Centre Pompidou

Structure Information

Figure 1 : Centre Pompidou

Centre Pompidou, also known as the Pompidou Centre, is a multipurpose building located in the 4th arrondissement of Paris. The project came in response to the desire of then-president Georges Pompidou to implant a unique multidisciplinary cultural center in the Beaubourg area. The final design had been selected among 680 others during an international contest that involved 49 different nationalities [1]. The building, considered as one of the most emblematic of the 20th century was designed by Renzo Piano, Gianfranco Franchini and Richard Rogers, all architects unknown of the Public at the time. The structural engineer in charge of the project was the renowned Ove Arup. Opened to public in January 1977 after 6 years of construction, the challenges of this building were to be able to cohabit different activities within the same complex while facilitating the relationship between them and, make possible the contact with the public through the art and cultural centers. Hence, Pompidou Centre serves as public library, national modern art museum, music creation center and contemporary arts exposition center. The project cost was 993 Million of French Franc in 1972 and since the President was himself the pioneer of the project, it received public funding and had been government-owned since.

 

Historical Significance

Figure 2: Elevation East (detail) [2]

The structural engineering design for this complex was unique and its originality reflects through the total clearance on each of the ten floors of 7500 m2. The area had to be free of any physically obstructing structure, hence involving long spans between the columns that were designed to be outside. As noticeable on the picture below, the architects also wanted any piping to be visible from the exterior; providing the sense of “clarity and transparence” to viewers. They’ve combined the need for space with the materialization of their vision: Nothing need to be hidden in a building, everything need to be revealed. This approach was for them a game and a taunt. The structural engineering design had to adjust to those need in sort to make it possible: this required 15,000 tons of steel and 11,000 m2 of glass; unusual practice for the construction world of the time. This innovative and revolutionary character of the building was the fuel that boosted the Pompidou Centre to its rank between the most popular of the twentieth century.

 

 

 

The design and impressive architecture of the Pompidou Centre had laid foundations for a totally new ideology in terms of design across the world. Not just for the Centre itself that expanded internationally -Europe, Asia, North & South America- but also for the following generations of designers.

 

Cultural Significance

The Building had seen eleven presidents since creation, all of them appointed by the Ministere de la Culture; equivalent of the U.S Department of Arts and Culture in France.

Figure 3: Inside of the center

In the 70s and 80s, the center offered to visitors, majors expositions that contributed to the art world during the twentieth century. Among others, multiple tv series such as “memoire du future”, “les immateriaux”. The center had been used for the casting of the movie Moonraker of James Bond. Expositions from artists of different background, renowned or beginners had been presented at the Pompidou Centre. Among others, we could cite Paul Davis, Henri Michaux, Bonnard, Etienne Martin, etc.

 

This building has been loved from day one and had become one of the most visited cultural center in the world and the most visited in France. The center had a daily average of 16,000 visitors in 2000. In general, the center is said to handle between 3.5 and 3.8 million of visitors on a yearly basis the past couple of years.

The center is used to promote modern and contemporary arts through multiples expositions. As said earlier, the structure serves today as public library, national modern art museum, music creation center and contemporary arts exposition center. Street performers are constantly performing on the outside of the building. I’ve personally witnessed this around little before midnight despite the fact that the center was closed couple of hours earlier! I was amazed by the dedication, or passion I should say.

 

Structural Art

With the main structural elements clearly exposed as shown in the pictures, it was clear and evident to identify the load path throughout the building. Initially, all of the functional structural elements of the building were color-coded: green pipes for plumbing, blue ducts  for climate control and electrical wires encased in yellow, and circulation elements and safety devices in red. Check the following picture for an illustration.

Figure 4 :Color coded piping visible from exterior [3]

 

 

I would also argue that Elegance was there. Certainly, it’s a relative appreciation but considering the purpose to which the building was dedicated and everything else about it; I believe majority of readers would agree that this marvel is just Elegant! Economic aspect? The expected functionality of the structure had impacted a specific design which could have been less costly without those constraints. However, with all the income generated by the center since its creation, I believe that the Building had paid for itself long ago!  That was actually one of the greatest investment the government had made so far, in my opinion!

So, Yes!  the structure demonstrates Structural art.

