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HAMILTON COUNTY, OHIO — On Tuesday night of May 20, a flatbed trailer carrying an old 80-ton locomotive broke free from its truck hitch. The trailer drifted forward along the southbound lane of I-275 and crashed into a pier supporting the eastbound I-74 overpass. The 32-year-old steel bridge sagged, but didn't collapse. Eastbound traffic on I-74 traveled over the damaged bridge for about ten minutes before officials arrived to close the bridge and reroute traffic.
According to Brandon Collett, PE, Structures Planning Engineer for the Ohio DOT, the four-span bridge consists of six lines of continuous steel rolled beams with a non-composite, reinforced concrete deck. “Concrete stub abutments along with reinforced cap and column piers support the beams,” he said. “The impact of the locomotive and trailer destroyed two of the three columns. The pier cap failed just north of the third remaining column, dropping the north end of the pier cap more than five feet.”
Collett notes that only one of the six beam lines supported the remaining portion of the pier cap. The other five beams spanned unsupported across from the rear abutment to the next pier. He cited three factors that contributed to sufficiently redistributing the load, preventing collapse:
• continuous redundant steel beams
• steel crossframes spaced at 15 feet
• a reinforced concrete deck |
Collett says that the exterior beam line deflected only about 9.5 inches. “A beam-line analysis by the contractor's engineer showed that more than 20 inches of deflection would have occurred if not for the ability of the redundant bridge design to share load between the beams,” Collett says. “Ohio DOT will replace a few bent crossframe angles, but the steel beams do not appear to have been overstressed and will be left in service once the pier is reconstructed.”
Within three days of the accident, the Ohio DOT constructed and opened a temporary crossover to restore at least one lane of all movements at the interchange. To stabilize the bridge and remove the train, a contractor constructed a temporary pier. A new pier will be reconstructed in the same location as the existing pier. The bridge is expected to reopen within two months of the accident, and cost as much as $600,000.
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