ABSTRACT
The Humber Bridge is a Grade 1 Listed structure which remains one of the longest single span suspension bridges in the world, connecting the East Riding of Yorkshire with North Lincolnshire. The suspension bridge carries the A15 dual carriageway over the River Estuary. The bridge has a main span of 1410m and two side spans of 280m and 530m. The bridge deck is connected to the main suspension cables by spiral wire rope hangers with socketed end connections. The bridge opened to traffic in 1981. The two next longest-spanning UK suspension bridges, the Severn Bridge (opened in 1966) and the Forth Road Bridge (opened in 1964), had both already had their hangers replaced because of concerns over their deterioration. As a result, additional visual inspections were carried out on the Humber Bridge hangers which suggested that the condition remained generally good. However, hanger internal environmental or fatigue deterioration to the internal wires could not be detected solely from visual inspection so three hangers were selected for trial replacement and testing. The hangers were selected based on those with the greatest peak stress, greatest fatigue stress and greatest apparent corrosion. This paper discusses the global analysis of the bridge to identify the predicted stresses in the hangers, which was complicated by the triangulation of the hangers and uncertainties in the actual original construction sequence and methodology. It then covers the selection of the three trial hangers to be replaced, the specification of the replacement hangers and the testing specified to determine the residual life of the original hangers. The design, fabrication and installation of the works involved in replacing the hangers is described and the paper concludes with a discussion of the results of the hanger testing and how this has informed the strategy for management of the remaining hangers.
