There were more than 617,000 bridges in the United States as of 2019.
Out of these, close to 260,000 of them – or 42 percent – are at least 50 years old. In addition, it’s been reported that 46,154, or almost eight percent of our nation’s bridges, are considered structurally deficient (SD). These statistics come from the 2021 Infrastructure Report Card issued by the American Road and Transportation Builders Association.
The report noted that while the average age of our highway bridges has increased to 44 years, the total number of structurally deficient bridges have continued to decline over recent years. This is due largely to the renewed infrastructure efforts and the ongoing program of routine bridge inspections.
However, the need nationwide is still pressing. According to the report’s Executive Summary,
“A recent estimate for the nation’s backlog of bridge repair needs is $125 billion. We need to increase spending on bridge rehabilitation from $14.4 billion annually to $22.7 billion annually, or by 58%, if we are to improve the condition. At the current rate of investment, it will take until 2071 to make all of the repairs that are currently necessary, and the additional deterioration over the next 50 years will become overwhelming.”
Federal Bridge Inspection Standards and the Need for Under Bridge Inspections
On December 5, 1967, the worst bridge collapse disaster in the United States happened as the Silver Bridge between Point Pleasant, West Virginia and Gallipolis, Ohio fell into the Ohio River. The disaster claimed 46 lives and triggered a demand for improved highway bridge safety.
As a result, legislation was passed and the National bridge inspection program (NBIS) was created.
A significant component of the program was the establishment of regular inspections of roadway bridges throughout the United States that include extensive under bridge inspections.
According to the U.S. Department of Transportation (USDOT),
“The NBIS requires safety inspections at least once every 24 months for highway bridges that exceed 20 feet in total length located on public roads. Many bridges are inspected more frequently. However, with the express approval by FHWA of State-specific policies and criteria, some bridges can be inspected at intervals greater than 24 months. New or newly reconstructed bridges, for example, may qualify for less frequent inspections.”
Along with a bridge inspection program and regulations, the National Bridge Inspection Standards were established. In addition, a bridge inspector’s training manual was prepared along with a training course to provide specialized training.
Because of the various requirements and different types of bridges throughout the country, many state and local inspection standards have been established in addition to the federal standards.
Regular Bridge and Under Bridge Inspections
Not all bridges are subject to the same inspection schedules.
Most bridges are inspected every two years, unless they’re rated as being in “very good” condition, in which case they are only inspected every four years. Highway bridges that are labeled as “structurally deficient” are required to be inspected annually, though many states inspect these bridges far more often.
Information from the USDOT shows that approximately 12 percent of the nation’s highway bridges are inspected annually. Just five percent are inspected every four years. That leaves 82 percent of bridges that are inspected every 24 months.
According to the USDOT there are “five basic types of bridge inspections” that are conducted:
- Initial inspections
- Routine inspections
- In-depth inspections
- Damage inspections
- Special inspections
“The ‘routine’ inspection is the most common type of inspection performed and is generally required every two years. The purpose of “routine” inspections is to determine the physical and functional condition of a bridge on a regularly scheduled basis.”
It is these routine inspections which make up the bulk of bridge inspections carried out by contractors, engineers, and state DOTs most frequently. And they almost always involve under bridge inspections and under bridge inspection equipment.
Routine Inspections and the Need for Under Bridge Inspection
The primary purpose of routine inspections is to determine the physical and functional condition and integrity of a bridge structure.
However, bridge structures are not limited to the bridge deck and superstructure. Just as critical is the bridge substructure, which includes all the vertical supports, piers or columns, caps, and other components that are located underneath the bridge deck.
Bridge inspectors conducting under bridge inspections look for flaws, defects, or potential problem areas that may require maintenance. The goal is to identify these issues early to avoid more extensive problems. Routine inspections are often visual inspections using a variety of tools for cleaning, probing, sounding, and measuring.
Some of the techniques used include:
Inspectors visually assess the condition of the bridge structure by standing directly in front or beneath components, usually from a bucket or platform on an under bridge inspection unit.
Hammers and other tools allow inspectors to observe changes in sound pitch. This technique can detect defects in the bridge materials, such as coating splits or delamination issues.
Thermal or infrared tools can detect changes in infrared radiation from the surface areas of bridge components, possibly indicating degradation or delamination in the concrete.
Inspectors performing routine inspections assess the condition of the bridge and note changes since the last inspection. They look for defects like cracking in the concrete, unusual movement in the bridge, or issues with any bearings that may be used.
In addition, signs of decay such as rust, corrosion, or paint loss, can be indications of underlying structural issues that have developed over time.
The goal is to ensure that the bridge is still safe to operate according to existing standards.
Under Bridge Inspection Equipment and Under Bridge Inspection Truck Rental
According to a 2007 testimony transcript from the U.S. Department of Transportation,
“Bridge inspection techniques and technologies have been continuously evolving since the NBIS were established over 30 years ago and the NBIS regulation has been updated several times, as Congress has revised the inspection program and its companion program, the Highway Bridge Program (formerly Highway Bridge Replacement and Rehabilitation Program).”
A large part of these bridge inspection technologies includes the various types of vehicles that have been used for under bridge inspections, repair, and maintenance work.
The most common and efficient method for gaining under bridge access is with an under bridge inspection unit. These versatile under bridge buckets or platform vehicles are often the only reliable means for access under bridge areas.
Most every professional that works with bridge repair, cleaning, maintenance, and inspections makes use of some type of under bridge inspection platform.
Turn to the Experts in Underbridge Inspections – McClain & Co., Inc.
At McClain and Company, we offer a wide variety of several different types of truck-mounted and trailer-mounted under bridge inspection equipment. These units are available as under bridge inspection truck rentals for inspectors, contractors, and engineers working on bridges and similar structures. To find out more, reach out to us at email@example.com or call us at 1-888-889-1284 today!