Emirates Stadium

Quite possibly my favorite part of visiting Emirates Stadium was being able to read the stories written on the outside walls. Some of them were about inspired players practicing all their lives to play for Arsenal. Some were historical, regaling the tales of its founding members or defining play off games. But my favorite one happened to be one tucked away on the end of a series of stories. It was from a random fan of Arsenal talking about one night in a bar, with the time approaching 1:30. He looked to his left and saw Arsenal’s goalkeeper. He stammered out a hello and began talking to him. Around 3:00 the two are quite drunk and the fan suddenly remembers an important fact and asks the goalkeeper ‘Say, don’t you have a match in 12 hours, when are you calling it a night?’ The goalkeeper responded ‘When the sun starts to come up, kid’. The fan attends the Arsenal match the next and saw the players run out of the tunnel. Sure enough, the goalkeeper also ran out. The fan noticed the goalkeeper looked like he had been awake for a week straight (that’s the polite version of how he looked). Anyways, the match started and Arsenal ended up winning the game in a shutout. The very hungover Arsenal goalkeeper allowed no goals. Being in Europe and not having as cranky of people is great, and one reason is that a story about a goalkeeper staying up all night to drink before a match can be put on a stadium alongside all the other important and famous moments in this football club’s storied history.

Structure Information

Emirates Stadium was first opened on July 22, 2006 [1]. Construction began in July of 2003 [1]. The building is home to the Arsenal Football Club. The architect for this project was Populous (formerly known as HOK Sport) [1]. The structural engineers for this project were from Buro Happold [1]. The funding for the project was all private. Arsenal secured a total of 260 million pounds from loans from various banks [1]. However, one of the banks pulled out as construction started so the stadium’s building was delayed. Middle Eastern airline, Emirates, jumped at the opportunity to help with funding. They lent 100 million pounds in exchange for a 15 year shirt deal with the club and naming rights to the stadium [1].

Figure 1, Emirates Stadium

Historical Significance

The structural design of the roof was very unique. Its four trusses that support the roof is something that is not seen very often. It is presented here because of the type of events taking place at the stadium. The roof only needs to cover the fans in the stands, so there is a rectangular portion taken out of the ceiling about the size of the pitch. The cut out in the roof is not unique, but the four trusses supporting them is.

A special technique used during the construction of the stadium was the attention that was given to the seats. The concrete that makes up the stands was tested repeatedly for dynamic loading that would occur when fans jump/move around during the games [1]. The seating for the stadium was also outfitted with Ferco seats to make the fan experience even more enjoyable [1]. The thought was that if the stadium treated both fans and rivals with respect that they would respect the club in return. You can go to a game yourself to see if that holds true.

Regardless of how that strategy worked out, Emirates Stadium has gained a reputation as the most comfortable seating on the market. Another very cool thing that the stadium has going for it is the lighting for the pitch that the designers employed. They used computer modeling to make sure the lighting and air circulation was adequate for the level of quality they wanted in the grass [1]. The moving air also increased spectator comfort.

The best existing example of this stadium’s design is Estádio da Luz. This stadium is in Lisbon, Portugal and is primarily home to the Portuguese club S.L. Benfica. The stadium also features the same four truss design seen in Emirates Stadium. The view for fans in the stadium is also completely unobstructed. In addition to the unobstructed view, fans are mostly covered by a roof that extends out from the trusses. This roof structure can be a model for future buildings as it accomplishes one important task and one essential task: cover the fans from rain/sun and provide them with a clear view of the pitch.

Figure 2, Estádio da Luz [2]

Cultural Significance

No one died at the stadium during construction, but one worker was badly injured. Michael O’Donovan was kneeling to clean steel shuttering that is used to form reinforced concrete structures when a dump truck ran over his right leg [3]. His pelvis was fractured from the accident and his leg had to be amputated above the knee because the injury was so severe [3]. The City of London Magistrate’s Court determined that the site did not properly separate pedestrians and vehicles [3]. The companies in charge of construction were fined a total of 66,000 pounds in damages [3].

The beginning of the stadium’s tenure as the home of Arsenal was not good. Arsenal is a historically great team and their fans have very high expectations. However, they drastically under-performed in their first seven years. But once the 2013 season finished, Arsenal went on to win three out of the next four FA Cup titles, marking Arsenal as the most successful club in the history of the competition.

The stadium was loved by fans once it was opened. There had been some grumblings about the length of construction but once the stadium was open fans were more than at ease. The new stadium more than doubled the old stadium’s capacity, now allowing 59,867 people to attend games [4]. The land was undeveloped when it was bought and the surrounding area has had a major face lift as a result of the new stadium. The stadium is still used as the home of the Arsenal Football Club.

Figure 3, Arsenal’s Asia Cup Championship in 2015 [5]

Structural Art

To evaluate this stadium on whether it qualifies as structural art we can use the three fundamental principles of structural art: efficiency, economy, and elegance. The main concept behind each of these is to create a structure that utilizes the least amount of material, the least amount of cost both in design and social aspects to the people that will use it, and the most pleasing aesthetics possible.

Looking first at efficiency, this stadium does not seem to utilize the least amount of material from a first glance. The stadium was built to be ‘dramatic venue that highlights their ambition to become a global force in football’ and they used a large amount of materials to do that. Some materials were for the structure, others were used for fan comfort like the roof that extends over the seats. While it is something that was put into place for the fans, it is technically a waste of material. Other stadiums do not have a covering like Emirates. The load path of the building itself is also unclear. Much of the concrete that supports the stadium is covered up by facades making it hard to determine what is happening structurally without building plans. However, the truss structure that composes the roof does have a very light appearance to it. In this aspect, the roof does succeed in a light form with less materials. But, overall as a structure, I would say that this building does not check off on efficiency.

Figure 4, Emirates Stadium’s Dramatic Size

Economy was a problem for this stadium, with construction even being delayed because of it. However, the stadium’s cost can be looked at in a different light when the people funding the stadium are revealed. This stadium, unlike many in America, was entirely privately funded. Arsenal secured loans from various banks and companies to fund the building of this stadium. In terms of the social cost of this stadium for people, there was almost none. They did not have to chip in for this stadium unless they wanted to invest in bonds that Arsenal was selling (one of their other fundraising efforts). The fact that the stadium was privately funded does not entirely qualify it as hitting the economic checkbox though. David Billington, creator and major proponent of the three fundamental principles of structural art, notes that an unlimited budget is a hindrance to economy because designers will add unnecessary things because they have the budget for it. However, Arsenal privately funding this project (and requiring loans because they did not have the money outright for the stadium) means they wanted the stadium as good and cheap as possible. Taking these thoughts into consideration, the stadium does meet the economy criteria.

Finally, we look at elegance. Elegance as mentioned above, refers to the structure’s ability to create the maximum aesthetic possible. I, along with most everyone that goes to this stadium, would agree that the stadium is beautiful to look at. It stands tall and massive when you walk up to it, but it does not stick out in the skyline. When I got off at the Arsenal tube stop, I had to get directions to the stadium because I could not see it. The stadium emphasizes its massiveness for those that want to experience it, but does not do so in an ostentatious way. The stadium serves as an important symbol for the tradition of Arsenal as a powerhouse football club. The increased revenue from everyone attending this stadium has allowed them to sign better players and continue their dominance on the pitch. The stadium is a symbol for the powerful Arsenal team and is a meaningful place for every fan that attends it. With everything considered, I would argue that the stadium does meet the elegance standard.

Taking the three principles into consideration, the stadium almost passes the test of structural art. It meets two of the three requirements, but does not meet the efficiency criteria. This of course, was intentional. As mentioned previously, the goal of Arsenal was to make their new stadium a dramatic venue to symbolize their prominence in the world of football. Thinness and light form do not meet that idea. Architectural elements added to the stadium like facades out front and decorations adorning the structure serve that purpose. While the stadium is impressive from an architectural art perspective, it does not meet structural art standards.

Structural Analysis

Reinforced concrete was used for the flooring and framing of the first three levels of the stadium [1]. The lower, club, and box tier are supported by reinforced concrete rakers while the frame and structural steel rakers support the upper tier and level 4 [1]. The angle of a stand is known as the rake and the members used to support the stand are called rakers. The main stadium structure was able to be built at the same time as off site steel and precast concrete members [1]. Eight concrete cores are just inside the elliptical perimeter of the stadium to support it and transfer loads into the ground [1]. The stadium’s roof has 3,000 tons of steel and the entire stadium has 10,000 tons of steel throughout [6]. The stadium used 60,000 m^3 of concrete throughout the stadium [6].

The main concept of the structural system that is employed for the roof is actually a complicated version of a simple column and beam set up. This allowed the roof to cover fans while also keeping the view of the pitch unobstructed. The roof consists of three trusses: a primary, a secondary, and a tertiary set. A fourth perimeter truss also encompasses the entirety of the stadium. The length of the primary truss has a span of 204 m [1]. There are eight ‘tripods’ that transfer all of the vertical load to the columns.

Figure 5, Structural Components [1]

The load path of the roof is fairly simple once you visualize it as a beam and column structure. The tertiary trusses are in place all along the perimeter to help support the load of the roof and brace the primary trusses. The secondary trusses also help to support the roof and transfer load to the perimeter truss. The primary truss takes load from the tertiary and secondary trusses, as well as the roof itself and transfers that load to the tripods placed along the perimeter. There are also four additional tripods along the perimeter for stability reasons to make eight total tripods. Once the load has reached the tripods, it is transferred into the concrete cores and then into the ground.

