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Bank of America Plaza

Bank of America Plaza

Structure Information

Bank of America Plaza, originally named NationsBank Plaza, was built in 1992 in Atlanta, GA.

Figure 1. Bank of America Plaza [1]

The building was built as a headquarters for NationsBank. Once NationsBank was bought out by Bank of America, the building’s name was changed to Bank of America Plaza and became an office space for Bank of America and other tenants. As Atlanta’s tallest building, Bank of America Plaza was also designed as an “anchor between Midtown and Downtown” [2]. Bank of America Plaza has become a symbol of Atlanta.

Bank of America Plaza was designed by Kevin Roche, John Dinkeloo and Associates (KRJDA) [1]. CBM Engineers were the structural engineers [1]. Beers Construction Company was the main contractor [1]. NationsBank, in coordination with Cousins Properties, funded the project [3].

Historical Significance

At 1023 feet tall, Bank of America Plaza is the tallest building in Atlanta and the Southeast [3]. It is also the 13th tallest building in the United States, and the tallest in the country outside of New York and Chicago.

The architectural vision for the building was a mix between the art deco and postmodern architectural styles. This causes the building to have an appearance resembling more traditional skyscrapers, like the Empire State Building [4]. The building is accented with a 23-karat gold pyramid that is illuminated at night, as shown in Figure 2. When the building was constructed, Atlanta was preparing to host the 1996 Olympic Games. Bank of America Plaza symbolized Atlanta’s hope to emerge from hosting the Olympics as an internationally known city.

Figure 2. Illuminated Spire [1]

A unique feature of the building is its 45-degree angle with its bordering streets [1]. This means that the primary sides of the building form a square in plan, but at a 45-degree angle to the adjacent streets, as shown in Figure 3. This design choice was made in an attempt to provide “undisturbed views in all directions” [1]. The placement of the curtain wall was also chosen to help provide stellar views to the building’s tenants.

Figure 3. View from bordering street

In addition to being constructed on-budget and on-time, the Bank of America Plaza was constructed in 14 months, one of the fastest constructions of a building with a height of over 1000 feet. [5] The building was also awarded Atlantic Business Chronicle’s Best Community Impact and Architectural Deal of the Year awards [1]. While the building was modeled after existing skyscrapers, Bank of America Plaza’s features and statistics show that it is a remarkably unique structure.

Cultural Significance

The building was originally proposed as a new headquarters for Citizen and Southern Bank (C&S). Before construction was completed, C&S was bought out by NationsBank, and the building was named NationsBank Plaza. In 1999, after NationsBank was bought out by Bank of America, the building’s name was changed to Bank of America Plaza [6].

The building came to life when Atlanta and real estate were booming. In 2006, Bentley Forbes bought the building for $436 million [6]. When the U.S. economy fell into a recession, more and more vacancies began to fill the iconic tower [6]. In 2012, the building faced foreclosure. Even today, the 55-story building is only half-filled [7]. The history of Bank of America Plaza demonstrated that economy can have a dramatic impact on even iconic buildings.

The new symbol of Atlanta was not loved by all. Critics called it “conventional” and said it looks like a pencil [7]. When I first visited Atlanta after getting accepted into Georgia Tech, I loved everything about Atlanta. Except for this building. Something about the skeletal pyramid on top bothered me. The vast number of members confused me and made me feel like they left it unfinished, rather than intended it as art.

Flash forward to my first weeks at Georgia Tech. I learned that students fondly refer to Bank of America Plaza as the “Pencil Building”. I also learned that the clarinet section of the Georgia Tech Marching Band loved the building so much that they would sacrifice pencils to the Pencil Building ahead of a Georgia Tech home football game for good luck. The building grew on me as I saw its effect on Tech students. As the tallest building in Atlanta, it gives students a sense of direction when exploring the city and provides a feeling of home when returning to Atlanta after time away. While there are mixed opinions on its appearance, Bank of America Plaza is an important symbol in Atlanta.

Structural Art

A building demonstrates structural art if it is efficient, economic, and elegant. Bank of America Plaza features a column-free interior [1]. Its external columns and central core carry both gravity loads and wind loads, making the structural system efficient [1]. In addition to benefitting the building’s efficiency, a column-free interior lowers cost [1]. However, the building features a decorative 23-karat gold spire above the building’s usable space. While this addition seems excessive, the spire “encloses the cooling tower, elevator penthouses and other mechanical equipment.” [1] The space beneath the spire has a use in addition to being an aesthetic highlight. However, the argument can be made that the spire’s “closely-spaces horizontal tubes” reduce the efficiency of the spire and increase cost. 23-karat gold itself unnecessarily raises the cost. The horizontal tubes also reduce the transparency of the structure, making it harder to determine how the spire carries load.  As mentioned earlier, there is debate over whether the building has an aesthetic appearance. Based on my initial reaction to the building, I would say that the building is not elegant. While Bank of America Plaza contains some noteworthy features, the gaudy nature of the golden spire demonstrates excess economy, reduced efficiency, and questionable elegance. Therefore, Bank of America Plaza is not structural art.

Structural Analysis

According to KRJDA, the building was designed to be a “modern interpretation of art deco with an enduring iconic stature.”[2] This is achieved with a red granite and glass façade that is accented with a golden spire [5]. Columns are used to emphasize the vast vertical height of the building. The building’s core is made of reinforced concrete and 4 concrete encased steel columns [3]. The building features 4 towers, each of which has 2 large concrete encased steel columns [1]. Steel is used as the floor spanning [3]. Figure 4 shows the building during its construction.

