The good news is that the vital, 55,000-vehicle-a-day bridge spanning the
"I can't tell you for sure [when a collapse might have occurred], I just know it was very tight," said PennDOT district bridge engineer
He said temperatures exceeded 1,200 degrees from the fire that occurred early Friday afternoon. He said it was due to errant sparks from a welder's torch that ignited plastic piping, which then lit afire a tarp draping the bridge during its two-year,
It took firefighters a half-hour or less to extinguish the blaze, but it already had severely damaged a 30-foot-long steel beam -- a compression cord of the deck truss that is essential for the 88-year-old bridge's support. The fire shortened the beam and put it 6 inches out of place, putting added pressure on all of the other cords supporting the bridge,
"It buckled and moved over" in an S shape instead of straight, he said. "The effect of that is when you don't have a steel member like that that's straight, the forces [stabilizing the bridge] don't go through that member correctly the way it was designed, so [they] ended up going through other parts of the bridge. ... The worst-case scenario was the whole section could fall."
When asked how much would fall,
When the fire occurred, dozens of workers were engaged in various work on the bridge and three lanes of vehicular traffic were open. Officials said the bridge was quickly closed to traffic -- as has been the case since then -- and construction and emergency vehicles also were removed from it, as the span should be avoiding any weight until repairs are made.
He said they developed a plan that involves installing a plate over the damaged section and creating a strut to allow installation of a new beam on both sides of the weakened cord. "We will ultimately be jacking the bridge to redistribute that load correctly back off of that damaged support,"
Officials will determine later if that technique will be sufficient for the long term or if a more permanent repair is needed.
"That's a decision we will deal with down the road -- our goal right now is getting the bridge reopened," with next Monday's morning rush hour the goal, he said.
Until then, the bridge will have to be continuously monitored for safety, he said. The concern is such that repair materials and equipment are to be delivered to the bridge by a crane anchored some 30 feet below in the
In the meantime,
"We really want to stress to motorists to plan ahead for additional travel time, because honestly, we can't assess that impact," he said.
Posted detours will encourage use of the
Off-duty police are to be stationed to assist traffic flow during the detours.
He also said a review will be done of how the fire started from the welding on the bridge -- workers were cutting and removing an I-beam from the bridge deck as part of the ongoing reconstruction -- in order to try to prevent any similar incidents.
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