丸山 喜久

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.