"Fracture Critical" Bridges Require State's Special Attention

4:53 PM, Oct 26, 2011   |    comments
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Sherlock Hollow bridge closed in Hinsdale

By JOSEPH SPECTOR

Albany Bureau Chief

ALBANY -- Nearly 1,100 bridges in New York are deemed "fracture critical," records show, and are subjected to a high level of scrutiny to ensure their safety.

A fracture-critical bridge is an engineering term defined as lacking "redundant supporting elements," meaning if a key support fails, the integrity of the whole bridge could fail and potentially collapse.

The state Department of Transportation said the bridges are properly inspected and maintained and pose no danger.

"The term 'fracture critical' which is an industry-standard term, should not be confused with the mistaken notion that a bridge is unsafe," state DOT spokesman Bill Reynolds said in a statement. "If a bridge is unsafe, we close it."

The bridges on the DOT list are the most traveled in the state, including the major New York City-area bridges -- the Brooklyn Bridge, the George Washington Bridge, the Whitestone Bridge and the Tappan Zee Bridge.

Also on the list are the Bear Mountain and Newburgh-Beacon bridges and the major bridges in western New York, including the Frederick Douglass-Susan B. Anthony Bridge that leads into downtown Rochester and the Peace Bridge between Buffalo and Canada.

Experts said fracture-critical bridges may have an alarming name, but they are structurally sound as long as proper inspections and maintenance are undertaken. At a time when infrastructure funding is being debated in Washington and Albany, the oversight of the fracture-critical bridges shouldn't be overlooked, experts warned.

"That's the challenge with these bridges. They are safe as long as they have extraordinary maintenance and attention paid to them," said Thomas Fisher, dean of the College of Design at the University of Minnesota who has studied fracture-critical bridges and is writing a book on them. "They work fine if everything works perfectly."

Because of their unique design, fracture-critical bridges have added inspection requirements. Like all bridges in New York, they have to be inspected every two years, but they require engineers to get within two to three feet of the bridge's major components to do a hands-on inspection.

The state's records showed that all the fracture-critical bridges were inspected since 2009.

"They are subjected to a more stringent inspection -- where the inspectors actually have to get within arms reach, where they essentially put their hands on the parts," said Jennifer Post, a DOT spokeswoman.

There are about 18,000 fracture-critical bridges in the country, according to the Federal Highway Administration, or about 3 percent of the nation's 600,000 bridges.

New York has roughly 17,300 bridges, so the fracture-critical bridges represent less about 6 percent of the state's inventory.

Still, they provide another challenge to a state bridge system that is aging, an ongoing series by Gannett's Albany Bureau has found.

About 36 percent of the state's bridges have a condition rating under 5 -- the threshold that requires repair, Gannett's review found. A similar percentage had been deemed either structurally deficient or functionally obsolete.

The state Comptroller's Office estimates New York needs $250 billion to maintain its transportation, sewer and water systems over the next 20 years. About $80 billion is unfunded.

Fracture-critical bridges in New York are on average about 60 years old, and most bridges have a usefulness of about 50 years. Overall, bridges in New York were built on average in 1965.

Many of the fracture-critical bridges were built around World War II as a less expensive method that lack redundancy in the design, which would provide more support for a bridge. It could mean that if one segment of the bridge falters, the whole bridge could be imperiled.

"If one of the elements fail, there's a chance for a serious collapse," said city of Rochester engineer Jim McIntosh.

The fracture-critical bridges are built often over long waterways, such as the Hudson or Niagara rivers or railroad tracks, and many times in places with little clearance between the bridges and surface below - such as bridges with trusses, arches and suspensions.

Asked about the Peace Bridge, which has long been eyed for replacement, Sen. Charles Schumer said it's one of many bridges in New York that need rehabilitation. He and other Democrats have been pushing for an infrastructure bank to borrow money to fund road repairs.

"There are hundreds of bridges in the same kind of condition as the Peace Bridge in New York state," Schumer said. "They had good construction, they were solidly built, but they are old and have had a lot of wear and tear and they have to be upgraded and rehabbed."

The city of Rochester finished a roughly $9 million project in 2009 to repair the Smith Street Bridge, a fracture-critical bridge over the Genesee River. In 2006, the state replaced the Douglass-Anthony Bridge, changing it from an eight-span bridge to a three-member steel arch structure 433 feet long that crosses the Genesee and has become a fixture of the city's landscape.

McIntosh said the city has its own set of engineers who, along with state inspectors, regularly inspect the bridges.

The Exchange Street bridge in downtown Binghamton is a fracture-critical bridge that is expected to undergo a roughly $1 million rehabilitation next year. The bridge was built in 1901 and had a rating of 4.17 when it was last inspected in September 2010, records show.

Because of the sensitive nature of the bridge, it's unclear whether the entire bridge will need to be closed during the repairs, said city engineer Philip Krey.

"Fracture critical is really just like a category or a classification of the bridge. If you were going to do work on the bridge, it may be more difficult," he said.

Orleans County, with a number of bridges straddling the Erie Canal, leads the state in the percentage of fracture-critical bridges, with 28 of its 138 bridges, or 20 percent listed in that category, records show.

Gerald Gray, the county's highway superintendent, said the county is undertaking an inventory of the bridges it owns, saying many factors go into a bridge's condition.

"There's a lot of thought and more than just an inspection into what makes a road or a bridge critical," he said.

Outside New York City, Erie and Westchester counties ranked first and second for the most fracture-critical bridges in the state, with 50 and 41 each, respectively. But those counties have the most bridges in the state, and the fracture-critical ones represent about 5 percent of them.

Fracture-critical bridges often raise concern because some of the worst bridge collapses in U.S. history happened on them: the 2007 collapse of the I-35W bridge near downtown Minneapolis was one.

Robert Connor, an associate professor of civil engineering at Purdue University, said the Minneapolis collapse was one of perhaps three major collapses involving fracture-critical bridges in modern times. In most cases, problems occur because of inspection difficulties or weak design.

The Minneapolis bridge collapse, which caused 13 deaths and led to stronger inspection laws, resulted mainly from a design flaw of undersized gusset plates in the steel-deck truss bridge's span.

In a national study a few years ago, Connor and his colleagues found that fracture-critical bridges, despite the fears about them, perform well overall. He is now studying how to effectively repair and build new fracture-critical bridges.

"The performance of those types of bridges has been excellent," Connor said. "So we worry about it, but I think part of the reason it has been excellent is because we do take this care to look at them a little closer."

JSPECTOR@gannett.com

Includes reporting by Journal News staff writer Tim Henderson and WGRZ reporter Claudine Ewing.

Findings

-- The state has roughly 17,300 bridges and 1,096 of them, about 6 percent, are deemed "fracture critical," which means they do not contain redundant supporting elements. So if a key supports fail, the bridge would be in danger of collapse.

-- The state Department of Transportation said "fracture critical" bridges are inspected every two years like all bridges, but must include a "hands-on" inspection within arm's length of the major bridge components.

-- The average fracture-critical bridge was built in 1940, compared to an average of 1965 for all the state's bridges.

-- About 20 percent of Orleans County's bridges were deemed fracture-critical, the most in the state. Outside New York City, Erie and Westchester counties had the most fracture-critical bridges, and represented about 5 percent of their inventory.


About this series

New York has more than $80 billion in unfunded needs to repair its infrastructure over the next 20 years, but no long-term plan to pay for it. In an ongoing series, Gannett's Albany Bureau will look at the state's troubled infrastructure, where the money to fund projects goes and what changes are needed.

 

Gannett Albany

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