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Damage May Be 'Tip Of The Iceberg'

Calling the situation "the tip of the iceberg," the engineer who sounded the alarm to evacuate the 18-story Brickell Harbour condominium along Miami's Biscayne Bay strongly suspects the building is not the only one in the area with destressed post-tensioning cables in concrete slabs. But in an effort to prevent panic, building officials are awaiting the engineer's damage report, due by April, before taking any other action.

"We're going to see more of these [buildings]," says John Pepper, a principal of The Pepper Engineering Group, Miami. He attributes the problem to the building's age, the poor state of knowledge of post-tensioning in harsh environments in the late-1970s and the way the 168-unit condo was built.

"This could be an isolated incident," says Hector Lima, director of the City of Miami Building Dept. "We're waiting for [Pepper's] damage assessment before beginning any inspections of other [similar] buildings."

Both the report on the 168-unit building and the critical repairs are likely to be completed by April. Minor repairs will continue after residents move back in. "This is a very serious matter [but] the building is reparable," says Pepper.

The 6.5-in.-thick concrete slab of the 204.6 x 74-ft footprint has bands of unbonded tendons—beams within the slabs—in the long direction, and uniform tendons in the short direction. The building contains 3,000 tendons.

While doing remedial work on the 12th floor relating to cracking and corrosion of anchor bars behind post-tensioning anchors, Pepper found three of six tendons in a single band destressed. In another band, he found six of 10 tendons destressed. "The primary problem is with the band lines" on the south end facing the bay, says Pepper. The harsh environment infiltrated the tendon anchors, which are not encapsulated with plastic epoxy.

Pepper informed the Building Dept. March 3 that "the building is currently unsafe for occupancy until repaired." The conclusion was based on the percentage of tendons destressed, review of drawings from Atlas Prestress (now defunct) and analysis of load-bearing capacity. Residents were evacuated that day.

The Ft. Lauderdale office of Structural Preservation Systems has installed steel shoring and is doing remedial work to "modern" standards, says Pepper.

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