Scour Concerns for Short-Span Masonry Arch Bridges

Short-span masonry arch bridges constitute a significant proportion of the existing bridge inventory in the UK, Ireland, Europe, and the northeastern United States. These historic structures are founded typically on relatively shallow footings of unknown depth and configuration or on timber piles weakened by age and environmental exposure. Flume experiments used two common forms of short-span, masonry arch bridge and showed how local scour may readily undermine such structures. The experiments demonstrated that traditional hydraulic adjustments do not significantly reduce scour depth: streamlining abutments with wing walls and using cutwaters on piers. The usefulness of stone armor placed around abutments and piers was proven, but such armoring may relocate scour downstream of the bridge. The findings emphasize the scour-countermeasure benefits of foundation strengthening, flow bypassing by means of relief culverts (where feasible), and the use of channel armoring and energy-dissipation structures downstream of the bridge.