For the Yokohama Bay Bridge, Rainbow Bridge and Tsurumi Tsubasa Bridge, the basic principles were developed for seismic assessment for level-2 ground motions and for selection of seismic retrofit structures. Level-2 ground motions were defined for seismic assessment. For level-2 ground motions, plate boundary earthquakes with magnitude of 8 and near-field inland earthquakes with magnitude of 7 were assumed. The strong ground motions of plate boundary earthquakes with magnitude of 8 were defined based on the source model of the 1923 Kanto Earthquake. The asperity size and those locations were determined so that the ground motions were composed of numerous periods identical to the natural periods of major normal modes of vibration of the bridges, and that rupture was propagated toward the location of the bridge. For the ground motions of near-field inland earthquakes with magnitude of 7 in the Tokyo metropolitan area, the ground motions of the 1995 Hyogo-ken Nanbu Earthquake, the highest existing criteria, were adopted.

View full abstract

Concrete tunnels subjected to the ground pressure usually show a compressive failure mode. Moreover, due to an unbalanced soil constraint, deformed tunnels under an additional concentrated load will show more complicated compressive failure behavior with the propagation of multiple concrete cracks. Therefore for a better understanding of compressive failure mechanism of deformed tunnels, a parabolic compressive softening model and the concept of compressive fracture energy are introduced and discussed in this paper. It is found that the final failure, load-carrying capacity and structural deformation behavior of deformed concrete tunnels depend on the compressive behavior of concrete significantly.

View full abstract

An M_J6.4 earthquake occurred on July 1, 2000 offshore of Kohzushima Island in the Tokyo municipal jurisdiction. Large tremors also were felt on Kohzushima on July 9 and on Niijima on July 15. This is the damage investigation report on the 2000 Kohzushima Kinkai earthquake mad e by a JSCE reconnaissance team. Earthquake swarms continued near Kohzushima, Niijima, and Shikinejima islands for about three months. A JMA seismic intensity of lower 6 was recorded twice on Kohzushima during July, 2000. An outline of the earthquake and aftershocks and the damage done to civil structures is given. Slope failures, damage to retaining walls and disaster responses, in particular, are focused on.

View full abstract

The necessity of effective method to estimate low failure probability is increased from the standpoint of life cycle cost, risk and probabilistic safety assessment (PSA). We proposed an effective Monte Carlo Simulation method combining with the progressive subspace concept which searches distributed failure event regions step by step. Samples to search the failure region are generated in each subspace by using MCMC (Markov Chain Monte Carlo). Efficiency of MCMC is improved by simplifying the sampling procedure based on a uniform distribution from which it is very easy to transform into arbitrary distributions such as normal and log-normal distributions. Effectiveness of the proposed method is verified through numerical examples with simple limit state functions, then fragility curves of a bridge pier and a slope are calculated by the proposed method.

View full abstract

The Metropolitan Expressway, which is located in the Tokyo Metropolitan Area, has the complicated network and has been served over the years under the harsh condition of a huge number of traffics. Partial damages of the structures have been noted recently due to heavy traffic so that the importance of maintenance is increasing. However, more efficiency of inspection and repair is required for reducing the maintenance cost. The Metropolitan Expressway Public Corporation has been conducting the Origin-Destination surveys periodically and checking vehicular axle loads at the toll gates to crack down on overload offenders. This paper proposes the procedure to evaluate the effect of heavy traffics against the fatigue of the structures using the Origin-Destination surveys and the vehicular axle loads and also evaluate the fatigue environment for the Metropolitan Expressway.

View full abstract

A new type shape-steel bridge is proposed, to rationalize fabrication and erection by integrating main girders and composite slabs with steel panels, by elimination of slab-haunch and simplification of connection between slab and girder, by reducing transverse stiffening structures, and by changing simple girder into continuous girder on site. This paper describes the validity of developed design methods through analytical and experimental studies. It is expected that this study contributes to expand the application of steel bridges.

View full abstract

The present study aims to obtain fundamental properties of LWA concrete, its stress-strain model under confinement and seismic properties of LWA concrete members. The tests showed LWA concrete has lower tensile strength and modulus of elasticity compared with normal concrete. Under compression LWA concrete members showed brittle failure and little confinement effectiveness of lateral hoops. The complete stress-strain curve was proposed. Cyclic loading test showed that LWA concrete column has almost the same flexural strength and displacement capacity compared with that of normal concrete. Higher energy dissipation and damping ratio found in LWA concrete column. Simulation for load-deformation relationship of LWA concrete column has been done.

View full abstract

In the railway bridges, steel hinge support rigid frame piers are used for important bridges to cross over another railway or road. Since the damage of these bridges causes a serious impact for society at large-scale earthquakes, it is needed to establish the aseismic evaluation method for these piers. The cyclic loading tests were conducted to verify the elasto-plastic behavior of the beam-column connection, hinge support and steel hinge support rigid frame pier that were removed from real bridges used on Tokaido-Shinkansen for thirty-five years. This study is aimed at establishing the aseismic evaluation method that obtains accuracy and simplicity considering the test results. We therefore propose the analysis model that expresses the beam and column member including connection part and hinge support by beam elements. Especially for the beam-column connection, elasto-plastic characteristic was determined based on the test and FEM analysis results of the beam-column connection specimens. Besides, the modeling and evaluation method of hinge support were examined. This modeling method was verified by the test result of the steel hinge support rigid frame pier specimen.

