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Safety measures delay opening of Liberty Bridge

| Friday, Sept. 16, 2016, 11:18 a.m.
A construction barge sits under the Liberty Bridge, Tuesday, September 13, 2016, lifting replacement parts to crews working to repair damage from the Sept. 2 fire.
Andrew Russell | Tribune-Review
A construction barge sits under the Liberty Bridge, Tuesday, September 13, 2016, lifting replacement parts to crews working to repair damage from the Sept. 2 fire.
PennDOT District 11 Executive Dan Cessna discusses Liberty Bridge repairs on Friday. The damaged bridge in the photo’s background has been closed since a fire on Sept. 2.
PennDOT District 11 Executive Dan Cessna discusses Liberty Bridge repairs on Friday. The damaged bridge in the photo’s background has been closed since a fire on Sept. 2.

The fire-damaged Liberty Bridge in Pittsburgh could remain closed for weeks as engineers and officials work to avoid a potential bridge collapse and other possible safety problems during a complex and delicate repair process.

The bridge shut to traffic after a Sept. 2 fire damaged and warped 30 feet of a deck truss compression chord. PennDOT officials are working to repair the bridge through a process that involves heating and straightening the damaged chord, but no one knows how the chord will react to heat.

PennDOT District 11 Executive Dan Cessna described the repair process as "complicated" and requiring "diligent and thorough analysis" to prevent a collapse and to ensure worker safety, even in the event of issues less serious than a collapse.

"This is a very twisted and mangled chord we're dealing with," he said. "As you start to apply heat and force to straighten it, you don't know exactly where that twisting and mangling is going to react."

PennDOT officials had hoped to reopen the vital Monongahela River crossing that links the south suburbs to Downtown this coming Monday, but on Friday they delayed that plan after they decided to install an external bracing system around the damaged area as an additional safety precaution.

Cessna said the bridge could remain closed for weeks, and said the repair timeline won't become more clear until the additional brace is in place and the "methodical and slow" heat-straightening process begins.

That process involves crews heating the damaged chord with torches reaching temperatures between 400 and 500 degrees. They'll then try to bend and straighten the steel back to its original shape, Cessna said. If that works, a jack requiring a minimum of 2 million pounds of force can than be used to physically move the bridge between 1 and 2 inches to redistribute its load.

The jack will move the bridge in slow increments of about 1/8th of an inch while engineers read gauges attached to the structure and monitor whether the repair requires real-time adjustments, Cessna said.

If the chord is successfully repaired, crews will then attach new steel on top of it, he said. Officials have also developed a backup repair plan that, if necessary, will involve cutting the damaged chord.

Cessna added officials believe this marks the first time a structure such as the Liberty Bridge has been damaged in such a way.

"That is why we brought in additional experts," he said. "Safety is paramount. It's why we're not rushing the process."

The fire started while contractor Joseph B. Fay Co. of West Deer worked on an $80-million bridge rehabilitation project that's expected to stretch into the 2017 construction season.

Cessna said PennDOT is working with Fay to determine how the fire and subsequent repair will affect the greater rehabilitation project's timeline. An additional permanent repair will be required after the initial fix, but that work can occur while traffic uses the bridge.

About 55,000 vehicle depend on Liberty Bridge each day. Since its closure, motorists have reported traffic congestion and backups along alternative routes, including the Fort Pitt Bridge and Tunnel and the West End Bridge.

Fay is ultimately responsible for all repair costs associated with the project, and is being financially penalized during the closure based on provisions of its contract with PennDOT.

The contract assesses an $8,400 penalty for each hour the bridge is out of service beyond scheduled closures. It also assesses a $12,000-per-day fine for unscheduled closures of the ramp linking the bridge and the Boulevard of the Allies.

Fay Executive Vice President Jim Wilkinson said in a statement that the company is "investing considerable resources in outside experts and other assets to ensure that the repair is completed safely and swiftly."

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