Blog 2
Blackfriars Bridge

Blackfriars Bridge

The first time I was able to visit this bridge was on my second day in London while our class was on a bike tour. The bridge stood out to me because of its name and certain features. One of the cooler features of the bridge are the small statues of birds on each side of the bridge. These birds represent the saltwater of the sea and freshwater of the river meeting under this bridge. Fresh water birds like swans face west while seabirds like gulls face the east. Regarding its name, the Blackfriars Bridge actually gets its name from a monastery that used to be by the river that had friars that wore black robes. That’s not a very complex background to the name but it still sounds very cool. I think the friars that play for the San Diego Padres need to look into re-branding!

Figure 1, San Diego Padres Baseball Team [1]

Structure Information

In 1756, the Mayor of the City of London received permission from Parliament to build a bridge at Blackfriars, the third bridge to cross the Thames in the London area [2]. The young Scotsmen Robert Mylne was the designer. Construction on this bridge started in 1760 and was opened to traffic in 1769 [2]. A toll was installed to help the British government fund the bridge [2]. It was removed in 1785 [2]. This first bridge lasted for over 100 years [2]. The bridge that you see today was designed by Joseph Cubitt and commenced in 1869 [2]. It was funded in a similar manner as the first, and no longer has a toll on its road as well [2]. The main purpose of this bridge, when it was initially constructed, was to direct more traffic away from the overwhelmed London Bridge [2].

Figure 2, The Old Blackfriars Bridge [3]

Figure 3, Current Blackfriars Bridge [4]

Historical Significance

The design of the current bridge is not an innovative one. The bridge is supported by five arches which was a standard material and design used in 1800’s [5]. However, there is an innovative part to its foundation. The piers themselves are pointed to help direct water flow, and the caissons are made out of iron to prevent scouring [5]. Scouring is the erosion of soil surrounding a bridge foundation. This was the beginning of a period where pointed piers began to be used as a construction technique.

The best existing example of this bridge had been the previous Blackfriars Bridge. Much of the design had not changed but instead updated. The same columns remain along the bridge for people to sit on and look down the river, and the ornamental designs of the original were kept in mind for the second bridge. This bridge is not a model for future bridges as it did not innovate a significant way. The caisson design would be used in future bridges, but the visual component of the bridge did not innovate.

Figure 4, Bridge Scour [6]

Cultural Significance

There was a great bit of drama surrounding the first Blackfriars Bridge. The City of London had not made many civic changes since the Great Fire of 1666, but needed another bridge that led into the city [7]. At the time, London Bridge was overburdened with traffic and was always crowded. The city was against creating a new bridge that would harm the business of the Thames watermen, and buildings would need to be bought and demolished to create a new approach road [7]. However, an engineer, John Smeeton, suggested the creation of a bridge at the western extreme of the city as to not require the demolition of any buildings. The area was also known for being impoverished and was stricken with criminal activity, so the bridge provided the opportunity for improvement. A bridge design competition was held, with a decent amount of propaganda being spread around the final fourteen candidates. 25 year old Robert Mylne won the competition with his elliptical arch design [7]. Mylne had just arrived in London the previous year after excelling in architecture courses at St. Luke’s Academy in Rome.

The bridge was found defective in the 1832, and the city demolished the old bridge in 1865 and finished building the new one in 1869 [5]. The new bridge was not as well received as the first bridge. The new bridge was rotated and moved slightly to make construction easier, to make access to the bridge easier, and to provide pedestrians of the bridge a better view while on it [8]. To do this, several buildings were demolished to create the new approach road [8]. The people that used to live in those buildings were understandably, extremely unhappy. They were so unhappy that when Queen Victoria came for the Royal opening of the bridge, she was booed and hissed at during the ceremony [8]. The fact that she had not been seen in public for over five years also did not help her case.

Figure 5, A Cold Reception for the Queen [9]

The second Blackfriars Bridge is primarily used to provide cars and pedestrians a way to cross the Thames River into London. However, it was used for a more gruesome purpose in 1982. The body of one of Italy’s most prominent bankers Roberto Calvi was found hanging from the bridge with his pockets stuffed with $14,000 and 5 bricks [8]. The Metropolitan police initially treated this as suicide [8]. However, in 2002 evidence arose that Roberto had actually been murdered by the mafia [8].

Structural Art

There are three components that are used to determine if a structure can qualify as structural art. They are efficiency, economy, and elegance. The ultimate goal of each of these three is to be found in a structure. This means that the structure minimizes the amount of materials used to make it, does not provide unnecessary costs and expenses, and provides the maximum amount of aesthetics as possible.

Looking at this bridge initially, the first thing a person can see is the very simple design of the bridge and its arches. This paints a very clear picture as to what is going on in terms of its load path. If we were to not go any closer to the bridge, it would pass on this aspect. However, when you approach the bridge on foot, you can see all the extra ornamental decorations that the bridge contains. There are small architectural flairs all along the bridge, a requirement by the City of London [7]. There are also large columns along the outside of the bridge that serve no structural purpose. They only exist to give people a place to sit while walking and to provide more opportunities for ornamental design. Taking in the sum of all its components, I would argue that the bridge does not check the efficiency box.

Figure 6, Example of Ornamentation

From an economy perspective, the bridge actually was not too strenuous on the City of London. The bridge only needed a toll to help pay for expenses for less than 10 years each time it had been built. The social gain that citizens were provided was also a tremendous boon. The area started as a place of thieves and low class people, but the bridge provided economic growth and improvement to the area. Today it is the scene of many large businesses and serves as a business powerhouse in the City of London. In terms of economy, I would say that this bridge did in fact meet and exceed this standard.

