Effect of bending and compressive modulus of elasticity on the behaviour of timber-alternative railway sleepers supported by ballast

Abstract

Alternative railway sleeper technologies for replacement of timber are made of materials possessing a wide range of bending and compressive moduli. This poses a great challenge to railway authorities and engineers in designing a railway track supported by different sleeper technologies. This study evaluates the static behaviour of a railway track supported by different alternative railway sleeper technologies, i.e. recycled plastics (1.0 GPa), synthetic composites (7.4 GPa), timber (13.0 GPa), and low profile prestressed concrete sleepers (38.0 GPa), using a ballast box test representing a single sleeper section of a track. The deflection profiles along the length of the sleepers under a full service load was captured using Digital Image Correlation technique combined with the strain measurements at the top-centre of the sleepers. Three-dimensional Finite Element simulation of the sleepers’ behaviour based on the Beam on Elastic Foundation theory was implemented and validated by the experimental results. The results show that sleepers with bending modulus of less than 13.0 GPa will have W-shape deflection profile and a high rail seat deflection while sleepers with a bending modulus of 38.0 GPa will show nearly flat behaviour. Local deformation at the rail seat region accounts for almost 6 % of the total deflection of sleepers on a low subgrade modulus and as high as 10 % for high subgrade modulus. The results of this study provide a better insight into the in-track behaviour of alternative sleeper technologies having distinctive material properties.

Keywords

• Composite sleeper
• Timber-alternative sleeper
• Ballast box test
• Beam on elastic foundation (BOEF)
• Modulus of elasticity
• Compressive modulus