The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its Design

The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its Design Abstract Constructed in the 1970s, the John Hancock Tower is the tallest skyscraper in Boston. Its reputation lies in Henry N. Cobb’s innovative design that preceded its time, but also in its grandeur glass failure occurred from 1971 to 1974. The glass failure had resulted in the loss of economic profits and public criticisms of the Hancock Tower as the modern “plywood palace.” 1 The failure has led to the legal dispute, in which the gag order was placed to conceal the cause of the glass failure. For decades, many hypotheses of its cause circulated, including the swaying of the building and wind suction pressures. Eventually, in 2000, the Principal Investigator of the glass failure revealed that the fault lied in Libbey-Owens-Ford’s reflective Thermopane window unit, Vari-Tran Cr. Even after the glass failure incident, the Hancock Tower remains Boston’s the most beautiful and favoured skyscraper. Given this reputation of the Hancock Tower, this report aims to analyse and expand on the cause of the glass failure, lessons learned, aftermath, and the birth of the Hancock Tower’s design.

Keywords John Hancock Tower, glass failure, Vari-Tran Cr Thermopane, Henry N. Cobb, Boston

Author details Yeong Gyeong Son Student ID: 654394 Email: y.son@student.unimelb.edu.au Prepared for ABPL90085 Construction History, semester 2, 2020 Date of submission: 20 November 2020 Faculty of Architecture, Building and Planning, University of Melbourne

John Kifner, “Problems Still Plague Boston Tower,” The New York Times, April 15, 1976, https://www.nytimes.com/1976/04/15/archives/problems-still-plague-boston-tower.html.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

Figure 1. John Hancock Tower, I.M.Pei & Partners. John Hancock Tower, n.d.. Pei Cobb Freed & Partners.

Introduction Boston’s the tallest skyscraper erected in the 1970s, the John Hancock Tower (hereafter, the Tower) boasts its 240.8 meters tall, reflective skinny rhomboid body designed by Henry Cobb from I.M. Pei & Partners (Figure. 1). At the time of its construction, it was the “largest monolithic glass façade ever built” 2 in Boston, and it won many awards 3 and the hearts of local Bostonians. On the contrary, the Tower is also infamous for its remarkable glass façade failure

Thomas A. Schwartz, “The John Hancock Tower Glass Failure: Debunking the Myths” (Paper presented at the Structures Congress 2000, Philadelphia, Pennsylvania, United States, May 2000), 1, doi: 10.1061/40492(2000)97.

3 The John Hancock Tower was awarded the American Institute of Architects’ National Honour Award in 1997, Harleston Parker Medal in 1983, and American Institute of Architect’s Twenty Five Year Award in 2011.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

from 1971 to 1974 that risked damage to the adjacent 19th century Trinity Church façade and caused conflicts with the locals. The glass failure brought substantial economic loss, leading the John Hancock Insurance Company to nineteen counts of lawsuits against partners and building contractors in 1975. 4 Since the legal settlement in 1981 silenced all affiliated parties about the cause of this phenomena, 5 many speculations were disseminated, until the Principal Investigator of the Tower’s glass breakage, Thomas A. Schwartz cleared the air in 2000 that the cause lied in the window unit itself.

Given these contradicting legacies of the Tower, this paper aims to dissect and analyse the cause of the glass failure and how the Tower has gained its popularity after its construction. The report is divided into two parts: •

Part 1: To analyse the Tower’s glass breakage incidents from 1971 to 1974, and extract two popular myths and Schwartz’s report on the cause of the glass breakage.

•

Part 2: To investigate how the design of the Tower was born, and how the Tower won the interest of the Bostonians after the glass failure.

During this research, there were limitations on access to the primary records of the accurate wind speed, total numbers of shattered windows, and the cause of the glass failure from the glass manufacturer, Libbey Owens Ford Glass Company (L.O.F.). Therefore, a mixture of primary and secondary sources has been referenced for these details.

The partners and contractors include “Gilbane Building Company of Providence, R.I., general contractor for the project, the N.H. Robertson Company of Pittsburgh, subcontractor for the curtain wall, the Libbey Owens Ford Company of Toledo, I.M. Pei and Partners, the Aetna Casualty and Surety Company of Hartford, which furnished the performance bond for Gilbane Building, and the Federal Insurance Company of New York, which furnished the performance bond for H.H. Robertson. The complaint alleged John Hancock suffered substantial damages, including the cost of labor and materials for removing and replacing the glass units, additional design, engineering and construction costs and increased operating expenses and other costs. Also claimed it sustained damages deprived of the use of the tower and lost income on rentals” “Hancock Sues Builders For Defects in Tower,” The New York Times, September 16, 1975, https://www.nytimes.com/1975/09/16/archives/hancock-sues-builders-for-defects-in-tower.html.

5 Schwartz, “The John Hancock,” 1.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design Part 1 – The glass failure and its cause 1. The glass breakage from 1971 to 1974

On the 27th November 1967, the construction plan of the new John Hancock Tower was publicly announced with a total approximate budget of USD 75 million. 6 The construction of the 62storey Tower began in 1968, 7 occupying one block in a diagonal alignment, on the Copley Square adjacent to the Trinity Church, built in the 19th century. Cobb’s design plan was to completely cover the Tower with 10,344 double-pane windows, 8 Thermopane, through foursided structural glazing technique. 9

Left: Figure 2. Bondermetic Thermopane unit, Libbey Owens Ford Glass Company (hereafter L.O.F.). Four important features of Thermopane, 1946. L.O.F. Archive.

