Obelisk's Scaffold Is First of Its Kind
Washington Post Staff Writer
Wednesday, December 30, 1998; Page B1 It is not a place, John Curry said, where you come to train men in the art of scaffolding. At the 500-foot level, where the Washington Monument begins to angle steeply toward its point, the wind whips and footing is a fleeting concept. "We're building it in the air, piece by piece by piece," Curry, the general foreman, said after spending a day scaling the heights of the capital's signature obelisk.
The scaffolding now enveloping the monument has 37 miles worth of aluminum tubing, assembled in modules light enough to be lifted by one or two workers yet capable of sustaining a million pounds when put together. The shiny metal grid already has altered the famous monument and by extension the look of the Mall itself particularly at night when lights on the grid create an eerie, shadowy pattern on the worn facade.
But what is most impressive about the platform from which workers will repair and repoint the tribute to George Washington is the scaffold itself, a monument in its own right and one being closely watched by experts across the country. For engineers, the challenge was to come up with something that was functional, conformed to a specific artistic vision and at the same time was respectful of the structure, a historic landmark that by definition imposes a host of restrictions and conditions on any renovation.
The scaffold is unique in that it tapers to the shape it envelops. Unlike almost all other scaffolding, it is not fastened to the structure it surrounds the National Park Service prohibited any contact for fear of damage. The elevator, or hoist, is on the inside, not the outside. The top conforms to the pyramid-like crown but does not touch it. Instead it sits like a hat atop the monument. The cost of the scaffolding is estimated at $2.5 million to $3 million, a significant part of the projected $9.4 million cost of the renovation.
"What you are looking at, essentially, is a shell around the monument, an armor. ... I don't know of any others like it," said John G. O'Connor, an engineer with Universal Builders Supply Inc. of Mount Vernon, N.Y., the scaffolding company at the monument and one known for tackling unusual and challenging projects, including the renovation of the Statue of Liberty.
Scaffolding in the United States always has been viewed as a strictly functional creation, wholly utilitarian in that it is designed to get workers and material up and down safely and efficiently. But from the onset, the Washington Monument's prominence in the capital's landscape encouraged a radically different approach to the renovation now underway, the most comprehensive face lift in the history of the 114-year-old landmark.
The result was an original concept by architect Michael Graves, who among other things wanted the design of the scaffolding to help draw attention to the importance of renovating buildings. Graves, in effect, turned the scaffolding into a 555-foot statement. Strips of architectural mesh will be attached to the scaffolding, creating an artistic grid but not obscuring the monument itself.
"It's unusual in the United States to take the appearance of the scaffolding really seriously," Mitchell said. "It's very often treated in an ad hoc way."
The concept by Graves was put on the drawing board by Alan Shalders, an engineer at Universal Builders who came up with the novel concept of tapering the scaffold to conform to the classical dimensions of the obelisk, which is 10 times taller than the width of its base. In practice, this means that the scaffold is at a 1.3-degree inclination from the base to the 500-foot mark, conforming to the sloping face of the monument. At the top, known as the pyramidion, the slope is at 17 degrees. Even the floor of the scaffold's elevator is at a slight tilt.
Shalders said the tapering was achieved by using horizontal and vertical cross-bracing tubing of differing lengths, each with predrilled holes to achieve the required slant. Another key to achieving "overall unformity of appearance," Shalders said, was constructing the stairway and the hoist within the scaffolding and thereby mirroring the classic taper of the obelisk.
The design by Shalders was reviewed and modified by James Madison Cutts Consulting Structural Engineers Inc., a D.C. firm that has been involved in other sensitive restorations, including the one at the Jefferson Memorial. Engineers at the firm determined that the sidewalk near the Washington Monument could not bear the load of the scaffolding. The solution was to dig out sections of the sidewalk and pour reinforced concrete in select areas. Steel connections then were used in a few places where the load was deemed heavier.
The scaffold derives its structural strength, in part, from "tension rings" placed every 26 feet up to the 500-foot level. Much like a belt around a person's waist, these rings are the only part of the scaffold that actually rests on the monument. The contact occurs at the corners and at the center of each facade, with specially designed pads resting on the monument but not mechanically fastened to it. Overall, there is a three-foot gap between the scaffolding and the face of the monument, and at points where it touches, the pressure is less than 100 pounds per square inch, significantly less than marble tolerates.
The National Park Service, the steward of the monument, had one principal restriction for the engineers in the project: The scaffolding could not be affixed to the obelisk. That went against the advice of some engineers, at least initially. "We wanted to penetrate, but they had certain restrictions, and we accepted that," Cutts said.
The design was modified to strengthen the scaffolding. "We were able to brace it against the four corners but not tie into it," Cutts said. Asked if the scaffolding now in place is as reliable as if it had been attached to the monument, Cutts said: "Yes, it is as stable. I was concerned that it might not be as stable, but after introducing these horizontal trusses and testing it ... we're very happy."
The scaffold, which was constructed in New Jersey and brought to Washington in stages on flatbed trucks, was erected by a crew of 26 working in three teams, one crew at the top, another at the middle and the third as ground support. The most delicate part was the scaffolding at the pyramidion, which was put in place by 12 men who had a support crew of six directly beneath them on a platform. Universal Builders had four foremen on the project, which is uncommon. The four Curry, Bill Surhoff, Robert Harmon and Elmut Leondardelli, all New Yorkers have 75 years' experience among them in the scaffolding business.
The design for the draping by Graves is being tested. The fabric will be attached to the scaffolding with tensioning ratchets that draw the material taut. The edges, in turn, will be secured at intervals with nylon tie wraps. The overall effect will mimic the masonry blocks that define the monument up close. The monument likely will not be fully covered by the fabric until the end of January, weather permitting.
Repairing and repointing will not begin until March. David M. Suarez, the president of Atlantic Company of America Inc., the principal subcontractor for the delicate restoration task, said the first job will be cleaning the monument. That will be done by eight men working, alternately, on two facades at a time or on all four.
During the busiest period of the renovation, as many as 20 stone workers, from Lorton Contracting Company Inc., will be on the scaffolding. Most of the work will be done in 100-foot vertical sections, up to the 500-foot level. Park Service experts must examine the results and approve the work before another section is tackled.
The condition of the monument is somewhat of a mystery because it has not been examined up close, so even at this stage there are more questions than answers about the extent of repairs needed.
But the scaffolding already has allowed a few people, other than workers erecting it, to see what lies ahead. "Certainly a lot of work to be done," said one of these select observers, Kate Beysselance, the project manager for Grunley-Walsh Joint Venture, the general contractor for the renovation.
© Copyright 1998 The Washington Post Company