Blackfriars Railway Bridge

Structure Information

The new Blackfriars Railway Bridge began development in 2008. The cost was estimated around 350 million pounds [2]. The bridge opened in February 2012 and began operation the following summer. The new bridge was a part of the Thames Link Project by Network Rail and First Capital Connect to decrease congestion and increase capacity of the passenger train routes in London [2]. Tony Gee and Partners of London designed the station-bridge and Jacobs designed the building [2]. The Department of Transport’s Safety and Environmental Fund funded the solar panels [2].

Figure 1: Blackfriars Rail Bridge

Historical Significance

The Blackfriars Rail Bridge has 4,400 photovoltaic panels that provide up to half of the energy for the London Blackfriars station located within [1]. The bridge is the world’s largest solar powered bridge and the largest solar array in London [1]. These panels required careful design and installation. They needed to be light so prevent exuberant additional load on the structure and crack resistant, for safety. The instillation also had to be paused for the London 2012 Olympic games.

Blackfriars Rail Bridge is also completely accessible to travellers with disabilities. Although this seems like the norm, it is quite uncommon in London [5]. On the tube it is particularly noticeable that only a few stations are handicap-accessible, this, however, could be due to the old age of the underground system in London. Even the accessible stations seem to be a challenge with ramped corridors and gaps getting into the trains. The new rail bridge station makes it easy for travellers with disabilities to make their way on the bridge and through the station.

The new Blackfriars Rail Station is the first in London to span the entire length of the Thames [2]. The deck station allows station access from both sides of the bridge and therefore both sides of the river [7].

The bridge also used innovative construction techniques to keep the lines functioning in the station and not impede traffic on the Thames. Most major new features (concrete pieces and steel arches) were prefabricated and brought in on barges and placed by cranes held by the old Blackfriars Road Bridge piers. The designers, Tony Gee & Partners, said that half of the work in the Blackfriars renovation and rebuild was construction engineering (figuring out how they would put their plan into action without much public disruption) [5]. See the rail bridge piers in Figure 2.

Figure 2: Blackfriars Road Bridge Piers

Blackfriars Rail Bridge exemplifies ideal features of modern bridges. The embodiment of Green structures and inclusion cover the main goals of society today. These two features alone make the bridge and station a perfect model for future buildings. The creative and efficient construction process also model futuristic construction, although each project differs in this regard.

Cultural Significance

The Blackfriars Rail Bridge is located above the remains of the original Victorian railway station [5]. This caused obstacles in the design process, yet it remains as a historic passageway, following the foundations of the existing bridge across the Thames.

The construction and rehab of the new and improved Blackfriars Rail Bridge was managed with both railways operational most of the time and without disturbing Thames traffic [5]. This connects to the true significance of the bridge, smooth passage in London. The station relieved previous congestion and has provided easy travel for all passengers, including those with disabilities. The train station located on the deck allows 12 car trains to function and permits over 24 trains per day to pass through [1].

Since the construction, the bridge has served as a reminder of London striving to become a sustainable city with its central location and functionality during the Olympics [1]. It is now considered an “Iconic Landmark” [6]. This rail station also, for the first time, connects London’s “cultural quarter”, the South Bank to a mass transit system [7]. This new location sparked conversation over renaming the bridges to “Blackfriars and Bankside” but, as we see today, this was never pursued [7].

Structural Art

The Blackfriars Railway Bridge is not a quintessential example of structural art. However, the Blackfriars Railway Bridge seems like a modern example of structural art. While it does have expensive features, each of these contributes to the efficiency of the bridge. The solar panels make an efficient green structure and the handicap features simply satisfy the necessities of today’s facilities. The extension of the deck allows for larger trains, which are occupied and will be heavily used as London’s population skyrockets. The foundations built off of existing structure and reinforced bracing, saving money and contributing to economy. The use of the existing road bridge piers and prefabrication also contributed to economy. The load path is clear and elegant, as the arches flow across the Thames. It seems clear that the Blackfriars Rail Bridge and Station are structural art.

