Liberty Bridge to be closed to all traffic next week due to fire damage

Sept. 05--The bad news is that the Liberty Bridge will be closed to all traffic for at least the next week as a result of fire damage Friday to a steel beam critical to the bridge's stability.

The good news is that the vital, 55,000-vehicle-a-day bridge spanning the Monongahela River didn't collapse Friday. That catastrophe may have been minutes away from occurring if the fire had not been quickly extinguished to prevent further damage, PennDOT officials said at a news conference Sunday.

"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 Lou Ruzzi. "I can't tell you if it was 10 minutes, 15 minutes ... definitely less than 30 minutes."

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, $80 million renovation project.

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, Mr. Ruzzi said.

"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, Mr. Ruzzi responded, "Most of the bridge," maybe 2,000 feet of the 2,600-foot span.

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.

Dan Cessna, PennDOT district executive for the Pittsburgh region, said department officials have been working since Friday with bridge contractor Joseph B. Fay Co., industry engineering consultants and academic experts from Carnegie Mellon and Lehigh universities to identify the best temporary repair that is both quick and safe to enable use of the bridge.

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," Mr. Cessna said.

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 Monongahela River rather than construction trucks.

In the meantime, Mr. Cessna is expecting a rather calamitous Tuesday morning rush hour, and perhaps many rush hours thereafter, even if they represent nothing so disastrous as a bridge collapse. He said officials are unaware of any time in its history that the Liberty Bridge has been completely closed to traffic on a weekday, even during its latest major rehabilitation in the 1980s.

"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 Parkway West's Banksville Road exit and Fort Pitt bridge and tunnel, though that bridge already carries nearly twice as much daily traffic as the Liberty Bridge. Some motorists going between the South Hills and Downtown or Oakland may also opt for the Birmingham Bridge, traveled by about 20,000 cars a day, but it is also presently undergoing repairs that restrict lanes. The 10th Street Bridge also connects the South Side with the Golden Triangle.

Mr. Cessna said the Liberty Tunnel is to be reopened Tuesday morning for inbound access to the South Side by McArdle Roadway. Outbound traffic on McArdle is also able to use the tunnel.

Off-duty police are to be stationed to assist traffic flow during the detours.

Mr. Cessna said the costs of the bridge repairs are expected to be covered by the Joseph B. Fay firm's insurance company rather than taxpayers, and the repair work is not likely to cause any serious delay in the two-year rehabilitation project beyond this week.

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.

Gary Rotstein: [email protected] or 412-263-1255.

___

(c)2016 the Pittsburgh Post-Gazette

Visit the Pittsburgh Post-Gazette at www.post-gazette.com

Distributed by Tribune Content Agency, LLC.