Figure 4. Bank of America Plaza Construction [8]

The structural system utilized the “super column” system by using large columns to both carry gravity loads and wind loads [1]. Each floor load is supported by beams, which are supported by the super columns.

Figure 5. Loads on whole structure

 

Figure 6. Spire Load Path

The tip of the building acts as a point load on the spire’s truss-like system. The spire is made up of diagonal, vertical, and horizontal members. The diagonal, vertical, and large horizontal members carry load similar to a truss. The smaller horizontal members and crossbars provide bracing. The bottom beams of the spire then act as line loads over the columns. Each floor’s slab is supported by steel beams that acts as point loads to the columns. The columns transfer load into the foundations.

Figure 7. Simplified Model of Building

Figure 5 shows the loads in relation to the super structure. The loads acting on the building are wind loads, dead loads, and live loads. The red lines demonstrate the load path due to gravity loads, while the green lines represent the wind load. The wind load increases as the height of the building increases. In contrast, the gravity loads are higher at the bottom of the structure, compared to the top of the structure. As seen in Figure 5, additional columns appear at lower elevations to add additional support to the super columns. Each of the columns are buried into the foundation which provides a horizontal force, vertical force, and moment. This means that the structure has one fixed end and one free end, like a cantilever beam.

Figure 7 is a simplified model of the forces on the building. Again, the green arrows show the wind load and the red arrow shows the gravity loads. The blue arrows show the support reactions. By examination, the horizontal reaction force is equal to the distributed wind load multiplied by the height of the building, or wH. The vertical reaction force is equal to the weight of the building and the live loads. Since moment requires a force acting over a perpendicular direction, the moment at the fixed end is caused only the distributed wind load. This moment is equal to w*H*H/2, with w being the distributed wind load and H being the height of the building.

The live load of the building comes from 3 components, the offices, the lobby, and the roof. For a standard office building, the live load from offices is 50 psf and the live load from the lobby is 100 psf [9]. The typical live roof load is 12 psf, but since the roof houses mechanical equipment, I assumed a live load of 25 psf [9]. Each floor plate is between 20,000 and 25,000 square feet throughout the building’s 55 floors [2]. Using the average of 22,250 sf, the office live load is calculated at 60,750 kips as a result of multiplying 50 psf by 22500 sf by 54 floors. Using the same method with an area of 25,000 sf, the lobby live load is 2500 kips. The roof live load, using an area of 20,000 psf, is 500 kips. The addition of these live loads results in a total live load of 63,750 kips.

The dead load on the building is a result of the floor slabs, mechanical equipment on the roof, and the spire. The weight of the mechanical equipment was assumed to be 20 kips. From counting the number of members in the spire at approximately 300, the weight of the spire was calculated to be 2883 kips, using steel with a weight of 0.283 pounds per cubic inch. The cross section of each member was assumed to be 6 inches by 12 inches with a hollow interior of 4 inches by 10 inches. The average length, based on the floor area, was assumed to be 70.75 feet. Assuming the steel floor spanning is 10 inches thick with a weight of 408 pounds per square foot, the dead load of the slabs is 495,720 kips. The total weight due to dead loads is 498,623 kips.

Combining the dead loads and live loads, the vertical reaction is 562,373 kips. Dividing this by the 8 columns, the force in each column due to vertical forces is 70,297 kips. The stress for each column under uniaxial loading is the force over its area. Given that the area of each column is 8 square feet, the stress felt by each column can be calculated as 61.0 ksi [1].

Personal Response

What started as my least favorite building in Atlanta, slowly grew on me as it became a symbol of Atlanta in my life. I chose to write this blog because of my changing opinions. After visiting the building for this project, my opinion changed again. As the tallest building in Atlanta, Bank of America Plaza can be seen all over the Atlanta area. From afar, the building appears as if it consists of really long columns of shiny, red metal. As I approached the building, I saw the evolution from one massive structure into its individual red granite stones. Once in front of the building, I was greeted by greenery and a long staircase leading to the grand entrance. While seeing the building in person was cool, its size and grandeur was intimidating. The plaza around the building sets the building back from the street making it seem exclusive and hard to reach. While I did read articles that mentioned the building’s poor connection with its surrounding area, it wasn’t until going there myself that I understood the uneasy feeling the building could bring to a person.

Figure 8. Building entrance [1]

Reference

  1. http://www.krjda.com/Sites/BankAmericaInfo1.html
  2. http://www.bankofamericaplaza.com/our-building
  3. http://www.skyscrapercenter.com/building/bank-of-america-plaza/429
  4. http://artsatl.com/rediscovering-atlantas-architecture-bank-america-plaza/
  5. https://www.emporis.com/buildings/121137/bank-of-america-plaza-atlanta-ga-usa
  6. https://www.ajc.com/business/bank-america-plaza-becomes-atlanta-priciest-repo/yKEFrl8ElBb2oAiPguIjfJ/
  7. http://www.atlantamagazine.com/90s/nationsbank-plaza-now-bank-of-america-plaza-rises-up/
  8. https://www.reddit.com/r/Atlanta/comments/29p2f6/bank_of_america_plaza_under_construction_1991/
  9. https://www2.iccsafe.org/states/Florida2001/FL_Building1/PDFs/Chapter%2016_Structural%20Loads.pdf