View full abstract

This paper investigates an empirical zoning map of seismic intensity and the zoning map of PS-P time from strong motion records observed by an array system in Sendai City. The empirical zoning map of seismic intensity shows a distinctive distribution reflecting local site conditions. In order to investigate such a distribution of intensity in connection to PS-P times at each site of Small-Titan, we analyzed the observed records of Small-Titan by receiver function and complex envelope. It is finally concluded that the distinctive distribution of seismic intensity in the Sendai City area has a correlation with the depth of the bedrock as well as the surface soil conditions.

View full abstract

The finite cover method (FCM) is known as the generalization of finite element method (FEM) and enjoys peculiar elements that partially have physical domains. We name them the generalized elements in this study and examine their performance by using higher-order finite cover approximation within the framework of the FEM. First, elemental deformability is studied in comparison with Wilson-Taylor's element (QM6), 8 node quadrilateral element (Q8) and lowest-order generalized element. Secondly, the sensitivity of the performance of the generalized elements to their distortion is compared with that of finite elements. Finally, after making the convergence study for the Cook's membrane problem and compiling all the results in this study, we conclude that the performance of higher-order generalized elements in the FCM are equivalent or slightly superior to that of finite elements. It is to be noted that the studies also apply to the X-FEM and the GFEM.

View full abstract

Seismic damage analysis was conducted on the Chang-Geng Bridge damaged in the 1999 Chi-Chi Earthquake in Taiwan. This bridge sustained peculiar damage that two girders fell to the ground even though the ground did not show any fault displacement. The cause of the fall was assumed to be the horizontal displacement of the girders when they collided under seismic loading. Through nonlinear dynamic analysis using field measurement results and detailed drawings obtained from the administrator of the bridge, it was confirmed that the girders were pushed toward the parapet and collided from the back under seismic loading, resulting in the fall from the piers.

View full abstract

In order to examine the effect of over-sized holes on the slip resistance and the yield resistance of the friction type of high strength bolted connection, the tensile tests have been performed on the bolted connections in consideration of slip to yield resistance ratio. As a result, following conclusions have been obtained. The slip resistance does not depend on the hole diameter. The yield resistance is decreasing in proportion to the reduction of net sectional area of the main plate due to the over-sized hole. However, the yield resistance can be regarded as about 1.2 times of one calculated from the net sectional area because of stress transmission due to the friction between a main plate and splice plates.

View full abstract

It will be an important task for local government officers to improve their engineering ability of foreseeing possible earthquake damages. To this end, this paper studies the standardization of seismic resistance design and the unified visualization of structure responses in whole city. Taking advantage of informatics, we reconstruct flowchart of various design codes such that the seismic resistance design can be presented in a common framework. The usage of integrated simulation system is studied for the visualization. The integration is achieved by an artificial intelligence that automatically makes an interpreter program which links the system to various simulation programs of structures.

View full abstract

Decision strategy of inspection, repair and safety levels of buried pipelines under corrosive environment and the third party incident risk is described. Pipe damages, which are caused by potential defect, corrosion, and the third party accident, are classified into three major damage modes which include tension/compression, bending and dent with gouge. The risk assesment are made for the transmission pipeline system which is surrounded with various hazards spatially distributed along the pipeline route. The effect of risk reduction by the maintenance activities including periodic inspections and repair works are also taken into consideration, while the insurance premium approach is discussed to transfer the risk from the owner to the insurance company. Numerical calculations provide useful information on the effectiveness of the proposed four maintenance strategies.

View full abstract

This study gives an enhanced simulation for low frequency noise considering reflection radiated from bridges due to moving vehicles. The sound pressure level at the observation point is estimated from the velocity of slabs taken from the traffic-induced bridge vibration analysis. The influence of the reflected sound wave at ground is considered in the analysis by using a virtual surface. The analytical results match well with experimental ones. It is observed that assessment of the low frequency noise regarding the sound wave reflected by ground provides better correlation with field-test data. It is noteworthy that both reinforcing end cross beam and increasing thickness of slabs provide reducion of the low frequency noise due to moving vehicles.

View full abstract

A computational method for the consistent simulation of fracture phenomena, such as exfoliation of material interfaces and cracking inside materials, is presented. The exfoliation of material interfaces is simulated in terms of the interface element which combined the Lagrange multipliers and the cohesive crack model, the cracking inside materials is rationally carried out by combining the criteria based on tensile strength and the cohesive crack model. The Finite cover method (FCM) can trace the path of discontinuities completely independent of the mesh structure, and connect these techniques smoothly. Representative numerical examples demonstrate well the performance of the proposed method.

