Case Study

Automated track / bridge interaction analysis

• Automated model building and analysis from user-defined spreadsheet data
• Fast assessment of track/bridge interaction
• Evaluation of forces in rails from thermal and in-service train loading

With a large percentage of track on modern high speed railways comprising 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. 

A new LUSAS product option, created initially for the Korea Railroad Technical Corporation (KRTC), permits track/bridge interaction analysis to the International Union of Railways Code UIC 774-3. It allows KRTC 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.

KRTC

KRTC is a subsidiary organization of Korea National Railroad. It is involved with performing planning, feasibility studies, design, and providing supervision for major rail and high speed rail construction projects throughout South Korea. Its stated aim is to enhance its competitiveness by developing advanced railroad technology. By using LUSAS Bridge to automate its track/bridge interaction analysis it is achieving this to good effect.

Model building

KRTC’s track and bridge interaction models are built automatically in LUSAS in 3D from geometric, material property, and loading data defined in a Microsoft 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.

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.