The Alexandre III Bridge

I was in Paris, France just this weekend only to see how much it resembled the city of London. Don’t see how? Let me explain. If you saw my last blogpost, you know that I did a bridge tour to see about 10 bridges in line that sit on the River Thames. Well, a similar thing happened. Except this was now a boat tour. And instead of 10 bridges, I’m pretty sure I saw double the amount of bridges. But there was this one bridge that stood out to me the most: The Alexandre III Bridge. It made me want to research about it due to how elaborate and extravagant it is and was designed to be. It actually represents how I see the history of Europe to be: old, exquisite and still standing.

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Figure 1: Pont Alexandre III (Alexandre III Bridge)

Structure Information

The Alexandra III Bridge, known as Pont Alexandre III in French, is a bridge that sits across the Seine River in Paris, France. Construction of it started on October 7th, 1896 and it was completed in 1900 [2]. It was constructed to fulfill two purposes: “to celebrate the achievements of the last century” and to allow pedestrians to cross the river. To elaborate on this first purpose, there was the 1900 World Exposition that was held to celebrate achievements in fields like architecture, engineering, science and technology. This bridge along with many other structures were built to be showcased and represent Paris during this exposition. Secondly, a bridge was needed to allow visitors to cross the River Seine from the one side consisting of the Champs-Elysees to the side of the Eiffel Tower. The bridge was designed by architects, Joseph Cassien-Bernard and Gaston Cousin and it was constructed by engineers, Jean Resal and Amedee d’Albly [1]. The bridge was funded by the French government and it was named after the Russian Tsar, Alexandre III in celebration of Russian and French diplomatic relations [3].

Historical Significance

Although the focus of the bridge is its architectural work, the structural forms of its time must be recognized too. The arch hangs low to make sure that it does not block the view of the Invalides and Champs-Elysees and this was rarely done before. The bridge was also made quite slender–“tape-like proportions and wide, flat profile”. These two factors raised doubts of if the bridge would still work or even stand. To emphasize once again, these two factors–a low-hanging arch and “the slender nature of the bridge”–were rarely used or even experimented with during this time [3]. Therefore, the bridge was able to use an innovative structural engineering design that made it a structural masterpiece while it was already an architectural masterpiece.

Up until the time of the construction of the bridge, steel was used and produced using a process called open-hearth. This process involved increased temperature usage for melting metals and using the heat released as waste [4]. Also, steel was used only in small quantities because it was expensive to produce at this time. For example, steel was used when supported by brickwork and even then, “intermittent columns” were used. Speaking in regards to the connections, only simple bolting was used to join different structural members. However, with the construction of the Alexandre III Bridge, new construction techniques were used to an extensive point. The connections that were used for this bridge included bolting or riveting to join members especially in steel framed structures. Pre-cast members were made off site, shipped to the site and then bolted together on-site [1].

The Alexandre III Bridge can be characterized as a great example of work of its time for two reasons or elements: it’s structural arch that is “both simple and fluid” and its architectural decor [1]. As mentioned above, the low-lying and very fluid arch was unseen of its time, and a risky venture but it stands today as a structural masterpiece. It is also said to settle in quite well into its surroundings. Talking about the time the bridge was designed and built, it was when architecture flourished and this can be seen by the statues and facia pieces that were designed and put upon by French artists. Together with the combination of planned structural engineering and architectural work, the Bridge was a success of its time [1]. However, it does not stand as a model for future building as the heavy and elaborate decoration does not go well with the structural members that were intended to flow [1].Image result for old alexandre iii bridge

Figure 2: An old image of the Bridge

Cultural Significance

This bridge has been in use for about a century and it was built in the late 1800’s. Considering this fact and all the research I was able to do, I was not able to find the impact the bridge had on lives–both living and dead. As for those who lived at the site of the bridge, that is not applicable as the bridge was built on tourist/visiting areas to allow pedestrian traffic to flow across the bridge.

