ST. PETERSBURG - It is a building design that draws mention across this country and several in Europe: a skinny, wavy triangle of a structure reaching 366 feet into the air with walls of glass and a "garden park in the sky."
Signature Place, a $125-million condominium tower planned for downtown, promises to be true to its name. But can such a design, which looks fragile and shimmering in drawings, withstand violent storms?
The death and destruction from Hurricane Katrina graphically illustrate just how vulnerable structures can be in the face of raging wind and water.
How do designers and engineers make a special building such as Signature Place - 35 stories high with 221 units - strong enough?
It has to do with location, foundation, materials, testing, reinforcements during construction and stricter building codes.
The location
The complex will be built on a block near St. Petersburg's waterfront where the former Cramer Federal Building stands. It has had several names. From Cramer it became BayView Tower as an office building. Then it was named Peninsula when developer Joel A. Cantor first decided to bring residential units into the mixed-use complex. After the unusual design was adopted, Signature Place became the name.
Even though the water is close, the building is 14 feet above sea level and not in a flood zone.
"The federal government doesn't build in flood zones," said Cantor, president and chief executive officer for the company building the tower. He said the location stands a chance of flooding once every 1,000 years.
The foundation
A high-rise must have a strong foundation. For Signature Place the starting point was finding solid ground. Boring tests already have been done; rock was found 105 feet down, said Cantor.
"We are using 100 5-foot diameter caissons that will be drilled into the site," said Mark L. Lutz, an architect with Perkins+Will, the international firm creating Signature Place. Caissons are made of concrete. They form a "foundation that is like fingers in the ground that will not wash out in a storm surge."
The tests
A model of the building and surrounding buildings in St. Petersburg will be put through wind tunnel tests in Colorado. Cantor said those tests are not required by building code.
"They make a clay model and put it on a turntable," and subject it to different speeds of wind, Cantor said. The tests will uncover the weak points.
"We will have to beef up some areas, and they may say we have too much strength in some area. A wall designed to be four feet thick ... can be three," Cantor said.
Tall buildings move slightly in high winds. But the object is to limit the movement, said Joe Ales, a principal in Walter P. Moore & Associates, the structural engineering firm in Tampa working on the project. Wind tunnel tests will tell designers where shear walls of concrete must be added to steady the structure.
"We don't want people living on the 34th or 36th floors getting seasick," Lutz said. Ales said the same.
The materials
In the drawings, Signature Place may look like nothing more than glass and aluminum. It is more.
"The building is cast-in-place concrete," said Ales.
As for all of the glass, it will be designed after the wind tunnel tests, said Ales.
"Whoever supplies the glass, we have an engineer who will design the glass. He will use the wind pressure to design the glass."
Lutz said plans call for windows to be made of two quarter-inch panes of glass with a laminate in the middle. That helps keep out noise as well as withstand wind.
Different portions of Signature Place will have to withstand impacts of regular items that might be turned into missiles by the wind. A glazing product will be applied from ground level to 30 feet up on the building to withstand large missile impact, said Lutz.
A 2-foot by 4-foot piece of wood will be ejected out of a cannon-like device to see how strong the exterior and glass are.
Above 30 feet, the glazing protects against small missile impact.
"Commercial structures, such as this, even though it has a residential component, will handle the wind loading on the structure better than a single family residence designed in the '70s," said Lutz.
Strict building codes
Hurricane Andrew, which devastated South Florida in 1992, prompted stricter building codes, including elements such as the impact resistance.
"A lot of hurricane impact issues were injected (into the building codes) for obvious reasons," said Lutz. "The state knew it had to put pressure on all builders. The state says you will do this, this, this and this. You do it or you will not build."
* * *
Construction cannot begin on Signature Place until the old federal building is torn down. That should start toward the end of the year. It will take seven weeks to tear down the building, by dropping a wrecking ball on the top of it, and to clear the site.
Once construction begins, the first units will be ready to be occupied in 14 months, Cantor said. Those will be the office condominiums and less expensive residential lofts above the offices and parking. Once those are finished, construction of the tower will take another 16 months.
The tower will have 179 units and 42 lofts. Prices range from $350,000 to $7-million. Cantor said last week he already had more than 2,600 people on a list, saying they are interested in buying a unit at Signature Place.