 

Structural Analysis

Figure 8: Structure of the building

Some massive earthworks of 300,000 m3 was needed on the site to reach the 60 feet deep. As reflected in the images, the building is a typical one with concrete slab over beams and column. Hence, we are in presence of a uniformly distributed load that carries over to the reactions (columns) through the beams. The structure is essentially metallic -columns, beams, connection elements- and with 50,000 m3 of concrete poured to make up the flooring. Of course, they were prefabricated off-site (Germany) and assembled on site. The assembly of the metallic structure began from the first floor and involved the creation of a fixed connection of the posts (columns) inside concrete. On the top of each of these erected posts, exist a pin connection which will be used to hold where needed, the beam that serves as support for the slab.

Figure 5: Typical device for connection column-beam [7]

 

 

 

 

 

Figure 6 : Earthworks

 

 

The metallic beams were 45 meters long and weighted 75 tons while the columns were of various height of 5, 21 and 23 meters with diameters as big as 3 feet. The escalators were strategically designed as a corridor in cantilever with the building as shown on the first picture. As most structures, the load path for the overall structure is from the top to the bottom. Each floor’s load is added to immediate one beneath it and so on until it reaches the foundations. A better description would be: the outmost slab -designed with the dead load and live load- would transmit its weight to the beams according to the tributary area rule. That tributary “weight” is then carried to the metallic columns which got bigger as we go down the stairs. The constraints of longer spans drag along the need of having column’s drop by location in order to contend the flexural and compressive moment due to the live loads essentially.

Figure 7 : Inside the outside escalator [5]

 

As decrypted in figure 9, different layers of materials consist the slab.

Figure 9: Different layers of materials

 

 

 

 

 

 

 

 

A partial section throughout two floors reveals much details about the structure in Figure 10.

Figure 10: Partial section of slabs

Load path

As shown in the figure above, the load -in red- from the slab and the cantilever items -escalators mainly- goes through the columns which are in compression. The warren trusses under the slab provide extra support/ resistance against flexure. Maximum moment for the structures in cantilever are observed at the joint and maximum shear for the slab is expected to happen right at the connection slab-column while maximum bending should be expected at mid-span.

In the following, a lot of assumptions about the numbers will allow us to attempt the analysis. Assuming that beams are distant from each other for about 12 feet and that the span between the columns are 100 feet. This leave each beam (except the periphery ones) to have a tributary area 12’x100′. Thickness estimated to be 8 inches. During my searches, Ive came across the value of 5000 psi for concrete. Assuming that the thickness was taken into account, I’ve converted that value to a linear weight by multiplying it by the tributary width which is 10’x12”. The linear weight of 7200 k/ft. as then obtained. From here we could deduct the reaction by each of the column to be wl/2 which is equal to 3,600 K.

Assuming the same load considerations for the following floor, we’ll have this weight plus another 3,600K at that level and so on. The increasing weight as we go down the fl0or levels result in an increasing section of the columns as well.

Personal Response

The Pompidou Centre is a really impressive structure. The designers of this marvel have constructed something innovative from a very playful background. They  were able to draw attention and create uniqueness while having fun, which is very inspiring. We gotta do what we love and do it big to the point of inspiring generations to come.

 

 

 

 

 

References

[1] https://www.centrepompidou.fr/fr/Le-Centre-Pompidou/L-histoire

[2] http://mediation.centrepompidou.fr/education/ressources/ENS-architecture-Centre-Pompidou/comment_ca_fonctionne/p1.htm

[3] https://www.centrepompidou.fr/fr/Le-Centre-Pompidou/Le-batiment

[4]https://www.google.com/search?q=centre+georges+pompidou&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjI84Tmgb3bAhXBFywKHVC_AnUQ_AUICigB&biw=1408&bih=667#imgdii=_-XlB1TewReOKM:&imgrc=vHOEOtkxYVqBIM:

[5] https://cca9bparch2230.wordpress.com/2014/12/07/centre-georges-pompidou/

[7] http://mediation.centrepompidou.fr/education/ressources/ENS-architecture-Centre-Pompidou/comment_ca_fonctionne/p2.htm

Blackfriars Bridge

Structure Information

Figure1: Location of Blackfriars Bridge [1]

I’ve came across Blackfriars Bridge during my last bicycle ride around Jubilee Gardens. Blackfriars Bridge is an arch designed structure that crosses the River Thames about a mile away from the famous London Eye and located between Waterloo Bridge and the Millennium Bridge.

