Known issues

Linux: glibc requirement

On Linux, the runtime requires GNU C Library (glibc) version 2.39 or newer. This is typically needed by native dependencies used by Kratos and related tooling.

How to check your glibc version

Run one of the following in a terminal (they may differ per distro):

  • ldd –version

You should see a version like “glibc 2.39” or newer.

Upgrading glibc (high-level guidance)

It is recommended to upgrade your distribution to a release that ships glibc >= 2.39. Most recent Linux distributions include this version or newer by default.

Notes

  • If you can’t upgrade the host OS, consider using a Pod or Docker container that matches the required glibc version and provides Kratos and dependencies. You can find a Docker file to run STEM in the STEM repository.

  • After upgrading, re-create your Python virtual environment to avoid binary incompatibilities.

Problem generating a geometry with volume sleepers

When generating a track with volume sleepers, it can happen that the geometry generation fails when the underlying geometry contains a point which is exactly on the same coordinate as the origin point of the track generation. The code below illustrates this issue. In this code, the origin point of the track is included in the coordinate list of the ballast layer, which leads to a failure of the geometry generation as shown in the figure below.

from stem.model import Model
from stem.soil_material import OnePhaseSoil, LinearElasticSoil, SoilMaterial, SaturatedBelowPhreaticLevelLaw
from stem.structural_material import ElasticSpringDamper
from stem.default_materials import DefaultMaterial

ndim = 3
model = Model(ndim)
model.extrusion_length = 2

# note that the origin point of the track is included in the ballast coordinates
origin_point_track = (0.75, 21.0, 0.0)
ballast_coordinates = [(0.0, 20, 0.0), (3.0, 20.0, 0.0), (2, 21, 0.0), origin_point_track, (0, 21, 0.0)]

material_ballast = SoilMaterial("ballast",
                                OnePhaseSoil(ndim, IS_DRAINED=True, DENSITY_SOLID=1800, POROSITY=0.0),
                                LinearElasticSoil(YOUNG_MODULUS=200e6, POISSON_RATIO=0.3),
                                SaturatedBelowPhreaticLevelLaw())

model.add_soil_layer_by_coordinates(ballast_coordinates, material_ballast, "ballast_layer")


# parameters for the track generation
rail_parameters = DefaultMaterial.Rail_60E1_3D.value.material_parameters
rail_pad_parameters = ElasticSpringDamper(NODAL_DISPLACEMENT_STIFFNESS=[0, 750e6, 0],
                                          NODAL_ROTATIONAL_STIFFNESS=[0, 0, 0],
                                          NODAL_DAMPING_COEFFICIENT=[0, 750e3, 0],
                                          NODAL_ROTATIONAL_DAMPING_COEFFICIENT=[0, 0, 0])

material_sleeper = SoilMaterial("sleeper",
                                OnePhaseSoil(ndim, IS_DRAINED=True, DENSITY_SOLID=2400, POROSITY=0.0),
                                LinearElasticSoil(YOUNG_MODULUS=2400, POISSON_RATIO=0.2),
                                SaturatedBelowPhreaticLevelLaw())


sleeper_width, sleeper_height, sleeper_length  = 0.234, 0.3, 2.8 / 2
sleeper_dimensions = [sleeper_width, sleeper_height, sleeper_length]

direction_vector = [0, 0, 1]
sleeper_spacing = 1
number_of_sleepers = 3
rail_pad_thickness = 0.025

# generation of the track
model.generate_straight_track(sleeper_spacing,
                              number_of_sleepers,
                              rail_parameters,
                              material_sleeper,
                              rail_pad_parameters,
                              rail_pad_thickness,
                              origin_point_track,
                              direction_vector,
                              "rail_track_1",
                              sleeper_dimensions,
                              origin_point_track[0])
model.show_geometry()
Wrongly generated geometry with volume sleepers

This issue can be avoided by ensuring that the origin point of the track is not included in the coordinate list of the ballast layer. In this case the ballast coordinates should be defined as follows:

ballast_coordinates = [(0.0, 20, 0.0), (3.0, 20.0, 0.0), (2, 21, 0.0), (0, 21, 0.0)]

This will lead to a correct generation of the geometry as shown in the figure below.

Correctly generated geometry with volume sleepers