The forecast called for snow, the first storm of the season even though it was mid-January. Construction crews rebuilding the Pentagon had been working 20-hour days, six days a week and were making remarkable progress toward their goal: rebuilding and reoccupying the damaged portion of the Dept. of Defense headquarters on Sept. 11, 2002, the one-year anniversary of the terrorist attack. A snowstorm was not going to stop them.
|Unusual sequence (top) and formwork (below) are schedule-driven. Pentagon Renovation Program|
A concrete pour of a major deck, scheduled for Saturday, Jan. 19the day several inches of snow was expectedwas bumped to Jan. 18. Concrete subcontractor Facchina Construction Co. Inc., La Plata, Md., "dedicated their guys" on Friday to pour 600 cu yds , double the daily volume on a standard deck pour, so the job could stay ahead of schedule. No one wanted to risk losing one or even two days to weather. "That type of attitude is infectious," says Will Colsten, the Pentagon Renovation Program's rebuilding project manager.
|(Photo courtesy of Pentagon Renovation Program)|
The rebuilding, dubbed the Phoenix Project after the mythological Arabian bird that rose from the ashes, is now some three weeks ahead of schedule, says Colsten. Demolition of the most severely damaged section was finished in four weeks instead of the six to eight weeks originally estimated to take down about 500,000 sq ft of interior space and about 100 yards of the historic facade. Now, the concrete structure of several floors is nearly complete. Scaffolding will be erected shortly for installation of exterior blast-resistant windows, and workers will begin applying the facade's limestone cladding by mid-February.
Since the Sept. 11 attack, Lee Evey, head of the renovation program, has resolved to have the damaged wedge rebuilt, at least to the point where workers within the building's outermost corridor, or E-ring, could be at their desks watching a planned memorial service from their office windows.
That resolve has become the mantra of approximately 1,000 workers involved in the rebuilding and the concurrent phased renovation of the rest of the Pentagon. Prior to the attack, the first section of the multiyear, top-to-bottom renovation was just days from completion. The overall renovation includes five wedges, each about 1 million sq ft. Part of Wedge Two was damaged in the attack, leading to schedule adjustments as that section is rebuilt within the overall renovation. Officials are hoping to keep the entire project on schedule, due to wrap in 2013. The workers' "pride and attitude is just exceptional," says Colsten.
The aggressive schedule calls for the five-story reinforced concrete shell of the outermost concentric "ring," or corridor, damaged in the attack to be topped out in May. The next two rings are expected to be topped out in July. The two innermost rings do not require rebuilding. Colsten admits that building inward from the outermost portion of the building is "not the most efficient way" to sequence the project. From a national pride perspective, however, "it is more important to have the outside finished first," he says.
|FAST TRACK Limestone is cut in Indiana plant to match Pentagon's facade. (Photo courtesy of the Bybee Stone Company Inc.)|
UNUSUAL. The project maintains the accelerated schedule through creativity, innovation and expertise. For instance, Pentagon officials put a structural engineer in charge of the project's design and construction, rather than a construction manager. Allyn E. Kilsheimer, principal of KCE Structural Engineers, Washington, D.C., was chosen for his extensive experience in dealing with structural disasters, explains Colsten. He also has the "force of character" to take certain steps that others might not, says one source. For example, Kilsheimer devised a shortcut to installing the utility systems by removing formwork earlier than usual.
Testing the concrete slabs every few days, crews found the compressive strength had reached between 75 and 85% by day 14, says Kilsheimer. Because the project is on such a compressed schedule, workers are removing the shoring from formwork supplied by PERI Formwork Systems Inc., Hanover, Md., ahead of the typical 28-day curing schedule. Still, says Colsten, "safety is paramount when considering how to get work done while the concrete structure is still a green structure."
Kilsheimer says that it is not unusual to reach "at least 75% of the compressive strength" on day 14. But it is unusual to strip the formwork at that time, he says. Crews first remove the shoring, followed by the formwork. They then install a limited number of vertical aluminum reshores at a much wider spacingabout 11 ft on center instead of 2 or 3 ft. That allows electrical equipment to be installed about one month ahead of schedule, says Kilsheimer. The sequence is "almost never done," even in an expedited situation, according to Kilsheimer. He says it will also be used to install mechanical systems.
The concrete standard for a facility like the Pentagon is 4,000 psi, but government officials note that the rebuilding effort has incorporated changes in reinforcing methods, resulting in a higher strength concrete. The U.S. Army Corps of Engineers suggested a series of methods to improve construction from a force protection and life safety perspective, but officials decline to discuss specifics.
|WINDOWS Reinforced openings are blast-resistant. (Photo courtesy of Pentagon Renovation Program)|
TOUGHER WINDOWS. Another significant milestone will be installation of approximately 175 new exterior blast-resistant windows, beginning Feb. 5. The same type of windows designed for the renovated Wedge One will be used again, with some improvements. The strength of those windows, which weigh about 1,500 pounds each and cost $10,000 apiece, combined with specially designed reinforced steel frames, are credited with saving numerous lives on Sept. 11.
This time the reinforced steel frame will not be necessary. As part of the Wedge One renovation, the new windows were retrofit into the existing multiwythe brick walls, which typically do not have much shear strength. Now that the walls are being rebuilt with reinforced concrete, the reinforced frame will not be necessary. The new walls will be built to the same blast-reinforcement standard that was in the renovated wedge, says Colsten.
The current schedule calls for workers to begin placing about 18,000 cu ft of limestone on the facade by the end of February. Craft workers at Bybee Stone Co., Ellettsville, Ind., are fabricating limestone to match the existing exterior. The process is relatively simple, but the short timeframe "is a big issue," says Patrick Riley, a Bybee drafting supervisor.
Time is on everyone's mind. The Pentagon Renovation office has a huge clock on the wall that is counting down the days until Sept. 11. "Everyone is staying focused on that goal," notes Colsten. "The building is coming back." Walking up a new set of stairs is "emotional and wonderful," he says. As the building once again starts to look whole, Colsten expects there will be other "significant emotional events."