10. Method for evaluating train running safety during earthquakes considering non-linear behaviour of structures

As work progresses to implement measures against derailment or install derailment prevention guiding devices, there is a growing need to find a way to rapidly and accurately detect vulnerable sections of line on the network in terms of Shinkansen running safety during earthquakes.

The response of structures built according to old design standards, in some cases under L1 seismic motion fell into a non-linear domain, that was outside the scope of methods cited in existing design standards.
This created the problem that detailed numerical analyses then needed to be performed which were both costly and time consuming.

Dynamic interaction analyses between vehicles and structures were therefore carried out, and a comprehensive investigation was made into the influence of various factors such as vehicle type, running speed, vibration characteristics of structures and type of earthquake, on derailment limits considering the non-linear behavior caused by the yielding of the structure.
An evaluation method was then developed taking into account the coupled influence of structural vibration displacement (acceleration) and structural boundary differential displacement (angular rotation) (Fig. 1). The applicability of the new evaluation method was verified by comparing its output with results from the detailed numerical analysis.

The present method extends the scope of evaluation to non-linear domains that were beyond the area of application of the design standards.
In addition, by using structural design drawings and specifications, it is possible to rapidly and accurately extract vulnerable sections, to support the selection of countermeasures and prioritization of work (Fig. 2).