The bridge was constructed at a time that reflected the strength of France-Russian relations. This can be seen to have an impact on the bridge: “the first stone..[of the bridge]..was laid in 1896 by Tsar Nicolas II of Russia and the bridge was dedicated to his father Alexandre III” [1]. One of the decorative features of the bridge also reflects this alliance. The Nymph of the Seine and Neva rest on the keystone which represents the relationship between Paris and Russia. Built to be showcased at the World Exposition of 1900, the bridge served to represent Paris and its accomplishments in architecture which could be seen from the varying ornamental decor on the bridge [7].

The impact of the bridge is not limited to history; we can see it appear in pop culture–particularly films. The bridge has appeared in the last scene of the 2011 movie, Midnight in Paris [5]. It has made appearances in multiple other movies like Anastasia, Ronin, A Very Long Engagement, and A View to Kill. This reference is my favorite–the bridge has appeared in the background of Adele’s video of the song, “Someone Like You” which I have yet to notice [6]!

Although the behavior of the tourists and visitors of the bridge aren’t clear as to either being loving towards it or absolutely hating it, most people like or at least admire the bridge for its grandeur. Also considering that the bridge was designed to allow 50 million people to cross it, the bridge rose from a need or a purpose which would not allow hate to flourish [1].

This bridge is still used as a pedestrian walkway connecting opposite sides of the Seine River to each other. It allows tourists to visit both popular areas–the Champs-Elysees commercial area to Les Invalides–by just crossing the walkway. Till this day, the Alexandre III Bridge is known as “one of the most elegant and artistic bridges in the French capital” [3].

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Figure 3: Sketch of the Aleaxandre III Bridge

Structural Art

Although this bridge can be characterized by me as art, I would not consider this bridge as structural art. I have made this judgment based off of David Billington’s criterion of the 3 E’s.

Firstly, looking at the economy of this bridge, I was not able to find any values representing the cost of the construction. Nonetheless, an assumption can be made by looking at the grandeur of this bridge that it was quite expensive especially considering all the artwork that was put into place. Therefore, the bridge is not very economical.

Secondly, looking at the efficiency of the bridge, minimum amount of material was not used. Although the arch is smooth and low, it creates larger horizontal forces for which large abutments and foundations had to be put in place [1]. This takes away from the whole idea of structural art as one part of the bridge is smooth and minimal while the other part takes up the consequences (notably the abutments). Therefore, the bridge is not efficient.

Lastly, we talk about elegance which is more of an opinion. I do agree that the arch of the bridge is smooth and fluid, the load path can be easily seen and it has used methods that were not seen previously. However, as soon as my eyes move past the arch to the deck, I see these huge architectural pieces that I personally don’t think belong on a bridge. Instead of making it look grand and exquisite, it makes it look heavy and unnecessary. Therefore, this bridge is not elegant either!

In conclusion, the Alexandre III Bridge fails to pass the structural art test of the 3 E’s developed by Billington and used by me–so, it’s definitely not structural art!

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Figure 4: Alexandre III Bridge with Eiffel Tower in background

Structural Analysis

Although the bridge is analyzed from a structural engineering perspective, I still think it’s necessary to talk about the architectural pieces that sit on the bridge. There are two pillars on each side of the bank that stand at a height of 17 meters that act as counterweights for the arch. In front of each pillar, there is a female statue. On top of each pillar, there is a golden statue of Renommee, the Fame restraining Pegasus. There are also hammered copper sculptures at the keystones. Across the bridge, there are 32 candelabras, or lamp posts that light up the bridge [9].

Figure 5: The decorative pillar shown above and the candelabra shown beneath it.

The bridge is a three-hinged arch bridge with a total length of 16o meters. The main span that makes up the only and largest arch is 107.5 meters in length. The width of the deck is 40 meters [2]. The deck is so wide that it encompasses three traffic lanes of each direction, bike lanes, and sidewalks. The arch itself is composed of steel [3]. There are two masonry viaducts that sit at each bank on both sides. Since the arch hangs very low, it creates large forces that must be resisted by large abutment foundations [7]. Pneumatic caissons made of steel were put into place [1]. This is just an overall idea to build the picture of the bridge in your head–more details to come below!

