were constant by considering seismic incident angle. Thus the site effects computed by two-dimensional analytical method agree with the observed spectral ratios by considering the incident wave field related to the source and path effects.

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This paper describes seismic isolation effects of soft layers installed directly around a rectangular shape tunnel and placed beside the tunnel as vertical walls. 2D-FEM analyses with different properties and arrangements of the soft layers and the ground were conducted. The results show that the soft layers can restrict propagation of shear forces effectively; the layer directly around the tunnel with shear modulus of 1/100-1/1, 000 of the ground can decrease the section forces due to earthquakes to half of the case without the layer. In cases with the 10cm and 30cm thick soft layers installed besides the tunnel as vertical walls. the section forces due to earthquakes can be reduced to 60-70% and 40-50%, respectively, of the case without the layers.

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Performance of base-isolated bridges is evaluated using the observed records of the main shock as well as after shocks during 1995 Kobe earthquake. In the first half of the paper, the motion of the superstructure supported by lead-rubber bearings, is shown to be approximated by the single-degree-of-freedom system where the superstructure is assumed to be rigid body. In the second half of the paper, the stiffness and damping coefficients of superstructure identified from observed records are compared with those calculated through the equivalent-linearization using the cyclic loading tests performed prior to installation. The comparison reveals good agreement between the design values and observed dynamic characteristics and the performance of base-isolation bearing is confirmed.

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In the ductility design of a bridge pile-foundation, it is required that the pile foundation be designed for the lateral force and bending moment corresponding to the flexural strength of a column. It is required in such design that the flexural strength of the pile foundation thus designed should be larger than the flexural strength of the column so that the plastic deformation of the pile foundation be minimized. However, since the plastic deformation of the pile foundation is unavoidable when it is subjected to strong ground shaking, it is important to evaluate how larger flexural strength should be provided in the pile foundation. This paper presents a series of nonlinear dynamic response analysis of two bridge-column-pile foundation systems to clarify the relation between the plastic deformation of the pile foundation and the modified yield strength ratio which is defined as a ratio of yield strength of the foundation to that of the column.

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In order to investigate the cause of damage distribution in Kofu basin during the 1923 Kanto earthquake, strong-motion observation, underground-structure prospecting and numerical calculation are carried out. The strong-motion observation shows that ground-motion intensity is larger in the central and southern parts of the basin in comparison to the northern part of the basin and hills. Shallow and deep underground structures are constrained by using spot and array microtremor observations. Numerical calculation shows that amplification factor is consistent with the result of the strong-motion observation and the damage distribution during the 1923 event when shallow and deep underground structures and the angle of incidence to the basin are considered.

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The relationship between the soil amplification ratio and the ground condition was examined using strong motion records measured at 77 JMA stations in the period of over 8 years. The amplification ratio for the instrumental JMA intensity as well as the peak ground acceleration and velocity was obtained from the station coefficients of the attenuation relationships. The combined use of the geomorphological land classification and the surface geology was found to give the best estimate of the amplification ratio. This result suggests that the Digital National Land Information may be conveniently used for the estimation of strong motion distribution of a large area in Japan.

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The effect of vehicle loading on the seismic load of highway bridges is discussed. Dynamic structure-vehicle interaction of highway bridges is discussed. The effect of vehicle loading on displacement or force at bridge pier or foundation is obtained. Then the influence of heavy vehicles to seismic design of highway bridges is discussed.
The realistic model is developed by comparison with full-scale vibration test. On this basis, frequency response and earthquake response of bridges loaded with heavy trucks are obtained, and their implication to the seismic load of bridge structures is discussed. Structure-vehicle model based on actual traffic congestion, reasonable evaluation of effect of the dynamic structure-vehicle interaction is obtained. Then their implication to the seismic load of bridge structures is discussed.

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This paper deals with a model of a source time function to compute a acceleration pulse from a small earthquake. First, a source time function for kinematic model is proposed from chain-reaction model. Fundamental characteristics of the source time function are examined by parametric analyses. Effects of source distance and surface geology on the synthesized pulses are studied. A simple relation between a source parameter and a surface pulse is proposed through model analyses. Finally, comparisons between recorded acceleration pulses and synthesized ones are presented for two small earthquakes in Japan and in California using proposed model.

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Flutter of suspension bridges with temporary mass was studied by contribution of modal aerodynamic damping. The following are recognized through these studies. In case of conventional suspension bridges, 3rd symmetrical vertical bending mode is important next to 2 basic modes and this mode enhances flutter speed. In case of suspension bridges with temporary mass, flutter speed drops when the lateral bending mode accompanied with the torsional mode develops remarkably.

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As the first step of fluid-membrane coupled analysis, wind-induced static deformation of a two-dimensional suspended membrane is computationally studied. The equilibrium shape of the membrane was obtained by coupling two-dimensional finite element analysis of air flow based on Navier-Stokes equation using mixed elements and that of two-dimensional membrane using truss elements. Modified ALE method was used to compute the aerodynamic force efficiently, and the underrelaxation method and the incremental load method with limiter of displacement were used to suppress the numerical instability. The computed results qualitatively agreed with the previous experiment conducted by Okuda et al.

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In dynamic design of cable-stayed bridges, evaluation of damping of structure is important. However, because it is difficult to evaluate damping ratio theoretically, it is general to measure it through vibration tests. Many vibration tests were performed mainly on steel cable-stayed bridges in the past. But enough data is not accumulated on prestressed concrete cable-stayed bridges because they are relatively new bridge type.
In this study, measured damping ratio in 16 cable-stayed bridges were analyzed to study the relationship between damping ratio and natural frequency, comparison with steel cable-stayed bridges, and damping ratio in a construction stage under cantilever erection method.