Figure 6, Tripod

In addition to the tripods, there are props around the perimeter that help to transfer load down into the rakers. These props are responsible for getting the load from the perimeter truss to the ground.

Figure 7, Load Path of Primary, Secondary, and Tertiary Trusses on One Side

To analyze the structure and its load carrying capacity, we can model this structure as a truss. The analysis will be primarily looking at the primary truss. The simplified version of the truss is shown in Figure 8.

Figure 8, Truss FBD

The distance between each bottom connection is 14.5 m. The total length of the span is 203 m. This is not the exact length of the actual span but this allows a simpler analysis with the numbers involved. The load at each bottom joint signified by a blue arrow is equal to 10.4 tons [6]. The reaction at each end can be calculated as shown in Figure 9.

Figure 9, Solving for Reactions on Each Tripod

Another important aspect to consider for the analysis of this truss is the bearing stress that is induced on the tripod. The following calculations show the stress on the tripod. The radius of the pipe the truss connects to is 18 inches and the thickness of the pipe is 3 inches [6].

Figure 10, Bearing Stress

This means that the tripods need to be able to handle that amount of stress on the contact area it has with the primary truss.

A final set of calculations can be made for this truss structure, but it involves simplifying it even farther. If the truss, which only has loads on the bottom span, was reduced to a beam we can calculate the maximum moment occurring. To do this, we assume the same loads and reaction values that were calculated prior. From there we can solve for the shear diagram to get the maximum moment.

Figure 11, Shear Diagram

Using Figure 11, we can calculate the area of the first half of the graph that is positive to get the maximum moment. This value is equal to 3166.8 ton-ft. In calculating this number, it is obvious why the truss structure is braced so much. The bracing that occurs throughout this structure helps to prevent moment from deforming the truss. This extremely high moment value is definitely a large factor into the design conditions of the roof truss structure.

The design drawings were expressed well to Arsenal, even though there was not a firm need to. Populous had completed projects for Arsenal prior to this, so they were picked as the architects before a design was even in place. Of course, they wanted to do as best a job as possible so that they continued to receive work, but the initial design was not important. In terms of executing their vision, the break in construction as a result of the bank pulling their funding for the stadium was actually a blessing in disguise. With construction halted, Populous and Buro Happold were able to rethink parts of their building process and refine small details in their plans so that when the project started up again, everything would go smoothly. This was the case, as construction went on without any hitches when it started back up again.

Personal Response

It was a very humbling experience to visit the site of such a legendary and revered (or reviled if you are a fan of any other club in Europe) team. As a giant sports fan myself, I admittedly did not know much about the history of Arsenal before writing this blog. However, after talking to friends of mine it is clear why this stadium and team are so prominent in London and Europe as a whole. After reading about their accomplishments (and hearing from many salty friends) I better understand the connection this stadium has to Arsenal’s long history.

References

  1. https://issuu.com/jmurphy93/docs/dissertation_final-_emiratesstadium
  2. https://en.wikipedia.org/wiki/Est%C3%A1dio_da_Luz
  3. https://www.healthandsafetyatwork.com/arsenal-stadium-dump-truck
  4. https://www.boomtownbingo.com/history-emirates-stadium/
  5. https://www.unilad.co.uk/sport/internet-reacts-to-arsenal-winning-the-asia-trophy/
  6. https://www.designbuild-network.com/projects/ashburton/

Ponts des Arts Bridge

The Ponts des Arts Bridge is known by most people, especially tourists, as the bridge of Loveeee. Ever since the bridge was built, couples in love would write their names on a lock and lock it to the bridge gates, declaring their love to the world and making it everlasting in history. Sorry, I’m trying not to gag at the cheesiness. Talk about PDA. Anyway, the locks were removed in 2014, but the bridge still stands as the bridge of love to those who visited it. What most people don’t realize is that this bridge carries far more cultural significance than the locks. Technically this bridge is the second Ponts des Arts bridge, but since it is meant to replicate the original as closely as possible, the importance still stands. The original bridge was a symbol of France’s competition with Britain, and Napoleon ordered the original bridges creating personally. So, can we please move away from the love and focus on the interesting stuff? Because the both the past and present Ponts des Arts bridges are nothing if not interesting.

Figure 1: Ponts des Arts Bridge [1]

Structure Information

Okay, now we can get down to the basics, so stick with me.

Location: River Seine, Paris, France

Purpose: Connects the Louvre to the Insitut de France

Type: Deck arch pedestrian bridge

Main Material: Steel

Abutment and Piers Materials: Reinforced Concrete dressed in stone

Deck Material: Timber

Elements:

  • 7 arches
  • 6 piers
  • 2 abutments
  • Deck
  • Deck gates

Total Length: 509’

Arch Span Length: 72’

Width: 36’

Figure 2: Ponts des Arts Close Up

 

As I mentioned in my introduction, this is the second Ponts des Arts bridge. The first bridge in some ways is more historically and structurally significant because it was the first iron bridge in France, and Napoleon wanted it to compete with the Iron Bridge, the first bridge made of iron in the world. However, the bridge that currently stands is modeled to resemble the original, but has two main differences that must not be confused:

  1. The CURRENT bridge is made of STEEL. The original bridge was famous for being made of cast iron in the early 19th century, but since steel is much more efficient and widely used now and when the current bridge was built in the 1980s, it is made of steel, NOT IRON.
  2. There are SEVEN arches on the CURRENT bridge. The original bridge had nine arches, but when remaking it, they decided that it would fit in more with its neighboring bridges over the River Seine if it only had 7 arches.

Historical Significance

To properly explain the significance in terms of technology, I have to address both the original bridge and the current one. The original bridge was much more innovative for its time being the first even iron bridge in France and one of the first few in the world. It was far more lightweight and elegant when compared to the Iron Bridge

or other stone arches at the time.

Figure 3: Original Ponts des Arts Bridge circa 1804 [2]

Figure 4: Iron Bridge [3]

Every member of the Ponts des Arts held a purpose and it efficiently used material, whereas the Iron Bridge was designed to show off its designer’s iron working skills, not its efficiency as a structure. So, the original Ponts des Arts Bridge is extremely historically significant and could be considered structural art in its own right.

Now moving on to the current bridge and the subject of this blog, this bridge is not as historically significant in terms of technology. However, since it does make adjustments like using steel instead of iron and forming fewer arches, it can still be seen as historically significant in regards to a better version of the original. It is not however the first of its time to use steel or anything like that.

 

Cultural Significance

The Ponts des Arts bridge is massively culturally significant for three reasons. The first being that it is a replica of the original bridge which was a statement of French power and engineering competition. So, while the first bridge was destroyed, its symbolism is renewed and everlasting in the current bridge. So Yay.

Secondly, this bridge is hugely popularized as the bridge of love, and is known worldwide through movies, popular culture, writers’ and painters’ depictions, and celebrity social media to people. So, not surprisingly, the decision to remove all of the locks and place glass in their place so that no additional locks could be added was extremely controversial. Being the dork that I am, I think the glass better highlights the structural prowess (and yes, I just used the word prowess) of the bridge which was obscured and came in second to the wall of locks that stood before. But I by no means represent to universal person; I don’t even really represent the normal person considering I like to look at and analyze structures for fun, so I can see why this is a big deal to people. But, as a structural engineer, any additional and unnecessary weight (especially one that equals 50 tons) should be added if it takes away the structure’s ability to fulfill its primary function: to resist natural forces. If part of the bridge collapses, because of the locks, the locks have got to go. But like I said, many don’t agree with me, so this has been somewhat of a hot topic since the bridge gate collapsed in 2014. In fact, when you search the bridge on Google, headlines after headlines come up that look like the one below.

Figure 5: Lock Gate Collapse Headline in Independent Co [4]

Despite all of this, the bridge still is popularized by tourists, locals, and artists alike because it stands at the core of Paris’ draw and art center. And to mitigate the anger, Paris auctioned off the love locks and donated all of the proceeds to a charity for migrant workers and refugees, which I have to say is pretty fricken awesome! So don’t feel bad if your lock was removed, because it was for a good cause and we can now happily move on.

So, lastly, this bridge is popular simply because of what it connects: the Louvre and the Insitut de France. Tourists and students can be seen not only walking on it (which, duh because it’s a pedestrian bridge), but Ponts des Arts is also a common picnicking location, the site of different art exhibitions, and a hub for local artists to make money off of tourists (which can be quite annoying having just been harassed by street vendors in Paris). Nonetheless, the bridge is still widely loved both around the world and locally.

 

Structural Art

Now, let’s take a look at Billington’s Three Es (probably dreaded by those of you who have read of these over and over again, so sorry): efficiency, economy, and elegance.

Efficiency

This bridge is extremely efficient. It uses very little material, reduced the number of arches to seven instead of the original nine, and is very transparent.

Figure 6: Structural Transparency

 

When passing under it, you can see all of its members, which are not that many, especially when compared to the other bridges around it made of stone. However, stone is used to hide the reinforced concrete on the abutments and piers, which is inefficient. Nevertheless, this bridge is efficient in its design and utilization of steel as a material in its own right. The form fits the material.

Economy

For some reason, the exact cost of construction of the Ponts des Arts is extremely difficult to find. But not to worry, we can use look at its use of material to gauge its economy. As stated above, the bridge uses very little steel in the superstructure, but uses extra material in the abutments and piers. Since stone is unnecessarily added to the reinforced concrete, that choice is not economical, but the superstructure is economical. So, I’d say that this bridge achieves half credit in the economy category.

