A construction flaw more than two decades old caused the May collapse of part of a SouthPark area parking deck, according to a report from an engineering firm released Wednesday.
The four-story deck at 6100 Fairview Road was designed so its concrete columns and beams could move slightly as the structure expanded and contracted when the temperature changed.
But the structure didn't move as it should have.
The problem, according to the report, was that a steel slot used to hold pieces of the deck together was sloppily made in the field during construction, rather than in a steel fabricator's shop. The rough cut of the steel “didn't allow the bolts to slide freely,” according to the report.
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“It put excessive stress on the bolt,” said Thomas Koning, a senior vice president at Zapata, the Charlotte engineering firm hired to determine why the deck failed.
Two of four bolts connecting a beam to a column were damaged, leading to the early-morning May 13 collapse.
Another problem, according to the report, was that a portion of the horizontal beam supporting the floor was inadequately welded to the columns.
The collapse started on the fourth floor, sending tons of concrete crashing through the third floor. No one was hurt.
The deck is still closed. Koning said his firm has examined the rest of the deck and has identified ways to strengthen it before it reopens.
The office building's manager, CB Richard Ellis, hired Zapata. A spokeswoman couldn't be reached for comment Wednesday night.
It's unclear whether the flaw is in other decks in Mecklenburg. It's also unknown whether inspectors could have seen the flaw when they inspected the building before it opened.
The contractor for the deck was Metric Constructors, according to a 1986 article in The Charlotte Observer.
Mecklenburg building officials inspected the deck when it opened in 1987. And while commercial buildings are regularly inspected for fire safety, state law doesn't allow counties to make regular inspections in buildings to look for structural flaws.
The original inspections records on the deck have been destroyed, county officials have said. The state doesn't require counties to maintain records longer than six years.
Bobbie Shields, Mecklenburg general manager, said in May that county inspectors might examine other decks if they believe the problems at the 6100 Fairview Road deck are widespread.
Jim Bartl, director of Mecklenburg code enforcement, said Wednesday night he hadn't seen the Zapata report yet and couldn't comment.