By DONNA KENNY KIRWAN

PAWTUCKET — Do the Jersey barriers installed to keep traffic away from the weakest sections of the Pawtucket River Bridge on I-95 pose a weight hazard of their own? That’s a question that has been raised by several callers to The Times recently.

Soon after implementing the weight limit on the 50-year-old twin bridge spans, the state Department of Transportation had installed poles with orange paddle-like devices that  were designed  keep vehicles out of the shoulders of the bridge spans where there was the most corrosion. However, in around mid-June, those poles were replaced with cement Jersey barriers.
Charles St. Martin, a spokesman for DOT, acknowledged that the office has had several inquires about the matter as well, but said the Jersey barriers do not pose any kind of a safety hazard to the deteriorating bridge structures.
St. Martin said that the paddle devices are designed so that a vehicle can break through to the highway shoulder in an emergency situation. However, with greater concern over the bridges’ condition, DOT officials decided that a more definitive barrier was needed, so the concrete Jersey barriers were brought in. “This keeps traffic in the center part of the bridge, where it is strongest,” he stated. He added that motorists had struck the traffic poles with the paddles on numerous occasions.
St. Martin said, however, that the Jersey barriers have been strategically placed on top of the two large main beams that support the strongest parts of the bridges. He said the weight is a “static load” that is evenly distributed on the bridge, as opposed to a “wide load” or a “moving load,” such as is created by a heavy tractor trailer truck riding over the span.
“The Jersey barriers are heavy, but the pounds per square inch are well within the tolerance that the bridge can handle,” said St. Martin. He added that a heavy tractor trailor truck rolling on tires over the bridge places a lot more weight on the spans, especially when speed and other factors are considered.
“This has been done in many other places,” said St. Martin. He said that last August’s deadly bridge collapse in Minneapolis, which prompted some of the inquiries, was of a design that involved a lot of trussing and was
found to have had sub-standard concrete and other conditions that contributed to its weakness. “Many things are different about it,” he said, of the Pawtucket River Bridge.
According to a New York Times article from Jan. 15, investigators found that the 40-year-old bridge on Interstate 35 W in Minneapolis had a design flaw in that a “gusset plate” was too thin to serve as a proper junction for several girders. Since its construction in the mid-1960s, more weight had been added to the bridge from concrete structures that were built to separate traffic lanes.
At the time of the Aug. 1, 2008 collapse, in which 13 people perished, crews had brought tons of equipment and material onto the bridge deck for a repair job, according to the news article.
Last November, a weight limit was placed on the two bridge spans that carry I-95 acros the Pawtucket River after bridge inspectors noticed deterioration in the structural supports. Trucks weighing more than 22 tons, and later, 18 tons, have been ordered to take a detour from I-95 between exits 27 and 28. The weight limits will remain in effect until the bridge is repaired. Work is expected to begin sometime in the summer of 2009, according to DOT officials.
If any motorists have further questions or concerns about the bridge’s safety, they can call the DOT’s customer service line during regular business hours at 222-2450, said St. Martin.