Georgia bridges subject to new strength tests

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Posted 8:11AM on Monday, July 22, 2002

UNDATED - Georgia bridges will soon undergo required strength tests as a part of a new state law that allows heavier truckloads on state roads. The new law, passed July 1, increases the limit for truck shipments of most types of heavy cargo from 40,000 to 46,000 pounds per tandem (two) axles. "We're in the process of evaluating a whole lot of bridges," said Brian Summers of the Georgia Department of Transportation. "A lot of our bridges that were in the marginal area may now require a (load restriction) posting." Currently, about 2,000 of Georgia's 6,441 state highway bridges have load-limit postings, Summers told The Augusta Chronicle. It's uncertain how many more will be added after the upcoming evaluations, he said. Bridge inspections in Georgia and South Carolina are currently conducted visually. The South Carolina DOT hopes to adopt a new test using stress sensors within six months. Georgia DOT officials say they will study the success of South Carolina's new system, and may adopt a similar plan to test the state's bridges. The testing could someday give officials more accurate data on the strength of bridges and eliminate the need for some of the postings. "That's something that we may be thinking about in the future with the recent changes in the load-limit laws that the Legislature just passed," Summers told the Augusta newspaper. "I'd be interested in seeing any reports South Carolina has on how accurate their tests are." In South Carolina's protocol test, a strain gage - a 1-inch-by-3-inch aluminum stress sensor - is attached to a bridge in several areas, typically on the beams underneath the structure. Information is then sent via a wire to a computer. As a bridge flexes when a vehicle passes over it, the sensor bends and creates an electrical charge. Lee Floyd, a bridge-inspection engineer for the South Carolina DOT, said more accurate bridge inspections could aid the economy and state budgets. "You avoid putting a burden on the local economy that way," he said, adding that companies that receive large shipments by truck could then have access to more bridges.