Abstract
Currently most railway bridges in Australia require the frequent replacement of the timber transoms that reside in the railway system. Composite steel and precast reinforced concrete transoms have been proposed as the replacement for the current timber counterparts. This paper outlines the structural benefits of composite steel-concrete transoms for ballastless tracks when retrofitted to existing railway steel bridges. However, in existing studies, it is found that there is little investigation into the effect of derailment loading on reinforced concrete transoms. Therefore, this paper provides an investigation of derailment impact loading on precast reinforced concrete transoms. The paper herein investigates the derailment impact loading of a train through experimental testing and numerical analysis of conventional reinforced concrete transoms. The paper also evaluates the potential use of 3 different shear connectors; welded shear studs, Lindapter bolts and Ajax bolts. The results of the experimental tests and finite element models are used to determine whether each transom is a viable option for the replacement of the current timber transoms on the existing bridges in Australia and whether they provide a stronger and longer lasting solution to the current transom problem.
1. Introduction
Transoms are one of the most important components of a railway system. They are designed as load carrying elements of a railway bridge which span under the roadway and transfer the railway loads to the trusses and beams. Current timber transoms are the most commonly used however they are susceptible to biological and chemical degradation. This reduces their service life and requires frequent maintenance and replacement. In order to fulfill the current promotion of more sustainable material, alternative materials such as composite steel-concrete panels are starting to be implemented more. The reason being that composite steel-concrete provide a material which utilises the best attributes of each individual element providing higher strength, long service life and flexibility in design.
5. Conclusions
Three transoms were experimentally tested and modelled to determine the detailed failure behaviour of the transom and the feasibility in replacing the current timber transoms that reside on the existing steel railway bridge network. The transoms were varied using three different types of shear connectors: AJAX bolts, welded headed shear studs and Lindapter bolts to analyse the change in strength given by these shear connectors. The following conclusions were obtained from the research presented herein:
1. No signs of significant failure within the concrete transom or existing steel structure were observed for either the experimental or numerical analysis.