Opened  for public circulation in November 1869, the 5 spans bridge is 923 feet long and, was designed by the English Civil Engineer Joseph Cubitt. Due to an increasing traffic, the initial 70 feet wide structure had been widened to the actual 105 feet. Funding came from a charitable trust “Bridge House Estates” on behalf of the City of London

 

Figure 2: Blackfriars bridge in 2018

Historical Significance

The original Blackfriars Bridge was the third to be constructed in central London after London Bridge and Westminster Bridge. The present Blackfriars Bridge consists of five wrought iron arches and was built in replacement for the first crossing toll bridge “William Pitt Bridge” designed by Robert Mylne with nine semi-elliptical arches made out of Portland stone and was poorly executed. The use of wrought iron was unique at the time of the inauguration, however not the first time to be used. Joseph Cubitt was conjointly working on another similar project: the Blackfriars railway Bridge adjacent to this structure. Both structures look a lot alike with the use of the material iron which made construction much less time consuming (five years) versus the nine years of construction for the original stone designed by Mylne. The structure was inspired and also inspire tourists across the world. Here is an old image of the Original Blackfriars Bridge

Figure 3 : Original Blackfriars Bridge in 1775 [2]

Cultural Significance

Figure 4: Blackfriars at night

Blackfriars Bridge was inaugurated by Her Majesty the Queen Victoria herself on the 6 th November  1869. The international notoriety of the structure came into play thirteen years after the opening when a former chairman of a renowned Italian bank was found dead on one the arches. What seemed to be at first a suicide was later proven to be a murder by the Mafia to whom he was related and indebted. Sounds like a movie isn’t? Decorations on the structure are historically meaningful. It is said that this bridge marks the boundary between sea water and salt water in the Thames and the choice of bird subjects reflects this idea: sea birds on the downriver side, fresh water birds on the other. For instance, the pulpit-like shape at the ends of the bridge is purposely designed in reference to Black Friars while the stone carving on the piers of the bridge was in respect for the marine life and seabirds. The dedication of the bridge to Queen Victoria was represented by her statue which was by the way funded by a certain Alfred Seale Haslam. Used as road and pedestrian bridge, the Blackfriars’ structure boosted the pride of the Londonians, especially of the merchants crossing the bridge for their daily activities leading to donations from the wealthy ones for the funding of the House Estate Trust which is an organization in charge of four other Thames bridges. Guess who is the trustee? The City of London! Yes, the City relies on these funds to insure repairs and maintenance of the infrastructures within the limits of the city.

 

Structural Art

The Bridge has to qualify for the rule of the three E’s (Economic, Efficiency and Elegance) in order to be called a structural art. As shown in the following section, the load path for the structure is clearly represented despite the multiples decorative elements in place which consolidate the aesthetic-elegance aspect of the design. The load path could be seen from the deck trough the multiple trusses and transmitted to the piers. It has been relayed that the City of London had been clear during the design phase of their expectations of an ornamental structure which justify the decorative semi-circular columns on both side of the bridge. The bridge costed  £151,000 at the time; worth a roughly  amount of £17M in 2017 [3] , which make me consider the costs to be within the limits of reasonable during that period. Don’t get me wrong, I’m not saying that the same structure -if it had to be designed today- couldn’t be evaluated more cost-efficiently! Anyway, with the three E’s checked out, I could affirm that the Blackfriars Bridge is definitely a structural art.

Structural Analysis

Figure 5: Load path on Blackfriars Bridge

The bridge is a 5 spans structure made of cast-iron arches assembled on site with the deck made of reinforced concrete built on site as well. As the Thames was well-known to be a fast flowing river causing damage from scouring, iron caissons were used to help deep into the clay riverbed. These caissons were half filled with concrete and surmounted by the granite-faced piers. Thorn and Co. the builder of the structure had to deal with the use of caisson for the first time on this project for the piers which was a challenge that was won. In terms of materials, wrought iron was used for the ornamental elements. Portland stone, well-known for its strength and polished red granite was used for the piers. The 5 spans structure bridge has been designed to cover 922 feet over the river and in between we have the 3.3m high columns, said to weigh over 30 tonnes each carrying loads from the 56.4 m central arch of the bridge followed by the next two 53.3m span. As expected for the load path, the use of repeated circular arches helps reduce the lateral loads at connections (columns/piers) with the exception of the exteriors ones which are contained by the abutments on both banks of Thames. The piers collect both the dead load and live load according to the respective tributary area. The deck, by the way provides a uniformly distributed load on the top the structure over the entire length. The reaction of the soil below the piers prevent the entire structure from failure. In order to design this structure, I’ll assume the extreme cases scenario in terms of live loads especially; meaning I’m considering the following at an instant t on the bridge: 10 trucks of 10,000 lbs each, 100 pedestrian of 120lbs each. These assumptions are computed in the following as:

