Musée d’Orsay

Structure Information

Gare d’Orsay, Paris, France, 1900                                                    Musee d’Orsay, Paris, 1986

Figure 1. Gare d’Orsay [1]

Figure 2. Musee d’Orsay

 

 

 

 

 

 

 

 

In 1900, Gare d’Orsay was built as a new central railway station for the World’s Fair in Paris [2]. The new station, and its integrated hotel, needed to blend in with its architectural surroundings [2]. Three architects, Lucien Magne, Emile Bénard and Victor Laloux, were consulted by the owners, the Orleans railroad company, who chose Laloux’s design in 1898 [2]. With changing times, the station served many purposes and in 1975, it was proposed to be renovated into a museum [2]. The new museum would serve as a connection between the Louvre and the National Museum of Modern Art [8]. ACT Architecture transformed the station into the museum it is today with interior design by Gae Aulenti and financial support from the French government [2]. As mentioned previously, the Orleans railroad company was the original owner and funded the original construction [2].

Historical Significance

Because of its need to blend in with its surroundings, the station has a Baroque style façade, incasing its use of the modern materials, glass and iron [3]. The station shows Laloux’s use of cast-iron arches that allowed for larger openings and a glass façade [4]. This use of cast-iron was innovative for its time.

The renovation of the station to a museum was unique because the original roof was kept intact [5]. Keeping the roof when renovating is rare because the roof is more susceptible to damage from moisture and sun [5]. Because the roof was kept, modifications had to be made to the construction techniques that would have been used. One of the major changes was using smaller, more compact equipment instead of a tower crane [5]. In addition to equipment constraints, it was important to make sure the construction did not cause vibrations.

The Gare d’Orsay was a model for Penn Station in New York [6]. The president of the Pennsylvania Railroad, Alexander Cassatt, was inspired by the station when he traveled to Paris in 1901 [6]. Penn Station was built in 1910.

Gare d’Orsay’s architect, Laloux, was also a professor. One of his students was William Van Alen, architect of the Chrysler Building [4]. While Laloux’s Gare d’Orsay may have been the model for only one structure, his teachings contributed to a world-known skyscraper.

Cultural Significance

Originally on the site of d’Orsay was the Palais d’Orsay, completed in 1838 [7]. It was the home of the Court of Accounts and the State Council [7]. In the Paris Commune of 1871, a revolt against the government, the Palais d’Orsay was burned to the ground [7].

As mentioned previously, Gare d’Orsay was built in anticipation of the World’s Fair in 1900, but by 1939, the platforms were too short to accomodate for the modern, longer trains and the station only provided serve to the suburbs [7]. After 1939, the station served as a mailing center for packages going to prisoners of war during World War II [7]. By 1958, the station was no longer in operation [7]. The rail station’s hotel shutdown in 1973 [7]. The hotel is historically significant because it was the location of General Charles de Gaulle’s press conference that announced his return to power in 1958 [7].

By 1973, the Directorate of the Museums of France was considering converting the station to a museum [8]. There were also plans to demolish the building and build a hotel in its place, but the station’s architect led it to be added to the Supplementary Inventory of Historical Monuments in March 1973 and classified as a Historical Monument in 1978 [7]. In 1986, the museum was inaugurated by President Francois Mitterrand [7].

In 1900, the painter, Edouard Detaille, wrote “the station is superb and looks like a Palais des beaux-arts…” [7] At the time, the station was considered beautiful. Today, it is perceived the same way. While the station is home to the largest collection of impressionist and post-impressionist paintings, reviews from TripAdvisor show that the conversion of the old rail station into a museum is what impresses everyone. Even the people crazy enough to give the museum a 1 star review compliment the building’s architecture! Musee d’Orsay provides a unique museum experience because of the preservation of its rail station history.

