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Railroads on Bridges

The sound radiation by railway tracks on bridges or viaducts can be modeled in CadnaA by use of the option „Self-Screening“. This option is available on the Geometry dialog of the object „Railway“.

With the option „Self-Screening“ activated the following values can be entered:

  • additional width left/right (to consider the bridge plate's edge),
  • parapet height left/right (located at the plate’s edge), and
  • a stationing.

The use is explained using the example generated in the last section.

  • Load the file via File|Open menu.
  • Deactivate the track with ID „Track_002“.
  • Enter a relative height for the active track of 10.6 meters above to the ground (via button „Geometry“ in the dialog Railway).

Note

The entered height refers to the railhead.

  • Activate the option „Self-Screening“.
  • Close the Geometry and the Railway dialog by OK.

Vertical Grid

  • Select the object „Vertical Grid“ from the toolbox (symbol ).

  • Draw a line from two polygon points perpendicular to the active track, approximately in the middle of the track’s length.

  • Change to the edit mode (toolbox symbol ).

Railway track and vertical grid (in xy-plane)

  • On a double-click on the vertical grid the dialog opens.
  • For „Specification“ and „Appearance“, deactivate the option „global“ and set the grid spacing to 1x1 meter and the appearance to „Lines of Equal Sound Level“ and activate „Level Range“.
  • Now, click „Calculate“.
  • Click once with the mouse into the lower part of the dialog and zoom in or out the vertical grid using the mouse wheel.

As can be seen from the resulting vertical grid the diffracting edge is defined by the additional width entered.

Vertical grid: elevated railway track with self-screening activated

Activating Self-Screening

Besides the additional widths left/right and barrier heights (parapets) can be defined for the left and right side of the railway track. The additional width corresponds to the distance of the outer diffracting edge from the railway's axis.

Parapet by Stations

Furthermore, on dialog Geometry, the length of a parallel barrier (parapet) can be restricted to a certain part of the railway track using the option „from/to Station“ (see Generate Station).

Only of own Source is seen

The self-screening effect by the railroad track - including parapets, if any - refers just to this source itself (i.e. just to this railway track). For more information please refer to chapter Elevated Roads and Bridges in this manual.

Note

Additional widths and parapets defined using the option „Self-Screening“ for railways are not displayed in the 3D-Special view.