Development of UK NA for EN 1990 Annex A2

Annex A2 was published as an amendment to BS EN 1990 in 2005 to provide the specific load combination rules, load combination factors (:::) and the partial factors for permanent and variable actions (_G:Q), that are applicable to bridges.

The common basis adopted for road, rail and footbridges, was to aim for an equivalent level of reliability to that previously obtained using the British Standards (Highways Agency Design Manual for Roads and Bridges BD 37 and BS5400-2 for example). Calibration studies were undertaken by Atkins for the Highways Agency and by Scott Wilson and Mott MacDonald for Network Rail and RSSB.

The outputs from these studies were used as the basis for selection of the design rules and the values of the load combination factors and partial factors, selected. The paper describes the work undertaken and provides information about the background to the development of the UK National Annex relating to BS EN1990 Annex A2.