Page 279 - 360.revista de Alta Velocidad - Nº 5

Calculation and rational dimensioning of railway infrastructure materials using numerical modelling

5. Conclusions

From the point of view of numerical modelling, it is appropriate to model the materials of
the superstructure with a linear, homogeneous and isotropic elastic behaviour as these have
a high modulus of elasticity compared to that of the granular layers. On the other hand, it is
more advisable to carry out analyses that consider the elastoplastic behaviour of the materials,
especially if they are granular, since the remaining or irreversible deformations are important
because they can cause seats that can affect the longitudinal and transversal profile of the
track.
As for the results obtained with the numerical model we can clarify that regarding the use of
behavioural models. The use of an elastoplastic model leads to higher values of displacement
due to the appearance of the plastic component of deformation besides that the use of an
elastic model leads to an overestimation of the tensions with respect to those that would have
in reality if an elastoplastic behaviour were assumed.

Finally, based on the analysis of all the previous results, some design recommendations can be
used that can be used by the designer in the design of the railway platform:

1. If the Embankment or Subgrade has a high height, it is advisable to use an elastoplastic
behaviour model due to the high numerical error that would be in the calculation of seats
when considering an elastic model. If it has a smaller height, it is useful to use a model of
elastic behaviour and. more if Formation layer is not available.
2. With poor materials or low resistance it is advisable to use an elastoplastic analysis against
an elastic one due to the influence that would have in terms of seats and tensions, the la-
yers of the infrastructure in their joint interaction.

3. The use of an elastic model will lead to an underestimation of seats that would be in reality,
assuming that the railroad is more rigid than it really is.

4. Increasing the angle of friction of the Subballast from 35° to 45° does not imply any rele-
vant changes in the values of the tensions and vertical seats for the rest of materials.

6. Notation

The following symbols are used in this paper

´ = hardening parameter ε = plastic deformation

= modulus of elastoplastic deformation K = vertical track stiffness

= modulus of elasticity {} = stress vector

= material cohesion { } = strain vector

Φ = internal friction angle [D] = constitutive matrix

= vertical compression of each layer [D ] = elastic constitutive matrix
e

ε = deformation of the element [D ] = plastic constitutive matrix
p
ε = elastic deformation [D´] = elastoplastic constitutive matrix

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