Leap-FroggingWhen two placing booms and six Putzmeister towers were set up to handle a construction project the size of a city block, the idea of leap-frogging was more than just child's play — it was a necessity in meeting a compressed time schedule.
Employing an unusually large number of towers and two far-reaching 32-Meter Putzmeister placing booms, the project demanded the flexibility and ease of leaping from one tower to the next anywhere on site. It was also vital to keep the pours occurring on an as-needed basis to meet a fast-track deadline expected by its owners.
Ironically, the Technology Center of Americas in Miami counted on the same fast pace in building the center as what would be housed under its roof — Internet capabilities.
This is only the fifth public tier-one, carrier-neutral NAP site in the United States. It will provide high speed Internet data exchange and a connection point that ties Internet access between the Americas, the Caribbean and Europe all into the United States through its downtown Miami location. Therefore, to meet the high-speed approach, the project required thinking beyond conventional construction practices.
To get the project off the ground, the five-section Putzmeister 52-Meter provided the effective reach and versatility to get into awkward areas and used extensively for the 130,000-square-foot (12,000 m2) foundation. However, the congested city streets and large building footprint still caused problems, making it important to get the six towers erected quickly.
Highly efficient method developed for early tower installation
Normally, two or three poured floors are needed to set up a tower; however, a new way was devised to erect all six towers after only one elevated floor was poured. The exclusive "square" Putzmeister tower design was key to accomplishing this time-saving approach. First, a one-foot thick slab was placed at the base to support the weight of the tower.
With nothing to wedge the tower base against, steel angles were then bolted to the slab on all four sides of the box-shaped tower and typical wedges placed at the first elevated deck. All this was accomplished with minimal extra expense. Initially, the 50-foot (15m) tower was placed in this configuration; however as more floors were added, the Putzmeister tower was then raised with a tower crane and supported by a floor frame.
Jim Henegar, co-owner of Thomas Machinery in Miami, said, "The square shape of the Putzmeister tower design offered the only way of achieving this project's quicker installation process. The four-sided tower also protected the delivery line and connections inside the tower as well as provided convenient inside ladder access. Plus, it provided an easier and quicker way to block-out and patch square holes."
To further meet the needs of this particular job, a structural pre-stress, pre-cast framing system was utilized. This highly efficient process would provide quicker job completion compared to a conventional forming approach.
Lightweight placing booms accommodate on-site cranes
Although only a six-story building, the unusually large footprint demanded not only multiple towers, but also the full 105-foot (32m) horizontal reach of its booms. Two MXR 32/36 four-section, roll-and-fold Putzmeister placing booms were selected to handle the job. One separate placing boom was hauled to the site and one was detached from a truck-mounted 36-Meter.
Putzmeister's special "two-piece" slewing head design of its detachable boom allowed quick and easy separation from the truck. Its color-coded hydraulic quick disconnects provided easy identification for reconnection to the tower when flying the boom from tower to tower or when placing back on the truck.
Steve Merson, co-owner of Brothers Concrete Pumping in Fort Lauderdale, noted that "Although we encountered on-site cranes that could only pick 14,000 pounds (6350kg), our Putzmeister equipment solved the dilemma. With a simple and quick disconnect, the lightweight boom could be easily detached from the pedestal and each component flown separately." The pedestal weighed only 4,850 pounds (2200kg) and the boom only 13,812 pounds (6265kg), so two easy picks and quick reconnections were possible.
With its 4-section boom detached from the truck and used for placing concrete, the 36-Meter Putzmeister truck stayed on-site to pump. When two pours were going on simultaneously, a second Putzmeister 32Z-Meter boom pump was dispatched. Both units featured .16H pump cells capable of attaining outputs up to 200 cubic yards an hour (152m3/hr).
Paul Merson, Steve's brother and co-owner of Brothers Concrete Pumping, noted that, "We counted on the reliability of the Big Mouth S-Valve on both our Putzmeister pumps. Their large 9-inch intake openings and high-capacity hoppers gave us a superior filling rate and helped attain higher volumes for faster job completion."
Unique pipeline plumbing approach implemented
Another time-saving approach was plumbing the pipeline differently. For the entire 460-foot (140m) length of the job, two long 5-inch delivery lines ran parallel to each other, centered between two rows of three towers on each side. With each tower spaced 150 feet (46m) apart from the next, this arrangement offered numerous combinations in enabling contractors to put easy breaks in the pipe with a simple change of a 90-degree elbow and a few components instead of installing separate system to each tower.
"The setup of six towers would have been a nightmare without the newly devised pipeline arrangement," said Kenny Heath, co-owner of Form Works. "More importantly, this meant we could pump any two towers at any time with a minimal amount of labor and setup as well as less cleanup. The highly flexible leaping approach allowed us to handle the pours as different areas became ready, and it also avoided extra diversion valves, pipe and thrust blocks."
More than 38,000 cubic yards (29,000m3) of concrete for the pile caps, columns, slabs and shear walls will have been pumped when the 740,000-square-foot (68,746m2) building, initially started in August 2000, has its shell completed this January.
With several contractors thinking "outside the box," a faster and more efficient means of placing concrete will meet an accelerated completion target date, and perhaps these new methods will become the industry norm.
Owner: Terremark, Miami
Architect: Bermello Ajamil & Partners, Miami
General contractor (shell): Centex Rooney, Fort Lauderdale, Fla.
Forming contractor: Form Works, Fort Lauderdale, Fla.
Pumping contractor: Brothers Concrete Pumping, Inc., Fort Lauderdale, Fla. Ready-mix supplier - Rinker Materials, Miami
Equipment dealer: Thomas Machinery, Inc., Miami
Equipment: Putzmeister TG 10 towers (6), Putzmeister MXR 32/36 separate placing booms (2), Putzmeister 32Z-Meter truck-mounted boom pump, Putzmeister 36-Meter truck-mounted boom pump with Series II detach boom, Putzmeister 52-Meter truck-mounted boom pump