Cathodic Protection for Medieval Bridge
CRL carried out extensive repairs to Bideford Longbridge, a Grade One listed 24 span medieval masonry arch bridge with cantilevered concrete footpaths added in 1928, spanning 190m over the tidal estuary of the River Torridge. The concrete cantilevers were deteriorating due to corrosion of the reinforcement and the council had imposed a weight restriction.
Using scaffold access, CRL repaired the defective areas of concrete and installed an impressed current cathodic protection (ICCP) system to stop further reinforcement corrosion occurring. At the same time the underbridge lighting and lighting columns were replaced to enhance the overall appearance of the bridge at night.
The ICCP system was designed using a combination of mixed metal oxide coated titanium mesh and discrete mixed metal oxide coated titanium tubular anodes to ensure a uniform current distribution.
The ICCP system was one of the most challenging schemes ever undertaken by CRL since it first started installing CP on the Midland Links motorway network in the late 1980s. A combination of anode systems, services below and above deck and restricted scaffold access in a tidal zone challenged the management and site operative skills, all while the bridge remained open to traffic and pedestrians.
Devon County Council’s Chief Bridge Engineer, Nick Bott, commented that a high level of liaison throughout the design, consultation and procurement processes was required to successfully deliver this highly complex project, with the minimum disruption to the public.