丸山 喜久

After the 1995 Kobe earthquake, countermeasures against earthquakes got higher priority than before. As one of such earthquake countermeasures, Tokyo Gas Co., Ltd. introduced an earthquake monitoring and rapid damage assessment system called SUPREME. This system has been under operation since 2001. The intelligent gas meters have been deployed for 9.8 million customers in the area where Tokyo Gas Co., Ltd. provides the service. The gas meter stops gas supply if earthquake motion exceeds a certain level. SUPREME has a subsystem to estimate the number of gas meters which stop gas supply because of an earthquake. However, the accuracy of estimation by this subsystem is not good because the characteristics of gas supply shutoff by intelligent gas meter are not very clear. In this study, to improve the accuracy of estimation, the characteristics of gas supply shutoff by intelligent gas meter are investigated based on shaking table tests and the questionnaire survey among employees of Tokyo Gas Co., Ltd.

Emergency medical care is very effective to save the lives of injured people in traffic accidents. The heliambulance has been under operation since 1999 in Japan, and it is expected to contribute for the emergency medical care. However, the heliambulance is allowed to land on the expressway under only some restricted conditions in Japan, because the heliambulance generates strong wind, called downwash. It is afraid that the drivers in the other lane of the expressway may feel the difficulties in controlling their vehicles because of the strong wind generated by the heliambulance. In this study, the moving stability of vehicles under crosswind generated by a helicopter is investigated based on field experiments and numerical simulation. In the numerical simulation, a driver-vehicle model is employed to obtain the moving trajectories of vehicles subjected to crosswind. Based on these results, the possibility of landing of a heliambulance on expressways is discussed. © 2006 by School of Engineering and Technology, Asian Institute of Technology.

日本道路公団の行った2003年5月26日宮城県沖の地震時に高速道路を走行していた運転者へのアンケート調査をもとに, Simple Kriging法により推定した高速道路沿線の地震動強さと自動車運転者の反応の関係について検討を行った. その結果, 計測震度4.0未満の地域を走行中の運転者のうち, 地震に気付いた運転者は4割に達していないが, 計測震度が4.0以上になると8割程度以上の運転者が地震を認識するようになることが分かった. 地震を認識した理由には, 車両の異常な振動が最も多くあげられており, 震動が車両の走行安定性に何らかの影響を与えることが推測できる.

2004年10月23日に発生した新潟県中越地震における高速道路被害と地震動強さの関係について検討を行った. 新潟県中越地震の地震動分布を推定し, 高速道路の被害データと推定された地震動強さとの関係を検討した結果, 高速道路に被害が発生している区間の平均計測震度はいずれも 5.0以上であり, 平均計測震度が6.0以上の堀之内インターチェンジ (IC) ～越後川口IC間, 越後川口IC～小千谷IC間に多くの被害が集中していることが明らかとなった. さらに, 航空写真から判読される高速道路の被害程度が, 実際の被害報告とどの程度一致するか検討を行い, 航空写真による早期被害把握が可能性を示した.

高速道路走行車両の横風安定性を定量的に評価することを目的に, 車両モデルを用いた数値解析とドライビングシミュレータを用いた走行模擬実験を行った. 運転者の反応と車両の運動の相互作用を考慮できる人間-自動車系操舵モデルを用いると, 走行模擬実験の結果が比較的精度良く再現されることが分かった. これより, 車両に依存するパラメータが適切に設定できれば, 実車走行試験やドライビングシミュレータによる走行実験を多数行わずとも, 従来まであまり定量的に評価されていなかった強風時の車両の走行安定性について, 系統立てた評価が可能になるものと期待される.

After the 1995 Kobe earthquake, the expressway structures in Japan were retrofitted and they will not now be Seriously damaged under a certain level of strong earthquake motion. However, the stability of a moving vehicle has not been investigated yet. It has been reported that drivers feel seismically induced vibrations, especially in the transverse direction of vehicles. Owing to this phenomenon, drivers have some difficulty in controlling the vehicles during strong shaking. For further safety promotion of the expressway networks, it is important to understand the drivers' reactions to seismic motion. The present authors have performed a series of seismic response analyses of a moving vehicle to investigate its response characteristics based on numerical simulation. However, the responses of the driver were not considered in the simulation process. In order to investigate the drivers' reactions during an earthquake. a series Of virtual tests were conducted using a driving simulator. This driving simulator has six servomotor-powered electric actuators that control its motions. Several types of tests were carried Out for different examinees to investigate drivers' responses while controlling the simulator under seismic motion. The results of this study showed that a larger response time lag to strong shaking and over turning of the steering wheel may shift the vehicle into the next lane. According to this finding, traffic accidents Could possibly Occur under strong ground shaking in the case of heavy traffic. Copyright (C) 2004 John Wiley Sons. Ltd.

The seismometer network of the Japanese expressway system has been enhanced since the 1995 Kobe earthquake. Using earthquake information from the instruments, the expressways are closed if the peak ground acceleration (PGA) is larger than or equal to 80 cm/s(2). The aim of this regulation is to avoid secondary disasters, e.g. cars running into the collapsed sections. However, recent studies on earthquake damage have revealed that expressway structures are not seriously damaged under such-level of earthquake motion. Hence, we may think of relaxing the regulation of expressway closure. But before doing this, it is necessary to examine the effects of shaking to automobiles since the drivers may encounter difficulties in controlling their vehicles and traffic accidents may occur. In this study, a vehicle was modelled with a six-degree-of-freedom system and its responses were investigated with respect to PGA, peak ground velocity (PGV) and-Japan Meteorological Agency (JMA) seismic intensity using five ground motion records. It was observed that the response of the vehicle shows a larger amplitude for the record that has larger response spectrum in the long period range compared to other records. However, similar response amplitudes of the vehicle were observed for all the records with respect to the JMA seismic intensity. The response characteristics of the vehicle model may be very useful for decision-making regarding the relaxation of the expressway closure under seismic motion. Copyright (C) 2002 John Wiley Sons, Ltd.

我が国の高速道路では, 1995年兵庫県南部地震以降, 地震時通行規制の情報を得るための地震計ネットワークを増強している. しかしながら, 高速道路構造物は現在の地震時通行止め基準程度の地震動では被害が発生しないことも近年の研究で明らかとなってきており, 地震時通行規制の緩和の検討が議論されるようになった. しかし, 規制の緩和を行う前には, 地震時に運転者が走行困難に感じて事故を起こす可能性も否定できず, 地震動が車両に与える影響を調べる必要がある. そこで, 本研究では, 6自由度車両モデルを構築し, 道路路面に3成分の地震動を入力して車両の地震応答解析を行い, 地震動の特性が車両の応答にどのような影響を与えるかについてを検討した.

日本道路公団では, 1995年兵庫県南部地震以降, 地震発生直後に地震情報を集めて効果的な地震時通行規制を行うことを目的とし, 高速道路料金所の管理事務所内に新型地震計を増設し, 現在, 沿線約20kmに1ヶ所の割合で設置されている. しかしながら, この地震計の数は, 高速道路全体の地震動分布を把握するのに充分であるとはいいがたい. そこで本研究では, 常時微動と地震動の水平鉛直スペクトル比 (H/V) が良く似た振幅形状を示すことを利用して, 近傍の地震記録と常時微動観測結果のみから地震動推定を行い, 実測値と比較してその精度を検証した. この方法を利用することで, 高速道路に沿った連続的な地震動分布の推定が可能になると期待される.