| | Associated Press
CONCORD, N.C. -- The inquiry into why a footbridge at Lowe's
Motor Speedway collapsed onto a highway, injuring 107 people, will
be in the hands of the track's operators.
Because the speedway owns the walkway, no official agency is
overseeing the investigation and the track will use its own
engineers to determine what went wrong.
|  | | Aid workers treated injured race fans on the highway after the pedestrian bridge collapsed. |
"It's up to them to hire inspectors and to figure out what
happened, just as it was up to them to remove the debris from the
highway," said Don Idol, an assistant bridge inspection engineer
with the state Transportation Department. "It's their bridge."
Nick Graf, division administrator in Raleigh for the Federal
Highway Administration, said Monday that his agency is looking into
the collapse, even though neither his agency nor the state has
authority over the pedestrian walkway.
An 80-foot section of the 320-foot bridge collapsed late
Saturday as spectators walked from the speedway to a parking lot.
The bridge crashed 17 feet onto U.S. Highway 29 below as fans
left The Winston, NASCAR's all-star race. Forty-eight people were
still hospitalized Monday evening. One patient remained in critical
condition early Tuesday.
Investigators have so far blamed corrosion for weakening the
span's steel supports. A second footbridge was closed indefinitely
Monday after a rust spot was discovered. The walkways, 500 yards
apart, are five years old or less.
The fallen bridge was built of pre-stressed concrete, a
technique in which wet concrete is poured around stretched steel
cables to make slabs. After the slabs dry, the tension on the
cables is released and that strengthens the concrete.
All 11 cables buried in the concrete were corroded, and that
caused the bridge to bow and then snap, said Don Goins, the state's
chief engineer, who was at the accident site Sunday and Monday.
The collapsed walkway bristled with rusted, half-inch steel
cables, which wouldn't have been visible when it was intact, Idol
said. Several 3-foot cracks are visible beneath the three remaining
spans of the ruined bridge, another sign of possible corrosion, he
said.
"The cracks were going in the wrong direction to have been
caused by weight or anything hitting the bridge," Idol said. "It
had to be corrosion, but I've never seen anything like this before,
especially in a five-year-old bridge. A bridge like this usually
has a lifespan of 50-plus years before you see corrosion."
Federal highway bridges and North Carolina state pedestrian and
highway bridges are inspected every two years, but the speedway was
under no inspection timetable.
Track officials have been unable to say when the bridge was last
inspected. Speedway president Humpy Wheeler said two staff civil
engineers and project managers "are constantly monitoring
everything" at the speedway.
The speedway has retained two outside engineering firms that
specialize in concrete construction and catastrophic failure to
analyze the bridge.
The bridge met state and federal guidelines of supporting 100
pounds per square foot. A 1995 memo from a state engineer to the
state's utilities manager suggested the bridge should be 145 pounds
per square foot because of the heavy foot traffic at the end of a
race.
Speedway officials chose not to fortify the bridge as
recommended.
Goins said it wouldn't have mattered how strong the bridge was
because corroded cables would have caused it to collapse
eventually.
"Obviously, if we have corroded cables, the fact that there is
weight on there is a factor," Wheeler said. "But weight did not
cause the cables to be corroded."
The ruined walkway section was moved late Sunday to another site
at the speedway, where track investigators are examining it. The
rest of the structure remained in place, with a gaping hole over
the southbound lanes of U.S. 29.
| |
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