Page 18 - 360.revista de Alta Velocidad - Nº 5

De la Guerra, Eduardo

Anderson et. al (2005, 2007) suggested values with some typical carbody Eigen frequencies
fora high speed train, Table 2, and as can be seen are very closed to the maximum excitation
produced by the track.

Table 2. Typical Eigen frequencies

Mode direction Frequency (first mode)

Vertical 9-10 Hz
Lateral 10-11 Hz

Torsional 11-12 Hz

In term of strength, rail vehicle design criteria in Europe are based mainly in EN 12663-1 if
no other specific reference is given, usually applied category P-II for High-Speed passenger
vehicles, Wennberg (2010).
The stresses to which carbodies are subjected are of various types and defined in EN 12663-1:
• The stresses due to longitudinal, vertical and extraordinary forces caused by the normal
movement of trains.
• Also, there are the stresses of vibration of the carbody itself, which occur by the effect of
its mass and dynamic loads from the track and its effect on fatigue.
• Finally, stresses due to accidental collisions related with passive safety.

Furthermore, for high speed trains, it is also necessary to consider overpressure/underpressure
load cases due to the crossings with other trains particularly in tunnels, and stresses caused by
lateral winds.

Regarding carbody vibration behaviour, in the standard EN 12663-1 is only stated that the natural
modes of vibration of the carbody should be separated sufficiently, or otherwise decoupled, from
the bogie suspension frequencies, so as to avoid the occurrence of undesirable responses and
to achieve an acceptable ride quality according EN 12299. The fundamental Eigen frequencies
of the carbody in lateral and vertical directions should be above NHz. Commonly the value of
N is given by the fundamental resonance frequencies of the bogie frame and other influencing
factors like the track or the passenger load.

As a general rule, the natural frequencies of the vertical mode for a typical bogie with the
carbody installed are in the range f0,bf=6-8Hz. Therefore, the frequency separation requires
that the fundamental carbody Eigen frequency complies f0,cb>√2·f0,bfHz. With this values,
it is important to note that in some cases the ride quality according to EN 12299 could not be
achieved, due to possible peaks of frequencies that could appear on the track in the range of
10-15Hz (depending on the track default, as can be seen in Figure 7). Then, the stiffness of the
carbody must be optimised to increase as possible the corresponding carbody Eigen frequencies
o achieve the comfort requirements, i.e. as higher as possible, de la Guerra (2016).
Regarding the interface between bogie and carbody, as rule of thumb the input mobility of
mounting points for bogie elements (dampers, rods) shall be below -80dB re 1m/Ns. Alternatively,
the input impedance of mounting points for bogie elements (dampers, rods) shall be above:
80dB re 1Ns/m, Shabalin (2013).

4. Numerical and Experimental Analysis for design

16 360.revista de alta velocidad