Right: Figure 3. Bondermetic Thermopane unit, L.O.F.. Cross section of Bondermetic insulating glass showing ¼ in. thick lites of glass and ½ in. wide lead-tape spacer with soldered connection to glass, n.d.. Thomas A. Schwartz.

John H. Fenton, “John Hancock to Build 60-Story Tower in Boston; Based in Boston,” The New York Times, November 28, 1967, https://www.nytimes.com/1967/11/28/archives/john-hancock-to-build-60story-tower-inboston-based-in-boston.html.

7 John Kifner, “Boston Tower’s Plywood Windows,” The New York Times, July 18, 1973, https://www.nytimes.com/1973/07/18/archives/boston-towers-plywood-windows.html.

8 Robert Campbell, “Builder Faced Bigger Crisis Than Falling Windows,” The Boston Globe, March 3, 1995, https://www.penceland.com/hancock-windows.pdf.

9 Andreas Wolf, “New Development in the Field of Insulating Glass Units,” Construction & Building Materials 2, no. 3 (Sep 1988): 141 – 142, doi: 10.1016/0950-0618(88)90042-6.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design The type of the Thermopane unit chosen for the installation was Vari-Tran Cr Thermopane units (Vari-Tran), 10 a new product manufactured and distributed in the market from 1968 by L.O.F. 11 Similar to its preceding model, Vari-Tran unit also acted as an insulated “glass

sandwich” (Figure 2 & Figure 3). 12 It comprised of hermetically sealed two plate glasses with each thickness ranging from 0.63cm to 0.95cm, 13 separated by a 1.27cm thick lead separator that was hand-soldered to all edges of the glass with lead (Bondermetic seal). 14 The only difference from its preceding model was that Vari-Tran consisted of a reflective chromium layer attached on the interface of the outer glass pane through vacuum vaporisation. 15 VariTran was innovative and revolutionary at the time. The new reflective coating was more efficient than monolithic glass in not only reducing heat and glare 16 but also controlling the daylight transmittance. 17 The reflective layer also provided privacy inside a building with its mirror-like surface on the outer cladding of the building in the daylight conditions, without

In Schwartz’s report, Campbell’s article, and the news articles from The New York Times did not specify the name of the Thermopane unit installed at the Hancock Tower. However, their descriptions of the reflective Thermopane unit and its market release date matched with those of LOF’s Vari-Tran Cr. Vari-Tran Cr was also the only heat resistant reflective window with Bondermetic seal that could be installed on the building cladding.

Further, the historical record of the application of Vari-Tran is noted in Libbey Owens Ford Archive in box 28, folder 19.

11 Giorgio Marfella, ‘From Heat Absorption to Speculation: The Troubled Evolution of International All-Glass Architecture in Melbourne (1955 – 1985),’ in Gold, edited by AnnMarie Brennan and Philip Groad, 411, Proceedings of the 33rd Annual Conference of the Society of Architectural Historians, Australia and New Zealand, Melbourne, 06 – 09 July 2016.

12 Often known as an “air conditioned glass sandwich,” Thermopane unit was more energy-efficient and economical than other window units. The dehydrated air space sealed between two panels of the Thermopane unit acted as an insulation that blocked cold or heat from the outside. This also helped to maintain the temperature of the inner glass panel to remain at the room temperature, reducing the downdraft and heat loss from the room.

Libbey Owens Ford Glass Company Archive, Canaday Centre, University of Toledo, Ohio (hereafter L.O.F.), box 18, folder 27, “First Insulating Window Pane,” release to Science Writers, April 1944.

L.O.F., Canaday Centre, University of Toledo, Ohio, box 18, folder 27, “Things Every Home-Minded Couple Should Know About Thermopane Insulating Glass,” Thermopane promotion pamphlet, n.d..

13 Each glass panels of the units were produced in a thickness from 0.63cm (1/4inch) to 0.95cm (3/8inch), depending on the height and the position on the Tower. The total thickness of Vari-Tran Thermopane units installed at the John Hancock Tower were 3.16cm (1-1/4”), 2.86cm (1-1/8”), and 2.54cm (1”).

Schwartz, “The John Hancock Tower,” 4 – 5.

L.O.F., Canaday Centre, University of Toledo, Ohio, box 28, folder 19, “Reflective Glass Curtain Wall installation,” historic record and image description of the John Hancock Tower, 1972.

14 Schwartz, “The John Hancock Tower,” 4 – 5.

15 Marfella, “From Heat Absorption,” 411.

L.O.F., Canaday Centre, University of Toledo, Ohio, box 15, folder 45, “Glass For Construction 1968,” Thermopane promotion pamphlet, 1968.

16 Schwwartz, “The John Hancock Tower,” 4.

17 “Standard daylight transmittances are normally 14 and 20 percent. It can be furnished with any light transmittance from 5 to 40 percent and beyond to meet specific job requirements.”