View full abstract

This paper reports experimentation which were conducted for the purpose of grasping the nonlinear behavior at the ultimate state and for the check of the safty of the proposed extradosed cable anchorage structure for extradosed bridge with corrugated steel web. From the experimental results, the safty of the proposed extradosed cable anchorage structure at the ultimate and design load was confirmed. It was also found that the nonlinear behavior of this extradosed bridge with corrugated steel web can be correctly predicted by nonlinear analysis by the fiber model in consideration of the rigidity of a corrugated steel web.

View full abstract

A mapping of shear-wave velocity for all of Japan is performed using “Japan Engineering Geomorphologic Classification Map (JEGM)” which has been developed as a GIS-based ground condition map. At first, we calculate the average shear-wave velocity in the upper 30m (AVS30), which is a simple and useful predictor for estimating site amplification factors of peak ground velocity (PGV), for approximately 2,000 sites where shear-wave velocity has been measured in all over Japan. Geomorphologic units for all boreholes logging data are interpreted using landclassification maps that are the base paper maps for the JEGM. Next, we examine the correlation between not only geomorphologic units but also geographical information derived from the JEGM and the AVS30 values. The AVS30s show some dependency with altitudes, slope gradients, and distances from mountains or hills. In order to develop the estimating model of the AVS30, multivariate regression analysis is conducted using these geomorphologic indices. Then, we can achieve to create an AVS30 map with relatively high accuracy for all of Japan using JEGM.

View full abstract

An accurate estimation for long-term deterioration characteristics of bridge rubber bearings has been needed because of few data of the deterioration. This paper presents six types of accelerated aging tests that were implemented so as to research environmental deterioration characteristics of rubber materials for bridge bearings. For quantitative evaluation of deterioration of the rubber, heat oxidation, ozone, low temperature ozone, ultraviolet rays, salty water spray cycle system and acid water spray cycle system were considered. It was found that the damage due to the heat and the ultraviolet rays deterioration was severer than the other factors of deterioration.

View full abstract

Since the Great Hansin Earthquake in 1995, numerous researches on the seismic performance of steel high way bridge piers consisted of rectangular or circular cross section with constant steel plate thickness have been conducted. But effective results improving their seismic performance such as ductility under the repeated horizontal external forces have not been brought. Use of tapered plate at the bottom of the pier is considered to solve this problem. In this study, four main parameters are selected; 1) mold line of the tapered plate, 2) tapering ratio and failure mode, 3) rigidity of stiffeners, and 4) tapered stiffeners. Fundamental seismic behavior of the steel box section piers with tapered plate is disclosed by both experimental and FEM analysis.

View full abstract

Lateral forces induced by a person stepping on the shake table were measured. The table was forced to vibrate horizontally with frequencies from 0.75Hz to 1.25Hz and with amplitudes from 10 to 70mm. The measured lateral forces show regular waves but they have two dominant frequencies of 1.0 Hz and 3.0 Hz. The maximum lateral force ranges from 30 N to 130 N, and increases proportionally to the vibrating amplitude. The non-dimensional lateral force, the lateral force divided by the self-weight, is from 0.08 to 0.23. Some pedestrians synchronized the vibrating deck but some didn't. Phases of the lateral forces are different among the pedestrians, and the sum of the lateral forces of individual pedestrian overestimates the lateral forces induced by multi pedestrians by 30 to 70%.

View full abstract

Errors caused by numerical time integration procedures in the earthquake response of a ground are quantitatively discussed. Newmark's β method (β=1/4) and Wilson's θ method (θ=1.37) are investigated with several treatments of unbalanced forces. The unbalanced forces are carried into next time integral, neglected, or made small by iteration before carrying next time integral. Accuracy of the analyses is discussed by means of amplification and response spectrum at the ground surface, which are important indices in evaluating the ground response in the engineering practice. As the results, we strongly suggest the importance to evaluate errors included in the numerical integration procedure in practice, which can be done by comparing the solution with that under small time increment analysis.

View full abstract

In the region of Nanseit-Shoto (Ryukyu Island), it is well known that there are lots of peculiarities for geology and topography unlike those of other prefecture or metropolitan center of Japan. On taking an angle of earthquake disaster prevention for these local peculiarities in this region, to make earthquake disaster mitigated in this area, it is considered that it is important to grasp and evaluate characteristics of ground motion. Accordingly, as the beginning, this paper investigated the correlation between characteristics of geological structure and ground-motion characteristics on the basis of the analysis on seismic waves observed in region of Nansei-Shoto. As the result, it shows that Shimajiri Group bring some influence on ground motion characteristics in the region.

View full abstract

The relationship between the seismic intensity and the reactions of expressways drivers was investigated based on the questionnaire survey conducted by Japan Highway Public Corporation in the 2003 Sanriku-Minami earthquake. Only 40 % of drivers were aware of the earthquake in the areas where the Japan Meteorological Agency (JMA) seismic intensity is smaller than 4.0. On the contrary, more than 80 % of drivers recognized the earthquake in the areas where the JMA seismic intensity is larger than 4.0. The abnormal vibration of the vehicle was indicated as the reason why the drivers recognized the earthquake. Hence, the seismic motion is considered to affect the safe and stable driving.

View full abstract