Design and construction of Loughor railway viaduct with semi-integral abutments

The new Loughor viaduct, a 220 m long seven-span twin-track semi-integral railway bridge over the Loughor estuary replaced a life-expired 18-span timber viaduct originally designed by Isambard Kingdom Brunel. The focus of this paper is the design of the abutment pad foundations, which are semi-integral with the viaduct superstructure; that is, there is no moment continuity but viaduct expansion/contraction and traction and braking forces are resisted by the pad foundation soil–structure interaction. The viaduct substructure was sized to minimise deck longitudinal movements to allow rail expansion joints with 100 mm of allowable travel to be installed at each end of the bridge. Track–structure interaction analysis was carried out along with three-dimensional finite-element geotechnical modelling to ensure that the track rail stress remained within acceptable limits.