Structural Analysis

Blackfriars Rail Bridge is a wrought iron girder bridge with five arches [4]. Much of the originally wrought iron deck has been replaced with mild steel and concrete [4]. The foundations are made of wrought iron plated caissons [4]. The piers are concrete and stone, converted with granite and sandstone [4]. The abutments are made of cross arches of brick. The bridge acts as five separate arches as arch girders on the piers and abutments, which take the deck and arch load [4]. This could partially due to the bridge being built over an existing railway, which, at its time, had no standardization. Each precast concrete structure had to be individually measured and made off site [5]. A quick-stiffening concrete was needed so the pieces could be handled soon after being cast. The steelwork was also pre-assembled and brought in by barge. The existing piers from the old Backfires Road Bridge were used as support for equipment in demolition and expansion of the existing rail bridge. The existing rail bridge was reinforced to allow for the addition of lanes for trains.

Load Path

The loads on the deck are assumed to evenly distribute onto the arch. From here the arches send the load to the piers or abutments on either side of them, which translate the load to the ground. The load path can be seen in Figure 3.

Figure 3: Load Path

Info

Figure 4: Span Information [4]

Blackfriars Rail (m) 6.9 6.9 7.0 7.2

[8]

Passenger trains have a maximum live load of 1.71 tons per foot.

There are 15 steel arched members per arch.

Each arch weighs 45 tonnes [3].

Solar Panels each weigh 15kg  and there are 4400 of them [1].

Calculations

Each arch varies in size, and therefore produces a different load. Since the bridge built from a pre-existing structure, the piers are large enough to handle some of the force from the arch. Because of this, I assume all differing horizontal forces cancel through the piers although they are not equal. The dead load embodies the load of the steel and concrete deck and steel arches and the live load includes the train and people load. With this information, the reaction forces of each arch were calculated. These calculations are in Figure 5.

 

Figure 5: Calculations

Drawings were used to communicate the design to the stakeholders in order to show that components of the existing bridge could be retrofitted for the new bridge. By expressing this, the designers showed their cost effective solution for the congestion at this central London location. The drawings also conveyed the importance of handicap accessibility and energy conservation and how they were employed to the new bridge and station.

Personal Response

            By visiting the bridge and walking through the station, I saw first hand the attention to detail put into the structure. The combination bridge and station, green initiative of London, and handicap inclusion are all striking from within and around the structure. I also saw the true extent of 4,400 photovoltaic panels crossing the entire Thames. The bridge panels even stuck out from the top of the London Eye, which is when the bridge first struck me.

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

 

 

Coda Building

Structure Information

The new Coda Building began construction in 2016 and is expected to be completed in the 4th quarter of 2018 [1]. It is located in Midtown, Atlanta, just one block from Tech Square. Georgia Tech and John Portman & Associates announced their plan for the 750,000 square foot collaborative building and high performance computing center. 620,000 sq.ft. of the building will be office space, half of which will be available for companies and the other half will be occupied by Georgia Tech. There will also be 40,000 sq.ft. of retail space, which includes the historic Crum and Forster building, labelled as 1 in Figure 1 and in the foreground of Figure 2. and 80,000 sq.ft. of a data center, labelled as 2 in Figure 1 [1]. The building plans to offer an “unparalleled collaboration between research and industry” by giving major companies associated with Georgia Tech the opportunity to work closely with Georgia Tech and with each other with access to a high performance computing center and interactive community space. FS2 was commissioned for designing John Portman & Associates’ 21-story building [3].

Figure 1. Overall Picture [1]

Figure 2: The Historic Crum and Forster Building

Historical Significance

The Coda building itself embodies many state of the art design aspects.There are 5 stories of parking located below the building. The parking deck was put in place using a boring machine and soil nailing. Laser scanning has been used in every phase of construction and by plotting exact points, the scanner was able to catch that one wall was leaning a few inches. The soil nails were redone and this was taken care of thanks to the newly practiced laser scanning technology. The building is also the first ever in America to have TWIN elevators. The TWIN design has two elevators running at the same time in one shaft [3]. Because companies may have multiple floors, this permits someone who is going from floor 17 to 15 to hail the top elevator, instead of sharing with the lower floors. There is a holding place for the elevator at the top and bottom of the shaft so the elevator can go from the top floor to the bottom floor without being blocked by the other elevator in the shaft. The elevators can work with varying floor heights (i.e. a taller lobby) and go to any floor, without separating even or odd floors [3].  The difference is, passengers enter their desired destination upon hairling the elevator, so the paths and elevator can be selected in advance[4]. Initially, the building design had a low rise/ high rise solution, which required a physical barrier separating the lower and upper floors. This solution fit the requirements, but not the collaborative goal of the building. With the TWIN elevator system, the building can remain one part and keep the connection between the upper and lower floors [3]. More than 200 buildings around the world have implemented this elevator made by Thyssenkrupp, including their headquarters in Essen, Germany [1]. There have been many other collaborative spaces constructed and loads of research done on the topic, but the Coda building combines many different practices from floor plan to structural design. Other complete examples include Oregon’s Collaborative Life Sciences Building, the Bacardi headquarters, and the Hyundai Campus. Many of these buildings embody similar approaches to collaboration including open, connected spaces with natural lighting and open floor-plans. They strive to inspire with their spaces and promote the Green initiative [5]. A key difference is a few companies find that being in a suburb increases motivation and productivity compared to urban campuses [5]. The Coda building will definitely inspire future buildings. It is the newest example of a collaborative building, with innovations that are appearing for the first time in the US. Once complete, the Coda building will be the “thing to beat” as others aspire to create collaborative, innovation driven spaces. From design to furniture selection, Coda will have state of the art technology and research in every detail.