Elegance

This bridge is extremely elegant. For one, it is just plain pleasant to look at. But in terms of Billington’s criteria, the load path is clear in how it travels from the deck to its foundations, it is transparent and uniform in its design throughout the bridge. The stone abutments are a bit bulky, but in my opinion do not take away from the overall aesthetic of the bridge. So, without a doubt, I would say this bridge is elegant.

When taking all of the aforementioned factors into consideration, I would say that this bridge is structural art, although not the best example of it due to the piers and abutments. While casing the reinforced concrete abutments in stone was purely architectural, the elegance seen in the actual superstructure of the bridge overpowers that and wins for structural art in the end.

 

Structural Analysis

As stated above, this bridge functions like a typical arch bridge, with redundant arches next to each other to help with horizontal thrust. The spandrels also form semi-arches with diagonal bracing to help stiffen the deck and distribute the load throughout the arches rather than all at one point. This prevents the arches from buckling, almost as a flying buttress would. The load path, as demonstrated in the diagram below, starts at the deck as a combined uniform live and dead load, moves down into the arches either at the top of the arch or first into the spandrels and then into the arches. The load then transfers to the piers, which send the load down below water level and into the river bed.

Figure 7: Load Path

 

As any other typical arch, all of these arches are in compression, that is an arch’s defining characteristic. The spandrels are in tension, connecting the deck to the arches, each side pulling on the spandrel. The piers are in compression because they act like columns, with the load from the bridge pushing down and the normal force from the river floor pushing back up against the pier.

Figure 8: Members in Tension and Compression

 

We can use the principles of equilibrium to determine the forces acting on each member. To simplify the model, the following assumptions are being made:

  • Assume Deck is one solid surface
  • Assume pedestrian live load = 85 psf
  • tdeck = 1” = .083’
  • ρdeck= 35 lb/ft^3
  • ρsteel=490 lb/ft^3
  • Assume piers are made only of reinforced concrete with no added stone dressing
  • ρconc=115 lb/ft^3
  • Width of pier = 2’
  • Depth of pier = 31’

There are 5 arches in each span and 7 spans in the length of the bridge. So, for each arch:

The arches are made of steel which also have a dead weight. The free body diagram for each arch is the same and can be seen below. Note that the horizontal force that counteracts the arch’s thrust is either the thrust from the juxtaposed arch or from the abutment. Either way, the value should stay the same in order to achieve equilibrium.

Figure 9: Arch Free Body Diagram

The horizontal reactions caused by the thrust of each arch cancel each other out, and therefore do not require any extra calculations.

Moving onto the piers, each of the 6 piers in the middle hold a reaction from the arches on either side of it, and extend the width of 5 arches. So, each pier must support 10 times the point load coming from the arches. The free body diagram for the pier is shown below.

Figure 10: Pier Free Boody Diagram

There are 6 piers, so the bed of River Seine is actually supporting 6 distinct surface loads all equaling 5,714.64 psf.

The reason the reaction at the ground has units of force per area is because it is a surface load acting over the bottom of the pier, which has a length of 36’ and a width of 2’.

 

Personal Response

Okay, so this is probably more of a side effect to the program and having the three E’s drilled into my head continuously, but I can honestly say that my reaction when taking the boat tour and passing under the Ponts des Arts Bridge was “damn, that’s a piece of structural art”. While I ended up doubting that more when I took the time to analyze it as I did above, I just really admired how I could see the load path so clearly and it was so transparent. I didn’t even realize it was the love lock bridge I had seen so many times in movies, but clearly taking away the locks brought out the real character of the bridge rather than distracting from it.

 

References

[1] https://structurae.net/structures/pont-des-arts-1984

[2] https://en.wikipedia.org/wiki/Pont_des_Arts#/media/File:Paris,_Pont_des_Arts_by_Neurdein,_c1885-90.jpg

[3] https://www.shropshirestar.com/entertainment/telford-entertainment/2018/04/16/let-there-be-light-restored-iron-bridge-to-open-with-permanent-illumination/

[4] https://www.independent.co.uk/news/world/europe/part-of-paris-bridge-collapses-under-weight-of-love-locks-left-by-tourists-9512594.html

[5] http://www.eutouring.com/pont_des_arts_history.html

[6] https://www.napoleon.org/en/magazine/places/pont-des-arts-bridge/

[7] https://www.cometoparis.com/paris-guide/paris-monuments/pont-des-arts-s959

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

Walkie Talkie

Structure Information

Figure 1 – Picture by Me

Figure 2 – Picture by Someone Else

20 Fenchurch Street, known as the “Walkie Talkie,” was designed by Rafael Viñoly Architects and CH2M Hill structural engineers for Land Securities plc and Canary Wharf Group plc. This skyscraper, used as office space, residential space, and park space, has a really unique form—it curves outward on the front and back like a lens with an angled curve on the top (Figure 2). It’s pretty cool, especially when the building is 38 stories and 177 meters tall. This massive landmark began construction in January 2009 and opened in January 2015, being one of the newest additions to London’s skyscrapers. The Walkie Talkie is part of the booming skyscraper trend in the City of London (not “city of London,” but the confusing name for the smaller jurisdiction within the city), in the financial hub of the city. Even though it laser-beams cars (we’ll get to that later), this structure is a great addition to the skyline.

Historical Significance

This specific shape was unprecedented in skyscrapers when it was designed, and the shape is so unique that it has earned both praise and harsh criticism. With such a new building, the impact of the structure cannot be measured yet, but my guess is that it will inspire many architects and engineers to think outside the box in terms of form. I also think that the criticism earned by the building will motivate these designers be a little more conservative in design, still displaying new forms, but in a less exaggerated way. Outside of form and more on the engineering side, the unique cantilever approach (see structural analysis) used was basically custom-made for this building. Setting the core off center and cantilevering part of the curved façade in suck a specific way was extremely innovative, and we will have to wait and see if this technique gets adopted in other skyscraper designs.

Cultural Significance

The building’s culture impact is mainly through its divisiveness. The reception for the building has been very mixed. Many admire its innovative design and unique visual style, but the building is also hated by many for some pretty hilarious reasons. Besides some not enjoying the aesthetics of the skyscraper, many Brits are mad because it melts cars and causes wind tunnels, sometimes adding that it functions like “Bond villain tower.” If a building blew wind in my face and melted my car with a solar beam I wouldn’t like it either. The Walkie Talkie also affects the culture of the city through its environmental style. Along with various awards due to sustainable design, the building’s three-level park is an important fixture of the city. Although the park’s lack of complete public access is another point of criticism directed at the Walkie Talkie, this feature is still a positive.

Structural Art

In term of efficiency, this building’s structure carries complex loads extremely well. The architectural planning can be blamed for the poor performance in some areas (melting cars, channeling wind), but there have been no significant structural issues. Though the building is very new, and still must face years of trial, the efficiency required out of the structure

The whole point of this building is that it goes against what physics demands out of skyscraper form, and the result is poor economy. A tower of the same height could have been built with far less materials, so there is high cost is due to this over-the top design. Although this problem is due to the architectural design, it is impossible to say that this skyscraper minimizes cost for its particular function.

In the ideal of elegance, the Walkie Talkie building is difficult to measure. It succeeds in looking awesome, but using Billington’s concept of structural elegance shows that it does not succeed in this area. The visual aspects of the building were guided by architectural ideas, with the engineering just being done to ensure safety, and the load path is not on display.

Structural Analysis

One of the most challenging aspects of designing this skyscraper was that its architecture demands that its design is the opposite of a typical column. Columns carry gravity loads to the grounds, so a tapered shape toward the top is optimal, while increasing width toward the top is not preferred. The solution the team used was to set the concrete core of the building off center, since the building is heavier on one side, and also use perimeter columns of steel plate box sections. The loads travel downward through four main paths: the two outer columns of the inner core, and the two steel columns near the perimeter (Figure 3).

Figure 3 – Load Path

The distance from the core to the edge of the building range from 11 meters to 22 meters, and the solution was to have a max 18-meter span from core to perimeter column. Any beam distance above 18 meters is cantilevered. To get an idea of the forces present in these cantilevered, I calculated the forces in the beam with the longest cantilever, assuming simple supports (Figure 4). I named the weight per meter of steel beam w, the load transferred to the inner core column L1, and the load transferred to the outer column L2. Since max cantilever occurs just below the top floor, these loads are due to the slab and roof above.

Figure 4 – Cantilever Calculations

The calculations show that By is always supplying a positive force, but Ay only supplies a positive force if L1 > 52.6w. As the cantilever length decreases going down the building, L1 increases while w decreases, showing that the support in the inner core column increases significantly moving toward the base of the tower, due to both the weight above and the cantilever length.

The geometric changes at each floor demanded advanced technology to communicate the design and construction of the building to those outside of the design team. To tackle these challenges, advanced 4D-BIM modelling—3D building information modelling with time added as a fourth dimension—was used, allowing the team to anticipate challenges and maximize safety. This information was mainly used to communicate the building’s program with the clients and mitigate communication issues with the construction team.

Personal Response

The Walkie Talkie Building was only ever slightly impressive to me until I got up close. The first time I visited London I didn’t really give it a second thought. I thought it was a slightly cool building that was probably very difficult to build. When I stood under the amazing vertical curvature of the building, though, I was blown away. It was pouring rain, but standing in front of the building kept us out of the rain. Looking up, it looked as if though the building should be falling on top of me, and the curvature makes the building appear even taller than it really is. As a bonus, I also learned that the top of the building has a full park, which I would love to check out. Overall, I think this is one of the most visually impressive structures in the world with some very impressive engineering that allows a really unique form. 