L.O.F., Canaday Centre, University of Toledo, Ohio, box 15, folder 45, “Glass For Construction 1968,” Thermopane promotion pamphlet, 1968.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design impacting the visual transparency from the indoors. 18 With the benefits to reduce airconditioning costs and its appealing reflective surface, Vari-Tran was promoted as a “major promise to architects,” 19 including Cobb.

Left: Figure 4. John Hancock Tower, I.M.Pei & Partners. Boston Reflections are seen in Vari-Tran glass now being installed in John Hancock Tower, 1972. Libbey Owens Ford Glass Company Archive (L.O.F.).

Right: Figure 5. John Hancock Tower, I.M.Pei & Partners. Reflective glass installation at the 60-story John Hancock Tower, now under construction in Boston, is accomplished from inside the structure, 1972. L.O.F.

In the summer of 1971, the installation of the windows began (Figure 4 & Figure 5), 20 and the Tower was expected to open in that same year. 21 However, the opening of the Tower was delayed until 1976; in August 1971, the windows began to crack, and shards of broken windows showered the streets below. 22 Up until September 1972, the glass breakage was assumed to be a ‘normal construction damage,’ 23 and the same reflective Bondermetic Thermopane windows were re-installed by December 1972. 24 However, the glass breakage continued, and the L.O.F., Canaday Centre, University of Toledo, Ohio, box 15, folder 45, “Glass For Construction 1968,” Thermopane promotion pamphlet, 1968.

19 Marfella, “From Heat Absorption,” 411.

20 “The glass is being shipped to the construction site in crates with six panes to a crate. The 3,000 pound crates are hoisted by cranes to all levels where the glass is installed from the inside of the building.”

L.O.F., Canaday Centre, University of Toledo, Ohio, box 28 Folder 19, “Vari-Tran Thermopane,” historic and photographic record of John Hancock Tower, 1972.

Schwartz, “The John Hancock Tower, 2.

21 Kifner, “Boston.”

22 Schwartz, “The John Hancock Tower,” 2.

23 Schwartz, “The John Hancock Tower,” 2.

24 Schwartz, “The John Hancock Tower,” 2.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

surrounding streets were blocked off whenever the wind speed spiked to 75 kilometres per hour (kph). 25 By July 1973, more than 2,472 windows were shattered 26 and were replaced with plywood covered with flame-retardant paint, deeming the Tower with its new title, the modern “plywood palace” (Figure 6 & Figure 7). 27

Left: Figure 6. John Hancock Tower, I.M.Pei & Partners. John Hancock Tower with plywood window fillers, Copley Square (Trinity Street façade), 1974. Grant Spencer.

Right: Figure 7. John Hancock Tower, I.M.Pei & Partners. John Hancock Tower with plywood window fillers, Copley Square (Stuart Street façade), 1974. Grant Spencer.

2. The Swaying of the Tower The swaying and twisting of the Tower stressing the curtain walls was the first assumption.

Based on how the upper floor occupants of Hancock employees 28 experienced nauseousness from the Tower’s “cobra dance” 29 from wind, the swaying was assumed to stress the Tower’s Kifner, “Boston.”

Kifner, “Boston.”

27 John Kifner, “Problems Still Plague Boston Tower.”

28 374 Hancock employees were occupying on different floors of the Tower at the time.

Kifner, “Problems.”

29 Campbell, “Builder.”

25 26

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

curtain walls, possibly fracturing the windows. 30 The chief structural engineer of Citigroup Centre 31 in New York, William LeMessurier was called in to survey the Tower, as he installed the Tuned Mass Damper (TMD) at the Citigroup Centre to neutralise the swaying of the building. 32 Weighing up to 600-tons, two steel TMDs were installed on the Tower’s 58th floor (Figure 8). 33 Each steel weight was connected to the steel frame of the Tower via springs and shock absorbers, and on the bottom of the weights lied lubricated steel plate. 34 When the Tower moved, the TMD stayed in the same position, allowing the steel plate floor to slide underneath them to minimise the motion of the tall Tower. 35 Unfortunately, the additional investment of USD 3 million 36 did not stop the continuous glass breakage of the Tower but eased the lives of the upper floor occupants.

Figure 8. Tuned Mass Damper, William LeMessurier. John Hancock Tower – Tuned Mass Damper on lubricated steel plate, n.d.. LeMessurier.

Campbell, “Builder.”

Also known as Citycorp Tower 32 Richard G. Weingardt, “William LeMessurier,” Structure Magazine, September 2012, 36, https://www.structuremag.org/wp-content/uploads/D-GreatAch-Weingardt-Sept121.pdf.

33 Campbell, “Builder.”

34 Campbell, “Builder.”

35 Cambell, “Builder.”

Mir M. Ali and Kyoung Sun Moon, “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review 50, no. 3 (2007): 217, doi: 10.3763/asre.2007.5027.

36 Campbell, “Builder.”

30 31

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design 3. Wind suction pressures

Figure 9. John Hancock Tower, I.M.Pei & Partners. Isometric Schematic of John Hancock Tower’s affected area after the storm in November 1972, n.d.. Frank H. Durgin.

