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 tendonsbeams
within the slabsin 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.