Abstract
After Hanshin-Awaji earthquake in 1995, many highway piers have been strengthened and they cant be collapsed by small or medium earthquake. And some drivers on the elevated highway when earthquake occurred said they felt strange torque like a blowout through steering. So it is important to analyze the vehicle behavior include the human property to keep safety in highway.
In this paper, the fundamental vehicle behavior under an earthquake without the human property is investigated by simulation. Only the lateral earthquake (side direction) is considered in this study. The elevated highway is simply modeled as single degree of freedom model. Brush model is adopted for tire model. The fundamental tire construction consists of the wheel and tread base that remain rigid and the tread rubber and air, which deform elastically. The brush tire model treats this elastic deformation as a brush whose deformation produces a force. As earthquake input, ground velocity is given to the tire. The vehicle model in this study has nine degrees-of-freedom including the longitudinal displacement, lateral displacement, roll angle, pitch angle, yaw angle, and four tire rotations, and steering system is modeled by two degree of freedom model.
Simulations with the steering wheel angle fixed at zero and the steering wheel left to turn freely, which corresponds to no hands on the steering wheel, were carried out. Input earthquake is Elcentro (NS direction) and maximum acceleration is 3.0m/s2. This corresponds to the maximum strength of an earthquake that an ordinary elevated highway is designed to withstand. The results indicated that when human behaviors such as steering and pedal operations were not considered, the lateral displacement of the vehicle was very small, proving the dangers for accidents such as the contact with the roadside wall and the other vehicles to be unlikely.