After the windstorm reaching 88 kph shattered thirty-four windows of the Tower’s Trinity Place façade on the 20th January 1972 (Figure 9), 37 Frank H. Durgin conducted a wind tunnel test at Massachusetts Institute of Technology’s (MIT) Wright Brothers Wind Tunnel Facility. Up to 138 transducers were installed in the Tower, and a 1/600 scale model of the Tower was tested to measure the cladding pressure. 38 Durgin proposed that “under certain circumstances,” shortlived strong vortices could be formed on the triangular protruding roof of the Tower’s 9th floor facing the Trinity Place. 39 The increased negative suction pressures (Cps) from such wind loads could impact limited areas of the facade, leading to the glass fracture. 40 The most impacted areas after the windstorm were from the 10th to the 30th floor, 41 especially on the Stuart Street façade and the Trinity Place façade. Based on the wind tunnel test and the recorded measurements of the wind speed, Stuart Street façade experienced negative Cps near 37

Frank H. Durgin, “Lessons from Studies of Cladding Pressures at the John Hancock Tower in Boston,” in Advanced Technology in Structural Engineering, 1, proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)96.

38 Durgin, “Lessons,” 2.

39 Durgin, “Lessons,” 5.

40 Durgin, “Lessons,” 5.

41 Durgin, “Lessons,” 3.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design the edge of the protruding roof from the South-Western winds (Figure 10). 42 The 14-storey

YMCA building on the opposite side from the Stuart Street façade could have trapped the SW

Right: Figure 10. John Hancock tower, I.M.Pei & Partners. Peak Negative Cps on Stuart Street Façade from the Wind Tunnel Test, from all wind direction, n.d.. Frank H. Durgin.

Left: Figure 11. John Hancock tower, I.M.Pei & Partners. Peak Negative Cps on The Trinity Place Façade from the Wind Tunnel Test, from all wind direction, n.d.. Frank H. Durgin.

winds to blow along the Stuart Street façade, experiencing high negative Cps (Figure 12). 43 As the SW winds blew around the corner of the Stuart Street façade and the edged roof, the winds enlarged and formed a vortex momentarily. 44 Meanwhile, the Trinity Place façade experienced

The peak negative Cps measured on Stuart Street façade from the wind tunnel test (from all wind directions) measured -4.5 from the 10th to 20th floor. The recorded peak negative Cps measured on Stuart Street façade during the storm on February 23 1974 measured -13 on the 13th floor near the protruding roof.

Durgin, “Lessons,” 2 – 3.

43 Durgin, “Lessons,” 3 – 4.

44 Durgin, “Lessons,” 3 – 4.

42

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

low negative Cps from the North-West winds (Figure 11). 45 According to Durgin’s observation of the Tower, 46 another vortex could be formed from the NW winds on the edge of the protruding roof between the Trinity Place façade and St. James Street façade; and occasionally the vortex could blow towards the Stuart Street (Figure 12). 47 Although the recorded peak negative Cps were low and the vortices formed were often unstable, 48 Durgin concluded that how these vortices could be formed on the edged roof of the Tower’s 9th floor must be considered in the investigation of the glass failure. 49

Figure 12. John Hancock tower, I.M.Pei & Partners. After Durgin’s Map of Area near the Hancock Tower, n.d..

Ellen Yeong Gyeong Son.

The peak negative Cps measured on the Trinity Place façade from the wind tunnel test (from all wind directions) measured -4.5 on the 20th floor towards the Stuart Street façade. The peak negative Cps recorded on the Trinity Place façade during the storm on 10 March 1974 was -6.6 on the 20th floor near the St. James Street façade.

Durgin, “Lessons,” 4.

46 “…I was standing near [the 9th floor corner at St. James Street]. The wind was from the northwest, and I observed a vortex instantaneously create a hole about 1.5 feet [45cm] in diameter in 6 inches [15cm] of water that had collected in that corner of the roof of the 9 story low building. The resulting waterspout seemed to go straight up.

Later in the wind tunnel I was able to recreate that vortex, which went straight up next from the corner.”

Durgin, “Lessons,” 4.

47 Durgin, “Lessons,” 4.

48 Durgin, “Lessons,” 4.

49 Durgin, “Lessons,” 5.

45

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design 4. The failure of Vari-Tran Cr window unit

However, the Principal Investigator of the glass failure of the Tower, Thomas A. Schwartz contested Durgin’s theory. Schwartz admitted that there were indeed “hot spots” 50 of wind loads detected near the edged roof of the Tower, but the areas that experienced negative Cps were minimal (Figure 13). 51 The windows were designed to the Boston Code of 158 kilograms per square metre, and the recorded peak wind pressure did not exceed such designed load of the glass, based on the wind tunnel test conducted at the University of Western Ontario (UWO). 52 As the window units failed the oscillation test at UWO, 53 Schwartz confirmed that the cause of the glass failure lied in the window unit itself.

Figure 13. John Hancock Tower, I.M.Pei & Partners. Equivalent one-minute pressure experienced by glass from September 1971 to February 1973 based on UWO wind tunnel study, n.d.. University of Western Ontario.

Thomas A. Schwartz, “When Bad Things Happen to Good Buildings,” ArchitectureWeek, published on April 25, 2001, http://www.architectureweek.com/2001/0425/building_3-2.html.