Structural Art

Structural art demonstrates efficiency, economy, and elegance. If the structure’s load path can be seen, the structure is efficient. In Musee d’Orsay, the load path can be seen relatively clearly on the inside but is hidden by a stone façade on the outside. Even on the inside, the walls are decorated with ornamentations that only add to the building’s architecture. These added decorations reduce the efficiency and economy. The building used 12,000 tons of metal in its construction, which is more than was used in the Eiffel Tower [8]. In addition to the original building lacking economy, the renovations were 3 years behind schedule and millions of francs over budget [7]. Based on the positive public opinion of the building, it can be said the building has elegance. However, a lot of this “elegance” is from architectural ornamentation, rather than the beauty of the structure itself. While the building is beautiful, it is not considered structural art.

Figure 3. Outside of Musee d’Orsay

Structural Analysis

Figure 4. Construction of stone façade [10]

Laloux’s design for the building stemmed primarily from the need to create a rail station that would serve the future while blending in with its historical surroundings. Thus, the glass and iron arches of the main hall are covered by a stone façade. Stone structures were added to the building’s interior to help create the museum’s atmosphere [9]. These structures hold their own weight. While the construction process is unknown, assumptions can be made from construction pictures. The stone façade was constructed using scaffolding before the arches were built. Next, the arches, interior façade, and glass were all added. For the renovation, scaffolding was installed throughout the building to gain access to the high roof. Figure 6 shows the arch construction.

 

Figure 5. Renovation [10]

Figure 6. Arch construction

 

 

 

 

 

The structural system of the building is a cylindrical arch system. Most of the loads on the structure are carried by its arch system.

Figure 7. Exterior Load Path

Figure 8. Cross Section Load Path

The structure carries load by transferring self weight to the arches which transfer load to the ground. In cases where there are no arches, the weight is transferred to columns. The cross sectional arches connect to the outside arches at their supports. Horizontal iron members connect the cross sectional arches and provide bracing. Each end arch in the main hall has interior beams and columns that provide extra support and bracing.

To analyze the structure, I am going to focus on the three arches over the building’s cross section. The building is 75 meters wide and 180 meters long while the main hall is 40 meters wide and 32 meters tall [2]. The whole building has 12,000 tons of iron and 35,000 square meters of glass [2]. Assuming the glass is 10 millimeters thick, the glass weighs 25 kg per square meter [11]. The density of iron is around 7400 kg/m3  and has an approximate diameter of 15 mm [12]. Limestone has a density of around 165 kg/m3. When the densities were converted to line loads, they were also converted from kilograms to newtons, and then to kilonewtons because of their magnitude. With a width of 10 m and an approximate thickness of 0.5 meters, the distributed load of the stone is 8.085 kN/m. The building has 8 main arches with smaller arches in between. Each main arch is around 10 meters wide and the span between each main arch is around 20 meters. Figure 9 shows the tributary areas of the arches. The white areas show the main arches. Each tributary area will be used to determine the weight of glass and iron acting on each arch.

Figure 9. Tributary Areas for the main arches

Using the above data and approximations, arches 1 and 8 have a distributed load of 10.66 kN/m. The other arches have a distributed load of 13.24 kN/m. The following diagrams and calculations were used to determine the force in each column due to the arches. Summing the forces in the x direction and y direction confirm that the forces in all of the arches balance out.

Figure 10. Forces in arches 1 and 8

Figure 11. Forces in arches 2-7

Figure 12. Calculations

Gare d’Orsay was a design competition won by Victor Laloux. He had recently completed a rail station and hotel in Tours and was able to successfully integrate the building with its surroundings [7]. Laloux would have used blueprints like the one in Figure 13 to explain his idea to the Orleans rail company.

Figure 13. Gare d’Orsay blueprint [10]

ACT Architecture was chosen to renovate the station by the French president, out of six proposals submitted [7]. ACT Architect used models like the one shown in Figure 14 to explain how renovations would work around the existing building. Figure 15 may have been a cross section used to explain how art would be laid out throughout the museum.