At this time, mainly wrought or cast iron was used to construct large structures. However, this bridge was able to use mass quantities of steel due to the open-hearth process. The steel components were made in a French factory, Le Creusot. The caisson itself was made of steel  and its walls were composed of corrugated steel plates [1]. The girders are made of cast steel. Masonry was used for the side viaducts [7].

The bridge sees extensive use of wholly steel-framed structures that are made of bolted or riveted arrangement of members. Members were pre-cast off site and then brought on side to the River Seine to be bolted on parts of the bridges [1].

Now, we talk specifically about some of the structural systems put into place that allow the bridge to function as it does. Firstly, the arch stands at a height that is 1/17 to its length which is very low to the standards of that time. This steel arch is supported by bracing members. There are also 15 arch ribs that are arranged in a parallel manner in the front and back side of the bridge. Underneath the bridge, there is a complex array of braced-trussed structures as can be seen in the image below. As the arch is a 3 hinged arch, it must be recognized where each of the 3 hinges are: one at each abutment and the 3rd one at the apex, or the highest point of the bridge.Steel Structure

Figure 5: Steel bracing structure below the bridge

 

 

Figure 6: Parallel Ribs and Foundation at Right Edge of Span

Now, talking about the foundation, pneumatic caissons of heavy weight with open tops and bottoms were sunk and then used as abutment foundations of the bridge. Two masonry viaducts are put on each side of the arch at the banks that can be considered as part of the foundation to resist the thrust forces from the arch [1].

The load path of this bridge can be simplified to include the dead and live loads of the weight of the bridge, other structural and architectural members, occupancy and weather loads. This combined load is acting on the deck, downwards. From the deck, it gets transferred to the 15 parallel ribs that seem to hold up the deck in a stiff position. It is transferred in response to its tributary area from the deck. From there, the loads are transferred to the arch which is in compression. The loads that are being transferred from the deck have horizontal and vertical components. The vertical components are transferred from the arch to the foundation on either side of the arch then into the ground. The horizontal components from both the arch and each viaduct(because each viaduct is shaped like an arch which thicker ends but act as arches) are transferred to the abutments.

Figure 7: Load Path of Bridge

In the analysis of the central span, some assumptions and idealizations are made. Firstly, AASHTO Specifications were looked at to see the dead loads that could be applicable for this bridge. The dead load unit weight that is used for steel is 490 lb/ft^3 [8]. This measurement was multiplied by the width of the bridge, 131 feet, to get a load per linear feet. Although this load and the values seem quite high, it works out at the end because of the extensive architectural pieces resting on the bridge. In that case, the uniform load cannot be characterized as just dead loads.

Figure 8: Free Body Diagram of Middle Span with uniform load

Figure 9: Calculations to find Vertical Reactions

Figure 10: Cut made at middle hinge

Figure 11: Calculations for horizontal reactions or thrusts

The vertical calculations found in the image above are the loads that are transferred into the foundations at the ends of the span. The horizontal reactions are the thrusts that are developed from the compressing of the arch and they are transferred to the abutments.

Another analysis will be made about the stress experienced by the deck: this is applicable regardless if the load assumptions stated above are not true. The deck experiences heavy loading or forces and therefore will experience high amounts of stress. Therefore, from the stress equation (sigma/stress = force/area), it is reasonable to see what area of the deck is needed to maintain an allowable amount of stress under the force it experiences.

Since this bridge was built at an earlier time, the designers/architects and engineers were able to communicate the image they had in mind for this bridge through drawings. This allowed them to build the bridge in 2 years [7]. These drawings and drawn models were necessary to convince the French government that the bridge is in fact low enough to not obstruct Les Invalides as this was the main requirement by the government [3].

