Numerical and Analytical Evaluation of Load Distribution Patterns on Ballasted Concrete Railway Bridges

A. Eriksson, A. Ullrich, C. Wang, J. Gonzalez-Libreros, J. Johansson, O. Enoksson, J. Quist, G. Sas. Building for the Future: Durable, Sustainable, Resilient. fib Symposium 2023-Volume 2. Online 3 June 2023.


A significant portion of the reinforced concrete railway bridges in Sweden is reaching its designed lifespan and is scheduled to be demolished and replaced in the upcoming years. To limit the economic and environmental impact related to the replacement of this existing railway infrastructure, a comprehensive evaluation of their capacity is required with the aim of extending its lifespan. Experimental evidence has shown that some of these bridges may have a higher capacity than previously determined due to the conservative assumptions used during their design. The proper stress distribution pattern at the ballast-concrete interface is among the factors that need to be studied, as research on the topic has shown that some of the available guidelines to calculate it can produce conservative results. In this paper, available analytical models for computing the forces in concrete bridges due to train axle loads are compared to numerical models calibrated using the experimental results obtained from the test of ballasted reinforced concrete trough bridge, a typical structural type found in Sweden. As a first step, a literature review of existing numerical modeling strategies for ballasted concrete railway structures (e.g., finite element models, discrete element models, and their combination) is conducted. Then, appropriate numerical modelling strategies are identified and used to develop the numerical model of the bridge, including the ballast. Finally, results of contact pressure and vertical stresses in the numerical models are compared to those obtained analytically.

Photo credits: Nic McPhee