A 250 ft long canopy supported by stay cables will extend from the front of the SkyRise Miami tower. © Arquitectonica
Constructing a 1,000 ft tall observation tower on a jetty in Biscayne Bay, in Miami, Florida, will present significant challenges, including hurricane-force winds.
February 11, 2014—The City of Miami, Florida, is sometimes referred to as “Magic City,” a nickname earned by its rapid growth from a few hundred residents at the time of its incorporation in 1896 to more than 5 million residents by 2006. But soon the city may have another reason for bearing the enchanting moniker: a 1,000 ft tall observation tower that will seem to rise directly from the water.
SkyRise Miami, as the tower is known, is expected to become the new defining landmark on the Miami skyline. The tower will be located on an existing man-made jetty in Biscayne Bay, near Port Miami seaport, the Bayside Market shopping mall, and the American Airlines Arena sports and entertainment venue. The tower will have a distinct curved shape that may recall a large wave, a billfish jumping from the water, a vast fishing net, or, even, a dress flowing over a sensuous form, according to a prepared statement provided by Arquitectonica, an international design firm with an office in Miami and the architect on the project. But, more simply, the tower’s silhouette is intended to reference Miami’s tropical milieu, the statement says.
Jeff Berkowitz, the president and founder of the Miami-based Berkowitz Development Group, is the primary owner of the project through a limited liability corporation. It is anticipated that the tower will become an iconic landmark, joining the ranks of the world’s most famed observation structures, including the Eiffel Tower. But SkyRise Miami will offer more than dramatic views of the surrounding landscape. It will have 16 above-grade levels and a single underground parking level. Four of the above-grade levels will be within the tower’s podium, while the remaining dozen, including a mezzanine and mechanical level, will begin at elevation 650 ft and rise to the top of the structure. In addition to one indoor and two outdoor observation decks, the elevated levels will house such attractions as a “flying” theater—in which the seats will move during the show—a restaurant, a nightclub, a ballroom, and a free-fall type of amusement ride. People will also be able to bungee jump from the tower in a controlled environment that does not include a true free fall.
Constructing the ambitious project on a sliver of land in Biscayne Bay presents myriad challenges. The team responsible for resolving those challenges includes the structural engineer on the project, Magnusson Klemencic Associates, an engineering firm headquartered in Seattle, and the construction contractor, Coastal Tishman, a joint venture between Coastal Construction, a family-owned firm based in Miami, and Tishman Construction, an international construction management firm owned by AECOM. The project is intriguing because it’s “not really a building, and it’s not a spire like most of the other observation towers around the world,” says Ron Klemencic, P.E., S.E., M.ASCE, the chairman and chief executive officer of Magnusson Klemencic Associates. “There isn’t another one in the world, and there probably won’t be another one in the world. It truly is one of a kind.”
SkyRise Miami will be located on an existing man-made jetty in
Biscayne Bay, and will seem to rise out of the water.
The primary challenge of the project is designing the tower to withstand hurricane-force winds. RWDI, a wind-engineering consulting firm headquartered in Guelph, Ontario, Canada, is conducting the wind-tunnel analysis of the project. The first round of testing revealed that the tower moved significantly in the wind, and as a result, the team modified the initial design slightly to incorporate additional porosity into the structure. “We cut some more holes into the structure, and we introduced some reentrant corners on the northeast and northwest corners of the tower,” Klemencic explains. “Those two changes in the architecture settled the tower down substantially, and we actually cut the wind loads in half.”
The wind-tunnel tests also helped determine the materials that will be used in the tower’s structural framing. Rising from large-diameter, deep foundation elements that will descend as much as 150 ft, the tower will be framed in a combination of concrete and steel. It will have a concrete core on its north side and a set of 225 sq ft concrete megacolumns on its south side. The megacolumns will change shape and slope over their height, resulting in a Bézier curve and giving the tower its seductive form. Both the core and the megacolumns will be vertically posttensioned to stabilize the building agaisnt wind loads and overturning forces. “In a tall office building, you have all of the floors, and the weight of those floors actually helps hold the building down. But in this case there are only a few floors, so there is comparatively little weight to hold it down, and so the tower has a lot of tension in it,” Klemencic explains. “We are going to use vertical posttensioning in the megacolumns and in the core to induce vertical compression in the tower to combat the tension forces.”
The team studied a variety of options for tying the megacolumns to the core and initially considered using solid steel bracing elements. But those elements would have been too heavy for the construction cranes to lift. So instead, the team drew from bridge-building technology to develop a design using 6 to 8 ft diameter hollow steel tubes, which will be lifted into place and then filled with concrete. The concrete will then be posttensioned in the same manner as the core and megacolumns. “A big part of high-rise construction is the ability for the cranes to actually lift the components,” says Tom C. Murphy, the executive vice president of Coastal Construction, which plans to use cranes on barges to construct the tower. “Picking up a steel encasement and then filling it with concrete is surely a lot different than having it be all steel and then trying to pick it up with a crane.”
The 1,000 ft tall tower—which will offer viewing decks, interactive
theaters, and even a form of bungee jumping—is expected to
become the new defining marker along the Miami skyline.
A sweeping canopy, measuring approximately 250 ft long and 100 ft wide, will extend out from the megacolumns at the front of the tower. The canopy will be framed in structural steel in order to make it as lightweight as possible. It will be supported by a series of stay cables, which will tie back to the tower. “The canopy is the size of a roof over a football stadium,” Klemencic notes. “First and foremost, it’s meant to really be part of the architectural form, and then secondly, it will act as a shading device for the people who gather at the ground level.”
Both the canopy and the tower’s south facade will be clad in perforated metal panels. The cladding system will extend over the rooftop observation deck for shading from the harsh Miami sun. The team must study the results of wind-tunnel tests to determine the amount of perforation in the panels. “The exact design of the panels is still being sorted out by the architect, but suffice it to say, it’s going to be metal panels that are at least fifty percent porous to allow the wind to pass through and reduce the forces on the tower,” Klemencic says.
The tower’s construction is slated to begin this summer. Building such a large structure on a compact site in the middle of Biscayne Bay and near so many existing attractions requires a great deal of coordination. The contractor team anticipates using cranes on barges along with a temporary trailing deck system that will allow work to occur on multiple levels of the tower at one time, Murphy says. Furthermore, the team is considering wrapping the worksite in a mesh “cocoon” in order to contain construction debris. “You always have debris on construction sites,” Murphy explains. “We’re looking at working within what’s called a cocoon system, which will enclose the work area and will move up the building as you go up.”
The project’s completion is anticipated in 2017. The project team is confident the tower will become Miami’s defining structure—attracting and awing visitors from around the world, Klemencic says. “It will be such a unique-looking structure, sitting all by itself out there in the bay, that it will become the postcard of Miami, much like the Space Needle in Seattle and the Eiffel Tower in Paris are always on the postcard,” he says. “The tower’s landmark status will really bolster south Florida tourism.”