Sendai-shi, Japan
Sendai-shi, Japan

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Abukawa T.,CHODAI CO. | Hasegawa A.,Hachinohe Institute of Technology
Engineering for Progress, Nature and People | Year: 2014

Many bridges suffered serious damage in the 2011 Japan Tohoku Earthquake off the Pacific coast. In this earthquake, the damage to bridges caused by the tsunami was more serious than that due to the tremors themselves. In particular, the superstructures of large bridges were swept away by the tsunami. Kesen Bridge is one of the largest bridges damaged by the tsunami, having 5 spans, and with a total length of 181.5 m. All of the superstructures of the 5 spans were carried upstream approximately 300 m. Consequently, an important route for the region was blocked off, causing significant delays in the relief and restoration of the damaged area. The authors conducted hydraulic experiments in order to understand the forces that tsunami exert on bridges, and to consider corresponding measures for bridges that will be effective against tsunami. With respect to one such measure, an experimental study was performed to determine whether the force of a tsunami can be reduced by attaching fairings to a bridge, two types of fairing being investigated.

Abukawa T.,Chodai Co. | Hasegawa A.,Hachinohe Institute of Technology
IABSE Conference, Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges - Report | Year: 2015

The massive tsunami after the Great East Japan Earthquake in 2011 caused immense damage to people's lives and industries; some superstructures of long-span bridges were washed away. Even now, nearly four years after the tsunami, many people are still forced to live in temporary housing and other makeshift facilities. Because the major bridges had been on important roads in the tsunami-stricken areas, their loss caused significant delays to relief and restoration work. Taking measures to protect bridges from tsunamis is extremely important, as there are concerns that similar tsunami damage to bridges could occur in other areas of Japan. However, reliable technologies have yet to be established for protecting bridges from tsunamis. The authors' recent experiments have verified the effects of employing fairings, fairings with slits, and slabs with air holes as measures against tsunamis. This paper describes the outline of experiments, experimental results, and discussions on these experiments, as well as conclusions.

Abukawa T.,CHODAI CO. | Hasegawa A.,Hachinohe Institute of Technology
IABSE Conference, Nara 2015: Elegance in Structures - Report | Year: 2015

In the 2011 Japan Tohoku Earthquake off the Pacific coast, the superstructures of bridges were swept away by the tsunami. The authors conducted hydraulic experiments in order to understand the forces that tsunami exert on bridges, and to consider corresponding measures for bridges that will be effective against tsunami. With respect to one such measure, an experimental study was performed to determine whether the force of a tsunami can be reduced by attaching fairings to a bridge. From previous studies, it has been found that fairings are effective for horizontal drag, but it is not effective for vertical drag because of the buoyancy. Therefore, hydraulic experiments were conducted on the effect of having to open a slit in the fairing, to smooth the flow of water into the fairing within.

Ninomiya Y.,Office Ehime Prefecture | Okamoto M.,Office Ehime Prefecture | Tanaka G.,Chodai Co.
IABSE Conference, Nara 2015: Elegance in Structures - Report | Year: 2015

The Ikina Bridge spans the strait between the islands of Ikina and Sashima in Ehime prefecture, Japan. Since the particular geographic conditions at the bridge site of the Ikina Bridge pose certain problems in terms of balancing the bridge dynamically across the span length, a composite cable- stayed bridge structure combining light-weight steel girders and heavy concrete girders is adopted to ensure the correct dynamic balance. While steel girders and prestressed concrete (PC) girders are joined near the main towers in conventional composite cable-stayed bridges, in the Ikina Bridge, the PC girder ranges are expanded to positions approximately 1/4 of the main span length from each of the main towers, where they are joined to the steel girders in order to improve not only the workability and economic efficiency of the Ikina Bridge, but also the wind resistance. A main girder design that achieves excellent economic efficiency by taking simple and rational wind- pressure countermeasures was selected, and the wind resistance was verified through wind-tunnel tests. In addition, H-shaped concrete main towers are adopted due to their excellent wind-resistance and durability as well as their conformance to the narrow road width condition. Sufficient aseismatic performance of the concrete main towers is ensured by reducing the self-weight by adopting a hollow cross-section and reducing cross-sectional forces by allowing minor plastic deformations in the connecting beams at the top of the H-shaped main towers. Note that this bridge is the first composite cable-stayed bridge in Japan in which stay-cables are anchored diagonally at both steel and concrete girders along the main span.

Wang T.,Zhejiang University | Xie X.,Zhejiang University | Shen C.,Chodai Co. | Tang Z.,Zhejiang University
Earthquake and Structures | Year: 2016

Modified two-surface model (M2SM) is one of the steel elasto-plastic hysteretic constitutive models that consider both analysis accuracy and efficiency. However, when M2SM is used for complex strain history, sometimes the results are irrational due to the limitation of stress-strain path judgment. In this paper, the defect of M2SM was re-modified by improving the judgment of stress-strain paths. The accuracy and applicability of the improved method were verified on both material and structural level. Based on this improvement, the nonlinear time-history analysis was carried out for a deck-through steel arch bridge with a 200 m-long span under the ground motions of Chi-Chi earthquake and Niigata earthquake. In the analysis, we compared the results obtained by hysteretic constitutive models of improved two-surface model (I2SM) presented in this paper, M2SM and the bilinear kinematic hardening model (BKHM). Results show that, although the analysis precision of displacement response of different steel hysteretic models differs little from each other, the stress-strain responses of the structure are affected by steel hysteretic models apparently. The difference between the stress-strain responses obtained by I2SM and M2SM cannot be neglected. In significantly damaged areas, BKHM gives smaller stress result and obviously different strain response compared with I2SM and M2SM, and tends to overestimate the effect of hysteretic energy dissipation. Moreover, at some position with severe damage, BKHM may underestimate the size of seismic damaged areas. Different steel hysteretic models also have influences on structural damage evaluation results based on deformation behavior and low cycle fatigue, and may lead to completely different judgment of failure, especially in severely damaged areas. © 2016 Techno-Press, Ltd.