Evaluating for example the lateral and horizontal forces for the central span requires the following:

ΣFx= 0 => Cx = Dx

ΣFy = 0 => Cy + Dy – W (185’) = 0 but since there’s symmetry between both reactions,

We have Cy = Dy = (WL/2) = 7,832/2 = 3,916 K

The lateral load equals to Cx = Dx = (wl2/8h) = 42,333*1852/ (8*10.8 ft.) = 16,769 K

Resultant Force to be cancelled by neighboring arch Rx = Sqrt. (Cx2 +Cy2) = 17,220 K.

From here, with the same increment method we could determine the force coming from the immediate left’s span until the left side abutment. Due to symmetry, the value on the left side is more likely to be the one on the right side as well.

Furthermore, Shear and Buckling could also be checked out to ensure the appropriate section for the piers in order to avoid failure.

Personal Response

Maintenance on this structure has been said to occur on a yearly basis. However, my impression is that the maintenance is exclusively focusing on the structural aspect of the Bridge. The sidings looked rusty and off paint which, not only affect the aesthetic but could be a trigger for much bigger structural issues in the future. There’s always this strong feeling being in physical contact with structures constructed centuries earlier. I’ve never realized the need for a more thorough maintenance schedule for public structures until my eyes captivated the rusty trusses on Blackfriars.

Figure 6: Structural concerns, Please HELP!

 

References

[1] https://www.google.com/maps/d/viewer?msa=0&mid=1Yv2q2kSjL-2fqJczikCqxQGiJy8&ll=51.51021609855225%2C-0.10235587337115248&z=16

[2] http://www.thehistoryoflondon.co.uk/the-original-blackfriars-bridge/

[3] https://www.bankofengland.co.uk/monetary-policy/inflation

http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=693

Holy S…!

Holy structure! Yeah, structure. Don’t let your mind suggest something else!

 

Figure 1: The Basilica of The Sacred Heart of Jesus[1]

Structure Information

During one of my rare errands on Peachtree Street in Atlanta, I’ve came across this beauty and convinced myself that it might be a good time to be religious. Formerly known as Saints Peter and Paul, the Basilica of the Sacred Heart of Jesus is a church founded in 1880 that

Figure 2: Location[2]

was initially located a few blocks away westward. The needs for relocation occurred in response to the congregation’s increasing number and the commercialization of the area. A new denomination “The sacred Heart of Jesus” came along with the French Romanesque design of the architect W.T. Downing in 1897. The impressive creation won a place in the National Register of Historic Places in 1976 and was later consecrated as The Basilica of the Sacred Heart of Jesus by His Holiness Pope Benedict XVI himself! Funding came from diverse unrevealed sources. During my short tour guide, I came to understand that the facility is projecting important repairs and only fifty percent of the $1.25M needed is met. I’m not preaching here…your donation…lol!

 

Historical Significance

Figure 3 : Inside toward the tabernacle

Figure 4: Inside, toward main exit/entrance

 

 

 

 

 

 

 

 

 

 

 

 

 

The engineering design for this structure was not entirely new. As expressed earlier, the Architectural style was inspired from the Roman French with a final product that demonstrated a particular touch from Downing and his engineering team. Both the exterior and interior are predominantly consisted of arches and decorative columns which are literally Roman’s footprints/signature . The idea of improving pre-existing designs in order to obtain enhanced products could not be condemned, is it? The humanity has been long relying on old patterns to define new ones.

