The River Bann Bridge is a landmark 98m span bowstring arch bridge, and with a distance between unbraced arches of 28m is the largest bridge of its type in the British Isles. It carries the dual carriageway of the A6 Trunk Road, which connects Belfast to Londonderry over the Lower River Bann and forms the main structure on the Toome Bypass.

In 2001, a design and build contract was awarded to the contractor, FP McCann with Bullen Consultants as design consultants and Fairfield Mabey as steelwork fabricator.

The bowstring girder concept was developed to accommodate the curved horizontal alignment of the dual carriageway, radius 1800m, and the provision of a footway/cycleway adjacent to the westbound carriageway.

The initial 3 dimensional design model was developed to consider the linear elastic response of the structure using SAM-LEAP5. Following agreement with the main contractor and steelwork fabricator upon the construction sequence, the subsequent analysis and design incorporated a number of different SAM-LEAP5 computer models to represent the various stages of construction to assess the build up of stresses in the structural members and hangers.

Design loadings were calculated in accordance with BD37/01 with full HA and 45 units of HB loading. The design also considered the situation where one hanger had been removed accidentally or for maintenance. SAM-LEAP was also used to calculate the design load effects from the various highway load configurations.