Personal Response

By actually traveling on the boat underneath this bridge, I realized how much more exquisite it is in person. No seriously, it seemed like I was in an outdoor museum! I also realized how heavy those architectural members must have been. But, it is this bridge that gives Paris its historical and expensive feel! It makes me realize that some structures aren’t built for engineering purposes but rather for the city’s name and honor as Pont Alexandre III has been built for Paris. Nonetheless, we reflect on these structures and take the best from them–such as the low-lying arch from this bridge!

References:

[1] http://www.bath.ac.uk/ace/uploads/StudentProjects/Bridgeconference2009/Papers/STEPHENSON.pdf

[2] https://structurae.net/structures/alexandre-iii-bridge

[3] https://study.com/academy/lesson/pont-alexandre-iii-bridge-history-statues-facts.html

[4] https://www.britannica.com/technology/open-hearth-process

[5] https://www.cntraveler.com/galleries/2014-10-31/11-filming-locations-paris-you-can-visit

[6] http://www.parisprovencevangogh.com/paris/pont-alexandre-iii-%E2%80%93-the-most-spectacular-bridge-in-paris

[7] https://web.archive.org/web/20061125232017/http://www.v1.paris.fr/en/Visiting/SITE.ASP?SITE=10007

[8] https://www.inti.gob.ar/cirsoc/pdf/puentes_hormigon/25-Lecture06-Design%20loads.pdf

[9] https://www.travelfranceonline.com/pont-alexandre-iii-a-lavish-decoration/

The Southwark Bridge

Walking along the Thames River during the Walking Bridge Tour in London, I encountered so many bridges–10 to be exact–that I was slightly overwhelmed. Although I love bridges and I encountered many different types, I choose to research a bridge that is less known and even less used–the Southwark Bridge.

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Figure 1: Southwark Bridge

Structure Information

The Southwark Bridge lies on the Thames River like the many other bridges in London. This bridge can be seen as one of the older ones and even then, another bridge existed before the Southwark Bridge was constructed. The older existing bridge was known as the Iron Bridge and it was constructed to alleviate congestion as London and the existing London Bridge was getting extremely congested. This bridge had its construction commence in 1813 and finish in 1819. It was a toll bridge. Just the mention of a toll bridge made the residents not want to use this bridge and return to using the London Bridge near by. After demolition of this old bridge, the new bridge, now known as the Southwark Bridge, was rebuilt from 1913 to 1921. This new Southwark Bridge, which will be referenced as just the Southwark Bridge, was built to be stronger and wider than its predecessor without the use of tolls later on. It still fulfills the purpose the bridge was originally designed to do: alleviate the traffic and congestion due to growth in the city of London while getting ride of the negative aspects of the old, Iron Bridge. It linked the Upper Thames Street to the other side of the Thames River, or the city part. Specifically, the south end sits near Museums and tourist areas while the north end sits near the Cannon Street Station. The bridge was designed by a combine effort of architects, Ernest George and Alfred Yeates and engineer, Basil Mott. The contractor was Sir William Arrol but the bridge is owned by City Bridge Trust, a charitable trust run by the City of London Corporation.

Historical Significance

The Southwark Bridge was built in place of the old Iron Bridge that was demolished at the time of World War I. Although it does not have many innovative and striking characteristics, it has adapted to attain the best characteristics of the old bridge and has achieved a few standards for its time. The Iron Bridge was made to be the longest spanning cast iron bridge in London with 3 separate arches placed across the river. Innovation can be seen in this old bridge as the material of that time, cast iron, was used to attain an engineering structure that was large and vast. On the other hand, Southwark Bridge was not built along those lines or even as an innovative idea. Steel arches were constructed and steel plate girder ribs were used. It was built to fulfill the purpose of the old bridge and used materials and construction methods that were expected of its time. Nonetheless, 2 facts can be noted. Firstly, in order to assist with the painting process, 1,000 tonnes of expandable abrasives were put on the bridge to attain the original metal framework. Secondly, 13,000 liters of paint was used to maintain the color of the bridge: the yellow and the green that can be seen from far away. This emphasizes the metal work and the importance of it. Again, the emphasis here is the lack of innovation in the engineering design and construction method used as this bridge was added as a replacement of a previously functional bridge.

