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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
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| Publication Number: FHWA-HRT-15-081 Date: May 2016 |
Publication Number: FHWA-HRT-15-081 Date: May 2016 |
Qualitative methods provide a direct, descriptive indication of the bridge condition rather than using a numeric scale. The index is assigned after extensive assessment of the condition of bridge elements using element-level inspection. A typical example of qualitative health index is the Bridge Health Indicator developed by Roads and Maritime Services in Sydney, Australia.
The bridge health indicator is used by Roads and Maritime Services for identifying bridges that need maintenance, repair, or rehabilitation, but it is not used for prioritizing projects. The bridge health indicator does not report the condition of a bridge on a numerical scale. It describes a structure as having an indicator of “Poor,” “Fair,” or “Good” based on the condition state and importance of the element under investigation. The element’s importance is a reflection of the relative significance of the element to the overall performance of the structure. The significance or importance of an element is ranked as high, medium, or low. The element importance rankings are based on an expert determination of the proportion of similar elements that, if lost, will result in a collapse.(17) Table 25 describes how the overall bridge health is assessed based on the condition and importance of the elements.
| Bridge Health | Bridge Element Importance | ||
|---|---|---|---|
| High | Medium | Low | |
| Poor | Percent in condition state 5 > 10 Percent in condition state 4 > 40 |
Percent in condition state 5 > 25 Percent in condition state 4 > 50 |
Percent in condition state 5 > 50 Percent in condition state 4 > 70 |
| Fair | 10 ≥ Percent in condition state 5 > 0 40 ≥ Percent in condition state 4 > 0 | 25 ≥ Percent in condition state 5 > 0 50 ≥ Percent in condition state 4 > 0 |
50 ≥ Percent in condition state 5 > 0 70 ≥ Percent in condition state 4 > 0 |
| Good | 0 percent in condition 4 or 5 |
0 percent in condition 4 or 5 |
0 percent in condition 4 or 5 |
As an example, an element of high importance with 15 percent of the element in condition state 5 is considered to be in “Poor” condition. An element of low importance with 50 percent in condition state 4 is considered to be in “Fair” condition.
Although Austria has a BCI, most of the relevant infrastructure administrations do not use this calculation anymore but use simple ratings between 1 (no/minor damage) and 5 (critical condition).
Following the Austrian guideline for bridge inspections, the total rating of a bridge is based on the ratings of the bridge elements.(15) Each element is assigned a condition rating, ranging from 1 to5 (table 26).
| Rating | Description |
|---|---|
| 1 | No problems, minor problems; load-bearing capacity, operability, and durability not limited; no maintenance required. |
| 2 | Minor problems; load-bearing capacity and operability not limited; operability and durability will be limited if defects are not removed in the long-term; no restriction of use. |
| 3 | Moderate problems; indication of limited operability and durability; maintenance required in the medium term (within 6 years). |
| 4 | Severe problems; load-bearing capacity not yet limited but operability and durability already limited; maintenance within 3 years (short term) to reestablish regular use. |
| 5 | Critical condition; load-bearing capacity and operability limited; immediate initiation of repair, restriction of use. |
On the basis of the bridge element ratings, the total rating of a bridge is also assigned a number from 1 to 5. The following factors are crucial for this classification:
This approach is mainly used for general assessment of the bridge condition and identifying bridges that need maintenance. Qualitative methods rely on element-level inspection data and are able to provide a more objective assessment of the condition of structural elements by capturing both severity and extent of damages.
This approach cannot be used effectively for prioritizing and planning rehabilitation and maintenance programs because it does not provide a quantitative scale for ranking bridges in a network. For example, many bridges may be rated as being in “Poor” condition with no particular ranking regarding which ones are in dire need of repair or replacement compared with others when only a few of them could be preserved or replaced due to budget constraints.
