According to the 2017 Infrastructure Report Card published by the American Society of Civil Engineers (ASCE), almost 40 percent of the 614,387 bridges in the United States are at least a half century old. Almost 10 percent were structurally deficient in 2016. On average, 188 million vehicles cross structurally deficient bridges each day.
With so many bridges reaching the end of their planned design life (most built during the highway construction boom of the 1960s and ’70s had an expected lifespan of 50 years) or becoming deficient (unable to serve their usable function because of defects), people who manage them are constantly looking for more cost-effective ways to keep them in good repair.
Perhaps the biggest issue affecting people who maintain bridges today is that they are forced into being reactive in how they approach their work, rather than proactive. They must repair the worst damage to structures rather than use limited resources to keep them in good shape. As with most things, being reactive is never as effective as planning ahead.
A “worst first” approach is not a cost-effective way to keep bridges healthy. It evolves into a vicious cycle where more and more budget dollars go toward emergency repairs. This underfunds proactive maintenance projects that could keep bridges out of the deficient category entirely.
In this article, we’ll explore a wide range of ways to approach bridge maintenance. Then we’ll explain a few best practices that can help bridge stewards move away from being crisis managers, so they can focus more on preserving structures.
Did you know? According to ASCE, the current cost to rehabilitate the nation’s bridges is more than $120 billion.
Proactive versus reactive maintenance
Bridge preservation tactics are actions or strategies that prevent, delay, or reduce the deterioration of bridges or sections of them. They return bridges to working order, keep them in good condition, and extend their lives. Preservation activities may be done to prevent deterioration or to correct existing conditions.
Preservation is more reactive than proactive. However, maintaining and rehabilitating bridges while they’re in relatively good condition and before the onset of serious deterioration can delay the need for costly bridge reconstruction or replacement.
The elements that are typically part of a sound bridge preservation program include:
- A long-term commitment to strategies and practices dedicated to maintaining and improving bridges and extending their useful life.
- Adequate funding to maintain infrastructure today and long into the future.
- Access to the right number of people, tools, and equipment to ensure that maintenance takes place at appropriate and opportune times.
- Processes and procedures that ensure work gets done on time and on budget.
Preventive maintenance is a more planned — and generally more cost-effective — approach to maintaining bridges. It is proactive rather than reactive. Maintenance is done to preserve (not simply repair) entire bridges and their components, prevent future deterioration, and sustain or improve their condition. Preventative maintenance is most effective on newer structures that have a significant useful life ahead of them and few components that are damaged, decayed, or broken.
At its simplest, the key difference between preventive and preservative bridge maintenance is:
- Prevention is about keeping bridges from developing issues.
- Preservation focuses more on fixing or repairing problems.
A few things that are done to preserve bridges include:
- Washing and cleaning
- Sealing deck joints
- Clearing drainage areas
- Sealing cracks
- Painting exposed elements
- Removing trash and other debris
- Protecting against scour
- Lubricating bearings
The checklist at the end of this article provides more information about these and other preservative maintenance tactics.
Preventative maintenance includes doing scheduled, non-condition-based activities and repairs as they are warranted.
There are two other bridge maintenance categories that are hybrids of those outlined above:
1. Cyclical preventative maintenance activities
Performed on a pre-determined schedule, to preserve existing bridge conditions and keep them from getting worse. The elements being treated may not be improved. However, continued deterioration is usually delayed. The inherent value of this approach is that bridge managers may assign different levels of preventative maintenance to structures that have higher or lower usage patterns or traffic volumes.
Example: Some typical cyclical preventative maintenance activities and how often they’re typically done include:
- Wash and clean decking or the entire bridge: One or two years.
- Lubricate bearings: Two to four years.
- Seal and waterproof concrete decking: Three to five years.
- Zone coat steel beams and girder ends: 10 to 15 years.
- Install deck overlay on concrete decks: Approximately every 10 to 20 years, depending on usage and wear and tear.