References

[1] https://www.steelconstruction.org/design-awards/2014/commendation/20-fenchurch-street-london/

[2] https://www.telegraph.co.uk/business/2017/07/27/walkie-talkie-building-sold-hong-kong-company-record-128bn-deal/

[3] https://www.steelconstruction.info/20_Fenchurch_Street,_London

British Airways i360 (The London Eye’s Little Sister)

I went down to Brighton for the day to hang out with one of my friends from there. She toured me around and, of course, we ended up on the beach. She pointed out to me, in the distance, a huge column and told me it was their brand new observation tower. She also said it was pretty controversial because it was built with taxpayers dollars, so I thought it would be interesting to do more research into.


Structure Information

Figure 1: My View of the i360 on Brighton Beach

This observation deck on Brighton Beach is called the British Airways i360. The BAi360, as British Airways calls it, cost £46 million to design and build. It was funded by Brighton and Hove City Council, Coast to Capital Local Enterprise Partnership, and Brighton i360 Ltd. Brighton and Hove City Council was loaned the money from the Public Works Loan Board and Bright and Hove City Council receives a potion of the profits. The observation deck opened in the summer of 2016 and has already begun to promote other development along the shoreline in Brighton. [1]

The BAi360 can be used as an event space as well as for the typical 25 minute “flights” to the top. 175 people can ride in the pod at the same time! The BAi360 website boasts that the structure itself is 20 feet taller than the London Eye, which is considered the BAi360’s “sibling.” [1]

Speaking of the London Eye, the architect for the London Eye, Marks Barfield Architects, was also the architect for the British Airways i360. The structural engineer on the project was Jacobs. [2]


Historical Significance

Figure 2: i360 Construction [2]

The British Airways i360 has won many awards, but the most notable awards are being the world’s tallest moving observation tower in 2017 and holding the Guinness Record for the world’s most slender tower. The construction process was the first of its kind, without cranes for the height addition and from the top to the bottom, which I’ll discuss further in the structural analysis. This construction method meant that construction workers were only needed on the ground, which is must safer than being 162 meters in the air. Figure 2 shows how much shorter the crane used in construction was compared to the completed tower. The liquid dampers used were also revolutionary in the UK. [3]

 


Cultural Significance

Figure 3: The i360 at Night [2]

The i360 seems pretty out of place in Brighton next to the Brighton Pier with arcade games and festival food, and it seems some locals agree. The i360 gained many nicknames, typical of the British, one being the iSore, another the Brighton Pole, and many others which are very inappropriate [4]. Figure 3 shows how tall the i360 is compared to the rest of the shoreline.

The investment process was also extremely controversial because the construction was just getting started as the recession hit and suddenly there wasn’t money for the structure. Up until then, it was to be only privately funded. In 2012, Brighton and Hove Council pledged enough money to get the project restarted, and in 2014, it pledged even more money when more funding walked out the door and the architects could only put up so much to keep it going. [5] In an effort to subdue these criticisms, local residents receive half-price tickets and each public school students in Brighton and Hove got a free tickets the summer the i360 opened [1].

With revenue being what was expected and the new development starting in the area, it seems that the i360 is helping the economy in Brighton and promoting even more tourism. It also seems to commemorate the old West Pier that was falling apart and eventually burned down (the arsonists were never caught), which metal skeleton just sits in the sea now in front of the i360.


Structural Art

Despite the public backlash and perhaps its out-of-placeness, I do think that the BAi360 is structural art.

The efficiency is obvious – with the recession, the architects and engineers were under huge economic constraints. On top of that, being the most slender tower in the world means the i360 really doesn’t use much material. My friend from Brighton told me that most of the area is in the Green Party, Brighton runs some buses off of recycled oil from making fish and chips, and there is a wind farm in the sea for energy, the i360 even reuses its energy from descending to go up the next time; all of which indicates that being efficient is extremely important to the area.

As far as economy, the construction method was absolutely considered in the design. From the architects that came up with lifting the London Eye from the River Themes in under a week, the i360 was built using jacks and keeping construction workers on the ground because of the huge wind loads at the top of the i360.

Elegance may be harder to see because of the location of the i360, but it is clear that this structure’s load goes straight into the ground, since it is just a column. There is nothing extra to hold up the column and the simplicity truly makes the i360 structural art.


Structural Analysis

As mentioned earlier, the i360 was thought up by the designers of the London Eye and had a novel construction method. The tower itself is made of steel, covered with perforated aluminum to prevent wind vortices. Inside the tower are 78 jugs of Australian water to further resist wind loads. The construction was done by transporting pre-made materials on a barge to the beach. A jacking frame was put up and 17 50-100 ton “cans” were jacked up, like you’d jack up your car to change a tire, but much larger. [3]

Due to the wind, there is a little more complexity to the i360 tower than once first thinks. The columns is the first structural component I first thought of, the second being the observation pod. After doing research, the liquid damping system is the final structural component to consider. The liquid dampers were “tuned” to the three most common natural frequencies of an undamped tower [7].

Figure 4: i360 Load Path

The tower is 162 meters high and 3.9 meters in diameter, 4.5 meters including the covering [3]. The viewing pod carries 200 passengers and goes up to 138 meters [3]. The pod is 18 meters in diameter and weighs 94 tons [8]. The tower only closes once wind gusts are up to 44 mph, which is 243 N/m2 for this structure according to a velocity-pressure chart [5]. The foundation is 6.5 meters deep to hit chalk rock, and because of tides, the base had to be able to sit in water. The foundation is 4,150 tons while the tower is 1,200 tons. 200 people can weigh about 18-20 tons, and they need to be able to stand all on one side of the pod in case something interesting is happening for them to all look at. The code in Britain for wind loading is to withstand “the worst three second gust in the middle of the worst storm which occurs on average every 50 years.” Apparently, this translates to the structure being able to deflect over a meter safely. There were redundant measures put in the tower for dynamic loading, such as random outstands to “confuse the wind,” as Dr. Stewart would say. [6]

The load path for the i360 is very simple: the mass from the pod goes to the tower and then from the tower the load goes to the foundation. The load path can be seen in Figure 4.

Since the pod will only operate at conditions under 44 mph gusts, I chose to analyze the worst-cast scenario with 44 mph winds. This includes all of the people being at one point on the edge of the pod and 44 mph winds creating pressure along the entire structure. With these assumptions, I calculated maximum moment and maximum shear, which are at the base of the tower since the tower can be treated as a cantilever, as well as the reaction forces of the foundation on the tower. The calculations and diagrams I used are shown below. 

The idea of the the i360 came from the architects, not the city, which is somewhat unusual. The i360 was modeled in a computer, and views of the structure with the town of Brighton behind it were presented, as well as views of what the inside of the pods would look like during flight. Figure 5 shows the i360 from a beach-view while Figure 6 shows the inside of the observation pod. These models were shown to Brighton and Hove Council and members of the community.

Figure 5: i360 Model [9]

Figure 6: Inside Observation Pod Model [10]


Personal Response

I’m so glad I decided to look further into the British Airways i360 after visiting Brighton. The story behind the structure and how innovative it is was really interesting. By seeing the i360 in person, I was able to see just how much it contrasted the rest of the town and see all of the new development happening in Brighton just nearby the i360. Since the i360 has dampers, wind loading, and live loading, I feel like everything I have learned this summer really came together for me to learn about the BAi360 in this final blog post.


References

1 http://britishairwaysi360.com/about/faqs/

2 http://www.marksbarfield.com/projects/brighton-i360/

3 https://www.istructe.org/structuralawards/2017-winners/tall-or-slender-structures/2017/british-airways-i360-at-brighton

4 https://www.theguardian.com/artanddesign/2016/aug/02/brighton-i360-review-marks-barfield-british-airways

5 https://www.theguardian.com/uk-news/2015/aug/28/its-a-bonkers-outsized-flagpole-brighton-greets-the-worlds-tallest-moving-observation-tower

6 http://britishairwaysi360.com/latest-news/the-science-behind-the-i360-tower/

7 https://www.newcivilengineer.com/technical-excellence/super-tall-super-smart-the-brighton-i360/10010065.article

8 http://britishairwaysi360.com/wp-content/uploads/2015/05/i360-Media-Pack-Updated100717-1.pdf

https://www.absolutemagazine.co.uk/absolute-news/british-airways-i360-passenger-pod-interior_credit-british-airways-i360/

10 http://www.c-mw.net/brighton-i360-seeks-global-stage/

Le Pont des Arts

Structure Information

The Pont des Arts is an iconic bridge spanning across the Seine River in Paris, France. Construction of the current bridge began in 1981 and finished in 1984. Figure 1 below is a photo of the bridge today.

Figure 1: Le Pont des Arts, Paris, France

In english, “Le Pont des Arts” translates to “The Bridge of the Arts.” The name of this bridge is very fitting for its function because it serves as a pedestrian bridge that links the Institut de France and the central square of the Palais du Louvre. The Institut de France is a French learned society that houses French Academies such as the Academies of Music, Humanities, and Sciences. The Palais du Louvre is a former royal palace which is now the largest art museum in the world. Figure 2 below shows the bridge name carved in to the abutment closest to the Institut de France.

