scope:

This Code of Practice may be used for the assessment of all Railtrack owned underbridges and is applicable for permissible speeds up to a maximum 125 mph.

This Code of Practice provides recommendations for the assessment of underbridges constructed from steel, wrought iron, cast iron, concrete, timber, or composite steel/concrete construction. Recommendations for masonry arches, substructures and bearings are also included. Limit state principles are used for underbridges of steel, wrought iron, concrete and steel/concrete composite construction. Permissible stresses or allowable loads are used for other materials and forms of construction.

Where appropriate, guidance on the use of simple and more rigorous methods of analysis is given. Unusual forms of construction such as cable stayed, moveable or combined road/rail bridges are not specifically covered, but the principles outlined may be applied in checking the elements of such structures.

Purpose

The purpose of this Code of Practice is to recommend applicable standards and analytical methods which may be used to determine the load carrying capacity of existing Railtrack underbridges, in terms of British Standard Units of Type RA1 loading. The load carrying capacity is determined in the context of the performance requirements of an underbridge. The requirements are that the bridge meets safety and serviceability criteria whilst regularly carrying rail traffic up to a level of traffic load and speed in accordance with operational system requirements.