Demolition requires more than just ripping up and tearing down. It often involves significant deconstruction - a process that entails expert planning and execution.
Last spring, the Port Authorities of New York and New Jersey released its plans to modernize John F. Kennedy Airport in New York. The plans called for razing two obsolete structures including the JFK TWA Hangar 12 and the JFK East Hangar Extension.
Able Rigging Contractors, Inc. worked with its contracting partners to safely deconstruct the two facilities within a 100-day time period from mid-April to the end of July, while the busy airport functioned normally.
"Able was responsible for bringing down the structures in a controlled manner and according to a tight schedule," says Steven Laganas, managing director for Able Rigging Contractors, Inc. and Able Equipment Rental, Inc. "Some of the challenges facing Able included first securing, then supporting, the enormous structures as they were not capable of standing on their own during the dismantling process. This was due to their initial design and construction."
In preparation for deconstructing the East Hangar Extension, which was essentially a massive steel frame, Able Rigging installed a temporary guy-wire system on trusses A and B for control. A Manitowoc 16000 rigged with 137 feet of boom was used to conduct a core crane pick in conjunction with a Manitowoc 2250 rigged with 140 feet of boom and two Link Belt 348 High Lab 5s, each rigged with 140 feet of boom. After the 837,000 pound trusses had been cut from the frames, the cranes lowered them to the ground. The end frames and columns were supported during truss removal by two Liebherr LTM 1250 cranes. The four columns, weighing approximately 200,000 pounds each, were also dismantled.
JFK TWA Hangar 12 was one of the few remaining pre-1960 structures at JFK (built in 1955). The building measured 700 feet long, 340 feet wide and 65 feet high. It was constructed of a massive concrete core building with poured-in-place post-tension concrete slabs as roofing.
"The entire structure was made sturdy by the use of anchored cabling to secure the slab roofing to the core building - a now obsolete design," says Able Rigging's Master Rigger Bobby LaChapelle.
Able Rigging's crews engineered a process to contemporaneously de-tension the twin concrete slab roofing and its anchored cabling that extended from both sides of the core building. This was accomplished with the simultaneous use of four cranes - a Manitowoc 16000, a Manitowoc 2250 and two Liebherr TLM 1250s. Each side of the building had a two-crane pair.
The roof slabs were secured and supported through a load utilization system employing lifting frames, equalizing beams and rolling blocks. Once braced, rigging crews prepared the concrete slabs for sawing and made the final cuts in the rebar that connected the slabs to the core. The slabs, then deemed to be manageable, were each 145 feet long, 25 feet wide and weighed 370,000 pounds. There were 56 such panels to prepare and lower to the ground.
LaChapelle made the final split between each segment while giving instructions to the crane operators below to lift with the appropriate force to separate a panel from the structure in a safe and controlled manner. After partly lowering, each two-crane pair then tandem-crawled 200 feet away from the building before resting the panels in a staging area for downsizing.
The hangar core building will be completely demolished by September 2011.