Contrary to being an example or model for future buildings, the Southwark Building was in competition with the surrounding bridges–one of them being a similar bridge, the Blackfriars Bridge. It was built after this bridge and has a very similar appearance and form. Also, it should be noted that the piers of the Southwark Bridge aligned with those of the Blackfriars Bridge for ships and water vehicles to better flow through. In conclusion, the Southwark Bridge does not stand out as being a breakthrough structural engineered structure for the materials and processes it used but also because it followed other modeled bridges than becoming a model itself.

Southwark Bridge 1829

Figure 2: The old, Iron Bridge

Cultural Significance

There are less details behind the construction process and time of when the bridge was built so there are no facts to state the human cost or the number of deaths both while the bridge was being constructed and after it was built.

At the south end, there is the city of Southwark that is both quiet and not as well-known as some of the other areas. Therefore, there are no historical stories or events that characterize this bridge. However, popular culture has some link to this bridge. Some films have either been filmed at the site or have made referenced to it. For example, Charles Dickens references the Southwark Bridge in Little Dorritt and Our Mutual Friend not once but many times. The bridge has also appeared in films like Harry Potter and The Order of the Phoenix or Mary Poppins. It seems as though the location has been chosen due to the area being connected to London and the lack of population on the streets rather than the actual marvel of the bridge.

The Southwark bridge stands as being the least used bridge along the Thames River. It is not because the bridge is disliked but rather, it was a tolled bridge with narrow and steep lanes that made it inconvenient to use. The residents used the London Bridge that was close by. Also, it should be noted that the bridge runs through a quiet area while the London Bridge ran through a major road within the city. These reasons made the bridge less popular than it was intended to be but it should not be characterized as a bridge that is disliked. Now, the bridge is one of the quietest bridges connecting the two areas at the ends of the Thames River with only one-fortieth of the traffic from the other bridges but still allowing people and cars to cross it.

Structural Art

The decision of the Southwark Bridge being structural art will be made by me using the 3 E criterion.

Firstly, the bridge is efficient to a small extent. The load path can be seen clearly. However, there are some members that are either too heavy-looking or have no structural purpose. I am making reference to parallel ribs where it does seem a bit discontinuous. Less material could have been used to have an as efficient structure but I do realize that indeterminate structures are usually safer and preferred. In conclusion, the bridge is not as efficient due to the complexity that can been seen in the structural members.

Secondly, the cost of the project was about 2.5 million pounds. Other than the process of repainting, no major rehabilitation efforts were put into place. One more point should be noted: even after facing material shortages, the bridge was finished. Therefore, the economy of this structure is reasonable and can be considered an advantage.

Lastly, the elegance of this bridge is more of a personal opinion. I do not think that the bridge is very aesthetically pleasing of this time and generation and has a very heavy-structural feeling associated with it. It could have been considered to be aesthetic and elegant during its time. However, I do not classify this bridge as being elegant in comparison to the other bridges surrounding it.

In conclusion, this bridge does not classify as structural art. Nonetheless, I do not want to undermine its functionality and the purpose it fulfills.Image result for southwark ugly bridge

Figure 3: A very dull image of the bridge

Structural Analysis

Although there is lack of information about both the construction process and structural systems implemented, the Southwark Bridge will be analyzed below using engineering techniques.

Starting at the foundation, there are granite piers and turrets on each side of the arches that sit in the water. The piers can be seen to be slightly heavy and elaborate due to the time they were built: before the start of the War. They were designed by Sir Ernest George. 5 steel arches span over the Thames River: 2 spans of each being either 45 meters or 48 meters rest on the side and the 3 middle spans that are known as the central spans with length of 73 meters. These particular dimensions were designed for the span to match and align with the Blackfriars Bridge and The London Bridge. This would allow vehicular traffic on the waters to flow easily and smoothly. The arch system has specifically 7 arches layered underneath and attached by metal fixtures to make sure it would not bend. Then, each arch has parallel and vertical steel rods to allow for the loads to freely flow.