51 Schwartz, “When Bad Things Happen to Good Buildings.”

52 Schwartz, “The John Hancock Tower,” 3.

53 Campbell, “Builders.”

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

The glass panels and the bond strength (of the soldered edges) of the original Thermopane unit without the reflective chromium layer were already under a substantial amount of stress. 54 When reacting to the wind loads, the sealed air space between two panels of glass transferred the wind pressure from the outer panel to the inner panel, leading to a parallel deflection of these two panels. 55 The changes in the temperature and the barometric pressure caused inflation and deflation of the sealed air space. 56 This original Bondermetic Thermopane unit was distributed in the market from the 1950s 57 and had a consistent track record of its successful use since the 1960s. 58 On the contrary, Vari-Tran, the Bondermetic unit fused with reflective chromium coating, was of a new technology 59 that only began its distribution from 1968. 60 Vari-Tran became popular with its mirror-like quality and as an energy-saving solution, resulting in high demands for its production in larger sizes. 61 However, the performance of this new window unit manufactured relatively in larger sizes was not scrupulously anticipated.

According to Schwartz, the additional reflective chromium layer and the production of windows in larger sizes impacted the soldered edges and the behaviour of the windows. 62 The reflective coating increased the temperature of the outer glass panel, causing more thermal stress in the glass panel itself, especially on the interface near the separator. 63 The reflective layer further decreased the bond strength of the lead solder joining the separator and the interface of the outer glass, but not all areas lost bond. 64 The deflection, contraction, and expansion of the glass

Schwartz, “The John Hancock Tower,” 5 – 6.

Schwartz, “The John Hancock Tower,” 5.

56 Schwartz, “The John Hancock Tower,” 5 – 6.

57 Wolf notes that the soldered system (Bondermetic seal) along with sealed and edge-welded systems were the common window sealing systems prevalent in the 1950s and the 1960s. The preceding model of the metal-soldered Thermopane consisted of rubber gasket separator strip, also known as an organic seal. The organic seal was not efficient in sealing the air space tight; and the window unit with the organic seal was easily susceptible to water droplets, dirt and frosting. The metal soldered seal (Bondermetic) unit was developed to reduce the defective performance of the organic seal unit, and the metal seal system became the most adopted window sealing system in the 1960s.

Things Every home-Minded Couple Should Know About Thermopane Insulating Glass, 2.

Wolf, “New Development,” 134.

Schwartz, “The John Hancock Tower,” 5.

58 Schwartz, “The John Hancock Tower,” 5.

59 Schwartz, “The John Hancock Tower,” 5.

60 Marfella, “From Heat Absorption,” 411.

61 Each reflective Bondermetic Thermopane unit measured 1.37m width by 3.5m height.

Schwartz, “The John Hancock Tower,” 5.

62 Schwartz, “The John Hancock Tower,” 6 – 7.

63 Schwartz, “The John Hancock Tower,” 7.

64 Schwartz, “The John Hancock Tower,” 7.

54 55

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

panels from the wind loads, temperature change and barometric pressure continuously contributed additional stress on the outer glass and the soldered edges along the separator. 65 In due course, more areas of the lead solder failed, detaching the impacted areas of the separator from the outer glass panel. 66 During this process, the separator stripped away small pieces of glass from the interface of the outer glass panel and damaged the edges of the glass. 67 These detached pieces of glass remained bonded to the separator and induced stress along the damaged edges of the outer glass, whenever the glass panels deflected from the wind pressure. Eventually, the outer glass panels fractured. 68 Other buildings experienced similar glass failure with VariTran units, 69 but those records were not able to be retrieved from the L.O.F. Archive.

5. Resolution and lessons learned Once the cause of the glass failure became clear, the expensive and time-consuming lessons had followed. Given the timeframe between Vari-Tran’s market release date and his decision on choosing the unit, Cobb lacked a careful consideration in selecting window units with a relatively new technology. Schwartz stressed that one must choose construction materials based on the consistent record of its successful past use. 70 Unlike the original Thermopane unit produced in its usual moderate size, Vari-Tran with the reflective coating manufactured in larger sizes did not possess such record, but provided “an insufficient assurance of success.”71 Eventually, the undamaged 5000 Vari-Trans were sold for USD 100 each, 72 and all 10,344 windows were replaced with 1.27mm thick fully tempered monolithic glass windows 73 that could resist up to 732 kilograms per square metre, enough to withstand the recorded negative Cps. 74 As part of the “gag order” 75 resulted from the dispute with the Hancock Insurance Company, L.O.F. compensated up to USD 7.5 million for the glass repair. 76 In the case of possible future glass fracture, clear films were applied on all internal faces of the glass windows The bearing load on the outer glass panel must be equivalent to that of the inner panel to avoid glass fracture.

Schwartz, “The John Hancock Tower,” 7.

Campbell, “Builder.”

66 Schwartz, “The John Hancock Tower,” 7.

67 Schwartz, “The John Hancock Tower,” 7.

68 Schwartz, “The John Hancock Tower,” 7.

69 Campbell, “Builders.”

70 Schwartz, “The John Hancock Tower,” 8.

71 Schwartz, “The John Hancock Tower,” 8.

72 Campbell, “Builders.”

73 Schwartz, “The John Hancock Tower,” 8.

74 Durgin, “Lessons,” 5.

75 Schwartz, “The John Hancock Tower,” 1.

76 Kifner, “Problems.”

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

to hold broken glass pieces in place, in the case of future glass failure. Additionally, 1,500 tons of lateral bracings were installed along the core centre of the Tower to stiffen its structure, due to the suggested possibility of the Tower falling over. 77 As a result, the total cost of the project more than doubled and marked USD 175 million. 78 Although there were a few windows that failed after the replacement, 79 the Tower has not yet suffered another major glass breakage or other potential structural insecurities to this day.