Figure 2: Bridge name carved in to the stone of one abutment

The Pont des Arts was designed by Architect Louis Arretche, and the structural engineering was done by Enterprise Morillon Corvol Courbot (EMCC) [1]. The bridge was built as a replacement for the former bridge built under Napolean Bonaparte. This bridge is a structure paid for by French Public Works.

Historical Significance

As previously stated, the Pont des Arts was built as a replacement for a bridge that was built in the same place across the Seine in 1804. The current bridge is almost identical in design to the original bridge, so by modern standards, the current bridge cannot be considered an innovative structural engineering design. However, the original bridge, completed in 1804 was the first metal bridge to be constructed in Paris, 19 years after the building of Iron Bridge in England. Napolean Bonaparte asked engineers to design a bridge that resembled a garden that was suspended over the Seine [2]. The original bridge was elegant, lightweight and constructed from cast iron, placing it on the cutting edge of engineering in its day. The piers of the original bridge were constructed in masonry as were all the piers of bridges along the Seine, but the use of cast iron was a very new construction technique. The construction of the present bridge did not involve any new construction techniques.

The current Pont des Arts is a steel arch bridge. Its historical connection and consequently almost identical design to the original bridge in the same location makes it unimpressive structurally by modern standards. The best existing example of a steel arch bridge is the Syndey Harbour Bridge in Sydney, Australia. It is the largest steel arch bridge in the world. Figure 3 below shows an image of the Sydney Harbour Bridge.

Figure 3: Sydney Harbour Bridge

Cultural Significance

The current Pont des Arts bridge is internationally known and is one of the most famous bridges in Paris. It is first iconic because of its location–the link between two of Paris’ most iconic buildings. The Palais du Louvre on the bridges right end has housed French kings since its construction in the 1200’s, and is now the largest and arguably most famous art museum in the world. On the left end of the bridge, the Institut de France houses the agency that manages over 1000 foundations, museums and chateaux that are open to the public, making it a major cultural landmark.

In addition to its locale, the Pont des Arts is a cultural landmark because of its connection to history. The bridge that was originally in its place was ordered to be built at the beginning of the rule of Napolean Bonaparte. Napolean’s empire dominated the French Revolutionary wars and facilitated the development of Paris with structures such as the Arc de Triomphe and the Pont des Arts.

The original concept for a metal bridge in Paris in the beginning of the 19th century was largely rejected by famous Parisian architects of the day. These experts thought that it would lack monument because of its lightness and metal form. The aesthetic of metal was vastly different from the monumental stone bridges between which the Pont des Arts was to be built. However, when construction was completed, the Parisians “took the bridge to heart” [3]. As with most bridges of the time, the Pont des Arts was a toll bridge which cost one cent to cross. On the day the bridge was opened, 65,000 Parisians paid their penny to cross the new bridge [3]. The permanence of the original design that continues in the Pont des Arts today describes the iconic and loved nature of this bridge.

There is no record of injured workers in the construction of the original Pont des Arts built in 1804 or the new Pont des Arts built in 1984. However, the original Pont des Arts was demolished in 1980 because of structural weakening and damage from barges. There were barge collisions throughout the life of the original bridge, considered to be the human cost of the bridge.

Today the Pont des Arts is an internationally known landmark. The bridge is a favorite for artists, musicians and people in love. In 2008, a tradition began which gave the Pont des Arts the unofficial name of the “Love Lock Bridge.” Couples would write their initials on a lock, attach it to the side rails of the bridge and throw the key in to the Seine River as a symbol of eternal love. The tradition became so popular that there was an additional 45 tons of weight added to the bridge from the locks [4]. This loading caused structural weakening and eventual collapse of one railing section. In 2014 the railing sections were removed and replaced with plexiglass sheets. Figure 4 below shows a railing section with the love locks in tact.

Figure 4: Pont des Arts railing with love locks attached [4]

The Pont des Arts is still used as a pedestrian bridge and remains an iconic part of Paris.

Structural Art

The design of the current Pont des Arts was dictated by the original iron design in 1804. The structure has been described as “light” since its original construction, which has been considered a good and a bad thing depending on the critic. I think that the original design boldly rejected the heavy monument of stone that was the norm for Parisian bridges at the time. The structure was able to be made light because of the new material of iron. In this sense, form was dictated by function. I think this is a major requirment of structural art, and the Pont des Arts embodies this requirement. David Billington states that aesthetics should be the final judgement when deciding if something is structural art. I was immediately drawn to this bridge. It stood out to me while strolling along the Seine because of its elegance and lightness when compared to the countless bridges of heavy stone that span the Seine. I think that the only thing that subtracts from the status of the Pont des Arts as structural art is the fact that the modern bridge was designed by an architect and not an engineer. Similar to this, the piers of the modern bridge are made of reinforced concrete, but faced in stone to pay tribute to the design of the original bridge. Hiding the true material that takes load is a way that the structure does not demonstrate structural art.

Structural Analysis

The modern Pont des Arts is designed to replicate the original bridge that was built in 1804 and demolished in 1980. The original bridge was a cast iron arch bridge with nine iron arches spanning a total of 509 feet. The form of the bridge was modeled after the British metal arch bridges that preceded it. The supporting bridge piers were constructed of stone masonry using cofferdam systems to block the water around the pier and pump it dry with buckets. The deck was contructed using wooden planks.

The design of the modern Pont des Arts bridge is almost identical to that of the original bridge. The differences lie mostly in construction materials used. The current Pont des Arts superstructure is constructed in steel. Steel is lighter, stronger and more ductile than iron, making it the clear modern choice after the failure of the original iron bridge. The piers are constructed in reinforced concrete but faced with masonry to pay tribute to the original bridge. The deck is constructed in timber, another tribute to the original bridge design. Another departure of the modern bridge from the original bridge design is the number of arches. The current bridge has seven arches instead of nine, a design choice that was made to be consistent with the number of arches of the adjacent Pont du Neuf, and made possible because of the ability to make longer arch spans with modern construction materials and technology.

The structural system employed in this bridge is repeating three-hinged arches. There are seven arches from bank to bank and there are five repeating arch systems that span from edge of deck to edge of deck as shown in Figure 5 below.

Figure 5: Five arches which span from edge of deck to edge of deck meeting at one pier

Figure 6 below shows an elevation view of contiguous repeated arches meeting at one pier.

Figure 6: Arches meeting at one pier

The repeated arches are supported by reinforced concrete piers and abutments on either end of the bridge.

Load from pedestrian traffic and the timber deck is transmitted from the deck to the spandrels connecting the arches to the deck. The load moves through the spandrels to the arches. The arches are in compression. Since the structural system consists of repeated arches, the horizontal thrust generated by each arch at the arch connection to the pier is cancelled out by the horizontal thrust generated in the opposite direction from the contiguous arch. The vertical load at eah arch end is transmitted through the bridge pier to the ground. The only horizontal thrust that is realized is at each end of the bridge and is taken by the abutments. The load path is shown in Figure 7 below.

Figure 7: Load path of one repeated arch

Using this load path and assumptions about the dimensions of the bridge, one of the total 35 arches can be analyzed. The dead load of this bridge is calculated using the density of the timber decking which is assumed to be 41.8 pcf [6]. Assuming the deck is 1 ft thick, the area dead load is equal to 41.8 lb/ft^2.

European building codes specify that the live loading associated with pedestrian footbridges is typically 5 kN/m^2 [5] which is equal to 104.4 lb/ft^2. The deck has 7 spans totaling 155 m or 508.5 ft and a deck width of 10 m or 32.8 ft. By the principle of superposition, to get total linear loading, the dead and live area loads are added and multiplied by deck width as shown below.

(41.8+104.4) lb/ft^2*(32.8 ft)= 4795.4 lb/ft

The length of one arch span can be found by dividing total span by number of arches as shown below.

(508.5 ft)/(7 arches) = 72.6 ft/arch

Height of arch is assumed to be 24.2 ft based on the visual proportion to arch length.

From these data and assumptions, and assuming the the load will be transferred completely to the arch by the spandrels, the following model shown in Figure 8 can be used to perform the analysis of one arch.

Figure 8: Simplified model of one arch

To analyze find the reaction forces the arch will be cut at the center hinge. A model of the left side of the cut is shown below in Figure 9.

Figure 9: Left side of arch cut at center hinge

By symmetry using the global structure, reaction force By is equal to zero. Ay can be found using sum of forces in the y-direction as shown below.

Ay – (4795.4 lb/ft)*(36.3 ft) = 0

Ay=174073.0 lb

Using the sum of moments about the top hinge, reaction force Ax can be found as shown below.

Ay(36.3 ft) – Ax(24.2 ft)-((4795.4 lb/ft)(36.3 ft)(1/2)(36.3 ft))=0

Ax = 130552.6 lb

From these equations we know that 174.1 kips of force is being transmitted vertically from one end of the arch to the pier and 130.6 kips of horizontal thrust is generated, which is counteracted by the contiguous arch. Since there are 5 pin connections at each pier with two arches connected at each pin, the total vertical force exerted on the pier can be calculated using the following equation.

(174073.0 lbs)*(5 pins)*(2 arches) = 1740730 lbs

We can use this force and assumptions about the geometry of the cross section of the piers to calculate compressive stress in each pier. It is assumed that the piers are rectangular in cross section, 32.8 ft in length, and 2 feet in width. The area of the pier can be calculated using the following equation.

Area = (32.8 ft)*(2 feet) = 65.6 ft^2

Assuming the cross-section is constant, the stress in the pier is found using the following equation.