The bridge has two particularly complex and slightly hidden structural systems other than the ones that can be seen such as the deck, piers, etc listed above. Firstly, it is the layer of 7 arches underneath the deck. They are spaced out so that the inner 5 get the most load through them (based on their rectangular tributary area) while the arches on the outer sides get the least loads due to their smaller tributary area. Secondly, trusses within the system of arches are used for bracing and greater stiffness of the bridge. Although not visible clearly, the arches are connected through these rectangular and crossing sections.

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Figure 4: The 7 arches underneath the deck and the vertical rods

The load flows through the bridge from first the deck where all the loads are typically acted upon. The loads are then transferred to the vertical rods down to the arch. From there, it flows from each side of the arch to the nearest pier. As can be seen in the figure below, half of the loads flow to the left pier and half flow to the right pier. This load then flows into the piers and then into the foundation and the ground. And, that is how a bridge will transfer loads acting upon it into the ground.

Figure 5: Load Path on Southwark Bridge

The middle arch of the Southwark Bridge will be analyzed in the section below. I am looking at just one arch because when looking at the entire bridge, it acts like an indeterminate structure. Also, once one arch is analyzed, the others have a similar behavior.

Figure 6: Arch Free Body Diagram

I assumed that a uniform load of 5 Kilonewtons/millimeter squared or 105 pounds/feet squared was acting uniformly across the bridge deck. This was retrieved from an European engineering website which suggests typical loads on a short-medium span bridge. This value was multiplied by the thickness or in this case, the width of the bridge to get 5880 pound/feet which is the value as can be seen in the figure above (measurement per linear foot). From here, the vertical reactions at the base of the arch were calculated solely from statics. As can be seen from the symmetry of the Arch, the reactions at both points are equal to each other.

Figure 7: Calculations

Now, to calculate the horizontal forces, or the thrust enforced by the Arch, a cut was made at the middle. This cut allows an internal tension force to appear as seen in the figure below.

 Figure 8: FBD of Cut Arch

The horizontal reactions are calculated using a Moment equation.

Figure 9: Calculations of the Arch

Although the values do not reflect this, it can be seen that all the arches are in compression. The vertical forces are carried or held down by the piers while the horizontal forces, or the thrusts are cancelled out by each arch next the one being looked at except the arches at the ends. These arches at the end have their thrust force taken by abutments which are placed at the ends of the bridges. In all, the forces are calculated for the arch to see how it behaves and the overall behavior can be understood too. One more note should be made: to simplify the calculations and the results, a uniform load was considered. However, bridges are acted upon by combinations of dead, live, point, uniform and dynamic loads.

Bridge House Estates operates the City Bridge Trust which was used to build the Southwark Bridge. This Estate as well as all the stakeholders (engineers, architects, construction team, etc.) that were involved in the construction process of the bridge used drawings–newly rendered ones as well as inspiration from the old bridge to communicate the design on the bridge.

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Figure 10: The Iron Bridge vs. The Southwark Bridge

Personal Opinion

While standing near the bridge and taking pictures of it, I realized that the bridge does its job extremely well. It links two sides of the Thames River to allow for greater accessibility. Sure, it’s not the most eye-pleasing bridge like the 9 other bridges in its vicinity. Nonetheless, it’s a cool bridge that has peace due to the lack of people walking or driving across it. I would also like to admit that I felt particularly sad or empathetic towards it due to how it is seen by others. We should definitely give credit to this Bridge– after all, it still glows at night!

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Figure 11: The Southwark Bridge at night

 

References:

http://eurocodes.jrc.ec.europa.eu/doc/WS2008/EN1991_8_Calgaro.pdf

https://web.archive.org/web/20131215153238/http://www.southwarkbridge.co.uk/project

https://www.bristol.ac.uk/civilengineering/bridges/Pages/NotableBridges/Southwark.html

http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=667

http://www.southwarkbridge.co.uk/history/old-southwark-bridge.htm

https://historicengland.org.uk/listing/the-list/list-entry/1385913

http://www.towerbridge.org.uk/about/bhe/

 

Mercedes-Benz Stadium

Here is someone else talking about the Mercedes-Benz Stadium, AGAIN! What can I do?! It is one of the newer and more iconic structures located in my home city of Atlanta and hence, I couldn’t stop myself from researching it. Although I have yet to visit the stadium for a game, I’m in constant awe of the structure for good reasons!

