Delaying bridge inspections put everyone at risk
11 December 2018
How important are timely inspections and maintenance of bridges? Sadly, we often don't think about this until a catastrophe occurs.
In Genoa, Italy, more than 40 people died and dozens were injured when the Ponte Morandi bridge collapsed in August. While some investigators might look at design deficiencies, some will look at inspection and maintenance matters.
If this can happen to bridges about 50 years old, imagine what a bridge (road or rail) built a hundred years ago has been exposed to over its serviceable life. The possibilities include extreme natural hazards such as severe storms, lightning strikes, heavy rain, floods, earthquakes, extreme variations in temperature and bridge strikes. It may not have been designed to withstand any of these as single or repetitive events.
In addition, older bridges are likely to have been subjected to an increase in loadings over the years. The rate and volume of vehicles using the bridge would have also increased causing further stress and fatigue. In the case of tourist and heritage structures, the increased popularity and therefore demand has resulted in increased use and stress.
Now, ask yourself whether that “rickety old bridge” being used to transport passengers every day is as safe as you think. This is why regular bridge inspections are crucial in identifying the condition of the structure and the maintenance requirements for a particular bridge.
Regular inspections are important to:
- Establish if a structure is fit for purpose and poses no threat to public safety
- Maintain an accurate history and knowledge of the condition of a bridge or structure
- Plan, coordinate and implement maintenance, repairs and replacements
- Monitor existing deterioration and to repair and prevent failure and loss of service
- Monitor the performance and adequacy of previous repair works
- Determine when a structure needs to be replaced and the impact on the surrounding areas while doing so.
In general, there are three levels of inspection conducted for bridges, scheduled as follows:
Visual inspection for routine maintenance issues and to check on the general serviceability of the bridge structure.
Visual inspection to assess the condition rating of the structure and its components. The individual components of the structure must be inspected at close range, i.e. within touching distance.
2 years minimum
4-8 years maximum
Detailed engineering inspection to target specific issues and assess load-carrying capacity of a structure or group of structures.
The levels and frequencies vary between states and really depend on the structure’s type, condition and location. However, one thing is consistent, "No bridge inspection should ever be late," (as stated by one engineer after the 2008 collapse of a freeway bridge into the Mississippi River, Minneapolis, that killed 13 people). Although the risk of a bridge collapse occurring is generally low, it is important to have an intimate understanding of the current condition of the structure. As bridges approach the end of their design life, it becomes increasingly critical that these structures are actively managed to provide confidence to the owner and the public that the structure is safe to use.
Pictured: Kilcunda bridge
This article was created for Rail Safety News (RSN). Subscribe to Rail Safety News
RSN is produced by Rail Safety Victoria (RSV), a branch of Transport Safety Victoria (TSV), to help develop a strong safety culture in the tourist and heritage railway sector. Twice a year (June and December), we write technical articles and source case studies – highlighting local and international expertise and experience – to help inform safe rail operations as required under rail safety legislation.