Engineers will need at least two weeks to get a handle on the repairs needed to fix a heavily traveled bridge between Pennsylvania and New Jersey after one of its support beams fractured cleanly into two pieces — a highly unusual event that had some experts suspecting a flawed, six-decade-old weld.
The Delaware River Bridge, which connects the Pennsylvania and New Jersey turnpikes, was closed indefinitely after workers discovered the broken steel truss last week. Tens of thousands of motorists were told to expect "extreme delays."
Heavy traffic was reported at other river crossings in the area Monday, with one span reporting backups of up to 6 miles.
Photos posted on the Pennsylvania Turnpike Commission's website showed a massive I-beam under the bridge's westbound lanes sheared in half. Officials believe the 14-inch truss failed recently and suddenly.
"It's incredibly unusual for steel to break like that," said Joe Martin, an engineering professor at Drexel University in Philadelphia. "Pieces don't break. They stretch, they twist, they give you some warning to get out of there. ... Fractures are the bridge engineer's nightmare."
Karl Frank, professor emeritus of engineering at the University of Texas at Austin, told The Philadelphia Inquirer he suspects holes were mistakenly drilled into the beam during construction and were filled with plug welds.
Martin agreed with Frank's assessment, adding: "We would never allow that today."
Lehigh University scientists are analyzing a piece of the fractured beam to help determine the cause of the failure. Pennsylvania Turnpike Commission spokesman Carl DeFebo said that in addition to the suspected welds, experts are looking at a range of possible causes, including a flaw in materials or design.
Work is underway to stabilize the bridge, which sunk slightly. Crews have installed steel plates to brace the fractured beam and will be jacking the bridge back to its original position. The bridge will rest on eight temporary towers.
The span, which opened in 1956, carries more than 42,000 vehicles per day over the Delaware River.
With the bridge out of commission, transportation officials are urging commuters to carpool or consider working from home, changing their work hours or using public transit.
"All of that volume is going to need to be absorbed by the adjacent bridges if everyone makes the decision to get in their car," DeFebo said.