Structural Information

Figure 1: Mercedes-Benz Stadium exterior view

The Mercedes-Benz Stadium is located in the heart of downtown Atlanta, Georgia; it sits adjacent to what stood before, the Georgia Dome. Construction of the projected started in April 2014 and it finished in 2017. The first game was played in this stadium as early as September 2017. This stadium was built to replace the Georgia Dome and become the new home for the Atlanta Falcons National Football League team as well as for the new Atlanta United soccer team. Its purpose is not limited to just this; it will serve many other purposes for other teams and events.

The team responsible for this iconic design is BuroHappold Engineering and architect, HOK. The team at Birdair was chosen as the specialty contractor to construct the roof pillow system and the facade while a general contractor team consisting of differing firms worked on the stadium. The main member of the structure, the retractable roof, was designed by HOK and TVSDesign and put into place by Birdair. The funding to construct this project was a mixture of both public and private funds. The total cost to build it was about $1.5 billion and the Falcons partnered up with the Georgia World Congress Center Authority (GWCCA) to build it (GWCCA owns it while the Falcons operate it).

The stadium is set to be an optimal location for sporting events with big future plans for holding events like the Super Bowl and College Football Playoff Championship game.

Historical Significance

The stadium was designed to be as unique and iconic as efficient. Not seen in other stadium, the whole of the structure has something new and futuristic to offer. Starting at the top, the retractable roof acts like a camera lens and is made of three layered ETFE,ethylene tetrafluoroethylene, roof pillows resting on eight petals. This particular roofing material was chosen for 3 main reasons: aesthetics, performance and sustainability. It is inspired by the Roman Pantheon and when in action, behaves like a falcon’s wings. This facade can open within 10 minutes giving an outdoor feel to the indoors when pleasant weather allows.

A 360 degree Halo scoreboard lines the upper interior of the stadium to ensure that each spectator has the best experience possible.

Figure 2: Retractable roof and interior view of screens

The Mercedes-Benz Stadium has set the standard for stadiums across the U.S. It is the first LEED Platinum professional sports stadium achieving its goal of sustainability. Some of the features include reusing rainwater, use of solar panels, efficient lighting and encouragement of alternative transportation. It has achieved 88 LEED points–the most any sports venue has achieved in the world. The characteristics described above make the Mercedes-Benz stadium a model for future buildings particularly sports arenas as it shows that efficiency, sustainability and technology can all be achieved for a structure.

Cultural Significance

Although recently built with the newest technologies, there has been one injury reported in which a worker was injured while trying to move a metal tower. This individual is suing the general contractor and other companies for permanent and continuing injuries. Other than this particular case, no injuries or deaths have been reported during and post-construction of the stadium.

 

Figure 3: Construction of the stadium

One of the historical event concerns is the impact on poor neighborhoods near the stadium: English Avenue and Vine City. Arthur Blank has suggested that millions of dollars will go to improve these neighborhoods but it seems the opposite. The money in the form of either investments or revenues is not directed towards these neighborhoods at all. In fact, these areas are seen as blotted out neighborhoods and little to no money is spent on local businesses to generate their economy. Nonetheless, Blank is persistent on changing the quality of life of the people living in these areas through donations. As can be seen, the stadium is loved by the spectators of sports and disliked by residents of surrounding neighborhoods due to each of their interests either being upheld or tossed to the side.

As it is a recently-constructed system, the human cost in building it is seen to have low statistical values and it is still used today for the purpose it was built.