Cultural Significance

The Coda building will house both industry professionals and GT research and extend Tech Square. Over the past few years, Tech Square has become the innovation hub of the southeast and, with Coda, it will have three million square feet of commercial space attributed to it [3]. The use of new technologies in the building and collaboration spaces with researchers and professionals in the Coda building will add fuel to the innovation fire currently in Tech Square. The building will also have public spaces, an interactive media wall, and retail spaces for the public. The historic Crum and Forster building will be updated and accessible to the public as a gathering place and outdoor living room [1]. President Bud Peterson discussed how the collaborative building will also have a positive impact on Midtown by bringing people together in “a mixed-use community of innovation, education, and intelligent exchange.”

Structural Art

In regard to the basis of structural art, economy, efficiency, and elegance, the Coda building is very lacking in the first. There were no major monetary constraints, which violates the basic principle structural art, that creativity is fueled by the monetary constraints (economy). The historic building has features pre-dating the era of structural art and is not tall enough to be considered structural art. The Coda addition does embody some features of structural art including clear load path because it is a glass building and the beams are visible. Only necessary supports were used, but they were not always the most cost effective options (efficiency). The single beam support of the staircase and pop-out section of the building are examples of this. Also, by omitting beams through the walkway and having the large open space below, large expensive supports were needed to hold the structure up during construction, until it was tall enough to be stable. See Figure 3, Figure 4, and Figure 5 for the temporary supports and after removal.

Figure 3: Base of Temporary Support

Figure 4: Top of Temporary Support

Figure 5: Remanence of Temporary Support

Elegance is satisfied in the engineering sense as the supports and load paths used are visible and the engineering systems are innovative and impressive, although not affected by monetary constraints. The main focus of this building is aesthetics and that is it’s fault in structural art. In regards to scientific, social, and symbolic aspects of the building, Coda does a better job than compared to the E’s. Scientific is where the building is lacking, as the design and materials are not constrained by money, although the structural design is creative, clear, and safe. Socially, as I described in the cultural and historical sections, Coda will have a major impact on the innovation world, the workplace, Midtown, and future buildings. There are not many long term costs to society, and, as a privately funded building, there are not short term monetary costs. There are, however, short term costs in the noise and road closures. Symbolically, the building creativity and public gathering spaces embody the aspirations of the building, collaboration and innovation. Even the research and innovation being done within often does not have monetary constraints, so the building symbolizes the uses perfectly. Overall, Coda cannot be considered structural art because of the basis of creativity with economic constraints. The building cannot be compared to other examples of structural art or explained with the E’s and S’s other than economic because they all have a basis of monetary constraints.

 

Structural Analysis

The Coda building was designed to embody collaboration and innovation in every aspect. The staircase and pop-out side of the building are examples of structural innovation and the glass shows the connection and openness within the building. The speed and precision of construction shows how innovation and collaboration are being applied. Boring down five levels and using soil nailing while pumping out and lowering the water level below is almost unheard of. Forms and concrete pump trucks are adding floors constantly with a crane on site 24/7 to move the forms once the concrete has solidified. While concrete is forming floors, other sections of the building are getting the steel frame put in. The two sides of the building joined at the staircase are going up simultaneously with the crane in the elevator shaft because from there it can work with and reach both. These are just a few examples of how every aspect of the building embodies collaboration and innovation.

