Software Option for Plus
versions
Rail Track Analysis
With a large percentage of track on
modern railways consisting of continuously welded rails there is a
requirement for accurate modelling of the interaction of the track
with respect to any supporting bridge structures, and in particular,
to calculate stresses and forces induced in the track by both thermal
and train loading. The LUSAS Rail Track Analysis option
permits track/bridge interaction analysis to the International Union
of Railways Code UIC 774-3. It allows you to automatically build
models from data defined in MS Excel spreadsheets, run an analysis,
and quickly produce results in spreadsheet or LUSAS results file
formats.
A key feature of the LUSAS Rail Track Analysis
option is that it automatically updates the material properties associated with the
track/structure interface based upon the position of the train or
trains crossing the bridge.
Modelling to International Union
of Railways Code UIC 774-3
The UIC 773-3
Structural System
UIC 773-3
Track/Deck Modelling
Model building in LUSAS
Track and bridge interaction models are
built automatically in LUSAS from geometric, material property,
and loading data defined in a MS Excel spreadsheet. Both thermal
loading to the track and train loading due to acceleration and braking
forces can defined. In accordance with the UIC774-3 code of practice,
a user-specified element length is used to define the longitudinal
embankment and bridge features. Rail clips, ballast movement, bearings
and pier stiffnesses are all included in the analysis model. The model
building dialogs allow for either one train crossing one or more
structures, or for multiple trains crossing the same structure.
|
Spreadsheet
input data
Complete
embankment and viaduct model built by LUSAS
|
Enlarged
view of first span |
Exploded
isometric view of part of the model showing embankment
support and the beginning of the first span |
|
Analysis and results
When running an analysis, deck
temperature loading can be considered in isolation for subsequent
analysis of multiple rail configurations, or a full analysis can be
carried out considering the combined temperature in the deck and rail
loading. Because the response of the ballast and/or clips is nonlinear
a nonlinear analysis always needs to be carried out. Results can be
produced in either Excel spreadsheet or standard LUSAS results file
format. User-defined load combinations can be specified. Spreadsheet
results include axial forces in the rails for deriving in-service
stresses and forces and moments in the deck structure.
|
Typical axial
force results plot from LUSAS showing force in continually
welded rails from
temperature loading to the deck |
For multi-span and multi-deck structures
such as that shown above the interaction between the embankments / abutments and other decks means that the behaviour can be complex.
As an example, when considering only thermal loading on
a structure having continually welded track it is common to see a
reversal of the axial force / stress in the rails. Whilst
not apparent from the size of the model shown, the structure illustrated above
is 325m long and consists of two decks, each with two 25 m spans followed by three decks, each with three 25 m spans. One pier / bearing support for each deck is represented by a restraining spring which takes account of the deflection characteristics of the pier / bearing system in accordance with UIC774-3. All of the remaining piers / bearing supports are roller supports allowing longitudinal movement of the decks. Under the effect of temperature on the structure the axial force / stress in either of the tracks / rails
can be seen to vary. This is primarily due
to the interaction between the movable and fixed structural
components.
See also:
Back to Top
|