Part 2 – The birth of the design by Henry N. Cobb and winning the hearts of the locals

Figure 14. Trinity Church in Copley Square, Henry H. Richardson. Another view of Trinity Church at Copley Square, c.a. 1909. Library of Congress, Detroit Publishing Company Collection.

Until the mid-20th century, the majority of Bostonians did not favour tall buildings because they preferred the Colonial-Victorian-style city with church steeples and low-rise buildings

After the glass failure, Henry Cobb requested Swiss Engineer, Bruno Thurlimann, to inspect and review the structural integrity of the Hancock Tower in March 1975. Thurlimann suggested the possibility of the Tower falling over on its narrow side due to its rhomboid shape. There were just enough space to install diagonal steel bracings “along the walls of the service core, the central blob of elevators and toilets.” The project costed another USD$5million.

Campbell, “Builder.”

78 Dialynn Dwyer, “When they built the Hancock Tower – and it started falling apart,” Boston Globe Media Partners, July 15, 2015, https://www.boston.com/news/omg/2015/07/15/when-they-built-the-hancock-towerandit-started-falling-apart.

79 “…the fully tempered glass suffers from occasional breakage from an impurity known as nickel sulphide (NiS) inclusions. NiS inclusions have caused spontaneous breakage in fully tempered glass for decades.”

Schwartz, “The John Hancock Tower,” 8.

77

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design (Figure 14). 80 While the erection of tall buildings, like skyscrapers, began in New York and Chicago since the 1850s, no buildings in Boston, except a federation building, capped over 38.1 metres height due to the zoning rules until the late 1950s. 81 The 1960s came with the waves of proposals for high office buildings in Boston with an introduction to the innovative building technologies and materials. 82 The worrisome Bostonians raised issues with how these buildings could create shadows while attracting more population and traffic in Back Bay. 83 Yet, the proposals were approved, including the Prudential Insurance Company’s the Prudential Centre, the first skyscraper in Boston with 226 metres of its height completed in 1964 (Figure 15 & Figure 16). 84 The John Hancock Insurance Company felt challenged and

Left: Figure 15. Prudential Centre, Charles Luckman & Associates. Prudential Centre, n.d.. Matthew Salazar.

Right: Figure 16. Prudential Centre, Charles Luckman & Associates. Cladding of the Prudential Centre, n.d..

Terry Meyer Boake.

Tim Logan, “Why can’t Boston build taller,” The https://apps.bostonglobe.com/business/graphics/2018/04/tallest-buildings/.

81 The federation government tower was 151 metre Custom House Tower.

Logan, “Why can’t Boston.”

82 The 1960s in Boston was known to be “the era of master planning.”

Logan, “Why can’t Boston.”

83 Logan, “Why can’t Boston.”

84 Logan, “Why can’t Boston.”

Kifner, “Problems.”

Dwyer, “When they built the Hancock Tower.”

80

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Globe,

April,

2018,

ABPL90085 Construction History

Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

commissioned I.M.Pei & Partners in that same year for a taller building than its competitor. 85 However, the journey to its completion was not an easy one when I. M. Pei handed over the project to Henry Cobb. 86 Even before its construction, the plan of Hancock Tower was scrutinised by many local members. Most locals and the critics despised its rival, the Prudential Centre, which was publicly criticised as a “megalomaniac” 87 building, which its design with heavy steel metal façade did not harmonise with the surrounding buildings and the old Victorian City. 88 When the Hancock Tower’s controversial construction plan less than 300 metres away from the esteemed 19th century Trinity Church was confirmed, the locals were concerned of the problems with wind and the domination of Boston’s skyline by the corporate powers. 89 Given these situations, Cobb had to meet more restrictive requirements to produce a design that could please all stakeholders. Compared to how the initial plan by Pei was given two blocks to occupy, 90 Cobb had to come up with a new design occupying only one block with a tighter budget. 91 Besides, he had to ensure that the newly designed Hancock Tower was taller than the Prudential Centre without casting a gigantic shadow over its neighbouring Trinity Church, a “true superstar” in Copley Square. 92 Inspired by Ludwig Mies van der Rohe’s futurist glass skyscraper studies for Berlin in the 1920s (Figure 17 & Figure 18), Cobb’s solution was to align the Tower diagonally to prevent blocking the view of the Trinity Church and to design a Tower The John Hancock Insurance Company was already based in Boston occupying their previous headquarters constructed with limestone in 1947. Prudential Insurance Company was an “out-of-town competitor,” and the Hancock executives found the erection of the Prudential Centre bizarre. The Hancock executives commissioned I.M.Pei & Partners because the architectural firm at the time was already involved in multiple urban-renewal planning projects in Boston. According to Cobb, it was never explicitly mentioned, but it was “implied” that the new John Hancock Tower must be taller than that of the Prudential Centre.

Marc Myers, “A Cultural Conversation / With Henry Cobb: Mirror Over Copley Square,” Wall Street Journal, September 29, 2011, Eastern edition, https://search.proquest.com/docview/894597930?accountid=12372, 2.