Figure 14. Museum model [10]

Figure 15. Museum layout schematic [10]

Gae Aulenti, the museum’s interior designer, was also an integral part of the renovation. Figure 16 shows a schematic of a cross section of the museum’s interior design.

Figure 16. Museum interior design [10]

Personal Response

The first time I visited the Musee d’Orsay, I was overwhelmed by the amount of beauty contained in one building. While the paintings and sculptures were impressive, I spent a good portion of my time admiring the soaring arches that rose above me. When I needed a break from looking at paintings, I had the enormous structure to dazzle me. Visiting the museum a second time only renewed my love for the structure.

References

  1. http://paris-historic-walks.blogspot.com/2012/12/musee-dorsay.html
  2. http://www.musee-orsay.fr/en/collections/history-of-the-museum/home.html
  3. https://www.britannica.com/art/Western-architecture/Classicism-1830-1930#ref489557
  4. https://study.com/academy/lesson/architect-william-van-alen-chrysler-building-works-biography.html
  5. https://www.tandfonline.com/doi/full/10.1080/15578770802229466?scroll=top&needAccess=true
  6. https://www.revolvy.com/topic/Gare%20d’Orsay
  7. http://discoverfrance.net/France/Paris/Museums-Paris/Orsay.shtml
  8. http://justfunfacts.com/interesting-facts-about-the-musee-dorsay/
  9. https://www.britannica.com/topic/Musee-dOrsay
  10. https://artsandculture.google.com/exhibit/ARK7SK5T
  11. http://www.leadbitterglass.co.uk/glassroom/calculate-weight-of-glass/
  12. https://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html

Southwark Bridge

Structure Information

Southwark Bridge in London crosses over the River Thames and was built in 1921.

Figure 1. Southwark Bridge

The Southwark Bridge was constructed to provide an additional Thames River crossing with the goal of alleviating traffic on the London and Blackfriars Bridges [1]. The bridge that stands today was the second bridge to be built over this span. The 1921 bridge was designed to reduce the effects of tidal scour and cross currents [2]. This bridge was designed by architect Sir Ernest George with Basil Mott of Mott, Hay, and Anderson (now known as Mott MacDonald) as the engineer [3]. Sir William Arrol and Co. were the contractors [3]. It is owned by Bridge House Estates [2].

Historical Significance

Basil Mott worked with Benjamin Baker, designer of the Forth Rail Bridge in Edinburgh [4]. Besides the architect, this same group of engineers constructed the Forth Rail Bridge. While I haven’t found any thing stating Southwark Bridge is innovative or a model for future structures, the fact that it was designed by engineers who designed other remarkable bridges makes it noteworthy. Southwark Bridge is similar in appearance to Blackfriars Railway Bridge, Blackfriars Bridge, Westminster Bridge, Vauxhall Bridge, and Grosvenor Bridge, just to name a few. All of these bridges cross the Thames and were completed within the 50 years prior to the design of the Southwark Bridge.

As mentioned earlier, this is not the first bridge to be called the Southwark Bridge. The original bridge was completed in 1819 and designed by architect John Rennie [1]. It was a three span arch bridge made of cast iron and masonry [3]. It ended up being the longest cast-iron arch span ever built [5]. The original bridge was innovative because its centers were formed, reducing the disruption to the river during construction [3]. This was a new and unique way to construct bridges at the time.

Figure 2. Old Southwark Bridge Construction [3]

The Old Southwark Bridge form was also innovative because the cast-iron was formed into ribbed arches made up of blocks of iron, similar to how a stone arch would work [1]. This can be seen in Figure 2. This eliminated the need for bolts and the blocks were, instead, tied together [1].

In 1856, the old London Bridge was removed, changing the currents that flowed around the Southwark Bridge [3]. This increase in current caused the bridge to be subject to scour as seen in Figure 3 [3]. Scour is the erosion of the parts of the structure around the waterline due to rapid currents. To reduce this problem, the new Southwark Bridge had five arches that aligned with the piers of the Blackfriars and London Bridges [3]. It also has thinner piers to allow water to flow more easily around the structure. This was a method developed in the earlier similar bridges mentioned previously.

