Evaluation for Soil Liquefaction Due to Long Duration Earthquakes with Low Acceleration
Past studies show that soil liquefaction due to a long duration earthquake with low acceleration, for example as observed in the Tokyo Bay area in the 2011 Great East Japan Earthquake, is largely affected by liquefaction strength for a large number of loading cycles. It is, therefore, extremely important to know the liquefaction resistance for a large number of loading cycles. This paper describes the results of the hollow cylindrical cyclic torsion shear tests that were conducted to ascertain the effects of grain size distributions on liquefaction resistance for a large number of loading cycles. The test results clearly show that the tendency of a decrease in liquefaction resistance for a large number of loading cycles is influenced by mean grain size, inclination of grain size distribution, and so on. Finally, the effect of liquefaction resistance curve characteristics on the assessment of liquefaction potential is examined using the cumulative damage theory.
Strain Space Plasticity Model for Cyclic Mobility
ABSTRACT The cyclic mobility model proposed in this paper is of a generalized plasticity—multiple mechanism type. The salient feature of the present approach is that the concept of the multiple mechanism, within the framework of plasticity theory defined in strain space, is used as a vehicle for decomposing the complex mechanism into a set of one dimensional mechanisms. The other feature is that the undrained stress path is idealized with the concept of liquefaction front, which is defined in the effective stress space as an envelope of stress points gradually approaching the failure line. Once coded into the finite element program, most of the existing models suffer from serious difficulty in the numerical solution process when effective stress path becomes very close to the failure line. A numerically robust approach is proposed in this paper by introducing a scheme for gradually enlarging scale of shear strain with progress of cyclic mobility.
State estimation for integrated vehicle dynamics control
This paper discusses a vehicle controller and a state estimator that was implemented and tested in a vehicle equipped with a combined braking and chassis control system to improve handling. The vehicle dynamics controller consists of a feed forward body roll compensation and a feedback stability controller. The estimator is based on a non-linear vehicle model combined with an extended Kalman filter. The Kalman filter is also connected to an algorithm, which estimates the tyre-road friction coefficient. The developed estimator was tested in a vehicle. Good results were achieved for normal and extreme driving manoeuvers.