Stress in pier = (1740730 lbs/ 65.6 ft^2)*(1 ft^2/144 in^2)= 184.3 psi

This value can be compared to typical strength of reinforced concrete, equal to 4000 psi.

4000 psi >> 184.3 psi

Based on these calculations, the piers are designed with a safety factor of 21. This is very high for a bridge, and should be considered higher than actual design because of assumptions made.

Sum of forces in the x-direction can be performed to find the horizontal reaction force Bx as shown below.

Ax – Bx = 0

Bx=130552.6 lbs (in the negative x-direction)

It is assumed that Bx represents the compressive force in the arch. We can use this force and assumptions about the geometry of the arch cross-section to find compressive stress in the arches. It is assumed that the cross-section of the steel arches are rectangular and the area of the cross-section is equal to 10 in^2.

Stress in arch = 130552.6 lb/10 in^2 = 13055.3 psi

Steel has a compressive strength of about 25000 psi. Comparing the design stress to material properties of steel,

25000 psi > 13055.3 psi

This indicates that the steel superstructure is designed with a safety factor of about 1.9. This value is close to what would be used in the design of a bridge.

It is assumed that since this bridge was built as a structure of French public works, drawings or plans were made to the specifications of French bridge building codes and communicated to the the owner (French government).

Personal Reaction

I saw this bridge while strolling along the Seine River from Notre Dame Cathedral to The Eiffel Tower. As I previously stated, I was immediately drawn to this bridge because of its lightness compared to the heavily ornamented stone bridges around it. Standing on the bridge with two huge French monuments on either side of me, it was amazing to me how much history and culture could be built in to a structure as simple as a foot bridge.

 

 

[1] https://structurae.net/structures/pont-des-arts-1984

[2] https://www.cometoparis.com/paris-guide/paris-monuments/pont-des-arts-s959

[3] https://www.napoleon.org/en/magazine/places/pont-des-arts-bridge/

[4] https://www.citymetric.com/horizons/paris-has-replaced-padlocks-pont-des-arts-padlock-themed-graffiti-1113

[5] http://www.cbdg.org.uk/tech2.asp

[6] https://www.forza-doors.com/performance-guides/general-guidance/timber-density-chart.aspx

Grande Arche de la Défense (Great Arch of Defense)

Structure Information

            Wow, A huge rectangle and a cloud. That was my initial reaction when I first seen the structure.The Grande Arche de la Défense (Great Arch of Defense) not a rectangle is a huge arch located in La Défense, Paris business district. The view from the top of the steps are breath taking. The arch was built to mark the end of the Triumphal Way, the east-west axis that connects the Louvre with La Défense. The purpose of the building today is used for office space. This building was a part of a design competition in 1982, by the president François Mitterrand to commence new construction activity [2]. Architect Johann Otto von Spreckelsen and engineer Erik Reitzel designed the winning entry. They won because their design had stability, simplicity and purity of form [2]. This was cool, because a lot of the designers we talk about in class were involved in design competitions. The designers wanted this to be a place where diverse people could meet and converse. Construction started in 1985, and the building was complete 1989. This project was funded by the government through with a budget of 1.3 billion francs.

 

Figure 1:The Grande Arche de la Défense at Night

Figure 2:The Grande Arche de la Défense Currently

Figure 3:The view under the “Cloud”

Figure 4:The View from the Stairs

 Historical Significance 

            Based on other Paris monuments the arch is twice the size of the Arc de Triomphe and its archway is large enough to fit the Notre-Dame Cathedral. The arch is made of pre-stressed concrete. The cloud spans between the inside of the archway is a tent-like structure. It was created to reduce wind resistance and it also achieves the effect of seemingly reducing the gigantic proportions of the arch [2]. The cloud is made of white plastic panels that are suspended by steel cables to the sides of the arch [2]. Before the designer built the arch the designed three churches. It was stated that he relied heavily on simple geometrical figures, hence the hollow cube (The Grande Arche de la Défense) [3]. The pre-stressed construction tools were also used for the churches, so this material was not new to him. This was his first time building at this scale, so he wanted to make sure it was a cultural icon for the upcoming centuries.

Figure 5:Size of Paris Monuments

 

Cultural Significance 

The 158,000 sq. meters of space is used as a communications center for the La Defense District. It also has digital presentation auditoriums and office space for private parties [3]. The citizens loved the arch, because it was built to mark the end of the Voie de Triomphe (Triumph Way), a large road that connects the east and west of the city. In Paris, they have a thing, where monument mark the end of territories. When I searched for historical events, it was so funny to me that a person getting stuck in a toilet was historical. Margret Thatcher aka Iron Lady aka UK prime minister at the time, got stuck in the toilet. She was visiting the top rooftop, but had to go to the toilet. When she was trying to get out the handle broke, so her body guard had to bust the door open [4]. That was the start of the downfall of the arch.

In 2010-2014, the roof with its viewing platform, gastronomic restaurant, computer museum and conference center, which attracted around 250,000 people a year was closed to the public because of safety concerns. The area around the foot of the north side of the arch has been sealed off after fears of crumbling marble falling on people below, and staff of the French ecology and housing ministries, who occupy the south side, have complained of gloomy corridors and offices with oppressively low ceilings and no natural light [4]. The government gave €200 million to renovate the south side of the arch. Since the government did not give money to fix the north side, out of 30,000 sq. m of offices, 24,000 sq. m are empty and rents have fallen [4]. When I visited, there was renovations going on throughout the entire arch. It

 

Figure 6:The Grande Arche de la Défense during a busy Day

 

Figure 7:The Grande Arche de la Défense Under Construction

Figure 8:The Grande Arche de la Défense Construction Information

 

Structural Art

David Billington stated that structural art can be defined using three E’ principles: efficiency, economy, and elegance. The pre-stressed concrete is used in a wide range of building and civil structures where its improved performance can allow longer spans, reduced structural thicknesses, and material savings compared to simple reinforced concrete [2]. I was efficient to use his material for a structure of this magnitude. Economically the arch is doing okay. It cost 1.3 billion to build the structure, and a big renovation of 200 million. I am sure there are more renovation cost from what I seen. It makes money from tours and rent, so I am sure the cost balances out. It is a simple cubic structure that can be seen easily, so it has much elegance except when it is under construction. Based on those allegations it is structural art.

 

Structural Analysis

            The building is main component is pre-stressed concrete. It is based on a 21-meter grid, where it is mirrored on the top and bottom with four pre-stressed concrete transversal rigid frames of columns attached to main beams of roof and base components [3]. Four additional secondary pre-stressed cross beams in the roof and base are used to stabilize these rigid frames [3]. The roof beams are 70 m long, 9.5 m tall, and weigh 2000 tons each. Four gabled walls were created at 45 degrees, holding 6 horizontal mega-structures on either side. A seven-floor modular was utilized to create a substructure, repeating the modular five times and built simultaneously with the superstructure. For the base, there are twelve foundation piles resting on a limestone shelf 14 meters below ground level. The piles are 8 meters in wide at the base, and the piles flared to 15 meters to meet the structure’s base [3]. The cube’s dimensions are 117 m wide, 112 m deep and 111 m tall [3].

 

Figure 9:The Grande Arche de la Défense Load Path

 

The self- weight of the main beams is given and they are 19.99 m/ton. The self- weight of the secondary beams are considered point load and they are given at 22.04 m/ ton.. The length is 106.90 m, I will calculate the reactions and moments.

Figure 10:The bottom beams analyzed

Figure 11:The Reactions and Moments Calculations

These 3d drawings bellow, shows the structural composition of each component. Allowing the engineer to understand the drawings.

Figure 12:Base Beams

Figure 13:Shear Columns added

Figure 14:Roof Beams Added

Figure 15:Diagonal Shear Walls Added

Figure 16:Bracing Added

Figure 17:Perpendicular Beams Added

Figure 18:Final Overview

 Personal Response

I did not realize how big the cube like structure was. Being able to see the Notre Dame in person and seeing that the it could fit into the arch was amazing. From the pictures, I seen online, I did not know the entrance was steps. The steps blend in so well with the arch.

Figure 19:Me at The Grande Arche de la Défense

References

[1] http://www.aviewoncities.com/paris/archedeladefense.htm

[2] https://www2.deloitte.com/content/dam/Deloitte/cz/Documents/real-estate/Iconic_Buildings_La_Grande_Arche_Smart_16winter.pdf

[3] http://faculty.arch.tamu.edu/media/cms_page_media/4433/grandearche.pdf

[4] https://www.thelocal.fr/20140805/paris-the-not-so-grande-arche

[5] http://famouswonders.com/grande-arche-de-la-defense/

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.

Image result for southwark bridge

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.

Image result for southwark bridge deckImage result for southwark bridge

 

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.

Image result for southwark bridge drawing

Image result for southwark bridge drawing

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!

Image result for southwark bridge at night

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/

 

Cannon Street Railway Bridge

On our bridge tour today, the tour guide pointed out a low slung greenish bridge and began expressing his dislike of its “ugly” appearance. This made me feel like the Cannon Street Railway Bridge deserves some love so I was determined to analyze. The visible brute strength of the thick columns and flat spans caught my attention as it is clearly designed for massive railway loads rather than car or pedestrian passengers like other London bridges.

