Scour at bridge structures is a real and significant problem in the UK. During the Storm Desmonds floods of 2010, 26 bridges collapsed and many more were deemed to be at risk of failure. Edenvale Young Associates has considerable experience in assessing geomorphological change and the risk of scour to structures. In the past three years we have undertaken:
A risk-based approach to bridge design, maintenance and structural assessment is increasingly understood to be best practice. Assessing the risk of scour and undercutting of foundations, and the geotechnical or structural failure of a structure requires careful consideration of a range of factors which may affect the response of a bridge in exceptional flow conditions. Edenvale Young has extensive experience in this type of work.
Level 1 and 2 scour assessments (DB97/ 12) are rapid evaluation techniques to identify where there are potential problems associated with scour at a bridge structure. They are based on empirical techniques developed in the 1950. However, they are limited to a range of bridge types and forms. Hydraulic modelling using 2D and 3D software facilitates a step change in the evaluation of scour to bridges and other structural forms. Location adjacent to bridge piers and abutment where there are high velocities and bed shear stresses can readily identified and this gives more reliable assessment of scour.
Edenvale Young is experienced in the use of Three-Dimensional modelling with OpenFOAM/interFoam which has a number of significant advantages in terms of evaluating scour and the response of a bridge structures in extreme fluvial events. This includes improved understanding of flow velocities and bed shear stresses adjacent to a pier, abutment or caisson. Bridge Geometry including the configuration of cut waters, bridge piers, arches, foundations and abutments influence flow velocities around and through the structure and are critical to the process of scouring for individual bridges. The use of OpenFOAM modelling allows the configuration of the structure to be adjusted rapidly.
Any structure within the river and coastal environment will be subject to erosive pressures in extreme weather events. The need to undertake an evaluation of scour and erosion will depend on individual requirements but this could include: