The maintenance of highway structures can be defined as all operations necessary to maintain a bridge in a serviceable condition. This includes, regular inspections, maintenance, upgrading work, management of substandard bridges prior to upgrading and replacement. These operations are described below:

Inspections

Three different types of inspections are carried out on the County's Highway Structures - Principal, General and Specials.

Principal and General Inspections involve a close examination of the complete structure. Special access arrangements are usually required for Principal Inspections. Principal Inspections are only carried out on larger structures and those of historic significance every six years whilst General Inspections are undertaken every two years on all structures.

Special Inspections are used to investigate specific problems. Specific problems are those that compromise safety or reduce the structure's ability to carry the vehicles that use them. For example, a special inspection may be required following a vehicle collision with a structure or river erosion to a bridge support after severe weather.

Both Principal and General inspections identify maintenance works that are required on the structures.

Maintenance

To keep Dorset's highways structures in a safe condition maintenance is essential. Maintenance operations can be categorised as below.

Routine Maintenance - minor works carried out on a regular basis, e.g. removal of vegetation, watercourse debris etc.

Preventative Maintenance - this comprises work to repair defects or slow down the rate of deterioration, e.g. re-painting, re-pointing, re-waterproofing etc.

Essential Maintenance - this comprises rehabilitation work, undertaken when part of the structure is considered to be structurally inadequate.

Upgrading work

Upgrading works can be defined as works to bring the structure up to current standards (but exclusive of strengthening), e.g. upgrading of parapets, protection of vulnerable bridge piers etc.

Management of substandard bridges prior to strengthening

This has been brought about following the increase in 1999 of permitted gross vehicle weights from 38 to 40 tonnes and the Department of Transport's 15 year bridge rehabilitation programme. The Management of substandard bridges is concerned with the monitoring and, where necessary, the imposition of temporary weight restrictions or other measures such as propping, prior to the strengthening of the structures that fail to meet the 40 tonne loading requirement.

Replacement

When a structure reaches the end of its useable life and can no longer be satisfactorily maintained, it needs to be replaced. This is included as maintenance operation.

All of the above are classed as maintenance and are undertaken to ensure that the county's highway structures remain in a safe condition for all highway users.

The majority of these works are carried out by Dorset's Direct Services Organisation (DSO) Consortium, of which Highways Operations is a member.

The Structural Design Team of Highways Management carries out the assessments of Dorset's bridges as well as designing and supervising any maintenance or strengthening works found to be necessary. These works are often complex in nature, requiring innovative engineering solutions.

• Principal Engineer
  Name: John Burridge
  Email: j.burridge@dorsetcc.gov.uk
  Tel: 01305 225366
  Full details for John Burridge