Structural Art

The structure, in my opinion, does not demonstrate structural art no matter how beautiful, pleasing and futuristic it looks to my eye. This can be explained through the 3 E’s: efficiency, economy and elegance. As previously described, the structure is efficient in its purpose as it is sustainable and environmentally friendly (LEEDs too!). In terms of economy however, the stadium is quite costly as it ended up costing $1.5 billion to build and twice the material was used for construction compared to the Georgia Dome. Elegance could be seen as either aesthetically pleasing and environmentally-friendly but all 3 of the E’s are not satisfied.

Figure 4: Mercedes-Benz Stadium

Structural Analysis

Starting with the iconic roof, it is designed to be retractable and its functions are explained above. Specifically, eight cantilevered petals move to create the effect of a camera. Resting on these petals are ETFE cushion that are light-weight and allow smooth movement through the use of a cable net system. The eastern side of the structure has an a facade made of lightweight steel to allow openness and views of the city to be seen. Deep foundations and shallow foundations were put into place for the precast inner bowl. There are also 19 mega columns that support the roof and 8 other columns that support the mega columns. The foundational structures were made of thick high-strength concrete and longitudinal and shear reinforcements were used. Then, the precast seats were made of columns, vomitory walls, raker beams, and seats and placed in the inner bowl. The concrete bowl consisting of different sections such as top of seating, upper mezz and etc. was placed. A total of 150,00 cubic yards of concrete and 27,000 tons of structural steel was used to construct the stadium.

Figure 5: Depiction of the Mega Columns in place
Figure 6: Depiction of Seating

 

A detailed analysis of each of the sections was done through graphics and software such as SAFE software and designing of individual components was possible due to software like Enercalc. The design drawings generated from these softwares made it possible to communicate to the entire team what would be built and how it would be built. Manipulations and changes could easily be made to these models to make the structure’s design as best as possible.

Figure 6: Stadium Breakdown

A even more detailed analysis can be presented upon the stadium for which a whole powerpoint would not be enough due to the extensive detailing and design.

The loads on this structure include the dead load (weight of the stadium which increases as you go down since the lower parts have to hold the weight of the higher portions). The live loads can be considered to be the moving population of the spectators. No usually large dynamic loads are present as it is a very still and static structure. The total of these loads moves from the top to the bottom as following: the weight of the roof structure and the components inside moves to the triangular facade then which the increase in weight due to the facade will then move to the columns put into place. The columns then take the load of the weight and the people and transfer it to the ground through the closest column from the bowl structure. Although the system seems complicated from the outside due to the interconnectedness of the facades, the loads simple move from the top to the bottom through the closest structural member. Although stadiums and buildings weren’t covered for load paths, the idea works the same way.

Figure 7: External View of Load Path in One portion of stadium

Let’s look at a specific example. From figure 6, the blue foundation can be seen to upheld by many different columns. The load on this foundational slab will flow through/into the columns geometrically if the columns are spaced equally apart or portions of this force will go to the closest foundation columns. Then, these columns will transmit the loads to the ground. Of course, it should be noted that the force or load is the greatest at the bottom for which the columns handle a large load and must made be designed to handle the appropriate load.

Figure 8: Internal View of Load Path from slab to column

Note: Many simplifications were made due to the complexity of the stadium.

Personal Response

Although I have yet to visit the inside of the stadium, standing outside made me realized the innovations in Atlanta that have allowed such a futuristic building to be built in a still developing city! It put me in awe because of its size and the capability of the retractable roof.

References:

[1] https://www.burohappold.com/projects/mercedes-benz-stadium/

[2] http://mercedesbenzstadium.com/stadium-fast-facts/

[3] http://www.birdair.com/projects/mercedes-benz-stadium

[4] https://www.stadiumsofprofootball.com/stadiums/mercedes-benz-stadium/

[5] https://www.constructiondive.com/news/injured-worker-sues-gc-on-14b-falcons-stadium/422265/

[6] https://www.nytimes.com/2017/01/12/sports/football/atlanta-falcons-stadium-arthur-blank-neighborhood.html

[7] http://www.seaog.org/Presentations/MBS/MBS%20Presentation_SEAOG.pdf