2. Condition-based preventative maintenance activities
Happen only when issues are identified during bridge inspections. This type of maintenance is usually done on bridges that are in basically good to fair shape. Maintenance restores bridge elements to a state of good repair. Similar to other cyclical preventive maintenance activities, this type of bridge work is focused on extending the useful life of structures.
Some typical condition-based preventive maintenance activities include sealing and replacing leaking joints; installing deck overlays, cathodic protection systems, and scour countermeasures; and painting and sealing steel structural elements.
Crisis maintenance and repairs
Bridge restoration returns bridges to full structural integrity and corrects major safety defects. This is, by far, the most challenging, comprehensive, and expensive type of bridge repair project, and in many cases, it is easier and cheaper to build a new bridge.
Restoration work can be done on one or more elements or sections of a bridge. At its simplest, it may involve completely replacing the decking, which could take months and many millions of dollars to do. At a more complex level, it could include a complete overhaul of its piers and substructure. Often, bridges that go through rehabilitation are also widened or otherwise updated to handle more traffic.
Total bridge replacement means that all preventative and rehabilitative maintenance activities have failed, and a structurally deficient or functionally obsolete bridge must be replaced with a new one to serve existing traffic needs. Replacement may involve additional work on approaches and local roads to connect replacement bridges to existing infrastructure.
Replacing bridges is costly and time consuming. Preventative projects generally don’t require hiring design and engineering resources. Restoration and complete replacement projects do.
Replacing bridges can have a big impact on affected communities, often closing vital traffic arteries and impacting local business activity. Bridge replacement should only happen when a thorough cost-benefit analysis proves that it is absolutely necessary.
The bottom line
Shifting from reactive maintenance to proactive maintenance is critical for bridge managers to succeed. While it may seem impossible to make this change, it’s not. Many municipalities have successfully done so. Systematically reallocating budget dollars and resetting priorities over time is the best way to get started. Some of the most cost-effective maintenance activities to adopt include:
- Seal or replace leaking joints or eliminate deck joints. This helps minimize deterioration of the superstructure and elements under the joints.
- Seal deck overlays. This increases the life of the deck by protecting the surface from strong chemicals, weather events, and daily wear and tear.
- Install cathodic protection systems. This technology prevents steel corrosion.
- Employ electrochemical chloride extraction. This protects against corrosion by removing chloride ions that may be present on or around steel components.
- Repair concrete. This should take place at the same time as other preventative measures. It protects other bridge elements, including ones made of steel, from damage and corrosion.
- Frequently paint and treat areas that experience significant wear and tear. This extends the life of the most vulnerable bridge elements.
- Regularly paint and coat all steel components. This is the best way to prevent corrosion and avoid the deterioration of critical structural steel elements, often the most costly and difficult to replace.
- Proactively repair and replace fatigue- and fracture-prone details. Treating welds and connective sections can help prevent permanent damage to them and the areas they are connected to. Also, adding redundant systems is generally cheaper than replacing damaged ones.
- Install scour prevention measures. This prevents damage to substructure elements that can lead to failure.
- Remove debris. Trash and other debris may contain chemicals that damage structural elements. It can also block water flow, which may cause significant wear.
- Install jackets and other protective systems around concrete piles. This is the best way to protect against under-bridge corrosion and deterioration.
- Install utility infrastructure protection. Utility components installed under bridges are vulnerable to weather and environmental damage. Installing protective devices can extend their life for decades.
- Wash bridges regularly. Cleaning decks, joints, and drains, along with all superstructure and substructure elements, will slow deterioration of concrete and steel.
Have the right knowledge and equipment
Another concern bridge managers have about maintaining bridges is getting access to the equipment needed to get the job done and its cost. Surprisingly, this is usually one of the easiest issues to solve.
Companies like BridgeMasters rent highly specialized equipment on an as-needed basis. We can advise you on how to select the right lifts to get your projects done efficiently and effectively, or take over and complete entire projects for you. We specialize in bridge utility work, but also have extensive experience in seismic retrofitting and other bridge preservation strategies.