11. Critical wind speed of overturning based on actual measured lateral vibration acceleration

The crosswind stability of railway vehicles against overturning can be evaluated from the critical wind speed of overturning.
Using the detailed RTRI equation for calculating the critical wind speed of overturning, which takes into account not just vehicle and infrastructure specifications, but also many other factors, and based on a premise of the severest running conditions, including wind direction, lateral car-body vibration due to constantly changing track irregularity, it is possible to make safer evaluations.
However, for train operators to use this method on a daily basis for train operations, it would be more practical if the evaluation reflected more real track and other trackside wind conditions.

Consequently, this research makes a proposal to apply actual measured lateral car-body vibrational values to the vibrational inertia term in the RTRI detailed equation.
In this method, the existing assumption of the linear equation (in the RTRI detailed equation), is replaced with an adapted linear equation including the vibrational acceleration peak value of waveforms measured at different speeds (Fig. 1), resulting in some cases where the critical wind speed of overturning was calculated to be as high as 2-3 m/s (Fig. 2).

This method also allows stochastic interpretation of the critical wind speed of overturning following analysis of the frequency of occurrence of lateral car-body vibration (Fig. 3).
Adopting a new annotation of results of the calculation of the critical wind speed of overturning which separates the average (deterministic) and fluctuating (stochastic) parts, it is possible to calculate the critical wind speed of overturning with quantitatively incorporated safety margins that reflect the assumed probability of occurrence.
In turn, this makes it possible to take into account the balance required between safety and operational stability when setting wind speeds for operation control.