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Bridge Inspections Necessary for Long Term Planning

Kyle Leonard

The 2014 U.S. Department of Transportation (U.S. DOT) National Bridge Inventory database found that there are more than 2,000 fewer structurally deficient structures than there were in 2013. However, that means more than 61,000 structurally deficient bridges are still in need of significant repair.

Many communities in the past have relied on Highway Trust Fund dollars to pay for bridge repairs. The Federal Highway Administration (FHWA) has estimated that the nation would need to spend about $20.5 billion per year to eliminate the backlog of deficient bridges by 2028; the USA spends about $12.8 billion annually. The situation has worsened in recent years as Congress has failed to approve long-term funding of the trust fund leaving many projects in doubt.

Funding shortfalls however should not prevent communities from assessing and moving ahead with repairs or replacement of bridges in their communities.

Funding shortfalls however should not prevent communities from assessing and moving ahead with repairs or replacement of bridges in their communities. In fact, by keeping an accurate inventory of bridges and providing basic upkeep many bridges’ lifespans can be extended. The comprehensive analysis of bridge condition and inventory data, including what-if and level-of-service scenarios allows agencies to maximize the effect of their bridge budgets and achieve the highest possible Return on Investment.

Bridge Inspection

Inspecting the bridge for signs of deterioration.

Biennial Bridge Safety Inspections are mandated by law and consist of bridge safety inspections conforming to and meeting the requirements of the National Bridge Inspection Standards.

Biennial Bridge Safety Inspections are mandated by law and consist of bridge safety inspections conforming to and meeting the requirements of the National Bridge Inspection Standards. This bare minimum approach can be penny wise in the short-term but municipalities that take a long-term view can increase safety as well as the longevity of these vital infrastructure components.

Creating a database of bridges and setting priorities is not required by law but it is a best practice. Monitoring bridge conditions in order to apply timely preservation activities to keep “good bridges good” and prevent more bridges from being classified as deficient is a goal every municipality should embrace. Continuation of successful bridge-inspection programs throughout the U.S. is an important element of ensuring safe bridges and cost-effective decision making.

The mandated inspections must be conducted by state certified inspectors who are required to fill out inspection forms. However, a complete inspection should also include a Bridge Inspection Report with a narrative, recommendations and budgetary costs for the recommended repairs for each structure. This report should also include priority lists and a discussion of available funding for each structure. Ideally, a Bridge Master Plan can be created, which accounts for a client’s priorities and budgetary constraints. This plan can also include listings of needed repairs and maintenance by type of work so that maintenance packages can be developed, either to bid or to assign to maintenance staff.

Bridges, of course, come in all shapes and sizes. A short stream crossing may only require an inspector using a small ladder and a pair of good waders to perform the task at hand. Other larger bridges may require inspection by boat to pinpoint portions of the underside of the slab, stringers and bearings needing more detailed inspection. A more detailed under-bridge inspection may require a truck unit with a bucket attachment so the inspector can be lowered under the bridge for detailed investigation.

Inspecting the bridge for signs of deterioration.

A more detailed under-bridge inspection may require a truck unit with a bucket attachment so the inspector can be lowered under the bridge for detailed investigation.

The actual bridge itself is not the only target for inspectors. The streambed adjacent to the piers and abutments must be examined to determine if scour has exposed the pile caps or footings. If the stream is four feet deep or less, this can be done with waders and a section of steel rebar. If the top of the pile cap or footing is located in this manner, a probe is pushed down alongside the pile cap or footing to allow the inspector to map out the results in a sketch to be used for comparison during future inspections.

Deeper waterways will require a Hydrographic Survey and/or a diver. This method has the added advantage of allowing inspectors to compare surveys year over year, creating a visual image of what is happening below the surface of the water and determining how currents and debris may be impacting the bridge itself.

Regardless of the method, the inspection will ultimately include thorough, quantitative and qualitative descriptions of deterioration and defects observed on each structure. This allows for the accurate calculation of budgetary costs for repairs. It also allows future inspectors to compare their observations to a record of earlier conditions. By taking this approach rather than simply the legal minimum, regular inspections overseen by qualified structural engineers will allow for the maintenance of these vital infrastructure projects.

Bridge Upkeep

Throughout the life of a bridge structure there are anticipated activities that are necessary to realize the full potential of the capital bridge investment. The goal is to maintain the bridge asset at the lowest cost over the life of the structure. Historically, it has been found that a strong preventive effort is the most cost effective approach.

  • Preventive maintenance activities can be classified into two groups: scheduled and response.

Scheduled activities are conducted on a scheduled interval basis and include:

  1. cleaning decks, seats, caps, and salt splash zones;
  2. cleaning bridge drainage systems;
  3. cleaning bearing assemblies and deck joints; and
  4. sealing concrete decks or substructure elements.

Response activities are corrective or minor repairs, performed as needed and as identified through the inspection process.

Typical activities that are performed on an as-needed basis include:

  1. resealing expansion joints;
  2. painting structural steel members
  3. removing debris from waterway channels;
  4. replacing wearing surfaces;
  5. extending or enlarging deck drains

There will come a time when a bridge cannot be repaired and must be replaced. The work a community has done with the engineering firm in terms of inspections and repairs create a natural partnership in working on the replacement of the structure. Experienced engineers who have a detailed knowledge of the local environment can coordinate with utilities, state transportation departments, and other stakeholders.

In addition, experience within the community allows for knowledgeable coordination of public meetings with residents impacted by these kinds of major projects. During construction the impact of the project on traffic and local residents can be minimized by experts who have been on site, working with the municipality in the past.

HR Green contracts with numerous government bodies on bridge inspection schedules as well as having constructed bridges throughout the United States. Contact Robert Davies rdavies@hrgreen.com for more information.

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