86 Pei was unavailable to complete the project at the time as he was involved in multiple projects, such as Boston’s John F. Kennedy Library and Toronto’s Canadian Imperial Bank of Commerce.

Myers, “A Cultural Conversation,” 2.

87 “Renewal in Boston: Good and Bad,” The New York Times, April 19, 1964. https://www.nytimes.com/1964/04/19/archives/renewal-in-boston-good-and-bad.html.

88 Elihu James Rubin, “Insuring the City: The Prudential Center and the Reshaping of Boston” (Ed. D., University of California, 2009), 292 – 293. https://escholarship.org/content/qt4b75k2nf/qt4b75k2nf.pdf.

89 Logan, “Why can’t Boston.”

90 The initial design by Pei was a combination of tall cylindrical concrete and glass tower with low-rise buildings.

Myers, “A Cultural Conversation,” 2.

91 Myers, “A Cultural Conversation,” 2.

92 Myers, “A Cultural Conversation,” 1 – 2.

85

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ABPL90085 Construction History

Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

like an enormous mirror box. 93 The newly Vari-Tran unit would have been the best choice for Cobb for three possible reasons: the first reflective window unit produced by L.O.F. 94 that could satisfy the reflective quality of the Tower’s façade; L.O.F.’s preceding model with Bondermetic seal was widely used since the 1950s with a good successfully track record established from the early 1960s 95 that gave enough assumptions that Vari-Tran would behave similarly; and the Thermopane unit was more energy-efficient than monolithic glass. By minimising the use of mullions and spandrels, Cobb designed the Tower with 10,344 windows to provide more lightness and a unifying visual presentation of the mirrored landscape from the Tower’s reflective façade. 96

Left: Figure 17. Friedrichstrasse Competition entry, Ludwig Mies van der Rohe. photomontage, 1921. Ludwig Mies van der Rohe.

Right: Figure 18. Curvilinear glass skyscraper, Ludwig Mies van der Rohe. model, 1922. Ludwig Mies van der Rohe.

Despite this innovative all-glass façade design that could potentially appease all stakeholders, the sour relationship persisted with the locals in the area. The excavation work of the Tower’s foundation resulted in moving and twisting the earth, causing cracks in surrounding buildings

Myers, “A Cultural Conversation,” 1.

Marfella, “From Heat Absorption,” 411.

95 Schwartz, “The John Hancock Tower,” 5.

96 Myers, “A Cultural Conversation,” 2 – 3.

93 94

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

and the transept wing of the Trinity Church. 97 The John Hancock Insurance Company compensated USD 11.6 million to the Church, 98 and the reputation of the architectural firm was at stake. 99 Then the nightmares came true when the windows fractured and fell from the façade. More dramas spiked up as the windows continued to fail, and the nearby restaurants and shops sued the Hancock Insurance Company for the compensation of their loss of profit and visitors possibly from the glass failure events. 100 Nonetheless, the reflective quality of the Tower’s façade mirroring Boston’s urbanscape after the replacement of windows with monolithic glass steadily won the hearts of the Bostonians and critics. With its sheer reflective façade, the Tower subtly rose from Back Bay, submerged into the skyline and the city without overtly casting the sky (Figure 19 & Figure 20). Depending on the standpoint, the weather and the time of the day, the colours of the Tower changed

Left: Figure 19. John Hancock Tower, I.M.Pei & Partners. John Hancock Tower reflecting the nearby buildings and the sky, n.d.. Pei Cobb Freed & Partners.

Right: Figure 20. John Hancock Tower, I.M.Pei & Partners. Reflection of Trinity Church on John Hancock Tower, n.d.. Pei Cobb Freed & Partners.

Campbell, “Builder.”

Dwyer, “When they built.”

99 “"The critics were merciless, and some of it was personal," said Mr. Cobb, whose family's ties to Massachusetts date back to 1633. "During construction, I ran into a member of Trinity Church who knew my late father and questioned how the son of such a fine man could do such a thing."”

Myers, “A Cultural Conversation,” 2.

100 “Mama Leone’s, a nearby failed Italian restaurant, has gone into court charging that fear of falling glass deterred potential pasta lovers” Kifner, “Problems.”

97 98

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

continuously. 101 The diagonal alignment of the Tower provided more visual space on the intersection of Clarendon Street and St. James Street, where the passer-by to notice the Trinity Church from afar easily. 102 Moreover, the mirrored version of the Church on the Tower’s façade emphasised the presence of the esteemed Church even more. 103 With modesty, the Tower “refuse[d] to say anything about itself,” 104 but allowed the Church, city, and people to complete the picturesque appearance on its reflective façade.

Such simple and minimalist design could not have seen the success after the glass failure if Cobb failed to persuade the Hancock executives, who preferred to replace Vai-Tran units with smaller windows. 105 The altered plan would have potentially involved more mullions, visually interrupting the unified view of the city on the façade. Although the reflected picture of the fully tempered monolithic glass has a lightly warped visual presentation, the decision of this construction material with a history of its consistent past use 106 had been a worthwhile decision for Cobb without changing the initial design plan overtly.

