The impact vibration test is now regarded as a method to evaluate the conditions of bridge substructures. This test method focuses on the natural frequency of the pier, since it clearly shows the condition of bearing capacity of the foundation and the soundness of the pier. And compares the measured and standard value of the natural frequency of the pier judged it as "sound" when the former is sufficiently higher than the latter and as "unsound" when the former is lower than the latter. The standard value of natural frequency is calculated by statistical analysis by using several parameters, such as the height of the pier, weight of the superstructure and width of the pier. Although these parameters are highly correlated with the natural frequency, they don't have physical significance at all. This paper introduces a new and progressive idea for the standard value of natural frequency wholly based on the design concept for the foundation to determine the following discrete states.; Abnormal state (to allow train operation at a slow speed), The normal state (to allow train operation at commercial speed), A state with a margin of 0.2G level for the seismic force and A state with a margin of L1 level for the seismic force.

Copyright (c) 2002 Railway Technical Research Institute