The systems I will be analyzing are the staircase and the pop-out section of the building. The design load of an office building is 50 pounds per square foot per floor, although the measured load is only 10.9 pounds per square foot. The staircase goes from a line load from the roof through the walls, to a surface load of the floor, to a line load in the walls below and so on down the building until the surface load on the bottom floor is distributed into a point load in the single column to the ground as seen in Figure 6, Figure 7, and Figure 8. The glass panels around the staircase are shortened to account for the curvature. Assuming the windows are a foot wide, the diameter would be 12 feet. The stress would be the force over area. Force equals the number of floors (7) times the area (pi*6^2) times the force per square foot per floor (50) divided by the area (pi*6^2). The stress calculation for the floor above the column gives a stress of 350 lb/sq.ft. (1). The stress in column is the force (same as above) over the area of the column (pi*2^2). The stress calculation gives a stress of 3150 lb/sq.ft. (2). I am neglecting the self weight of the pole in this calculation because it is negligible. I found the diameter by comparing to the people standing by the pole and the windows. The critical buckling is (pi^2*E*I)/L^2. Assuming E is 7250 ksi (that of strong concrete, have to x12x12 to get feet), I is ¼ (pi*R^4), the height is 25 feet,  the critical buckling point is 207,171 lb, which is much greater than the P of (3150*A) which is 39,584lb. The change in shape (delta) is (P*L)/(E*A). In this case, delta is .075 feet. This could be explained in drawings by showing how the force over the whole area of the staircase/ room is initially distributed then all on one point, the column, therefore it is very large and requires such a thick column. The drawings would show the detailed supports that transfer the load to the column and how they connect.

Figure 6: Stairwell Load Path [1]

Figure 7: Process of Stairwell

Figure 8: Future Completed Pedestrian Walkway

The pop-out section of the building is a cantilever with 18 floors. The load goes from the roof, down as a line load to the floor below for each of the 18 floors above the overhang. From the bottom of the overhang, the load is transferred through a fixed connection, like a cantilever, to the main structure of the building. Refer to Figure 9 to see the load path.  Assuming each window is 3 feet wide, the side length is 25.5 feet and the width is ¼ of that so 6.375 feet. Therefore, the force on the cantilever is 50 pounds per square foot per floor *18 floors * 25.5feet * 6.4 feet, which equals 146,310 lb. Assuming there is one beam supporting each side and even distribution, each will hold 73155 lb total, which results in a w of 5852 lb/ft (73155 lb/25ft/2). Assuming the beam is 2×1 with the long side on top, the deflection is (wL^4)/(8EI). Assuming L is equal to the side length of 6.4, E of steel 29007*12*12, and I is of a 2ftx3ft beam (as observed in Figure 10), the deflection would be 0.14 feet. Fx at the base would be 0, Fy would be w*l 33650lb upward, and M would be 3.2ft*33650lb (107700 ft.lb.) clockwise. With this information you could explain the design by showing that a thicker beam will not break and that a heavier base will ensure the cantilever does not tip (i.e. a toothpick will break trying to hold a weight but a pencil would not, the pencil in an eraser would tip over but in a wall pencil holder will not) and explain how the force requires a thick beam and the building can hold the rotation caused by the force. The drawings could show exactly how to attach the beam and it’s dimensions.

Figure 9: Cantilever Load Path

Figure 10: Cantilever Process

Personal Response

Having been in the building, I learned a lot about how much more complex the construction activities are and that you never know what is going to happen. Very often on sites, unexpected bumps in the road are hit, causing delays. In the Coda case, the water continuously had to be pumped out to bore the parking, 24/7 for weeks. I also had never realized what it took to have large gaps and how expensive adding a truss instead of columns is. Material wise, it seems the truss is equal, if not better. However, on the construction side you see the semi-permanent, expensive to get and install, time consuming supports and scaffolding needed to hold the load until the truss is complete. In design classes and in final presentations or books on buildings, details like this are often omitted.

Resources

[1]http://www.news.gatech.edu/2016/04/20/georgia-tech-portman-announce-coda-tech-square

[2]https://archpaper.com/2018/01/georgia-tech-atlanta-coda-technology-jobs/#gallery-0-slide-0

[3]https://www.fs2ec.com/coda-in-tech-square

[4]https://www.wired.com/2016/05/thyssenkrup-twin-elevator/

[5] https://www.gensler.com/design-forecast-2015-the-future-of-workplace