Bridges

Rail Structure Interaction (RSI) is a complex phenomenon in rail bridges which involves a detailed study and effects of the forces transmitted between rail and deck and subsequently to substructure due to train loadings, temperature and time-dependent effects.

The Level Crossing Removal Project (LCRP) Caulfield to Dandenong entails removal of nine of Melbourne’s most congested level crossing along the Caulfield-Dandenong corridor. To achieve this, four multiple span elevated rail viaducts with maximum length up to 3.1km are proposed to be built over the existing level crossings.

This paper provides a framework to pursue RSI studies, estimate stresses induced in the rail, rail displacement relative to bridge deck and longitudinal forces transmitted to bridge components. Interaction effects include thermal effects between rail and deck, longitudinal deformation of sub-structure under temperature, train braking/tractive forces, vertical live load effects. Methodology and key parameters adopted during RSI analyses on a Continuous Welded Rail (CWR) directly fastened to concrete plinth via rail fasteners is also described here.

Particular focus is given to the rail fastener mechanical properties, which critically affects the structural behaviour. The paper finally outlines the potential options considered to reduce excessive rail stresses and deformations for redistributing the loads on the substructure. A key feature of the viaduct design includes the use of a direct fixed track which necessitated an approach that entail a gap analysis and discussion between the rail loadings prescribed in AS 5100.2, UIC 774-3- 2001, Eurocode standards and Project Requirements.

As the project is being delivered under an Alliance, a collaborative approach between the alliance design team and Metro Trains Melbourne (MTM) has been undertaken to overcome this issue. MTM has developed a design practice note that provide guidelines for computing the longitudinal rail vehicle traction and braking forces using a rational method applicable to this scenario.