The development of RL loading for bridges on the London Underground network

Loading due to railway traffic on bridges has developed over time to suit the evolution of the rolling stock operating on a network and the understanding of dynamic effects. For the London Underground (LU) network, the development of loading was achieved through research work undertaken by the London Transport Executive in the 1960s and 1970s. The resulting load models were designated as RL (Railways London) loading, which were included in the former British Standard BS 5400-2:2006 and its predecessor BS 5400-2:1978. These standards also included load models for bridges on the GB mainline railway. The current loading standard for mainline rail traffic is Eurocode 1 for traffic loads on bridges (BS EN 1991-2:2003). However, the load models in the Eurocode are only representative of the rail traffic operating on the GB mainline railway and are not appropriate for rail traffic operating on the LU network, where mainline traffic is not permitted to run. The inclusion of RL loading in the Eurocode was addressed through an amendment of the complementary UK National Annex to BS EN 1991-2:2003. The background to the development of standards for railway bridge loading in general, but specifically for the RL load model, is explained in this paper.