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It is predicted that plate girder bridges having a steel girder with a concrete slab connected by slab anchors behave as rather composite girder bridges actually. But the composite action due to slab anchors is ignored in present design of plate girder bridges. Therefore, there is a difference between the behavior according to the design practice and the actual behavior for continuous plate girder bridges.
In this paper, in order to investigate a behavior of a two-span continuous plate girder bridge under a service load level, a crack width of a concrete slab over the internal support, a deflection along the span and magnitude of the shear force of shear connectors is analyzed by employing a rigid-body-spring model having nonlinear material properties.

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A study has been carried out to evaluate the earthquake-resistance of buried gas pipelines subjected to lateral ground displacement due to ground liquefaction during earthquakes. In-plane bending experiments were conducted in the closing and opening direction for various kinds of elbows, where deformation are likely to concentrate. An FEA (Finite Element Analysis) were also carried out to represent the deformation behavior of the elbows using linear shell elements, and the validity of the numerical modeling technique over 20% of plastic strain was demonstrated. Furthermore, an analytical study was demonstrated for the evaluation of the deformation behavior of a typical buried pipeline with an elbow.

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As observed in the Hyogoken Nanbu Earthquake, brittle fracture is often triggered by preceding ductile fracture of steel members. The estimation of ultimate behaviors and deformation capacity of steel structures, therefore, critically depends on the ductile characteristics of its members. However, no reliable numerical method to investigate the ductile fracture of members is available because of the lack of the understandings of the quantitative aspects of such material characteristics. The objective of this work is to show a basic approach to a practical numerical analysis of ductile fracture. In the present work, we determined Gurson's model parameters using the proposed method to show that the FEM analysis with Gurson's model could be a suitable tool for the estimation of ductility limit of steel members.

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In urban highways, various types of bridge piers have been built depending on the condition of location. In this study, eccentrically loaded as well as central loaded steel bridge piers are tested pseudodynamically. Two types of models were designed in accordance with the proposal of high ductility steel bridge piers. Seismic responses of the two types of bridge pier models are compared and discussed.

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The cumulative strength method is generally used to evaluate shear strength of concrete encased steel members. In this method, shear strength of concrete encased steel members is given by adding up the one of reinforced concrete part and steel beam part. However, shear strength of steel beam part which characterizes shear failure of concrete encased steel members is not enough clarified. In this paper, based on a series of experiments with concrete encased steel beam models taking steel beam area etc. into account as experimental parameters, the application of the shear strength evaluation specified in the past design standards to the railway structures was examined. As a result, shear strength calculated by the past methods evaluates much smaller than experimental results. Then shear strength evaluation of steel beam part was revised to compensate the underestimating of calculations.

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In the earthquake resistant design and the reliability analysis of structures, the peak ground acceleration (PGA) is widely used as an intensity measure of earthquake motions. Since the PGA is a random variable, its probabilistic characteristics have to be examined. First, we have formulated the probability density function and statistical mean and standard deviation of the PGA ratio, and revealed that utilizing the ratio avoids estimating the mean of the PGA. Next, dense array seismograms in Japan and Taiwan are analyzed to examine the relationship between the statistics of the ratios and the separation distance. Finally, we have shown the standard deviations, means and 50- and 95-percentiles of the ratios, and discussed the expected difference between the PGAs at the neighboring two sites.

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This paper aims to propose a seismic performance evaluation procedure for steel framed bridge piers. In this method, the frame is substituted by an equivalent Single-Degree-of-Freedom (ESDOF) system based on the results from pushover analysis. Then the maximum seismic displacement demand and the residual displacement are determined through a time history analysis of the ESDOF or through some empirical ways such as using equal energy criterion. The obtained results are transferred to corresponding demands of the original Multi-Degree-of-Freedom (MDOF) structure. Thus, the safety of the structure can be checked by comparing the transferred demands with the corresponding capacities. Besides, several parametric analyses are carried out and it can be found that the difference in the maximum responses between the prediction from ESDOF system and that directly from the dynamic analysis of MDOF structure is 10% on the average.

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We investigate two attenuation equations for predicting the peak displacement of earthquake ground motions, which were presented by Tsuboi and Annaka et al. Tsuboi's formula is used for determining Japanese meteorological magnitude, while Annaka's one was presented for predicting the peak ground motions in wide regions including source area. It has been shown that both formulae are coordinated by using the same distance term in each formula.

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Surface layer that overlays a sloped base layer often suffers severely in earthquake disasters. To research this problem, a model experimental analysis on elastic wave propagation phenomena in slope layers was conducted. A model made of a material of low elasticity was used to facilitate the experiment. An elastic layer on a sloped rigid base has varying thickness. SH waves are thought to propagate from the deep to shallow part of the surface layer. The following conclusions were drawn: (1) Higher frequency waves propagate in shallow parts of the slope layer. (2) Wave behavior in the slope layer is similar to a Love wave propagaton through a layer of uniform thickness. However, this similarity does not hold for a slope layer inclined at more than 15°.

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Experimental works for steel bridge piers have been conducted in order to investigate their earthquake resistance. After the Hanshin-Awaji earthquake in 1995, not only static but also psudo-dynamic tests have been conducted to study the mechanical behavior of steel bridge piers. Those experimental results may be used to establish the design formulae. In this paper, new parameters are proposed to predict the ultimate strength of steel bridge piers. The validity of the parameters are confirmed by using the existing experimental results.

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