Miwa T.,EcoTopia Science Institute | Okada Y.,CHODAI Co. | Morikawa T.,Nagoya University
Transportation Research Record | Year: 2010

In recent practical transportation planning in Japan, the adoption of stochastic user equilibrium assignment models for traffic assessment has been discussed. Such models include a dispersion parameter that accounts for drivers' errors in perception of travel time at the time of route choice decision. In practice, setting a rational value for this parameter is an issue. Generally, the dispersion parameter is exogenously set to the same value for all origin-destination (O-D) pairs. However, it is not guaranteed that errors in drivers' perception of travel costs are equal for all O-D pairs. This study examines how the parameter is set and applies a multiclass stochastic user equilibrium assignment model to consider differences in drivers' errors in perception of travel costs in using an existing general-purpose road network. Results show that changes in the dispersion parameter affect the user class flows that make up the link flows rather than the link flows themselves. Setting a dispersion parameter according to the travel cost of an O-D pair rather than setting a constant parameter improves the reproducibility of the user class flows on each link. These findings encourage practical transportation planners to evaluate qualitative measures of traffic flows in the road network, such as the utilization of road links.

Wang T.,Zhejiang University | Xie X.,Zhejiang University | Tang Z.-Z.,Zhejiang University | Shen C.,Chodai Co.
Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science) | Year: 2015

The shortcomings of modified two-surface hysteretic model, which is a steel elasto-plastic hysteretic constitutive model that consider both analysis accuracy and efficiency, were taken as research object. The problem that under complex strain history, sometimes the stress results obtained by the model are irrational since the plastic modulus at the critical point between elastic and plastic stage tends to infinite, was to be avoid. The existing modified two-surface model was remodified by improving its criterion of stress-strain path. The improving method of the analysis model under uniaxial and multiaxial stress state was given. The comparison results with analysis results and uniaxial tensile and compression tests, and a series of example analysis show that the improved model can precisely predict the hysteretic property of steel under complex strain history. The accuracy and applicability of the improving method were validated at material and structural member level. Results show that improvement of existing modified two-surface model can effectively raise the computational precision under complex strain history of the model. ©, 2015, Zhejiang University. All right reserved.

Suzuki K.,Iwate University | Suzuki K.,Obihiro University of Agriculture and Veterinary Medicine | Asari Y.,Iwate University | Asari Y.,Obihiro University of Agriculture and Veterinary Medicine | And 3 more authors.
Acta Theriologica | Year: 2012

Short glides of less than 20 m seem energy inefficient for the Siberian flying squirrel Pteromys volans as with the northern flying squirrel Glaucomys sabrinus. However, Siberian flying squirrels in low-canopy forests frequently use short glides. Therefore, we sought to clarify the gliding patterns of Siberian flying squirrels for energy-efficient gliding transport in low-canopy forests (mean tree height, 15.3 m) in Hokkaido, Japan, based on records of 66 glides and 35 launch and landing trees. Mean launch height, landing height, and horizontal glide distance were 14.4, 2.7, and 21.4 m, respectively. For short distances, horizontal glide distance was strongly correlated with launch heights but not with launch tree height. For glides of more than 20 m, horizontal glide distance was significantly correlated with both launch height and launch tree height. The mean heights of launch and landing trees for short glides were 15.6 and 19.5 m, respectively. For long glides, these heights were 22.7 and 19.2 m. For short glides, mean launch tree height did not differ from overall mean tree height. However, for long glides, the mean launch tree height was greater than the overall mean tree height. Also, for short glides, the height of the landing tree was greater than that of the launch tree. Launch trees used for long glides were as high as the landing trees used in short glides. From these results, we conclude that Siberian flying squirrels in low-canopy forests save energy by gliding initially from a tree with sufficient height to permit a glide to a taller tree. This taller tree then permits long-distance glides that are energetically more efficient. © 2012 Mammal Research Institute, Polish Academy of Sciences, Białowieża, Poland.

Yorozu S.,Chodai Co. | Sasaki S.,Chodai Co.
20th ITS World Congress Tokyo 2013 | Year: 2013

This article reports on the construction of the "Kashiwa Cyber Physical Database" which comprehensively integrates traffic data which changes in time-space. Also, this system is targeted for Kashiwa City in Chiba prefecture.

Kita H.,Kobe University | Kouchi A.,Chodai Co.
Transportation Research Part C: Emerging Technologies | Year: 2011

This paper proposes a methodology for measuring the perceived quality of service (QOS) of a driver. The proposed method characterizes a driver's perception of the quality of traffic service as based on not the macroscopic or average traffic conditions but on the microscopic traffic conditions that the driver faces. To ascertain this, two methods are developed in this study. The first one is to estimate the driver's perceived QOS of traffic service on a point-basis that is formulated based on revealed preference data and a discrete choice model. Existence of order effect is, then, examined and the relationship between point-basis utility and point-basis perceived utility is clarified. The second method is to relate the point-basis perceived QOS with the section-basis perceived QOS. Through a data analysis, the existence of some formation structures for the QOS perception has been confirmed. © 2010 Elsevier Ltd.

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