 

Cultural Significance

While it was still Sacred Heart, Mother Theresa of Calcutta, an important figure of the Roman Catholic church, was there for a Mass in June 1995.  She came at the Basilica for the blessing of the Sisters of Charity AIDS hospice. The renowned Father Michael A. (Tony) Morris led the congregation during its growth and revitalization. The “artistically significant architecture” is said to have influenced the recognition to the National Register of Historic Places. All sort of religious education are provided on the premises in both English and Spanish.

 

Structural Art

The walls of the First Catholic Church of Atlanta are essentially made of masonry, pressed brick and terra cotta. Two twin towers with octagonal shape along with arches of various span were heavily represented. Columns are symmetrically placed, creating an aesthetic touch that follows the “function follows form” of David P. Billington [3]. Architect Downing used eyebrow windows to enhance the building’s aesthetic expression. The conic element on the top of the one-hundred and thirty-seven feet towers is visibly made from lighter material but stiff enough to resist wind loads; revealing the combination of what qualify, in my opinion, the building as a structure art.

 

Structural Analysis

The design principles were those associated with resistance to wind loads, dead weight. From the interior pictures -little dark by the way- we could perceive how the high ceiling in the shape of a dome -above the tabernacle, specifically- transmits its load to the symmetrically and strategically positioned columns. Considering the relatively small section of the columns and the thickness of the outside walls, I’m tempted to say that most of them were bearing-walls. However, the columns were collecting loads from the tributary areas of the roof and of the beams between the spans of the high-rise building. The base of the towers consists of cubic blocks containing tall, round-headed windows incorporated in recessed walls framed by strip buttresses. Depending on the cases, the arches were submitted to a triangularly distributed load which, in return are transmitted to the columns. For example, the Triple-arched doorway at the entrance displayed at the right present how the loads are applied. The reaction at the base of each column should withstand the weight of the associated tributary area. In this case, it’s clearly predictable that the pair of columns in the middle would more likely have the same design and a more consistent load compared to the others two.

Figure 4: Load below the beam on arches

Figure 5: Tributary area, load distribution

Figure 6: Collection of tributary load into the column

 

 

 

 

 

 

 

 

Due to symmetry, there’s a high likelihood to have multiples structural elements with the same sections; making the engineering duty less complex unless geotechnical conditions differ.

It was recorded that the building was built for $28,000 on a land initially acquired for $12,000[4]. I was not able to collect any technical information. I’ve resolute to focus on the design of the high ceiling with the following assumptions:

Figure 7: Load on arches

-Dead load for concrete = 145 lbs/ft3  [5]

-Live Load (snow) = 5 lbs/ft2 [6]

-Hmax = 25 ft (pure estimation)

-Slab thickness = 8 in (previous experiences input)

-Tributary Area A = 180 ft2 (pure estimation)

-Span L = 150 ft (pure estimation)

 

Figure 8: Determination of loads

 

With these information, I was able to compute the reactions on the buttresses and the load on the columns as displayed in the following figure.

The next step was to evaluate the bearing stress on the columns. With the diameter of the column estimated to be around 18 feet, the area of the column is estimated to be in the order of 36,643.54 in2. The bearing stress being equal to the force over the area, the bearing stress of the columns is evaluated at 80.41 psi. With a supposed Factor of safety of 11, I was able to conclude that the allowable stress should be 884.5 psi in order to prevent any eventual buckling. Furthermore, it’s imperative to appreciate the responsiveness of the columns to stress and since the maximum occurs at the center, that would be the center of our focus.

 

Personal Response

The physical presence inside an historic building of this type is more than insightful. Anyone else could have also suspected the building for being a little old but just not as much as a century. Its powerful in some ways to get so close of one of the oldest structures built in Atlanta which is still functional. Now I understand, how incertitude has influenced a relatively greater factor of safety for ancient structures; leading for massive sections not necessarily cost-efficient. Especially, in this case of a religious building, I just hope for my visit to have occasioned my sins to be washed away!

 

References

[1] http://www.sacredheartatlanta.org/directionsparking.html

[2] https://screenshots.firefox.com/UKHW08xvzEaflSA7/www.google.com

[3] David P. Billington  The Tower and the Bridge: The New Art of Structural Engineering

[4]http://www.sacredheartatlanta.org/about-sacred-heart.html

[5] https://www.atlantaga.gov/government/departments/city-planning/office-of-design/urban-design-commission/church-of-the-sacred-heart-of-jesus

[6] https://www.atlantaga.gov/home/showdocument?id=33495