Figure 1 – Cannon Street Railway Bridge from South Bank

Structure Information

The Cannon Street Railway Bridge was built from 1863-1866 by the South Eastern Railway Company (SERC) and designed by Sir Joh Hawkshaw, a famous English Civil Engineer. The SERC was in control of the rail lines to the London Bridge Station and wanted to expand the lines over the Thames in order to reach the Northern half of London, so they initiated the design for this bridge to the Cannon Street Station [1]. In order to carry a greater capacity of trains, the bridge was widened from 1886-1893 by adding a column on each side for a new total of six (from an original of four) and more decking on top. The bridge was strengthened from 1910-1913 in order to bear heavier trains and strengthened again in 1983 to account for both greater loads and general wear and tear [2].

Historical Significance

The simply supported beam bridge is the oldest and simplest type of bridge, and although the Cannon Street Railway Bridge doesn’t innovate in form it is unique in its massive appearance. With three spans of 45m, numerous thick columns, and 2.6m deep iron girders the bridge clearly looks capable of carrying the 10 rail tracks laid on top of it [2]. It was one of the first rail bridges over the Thames and the only one located in the Eastern part of London and as such a very important connection point in Victorian London as well as today, but it is not a model for modern railway bridges, nor the best example of a period bridge.

Cultural Significance

The bridge remains a very important railway link over the river Thames and helped bring development to the East side of the city when it was built, as this area was mostly still low income housing with little value. As it is almost entirely used for rail traffic and is not a very beautiful bridge it has never become a cultural symbol or tourist attraction. In fact many citizens of London actively criticize its appearance, and our tour guide today related the story of how it was originally going to be named after Queen Victoria, but she disliked its appearance and had them drop that name. In August 1989 two boats collided right next to the bridge in a tragic accident that caused 51 deaths and led to new lifeboat stations at the sides of the bridge [3]. After expansion and two strengthenings over the last 150 years, the bridge is still used today to transport massive amounts of commuters and tourists around London.

Figure 2: Cannon Street Bridge Looking Eastward to Tower Bridge

Structural Art

The three principles of structural art are: Economy, Efficiency, and Elegance. This bridge is most certainly not elegant as Billington would define it. Although the load paths are as simple as possible and clearly visible (bridge girders to columns to ground), the structure could never be seen as “light” or “graceful”. To me the bridge does not fulfill the category of elegance, even though I personally like the stolid appearance and appreciate the unique appearance of the thick repeated columns. When it comes to being efficient, it is difficult to create a beam bridge with massive railway loads that uses a minimum of material when using iron girders and concrete foundations. An arched bridge could have reduced the material usage and added elegance, so I don’t believe that the Cannon Street Railway Bridge fulfills the principle of efficiency either. For economy however, the materials (concrete and iron) were cheap and easily procurable as well as being inexpensive to build with at the time. The wrought iron girders in the bridge deck are all the same size which made production cheaper, these factors together allow the bridge to fulfill the economic principle of structural art. Overall, by hitting only one of the three principles, the Cannon Street Railway Bridge is certainly not structural art, but that doesn’t mean it is not a useful and functional bridge, and I personally like it a great deal.

(The following paragraph written after doing Structural Analysis, skip ahead then come back so it makes sense…)

After calculating just how massive the loads that each beam and column can take, I’ve reconsidered the efficiency of the bridge. This bridge is so redundant and overengineered that I can no longer think of it as efficient. The only possibility is that its so strong to deal with scour, but even that seems unlikely to me. This bridge is definitely NOT structural art!

Structural Analysis

The major construction materials used are iron in the girders (wrought) and the exterior of the columns (cast), and concrete in both the columns and the beam right above lateral beam right above them. There is also masonry and brickwork as the bottom foundation, and construction was began by digging small caissons to the bedrock under the Thames and building these foundations. The original four concrete columns were then poured to about the water level, where the fluted cast iron exteriors were placed and then filled with concrete. Originally the bridge did not have the tapered concrete rings at the top of the columns, these, along with one column on each side (new total of six) were added in later retrofittings. The long wrought iron girders were then transported to the site (most likely by barge) and lifted by crane onto the supports, then riveted together. Finally decking, railings, and rail lines were added to the top to complete the bridge. The bridge has three major spans of 45m and two approaches of 39.6m, the plate girders are 2.6m deep and thick I-beam shaped. The concrete columns, assuming same river depth as at London Bridge, are about 13m tall, and from visual comparisons with the known 2.6m depth of the girders, are around 3m in diameter.

Figure 3: Looking Up at 18 Iron Girders

The Cannon Street Railway Bridge is a simply supported beam bridge without any fancy arches or trusses, all strength and stiffening are directly from the girders in the deck. Load from self weight and live load from trains is transferred directly from the beams into the huge columns. There are no wind airfoils on the side of the bridge, but it has a small cross section, very stiff deck, and extremely strong supports without a long span so wind load has very little effect on overall design or performance. The bridge faces scour from the Thames, but there are no angled diversion bases around the column bases as they are curved and heavy enough to withstand massive lateral forces. This bridge looks so massive that it would take gigantic live loads to cause collapse, but the three possible sources of failure are: tensile yielding in the girders due to bending in the middle of the spans, bearing stress crumbling at the contact point between deck and columns, and buckling in the columns.

To calculate the max bending stress I first found the volume of a single beam over the longest span (45m) assuming a symmetrical cross section with a flange depth of 0.1m, flange width of 0.5m, and web width of 0.2m. The cross sectional area with these measurements is 0.62m^2, and the total volume per central span per beam is 27.9m^3. Using a density of 7.7g/cm^3 for wrought iron from the internet, the weight of a single girder is 214,830 kg and the self load de to weight is 4,774 kg/m. These are very conservative (high) estimates for the weight per beam. Next I used the formula of stress = My/I, where M is max moment, y is max distance to the edge from the centroid, and I is the moment of inertia. Y is 1.3 meters assuming a symmetric girder, and I calculated the moment of inertia to be 0.386m^4. Then to calculate maximum moment, I know that the max bending moment of a simply supported beam with uniform distributed load is w(L^2)/8. I decided that the max bending moment would be the tensile strength of wrought iron which is 160MPa, so I needed to calculate the max train load that the span could support per beam (of which there are 18). So my equation was: 160MPa = (4,774 + T)*(L^2)/8 using superposition where T is the distributed train load on 1 beam. Using this equation the max train load comes out to be almost exactly 183,000 kg/m which is ludicrously high for passenger trains, and shows the deck to be in no danger of collapse due to bending stress.

Figure 4: Distributed Train Load Calculations and Bending Stress Diagram

To calculate bearing stress I found the surface area of the columns, which have a diameter of approximately 4.5m at contact. This gave a bearing area of 15.9m^2, and as there are 18 beams, approximately three of these would be on each column, and I’ve already estimated the weight of a 45m section of beam to be 214,830kg. This means that each column will need to bear the self weight of the deck of 644,490kg along with additional live load from the trains. T find the max live load of the trains before crumbling I used stress = F/A where stress is the compressive strength of concrete which I found online as 25MPa. This gives the equation: 25*10^6 = (644,490 + T)/15.9 where T is now the total train weight on the tributary area (rather than the distributed train load). This gives a final answer of over 395 million Newtons which is PER COLUMN. That’s actually crazy high and basically unachievable for such a small space (the heaviest train ever was three times the necessary force, but over almost 10km) so the bridge is safe from crumbling.

Figure 5: Load Paths all Channel into Columns

Finally to calculate the critical buckling stress of the columns I used the equation: P= (pi^2)*E*I/(L^2). To calculate E (modulus of elasticity) I used the ACI code formula: E = 4700* sqrt(C) where C is the compressive strength of concrete (I used 25MPa just as before) and found E=23500MPa. I calculated the moment of inertia of the column using D=1.5m (ignoring the upper concrete collar) to find I=3.98m^4 and used the length of 13m as stated before. This gives another comically massive final answer of 8793.8 MegaNewtons/m^2 PER COLUMN!!!!!! No train could fit that into the 45m long tributary area, this bridge is crazy overengineered.

Honestly I have no idea how they pitched such a ridiculously strong bridge to the shareholders, I think they just asked for a permit to build any bridge from Parliament and then Hawkshaw went wild. Crazy stuff, maybe my assumptions of size of members was off, but I’m pretty sure they were close….

Personal Response

The first time I saw the Cannon Street Railway Bridge I just walked past it because it looked so lackluster compared to the other bridges (same for London Bridge to be honest). Once we looked at it on the tour I wanted to give it some love because it seemed so neglected, but now that I have analyzed it my opinion has changed. At first I appreciated the bridge because of its strong and thick appearance, but once I realized just how wasteful it is I no longer appreciate it as much. It seems almost sacrilegious (maybe too strong of a word) to make something so bulky and inefficient when there are structural art options available.

 

References

  1. http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=665
  2. https://www.bristol.ac.uk/civilengineering/bridges/Pages/NotableBridges/CannonStreet.html
  3. http://www.bbc.co.uk/news/uk-england-london-28839099

Lambeth Bridge

Structure Information

The Lambeth Bridge was constructed in 1932 across the Thames River between Westminster and Lambeth. See Figure 1.

Figure 1: Lambeth Bridge Area

This connection was initially necessary because there was a house of the Archbishops of Canterbury at Lambeth that needed to be constantly connected to the King’s palace at Westminster [2]. Initially the Archbishop made the passage across the Thames by barge, then later by ferry. The church bought the ferry so the Archbishop and his goods and servants could travel across freely [2]. The Ferries were taken out during the civil war, so no intruders could pass the Thames this way, but later ferries were returned as a mode of transportation across the Thames [2]. Bridges were proposed as early as 1665. In 1750 the Westminster Bridge was put in very nearby, ending Lambeth Bridge proposals until 1809 [7]. The new Westminster Bridge also ceased the operation of the Archbishop’s Horseferrry, as it was in poor condition and now unnecessary [3]. From the 1809 Lambeth proposal, nothing happened until the Lambeth Bridge Act in 1861, for a toll bridge to be put up [4]. A suspension bridge was eventually selected and opened in 1862 as an 828 foot long, three-span bridge [2]. The old bridge can be seen in Figure 2.

