This article is a brief review over different aspects regarding the bridge structure inspection procedure specified in the Ontario Bridge Inspection Manual (OSIM). The inspection manual has been used for bridge inspections in Ontario since 1985 with major upgrades to the document in the year 2000. According to the bridge inspection manual (section 1.2.1), “the main goal of the structural inspections is to ensure, within an economic framework, an acceptable standard for structures in terms of public safety, comfort and convenience.”
Objectives of Structure Inspection
The structural evaluation of bridges aims to:
- Keep bridges in safe condition;
- Prolong service life;
- Find if any aintenance, repair and rehabilitation is needed;
- A basis for a structure management system.
What is Detailed visual inspection?
A detailed visual inspection is Element-by-element “close-up” visual assessment of:
- Material defects,
- Performance deficiencies
- Maintenance needs
Close-up is defined as “a distance close enough to determine the condition of the element”. In many cases, the inspection should be conducted within arm’s length of the element, possibly involving tapping with a hammer or making measurements by hand. Appropriate special equipment can be used to facilitate this assessment.
Who can perform it?
A bridge inspector must be a professional engineer or a technician with bridge inspection experience working under the direction of a professional engineer. Additionally, bridge inspectors working for the Ministry of Transportation must complete the Ministry of Transportation bridge inspection course.
The following structures shall be inspected every two years (Biennially):
- All bridges, culverts and tunnels with spans of 3 metres or greater
- All retaining walls
- All movable bridges
What to inspect?
Different defects and deficiencies in materials and structural components are identified and scaled in the visual inspection process. The data is then used to determine the Bridge Condition Index (BCI), to determine if further evaluation is needed, or if repair or maintenance is immediately required.
Remarks on Structure Inspection using OSIM
Visual inspections are generally in line with accepted professional standards; however, there a few concerns about the inspection be subjective, including:
- Close-up access is not always possible when performing visual inspection according to the OSIM. In this scenario, it may be possible to inspect a portion of the bridge close-up and then estimating the condition of the remaining inaccessible parts by visually comparing them to the partial close-up inspection.
- Visual inspection of bridges is expected to take 2-3 hours in average. Visual inspection on new construction, as well as small bridges or culverts can be relatively shorter, while the inspection period might be more for larger and older bridges.
- There is no particular quality assurance and control regarding the practice, except the fact that it is supervised by a professional engineer.