Three different buildings in Boston, Massachusetts, have been known as the "John Hancock Building", and perhaps a fourth will be. All were built by the John Hancock Insurance companies. References to the John Hancock building usually refer to the 60-story, sleek glass building on Clarendon Street.

The building known by Bostonians as the John Hancock Tower, or colloquially, the "New" Hancock Tower, is officially named Hancock Place. It is a 60-story, 790-foot-tall (241 meter) skyscraper designed by I.M. Pei and Henry N. Cobb of the firm now known as Pei, Cobb and Freed. It was completed in 1976. In 1977 the AIA presented Cobb with a National Honor Award for the John Hancock Tower.

As of 2005, it is the tallest building in New England, the 43rd tallest building in the United States, and the 112th tallest building in the world.

Its street address is 200 Clarendon Street. The company uses both "Hancock Place" and "200 Clarendon Street" as mailing addresses for offices in the building. The John Hancock companies were the main tenants of the tower, but the insurance company announced in 2004 that some offices will relocate to a new building at 601 Congress Street.

Like all large, heavily glazed buildings, the tower requires substantial air conditioning year round—even with its reflective walls. Its cooling system is similar to that used in the IDS Center in Minneapolis, Minnesota.

Tall, skinny glass structures were a goal of modernist architecture ever since Mies Van Der Rohe proposed a glass skyscraper for Berlin. Such buildings as Gordon Bunshaft's Lever House, van der Rohe's Seagram Building, and Frank Lloyd Wright's Johnson Wax Headquarters attempted this goal, but many of these designs retained structural artifacts that prevented a consistent, monolithic look.

In 1972, Pei's design of the Hancock Tower took the glass monolith skyscraper concept to new heights. The tower is an achievement in minimalist, modernist skyscraper design.

Each bay of each floor is a single pane of glass; there are no spandrels between the floors, and the mullions are minimal. Pei added a geometric modernist twist by using a parallelogram shape for the tower floor plan. From the most common views, this design makes the corners of the tower appear very sharp. The highly reflective window glass is tinted slightly blue, which results in the tower having only a slight contrast with the sky on a clear day. As a final modernist touch, a pinstripe crevice on each of the shorter sides breaks this light contrast, emphasizing the vertical lines.

Problems with the building

It was a much-anticipated landmark from the country's most respected design firm. Unfortunately, the tower is more notorious for its engineering flaws than for its architectural achievement. Its opening was delayed from 1971 to 1976, and the total cost rocketed from $75M to $175M. It was an embarrassment for the firm, modernist architects, and the architecture industry.

Foundation

Hancock Tower was plagued with problems even before construction started. During the excavation of the tower's foundation, temporary steel retaining walls were erected to create a void on which to build. The walls warped, giving way to the clay and mud fill they were supposed to hold back. The inward bend of the retaining walls damaged utility lines, the sidewalk pavement, and nearby buildings—even damaging the historic Trinity Church next door. Hancock ultimately paid for all the repairs.

Falling glass panes

Inventing a way to use the blue mirror glass in a steel tower came at a high price.

The building's most dangerous and conspicuous flaw was its faulty glass windows. Entire 4' x 11', 500 lb (1.2x3.4 m, 227 kg) windowpanes detached from the building and crashed to the sidewalk hundreds of feet below. Police closed off surrounding streets whenever winds reached 45 mph (72 km/h). According to the Boston Globe, MIT built a scale model of the entire Back Bay in its Wright Brothers Wind Tunnel to identify the problem. The exact cause of the malfunction was never revealed due to a legal settlement and gag order. Most now diagnose the problem as a combination of the double-paned glass construction method, and the pressure differentials between the inside and outside air.

In October 1973, I.M. Pei & Partners announced that all panes would be replaced by a different heat-treated variety—costing between $5 million and $7 million. During the repairs, plywood replaced the building's windows, earning it the nickname "Plywood Palace" and the joke that it was "the world's tallest plywood building."

Nauseating sway

The building's upper-floor occupants suffered from motion sickness when the building swayed in the wind. To stabilize the movement, a device called a tuned mass damper was installed on the 58th floor. As described by Robert Campbell, architecture critic for the Boston Globe:

Two 300-ton weights sit at opposite ends of the 58th floor of the Hancock. Each weight is a box of steel, filled with lead, 17 feet (5.2 m) square by 3 feet (0.9 m) high. Each weight rests on a steel plate. The plate is covered with lubricant so the weight is free to slide. But the weight is attached to the steel frame of the building by means of springs and shock absorbers. When the Hancock sways, the weight tends to remain still... allowing the floor to slide underneath it. Then, as the springs and shocks take hold, they begin to tug the building back. The effect is like that of a gyroscope, stabilizing the tower. The reason there are two weights, instead of one, is so they can tug in opposite directions when the building twists. The cost of the damper was $3 million.

The dampers are free to move a few feet relative to the floor. LeMessurier Consultants says the dampers are located in relatively small utility rooms at each end of the building, leaving most of the 58th floor usable.

According to Robert Campbell, it was also discovered that—despite the mass damper—the building could have fallen over under a certain kind of wind loading. Ironically, it could tip over on one of its narrow edges, not its big flat sides. Some 1,500 tons of diagonal steel bracing were added to prevent this, costing $5 million.

September 11

An observation deck with spectacular views of Boston was a popular attraction. It was closed after the September 11, 2001 Terrorist Attacks and remains closed as of early 2006 (like the Transamerica Pyramid in San Francisco). Because of the closure of the John Hancock Tower's observation deck, the highest observation deck in Boston that is open to the public is in the Prudential Tower.

The building's owners cite security as the reason for the continued closure, but have used the deck for private functions and have expressed intent to replace it with more office space. Boston officials contend that security concerns are moot, since most similar attractions have long since reopened, and that a public observation deck was a requirement for the original building permits, though the city can't seem to produce documentary evidence.

(Source: Wikipedia)

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