Rushing to Repair Fire Damage to a Key Pittsburgh Bridge
Contractor and state say they are working to fix truss cord now out of alignment
General contractor Joseph B. Fay Co. and the Pennsylvania Dept. of Transportation say they are working around the clock to repair the fire-damaged Liberty Bridge in Pittsburgh, where a Sept. 2 blaze sparked by a welder’s torch damaged about 30 feet of a compression cord on the deck truss.
The fix needed for this key component of Pittsburgh's urban infrastructure involves installing jacking brackets and struts.
The fire began when a welder’s torch ignited tarps and plastic pipe being stored for the project, shutting the bridge beginning at about 1:30 p.m. Sept 2.
The fire broke out and was concentrated near the center of the span, where the heat caused a lower cord truss to go out of alignment by six inches, said H. Daniel Cessna, district executive for PennDOT Engineering District 11-0. Because of its central location, there is a lot of load going to the damaged structural member.
Carrying a main artery feeding downtown Pittsburgh, the Liberty Bridge is an 88-year-old steel cantilever structure leading to the Liberty Tunnels, both of which opened up Pittsburgh’s South Hills for development. The 2,663-foot-long bridge has a main span length of 470 feet and a water clearance height of 60 feet. About 55,000 vehicles cross it each day.
Although contractors and PennDOT had hoped to open the span earlier, the bridge likely will remain closed through the week.
“Due to the complexity of fabricating 150 repair parts, the contractor needs to extend the initial time projected to complete the repair,” said Cessna. “Due to the complexity of installing the repair parts, all bolt holes will be drilled onsite, rather than at a fabrication shop.”
But repair parts are being fabricated off site, PennDOT officials saiid, and must arrive before onsite installation and jacking operations can begin.
Joseph B. Fay Co., based in Tarentum, Pa., is facing $213,000 per day in liquidated damages since the fire closed the bridge.
A communications firm representing Joseph B. Fay Co. released a statement Sept. 13 emphasizing that safety is a primary concern during the repair work. The company's goal is "having the design thoroughly reviewed to be the right solution, and ultimately returning the bridge to service as quickly as possible after the unfortunate incident that led to its closing," according to the statement.
The repair is a “temporary fix that could last indefinitely,” Cessna said. It involves placement of a bracket system that is tied into the undamaged steel, beyond the fire-damaged strut.
“We’ll jack the bridge with 400-ton jacks to attempt to put the loading back where it should be,” Cessna said, adding that the task is being engineered with the help of readings from 12 strain gauges, and 3D modeling.
Joseph B. Fay Co. began work last year on an $80-million contract for full rehabilitation of the Liberty Bridge, with a target completion in early 2018. The work includes structural steel repairs, painting and deck replacement. The most-recent rehab was in 1982.
The contractor has many other projects, including renovation of the Birmingham Bridge, linking downtown to the South Side.