Finally looking at elegance, this bridge appears to be balancing between a light and gaudy form. The arches are very simplistic and tasteful, but the columns that are placed along the bridge break up the light form. There are also very complex lattice structures that break the flow of the load paths on the bridge. This bridge took a solid design base and added extra things for no reason. It actually reminds me of my brother and his teeth brushing habits when he was a kid. Instead of doing the simple act of brushing his teeth for a minute, he would close and lock all the bathroom doors, run the water and put some in his mouth to act like he brushed, squeeze some toothpaste out into a tissue… well you get the idea. Instead of keeping it simple, he tried to do all these complicated things in attempt to give the appearance of clean teeth. But in reality, they were not. This bridge could have kept the beautiful and simple arch design but chose to do complicated things for no reason. Well, the government telling them to is the reason. But this is a great example of why the engineer is the most capable of creating structural art.

Basing my opinion on the three aspects that were discussed, I would argue that this bridge is not structural art. It comes very close but the ornamentation adorning the bridge takes it away from structural art. However, the basis for a simplistic and elegant design is hiding under the surface.

Structural Analysis

Because there is little information on the bridge’s method of construction, assumptions have to be made regarding this part of the bridge. There are a few pictures that shed some light on the construction process. Figure 7 shows men in diving gear. The piers would be the first part of the bridge to be constructed and the caissons that were sunk into the river would need workers in the water to help with that process. Figure 8 shows workers fabricating metal on site. In doing so, the material did not need to be transported very far. This saved time and money for the project. While the arches are different sizes, they are close enough for the on-site fabrication to be feasible. This would also be consistent with the type of material the bridge’s arches are made of.

Figure 7, Bridge Workers [10]

Figure 8, Making of the Material [10]

The main feature of the Blackfriars Bridge is its five wrought iron arches [5]. These arches sit on piers that have granite stonework [5]. The central arch of the bridge is 56.4m long [5]. The next two arches are 53.3m and 47.25m respectively. The bridge’s total length is 281m [5]. The width of the bridge was originally 22.9m, but it was widened by 9m on the west side to accommodate tramways [5]. The arch is 3.3m high [5]. The main structural system employed for this bridge is the arch form.

The system carries load using its arch form to its benefit. The bridge experiences loads on top of it in various forms. There is the dead load of the bridge itself, live load of people walking across it, live load of cars driving over it, and possible rain/snow live loads. Arches are fantastic at managing compression forces, which is exactly what this bridge does. All of the loads mentioned are transferred through the arch down to its connections at the bases where it connects to either an abutment or a wall that has another arch on the other side. That is important because the thrust forces of two arches next to each other will cancel out. This is why repeated arch forms are so efficient.

Figure 9, Load Path

Figure 10, Repeated Arch Form

Now that the load path of the structure is understood, we can do an analysis of it to see what kind of forces this bridge is withstanding. The main loads were mentioned above, but some math is needed to get numbers to those. We will assume the worst possible scenario which would mean maximum traffic, maximum people, maximum amount of rain, and the weight of the bridge itself. Below is a very simplified version of the arch.

Figure 11, Simplified Arch

Figure 11 is a symmetric arch with linear loads going across it. We can solve for the reactions at the ends using the following math.

Figure 12, Solving for Reactions & Maximum Force on Abutment

The design drawings were able to communicate the idea of the bridge to the government very well. There was little in the way of disagreement amongst them, but the drawings were changed slightly. The government wanted more architectural flairs than what the original design called for, so the giant non-load bearing columns and ornamental designs were added to make the bridge ‘more appealing’.

Personal Response

After studying and researching the Blackfriars Bridge, I think it is a very important and historic bridge that could use a little less ornamentation. I enjoyed being able to bike across it so the expansion for the top of the bridge greatly enhanced my first experience with it. My first impression of it was that this was a very pretty bridge, but after having studied it I can now see the more unnecessary parts of it that I can do without. While the Blackfriars Bridge may not be the most famous bridge in London, it certainly stands out as one of its most important bridges.

References:

  1. http://www.peoplequiz.com/trivia-quizzes-5536-San_Diego_Padres_Baseball_History__Facts.html
  2. http://www.british-history.ac.uk/survey-london/vol22/pp115-121
  3. https://londonhistorians.wordpress.com/tag/blackfriars-bridge/
  4. https://www.mrsmithworldphotography.com/photograph-of-Blackfriars-Bridge-5-London-England/WOF_G043_0033
  5. http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=693
  6. https://blogs.scientificamerican.com/but-not-simpler/scour-why-most-bridges-fail/
  7. http://www.thehistoryoflondon.co.uk/the-original-blackfriars-bridge/
  8. https://lookup.london/the-old-blackfriars-bridge/
  9. https://www.gettyimages.co.uk/detail/news-photo/queen-victoria-opening-blackfriars-bridge-london-1869-news-photo/463951667
  10. https://www.theguardian.com/cities/gallery/2016/aug/02/how-london-was-built-tower-bridge-southbank-in-pictures
  11. https://www.quora.com/How-much-does-an-average-car-weigh
  12. https://www.ag.ndsu.edu/archive/dickinso/research/2004/range04c.htm
  13. https://hypertextbook.com/facts/2004/KarenSutherland.shtml

Comments

  1. ezaruvinsky3 says

    Even though you state it is not an “innovative design,” which I agree with, it’s nice to learn that they thought of little things that are important to the location of the bridge. I thought it was so cool that the piers were designed to help water flow! I would not have realized that myself.

    • jgarrett39 says

      Yeah it definitely has its little charms! Lots of cool things about the bridge, the final product is just a little lacking unfortunately. Still a very cool piece of history! And the piers were definitely a neat part of the bridge.