All hands on decks, piers, etc.

Bridges Article May 14, 2008
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Tennessee emerged from a January MSNBC analysis as one of only four states to have all its bridges inspected on schedule. MSNBC analyzed federal records for the National Bridge Inventory, which included inspections up to 2006, and reported at least 17,000 bridges in the U.S. went more than two years between safety inspections.

“I’m pleased to see Tennessee ranked at the top in timely inspection and want to commend TDOT’s bridge inspection program and employees for their commitment to making sure the more than 19,000 bridges in Tennessee are checked on time, consistently and thoroughly every two years,” said Tennessee Gov. Phil Bredesen.

Georgia, Delaware and Nevada were the only other states to report all bridges inspected within two years, according to MSNBC’s analysis. The National Bridge Inventory covers just fewer than 600,000 of the nation’s bridges located on public roads, including interstate highways, U.S. highways, state and county roads and publicly accessible bridges on federal lands.

The worst inspection records were in Hawaii, where 46.5% of the bridges were inspected late, according to MSNBC, Rhode Island (27.5%), Arizona (26.7%) and New Mexico (17.4%).

Tennessee thinks the best way to keep control over bridge inspections is to keep the inspection personnel within the organization. Of course, then it is up to TDOT to see that the inspectors get the training and equipment they need to do the job.

“We’re very fortunate in the state of Tennessee that years ago when the inspection program began, the department chose to develop the program with in-house forces rather than farming that out to the private sector,” Wayne Seger, head of TDOT’s Office of Bridge Inspection and Repair, told ROADS & BRIDGES. Passage of a new surface transportation bill in 1978 doubled the number of bridges Tennessee had to inspect, so they had to bring in consultants to help with the workload, but in time they expanded their program and eliminated the outside consultants.

“We have 17 bridge inspection teams sprinkled around the state inspecting those bridges on a day-to-day basis,” said Seger. “Periodically [every four to six weeks], we’ll send each of our teams, via our regional bridge inspection supervisory staff, a list of bridges that are coming due for inspection.”

Another helpful technique for keeping bridge inspections on schedule is keeping a database of the inspection schedule on the headquarters computer and having the computer send reminders to the staff.

Electronic eyes

TDOT maintains a computerized database of inspection findings as well as the inspection schedule. Inspectors can record their findings in the field either on paper or on a laptop computer. Then they transmit the information to TDOT’s headquarters electronically from their office.

The headquarters staff also evaluates the inspection reports that come in from the field. They keep an eye on what is happening.

“We keep in close contact with our regional bridge inspection supervisory staff as well as with our bridge inspection teams themselves,” said Seger. The state is broken up into four major regions, each with several bridge inspection teams. Each team has seven members.

The quality of Tennessee’s bridges has improved under its current inspection, repair and replacement program. With a solid inspection regime to identify bridges that need help, the repair and replacement program can be better targeted.

“Since about 1990 we’ve had a very aggressive bridge repair program,” said Seger. “For example, this year our funding for that program is $36.2 million, which will be able to touch about 69 bridges.”

A more targeted bridge replacement program helps too.

“With the replacement program that we’ve had over the years, which has also been very aggressive, we’ve been able to reduce the number of deficient bridges,” said Seger.

The state currently has 339 (4.2%) state-maintained bridges that are structurally deficient and 832 (7.3%) non-state-maintained bridges that are structurally deficient. As far as functional obsolescence, Seger said, Tennessee has 1,211 bridges on the state system and 1,701 bridges on the local level that are obsolete.

Structural deficiencies result primarily from deteriorated conditions on the primary components of a bridge. These structures typically require significant maintenance and repair to remain in service. The fact that a bridge is deficient does not immediately imply that it is likely to collapse or that it is unsafe. With hands-on inspection, unsafe conditions may be identified and, if the bridge is determined to be unsafe, the structure must be closed.

A functionally obsolete bridge generally is one that no longer meets current geometric and structural standards for the highway on which it is located.

Seger’s main worry is that Congress will cut federal funding, which makes up about 80% of Tennessee’s bridge rehabilitation and replacement funding.

The main challenges that face Tennessee’s bridges are the same as in other states, mostly freeze-thaw cycles and traffic volume that grows faster than all predictions.

The tools Tennessee uses to inspect its bridges also are mostly the same as in other states.

Inspection tools

“The tools and techniques are really described in the National Bridge Inspection Standards,” said Seger. “Nondestructive testing—we primarily use dye penetrant tests on areas where we may find cracks in steel and so forth. The normal inspection tools that one may use would include hammer, tape measure, putty knife, scraper to remove the corrosion.”

The state currently has a fleet of nine under-bridge inspection units including the recent addition of four new ones. Four old ones will be phased out, leaving five in the fleet.

“We do some ultrasonic inspection,” said Seger. The state has a program called Bridge Watch to monitor scour of bridge piers in water. “We’ve identified around 900 bridges in Tennessee as being scour susceptible.” The program monitors conditions such as weather and water surface elevations. “It will send out an alert based on a threshold value that we set to alert the inspector on rising waters or potential flood conditions. Then we discharge that inspector to the bridge to ensure its safety. That’s a relatively new technology.”

Luckily, Tennessee has no elaborate, ostentatious bridges. It has no Golden Gate or Tacoma Narrows or any other suspension or cable-stayed bridge. The vast majority of bridges in Tennessee are straightforward in design and relatively accessible for inspection. They range from as short as 20 ft to several longer than 1,000 ft.

The state has a total of 19,560 bridges to inspect on the National Highway System or on local systems, the most of any of the states with perfect on-time inspection records. Georgia inspects 14,303 bridges every 24 months. Nevada is responsible for inspecting 1,636 bridges, and Delaware inspects 841 bridges every two years. Tennessee ranks 10th among U.S. states in most bridges.

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