Figure X. Scour along the Thames

Cultural Significance

The Southwark Bridge was built into old steps that had been used by watermen waiting for customers [6]. Because of its low traffic volume, it is a popular spot for filming. The bridge was used in the broomstick flight scene in Harry Potter and the Order of the Phoenix [7]. The bridge was mentioned in Mary Poppins when the Banks family thinks that Mr. Banks had jumped off the bridge after losing his job at the bank [8]. In real life, a pleasure boat collided with a barge near Southwark Bridge and killed 51 people in 1989 [9].

Figure 4. Scene from Harry Potter featuring the Southwark Bridge [10]

The Southwark Bridge was built as another crossing over the Thames to alleviate traffic on the London and Blackfriars Bridges. Several factors resulted in the bridge being unsuccessful in relieving traffic. The Old Southwark Bridge charged a toll, unlike its neighboring bridges, causing people to avoid using the bridge [1]. A major problem was the bridge’s connection to the other roads on the North and South sides. The Old Southwark Bridge was also steep and narrow, qualities that made drivers feel less safe. Because of its lack of use and the fact that some coach drivers park their cars on it, some people refer to it as the “car park bridge” [11]. Today, it is said that if you’re on the bridge, you are either lost or will be lost soon. It is often used as a way to get around the traffic of its neighboring bridges, but even then its traffic is minimal as it is the least used bridge over the Thames.

In 2009, the bridge underwent restoration that included repainting the bridge in its original green and yellow colors [2]. The reason for the green and yellow coloring is unknown, but I think most people would agree that it is aesthetically pleasing.

Structural Art

The structure is comprised of 5 steel arches with 4 stone piers [2]. The steel members are relatively thin. It is easy to see how the load transfers from the deck to the vertical steel members to the large steel arches. There are 7 arches in each span that are connected by truss members. This contributes to the transparency of the structure. Especially when compared to other London bridges like the Vauxhall Bridge, the Southwark Bridge has little ornamentation, unlike Vauxhall’s large statues atop each pier. However, Southwark has some components that are nonstructural. The towers on each pier were originally designed to provide a space for sculptures on the bridges. It was later decided to not include sculptures so now the extra height of the towers serve no use. However, these towers are not much taller compared to the overall structure. Another nonstructural element is the lampposts. There are 30 lampposts on the bridge that each have 3 lamps. This is clearly an architectural choice. Looking back at the structure, the extensive truss stiffening of the arches makes the structure less efficient and requires more material, making it less economical. While the overall arch structure is aesthetic, the addition of material in the trusses and the towers make the structure less elegant. Overall, I would say that while the bridge has some successful components and was designed by engineers who have been involved in structural art, the Southwark Bridge is not structural art.

Structural Analysis

When designing Southwark Bridge, the engineers were very aware of the damage that scour was causing to the bridges over the Thames as mentioned previously. Scour ending up being a major design factor in this bridge. The bridge features a 5 arch span, very similar to the nearby Blackfriars Bridge. This was done to allow for a smoother flow of currents and boats through the bridge [2]. The arches of the bridge are made out of steel and are supported by stone piers [2].

While information about construction of the current Southwark Bridge could not be found, I was able to find information on the Old Southwark Bridge construction and on similar construction projects in the early 1900s. The construction of the Old Southwark Bridge began with the foundations, using a cofferdam for the necessary excavation [5]. The central arch was made of segments of iron connected by dovetails and sockets to form the 8 ribs that made up the arch [5]. The formwork used to construct the arch can be seen back in Figure 3. Like the Old Southwark Bridge, the construction for the new Southwark Bridge would have started with the piers. In the 1900s, it was common for caissons to be used for foundation work, so it is likely that the current bridge used caissons instead of cofferdams. In 1903 when the proposed concrete Vauxhall Bridge was being constructed, it was found that the clay soil would not be able to withstand the weight of the concrete [12]. After realizing this, the design was changed to steel [12]. While their relation is unknown, it is possible that the problems of Vauxhall may have affected the engineer’s decision to use thin steel members for the Southwark Bridge.