Figure 2: Old Lambeth Bridge

Less than 20 years later, the first Lambeth Bridge was falling apart. The bridge was progressively closed to vehicles and later to people [3]. The current Lambeth Bridge was proposed but delayed by the 1914-1918 war [2]. In 1924, Engineer, Sir George W. Humphreys, and the architects, Sir Reginald Bloomfield and G. Topham Forrest, designed the bridge for King George V and Queen Mary [2&3]. The bridge cost about 80,000 pounds and was fabricated and put up by Dorman Long & Co Ltb in 1932 [4]. See the new bridge in Figure 3.

Figure 3: Lambeth Bridge

Historical Significance

            In 1932, the current Lambeth Bridge was opened, made of steel and pre-stressed concrete [3]. Steel caissons were used to make the piers [4]. This caisson technique along with other details of the construction and design process can be seen in the similar predecessor of the Lambeth Bridge, the Westminster Bridge. The Lambeth Bridge was a common bridge of its time. The bridge itself did not have any major innovations about it and, therefore, was not a model for the future.

In 1965, however, the Lambeth Bridge became the first bridge in London to be tunneled under, making it the first bridge in London that could be walked under [1]. This provided pedestrian access along the embankment, which was not available as it is today. This tunnel and idea of pedestrian use of the embankment sparked the plans for the Albert Embankment to be used as the bustling pedestrian city spot we see today.

 

Cultural significance

Sections of the Lambeth Bridge are painted red to signify the seats in the House of Lords and pylons were added on each end and topped with stone pinecones or pineapples (there is debate over what is represented)[3]. The Bridge Tour guide insisted they were pinecones, a representation of hospitality, but many believe they are pineapples as the Garden Museum is just over the bridge with reference Christopher Columbus whom is known for bringing pineapples to London and presenting them to royalty. To this day, the pineapples/ pinecones cause debate throughout London. Look at Figure 4 and see for yourself!

Figure 4: Pinecones or Pineapple?

Another argument caused by the bridge is less playful. The ferry operators remaining were very opposed to the construction of the bridge. This opposition was to the original Lambeth Bridge, not the one currently standing. The new Lambeth Bridge was well reciprocated because the old bridge was dilapidated and unusable. Luckily, the old bridge caused no injuries or deaths as it was closed before any extreme damage. The new bridge re-opened the pathway across the Thames to cars and pedestrians, helping disperse traffic. Crowds flooded the streets for King George V’s procession, officially opening the new Lambeth Bridge as seen in the video and art piece below [12]. The celebration was so grand it even inspired art, like that in Figure 5.

Figure 5: Grand Opening Inspired Art

Today, the bridge serves the same traffic purposes for cars, busses, bikes, and pedestrians. The increasing traffic, however, has ranked the Lambeth intersections among the top 75 most dangerous in London [11]. A woman on a bike was recently killed in an accident at one of the Lambeth roundabouts. The Lambeth Bridge is soon to be overhauled with safer bike lanes and newly designed intersections [11]. The 12 million pound project is a part of London’s goal to have 80% of people travelling in London to be on foot, bike, or public transit by making the roads safer to travellers [11]. This new project will hopefully make travelling across the bridge a better and safer experience.

The Lambeth Bridge has also been used in a few major films recorded in London. Examples include Harry Potter and the Prisoner of Azkaban, when the Knight bus rescues Harry from a bad holiday with the Dursleys it speeds over the bridge; in Fast and Furious 6, the bridge is used for a view of “Moscow”; and in The Foreigner with Jackie Chan, a bus exploded on the bridge [1]. The Jackie Chan film explosion of a bus caused panic throughout London.

 

Structural Art

            The Lambeth Bridge could hardly be considered structural art. The load path of the bridge is slightly visible through the side panels and from various angles, but is not clear. The Bridge is carried on granite-faced reinforced concrete piers and abutments [4]. The side panels and granite hide the elegance of the structure. Granite facing also adds unnecessary material and requires a stronger structure, taking away from the efficiency of the structure and requiring more expensive structural support. The tall obelisks located at either entrance are solely for aesthetics, adding more to cost. The attention to aesthetics also adds to cost in the metalwork and painting added to the structure. The exposed truss structures that make the light posts, if no small metal decals were attached, could be considered structural art. Overall, the structure does not satisfy any of the 3 E’s and therefore clearly cannot be considered structural art.

In regards to the three S’s of structural art, the Lambeth Bridge presents a bit better. As explained in the cultural significance section, the bridge is clearly very symbolic of its era. The symbolism of the bridge is mostly achieved by aesthetic decals and details added to the structure. The structure itself symbolizes the older designs of its time, so it is not so much structurally symbolic. Scientifically, the Lambeth Bridge does not have any breakthrough innovations. As a “basic” bridge for it’s time, there is no truly scientifically significant details about the bridge itself. Socially, however, the bridge is very influential. From the huge parade and celebration of its opening and connecting two sections of the city and therefore two communities to supporting green transportation, the Lambeth Bridge clearly satisfies the social aspect of structural art. Even though the Lambeth Bridge does better with the three S’s, it still cannot be considered structural art, as it does not satisfy all three S’s.

 

Structural Analysis

Lambeth Bridge is a five span, steel arch structure, carried by reinforced concrete foundations [4]. Steel caissons were used to make the piers [4]. The caissons were dug to the ground and the reinforced concrete foundations were put in place. The steel arches and supports were attached with pin connections, followed by the addition of the reinforced concrete deck and design features. The Lambeth Bridge was constructed very similarly to the Westminster Bridge, which was nearby, and many other bridges of its time.

I will be analyzing the repeating arches and their reactions at the pin connections with live and dead load. The total length of the bridge is 236.5m, with a 50.3m center span, surrounded by two 45.4m spans, and two shore spans of 38.1m [4]. Each span has 9 ribs supporting the reinforced concrete roadway above. See Figure 6.

 

Figure 6: Under the Bridge

The arches are all two-hinged with pin connections. There is a 60’ span on top of the bridge in reinforced concrete. I am assuming the concrete is 12” thick and using a live load of 640lb/ft, that of a truck [9]. By using this live load the bridge reactions will be for worst-case scenario. Reinforced concrete weighs about 150lb/ft^3

Clearance Per Arch in meters [8]

Lambeth 3.1 5.0 6.3 5.0 3.2

 

Load path

The example dead and live loads are observed as a constant force per linear foot. The load is carried from the deck, along the arches into the caissons to the ground. If these were repeating arches of the same height and width, the horizontal loads would cancel except for those on the ends. The horizontal loads do not perfectly cancel in the repeating arches, because they vary in size. This requires abutments to absorb the extra load on the ends. See the load path in Figure 7.

Figure 7: Load Path

Arch Calculations

Tributary Loads, because the beams spread evenly to the edges of the bridge:

Inner: 60’/8 sections

Outer: 60’/(8 sections x2) *because each outer only takes half a section

See the calculations in Figure 8.

Figure 8: Calculations

My calculations show a very simplified version of the calculations necessary to design the foundations and abutments of the bridge. With the reactions at each joint, the load needing support is known and can be designed for.

Design drawings depicted detailed plans for the Lambeth Bridge to the stakeholders and to the construction workers. Calculations were used to show how the load was distributed into the ground via the abutments and piers and caissons. A model for this bridge working was the similar Westminster Bridge adjacent to the Lambeth Bridge. Because of Westminster’s similar design and construction techniques, it acted as standing proof or a full-scale model of the Lambeth Bridge.

 

Personal Response

I never realized how truly necessary having so many bridges was to London. By walking to and across my bridge, I saw the traffic flowing across it and the surrounding bridges. The Lambeth Bridge is a relatively heavily trafficked bridge, and there were cars and pedestrians crossing, on a Bank Holiday at that. Additionally, on the map the bridge seems very distant from Westminster Castle and the Archbishop’s home, however, upon walking, I saw that the bridge arrives just at the Victoria Tower Gardens of Westminster and the Archbishop’s home.

 

References

[1] https://londonist.com/london/history/secrets-of-lambeth-bridge

[2] http://www.british-history.ac.uk/survey-london/vol23/pp118-121

[3] https://www.greatlondonlandmarks.com/place/lambeth-bridge/

[4] https://historicengland.org.uk/listing/the-list/list-entry/1393007

[5] https://www.lambeth.gov.uk/sites/default/files/pl-listed-buildings-beginning-with-l_0.pdf

[6] http://landmark.lambeth.gov.uk/display_page.asp?section=landmark&id=2955

[7] https://vauxhallhistory.org/lambeth-bridge/

[8] http://www.pla.co.uk/Safety/Thames-Bridges-Heights

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

[10] http://thames.me.uk/s00140.htm

[11] https://www.newcivilengineer.com/tech-excellence/lambeth-bridge-and-waterloo-to-get-37m-overhaul/10021157.article

[12] https://player.bfi.org.uk/free/film/watch-opening-of-the-new-lambeth-bridge-1932-online

[13] https://www.npg.org.uk/collections/search/portrait/mw271297/Opening-of-the-New-Lambeth-Bridge-King-George-V-Queen-Mary-and-others