The structural system of Southwark Bridge is a three-hinged arch made up of six smaller arches connected by trusses for stiffening. Each arch is supported by pier towers.

Figure 5. Loads on the arches

Figure 6. Load Path of the arch

The deck and vertical members transfer traffic and dead loads to the arch. The arch then transfers the load to the supporting piers. The truss members that connect the arches together and connect the deck to the arches are primarily there for stiffening of the structure.

The following assumptions can be made to analyze this system: the arch is pin connected to the piers, the road paving has a density of 145 pcf with a 3 inch thickness, steel with a density of 489 pcf and a 6 inch thickness, and a live traffic load of 200 psf [13]. The resulting distributed load is 480.75 psf. This is then multiplied by the width of the bridge, 55 feet, to get the load over one arch. The linear distributed load is 26.4 k/ft. The length of each arch is approximately 160 feet [3]. Because the load is uniformly distributed, the vertical reactions would be equivalent to half of the distributed load. After summing the vertical forces, the vertical reactions are (26.4 k/ft)*(160 ft)*(0.5) = 2,112 kips. The horizontal reactions from the piers can be found by taking the moment about either end. The distance between the top and bottom of the arch is assumed to be 50 feet. The horizontal reactions, which are equivalent by sum of the horizontal forces, is 3,368 kips. Figure 7 shows the math behind this.

Figure 7. Calculations

The internal force of the arch can be found by using Pythagorean Theorem with the reactions. The internal force is found to be 3975 kips. As the resultant of the reactions, the force would be acting towards the center of the arch making the arch in compression, as it should be.

To communicate to the stakeholders, the Bridge House Estates, renderings such as the one in Figure 8 were developed. The Bridge House Estates also owns nearby Blackfriars Bridge which has a similar design and was built earlier. Since Southwark Bridge has a simple and common style, it was probably easier for the engineers to communicate with the stakeholders about the bridge because the design wasn’t innovative; there was no need to prove that the bridge would work.

Figure 8. Rendering of Southwark Bridge

Personal Response

After visiting this bridge, I can definitely say it is the bridge less traveled. The reduced traffic on the bridge was an interesting change of pace in a city as busy as London. I found it to be the calm in the middle of a city in addition to providing a good view of the city’s skyscrapers. Seeing the bridge in person gave me a better idea of the many components that make up the truss system under the bridge. But when looking at the bridge from a distance in person, it is hard to see just how many members make up the structure.

Figure 9. Underneath Southwark Bridge

References

  1. http://www.southwarkbridge.co.uk/history/old-southwark-bridge.htm
  2. http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=668
  3. http://www.thames.me.uk/s00070.htm
  4. https://www.gracesguide.co.uk/Basil_Mott
  5. https://www.icevirtuallibrary.com/doi/full/10.1680/ehah.2011.164.3.163
  6. https://web.archive.org/web/20131215153238/http://www.southwarkbridge.co.uk/project
  7. http://www.the-magician.co.uk/harry-potter-locations.htm
  8. https://www.revolvy.com/main/index.php?s=Southwark%20Bridge
  9. http://www.thepeoplehistory.com/1989.html
  10. https://aclbradio.blogs.lincoln.ac.uk/2016/02/12/walk-in-the-footsteps-of-the-stars/
  11. https://www.greatlondonlandmarks.com/place/southwark-bridge/
  12. https://www.revolvy.com/main/index.php?s=Vauxhall%20Bridge
  13. https://www2.iccsafe.org/states/Florida2001/FL_Building1/PDFs/Chapter%2016_Structural%20Loads.pdf

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