Conclusion The John Hancock Tower’s glass failure from 1971 to 1974 was one of the “predicament typical of emerging building technologies.” 107 Cobb’s design of all-glass reflective façade tower was indeed innovative at the time, especially in Boston, predominated by Victorian-style low-rise buildings. Released in the market from 1968, the new reflective Vari-Tran might have been the appealing choice for Cobb to fulfil not only the design quality of the Tower but also the energy efficiency within the Tower. However, it was an early choice to make without considering the short, inconsistent record of its past use in other buildings. The swaying of the Tower and the wind suction pressures were assumed as the cause of the glass failure. However, the oscillation test from UWO and report by Schwratz revealed that the reflective layer of Vari-Tran

Myers, “A Cultural Conversation,” 1.

Dominic Hill and Jane Gerber, “John Hancock Tower, Boston,” in Vertical City 5, Brighton, England: Electric Sky, 2008, video, 27:04, https://video-alexanderstreet-com.eu1.proxy.openathens.net/watch/john-hancock-towerboston/clips?context=channel:art-architecture.

103 Hill and Gerber, “John Hancock.”

104 “"It's the closest I've ever come to poetry," [Cobb] said. "As you can see, the building refuses to say anything about itself -- other than reflect on the rich formal qualities of Trinity Church below."”

Myers, “A Cultural Conversation,” 3.

105 Myers, “A Cultural Conversation,” 2 – 3.

106 Schwartz, “The John Hancock Tower,” 8.

107 Schwartz, “The John Hancock Tower,” 8.

101 102

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

manufactured in large sizes stressed the soldered joints of the window and eventually fractured the outer glass panels. The choice of relatively new window units led to not only the loss of economic profits but also the distasteful relationship with the Trinity Church and the local community.

After the restoration of the Tower’s façade with fully tempered monolithic glass windows, the Tower had taken a positive turn. Although the project budget had doubled due to the glass failure investigation and restoration of the façade, the possibility of other structural failures within the Tower has decreased due to the vigorous wind tunnel tests, and installation of both TMD and lateral bracings within the Tower. 108 Moreover, the wind tunnel tests of the Tower contributed to the reformation of the American building codes in designing the curtain walls, as the previous codes established the increase of wind loads based on that of the building height. 109 Based on the wind tunnel tests and glass failure of the Tower, the current building codes acknowledge not only the possible formation of the wind suction pressures along the edges of the curtain walls but also the credibility of the wind tunnel test to provide a plausible record of the wind loads for different curtain wall designs. 110 As Boston city remains flat due to the flight paths and building height restrictions, 111 the Hancock Tower even after 44 years of its completion still maintains its title as the tallest skyscraper in New England, Boston. With its sublime picturesque scene of Boston city captured on its reflective façade, the Tower won its competition against the Prudential Centre by becoming the most beautiful skyscraper in Boston. 112 Fortunately, the Tower has not (yet) suffered another major glass failure since the restoration of the windows. Although the construction industry has evolved and advanced in the last 50 years, the general lesson learned from the Hancock glass failure is still relevant to this day: “to break new ground and to innovate in the architectural field often come with a price. The leading edge is often the bleeding edge.” 113

Campbell, “Builder.”

Schwartz, “The John Hancock Tower,” 3.

110 Schwartz, “The John Hancock Tower,” 3 – 4.

111 Logan, “Why can’t Boston.”

112 Campbell, “Builder.”

113 Schwartz, “The John Hancock Tower,” 8.

108 109

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ABPL90085 Construction History

Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design Bibliography Archives

Libbey-Owens-Ford Glass Company Records, 1851-1991. Ward M. Canaday Center for Special Collections, University of Toledo, Ohio.

Books and book chapters Rubin, Elihu James. “Insuring the City: The Prudential Center and the Reshaping of Boston.”

Ed. D., University of California, 2009. https://escholarship.org/content/qt4b75k2nf/qt4b75k2nf.pdf.

Conference Papers Durgin, Frank H.. “Lessons from Studies of Cladding Pressures at the John Hancock Tower in Boston.” In Advanced Technology in Structural Engineering. Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)96.

Marfella, Giorgio. ‘From Heat Absorption to Speculation: the Troubled Evolution of International All- glass Architecture in Melbourne (1955-1985).’ In Gold, edited by AnnMarie Brennan and Philip Goad, pp. 405-417. Proceedings of the 33rd Annual Conference of the Society of Architectural Historians, Australia and New Zealand, Melbourne, 06-09 July 2016.

Schwartz, Thomas A.. “The John Hancock Tower Glass Failure: Debunking the Myths.” In Advanced Technology in Structural Engineering. Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)97.

Journal articles Ali, Mir M. and Moon, Kyoung Sun. “Structural Developments in Tall Buildings: Current Trends and Future Prospects.” Architectural Science Review 50, no. 3 (2007): 205 – 223. doi: 10.3763/asre.2007.5027.

Wolf, Andreas. “New Development in the Field of Insulating Glass Units.” Construction & Building Materials 2, no. 3 (Sep 1988): 134 – 144. doi: 10.1016/0950-0618(88)90042-6.

Periodicals Campbell, Robert. The Boston Globe. “Builder Faced Bigger Crisis Than Falling Windows.”

March 3, 1995. https://www.penceland.com/hancock-windows.pdf.

Dwyer, Dialynn. Boston Globe Media Partners. “When they built the Hancock Tower – and it started falling apart,” July 15, 2015. https://www.boston.com/news/omg/2015/07/15/whenthey-built-the-hancock-towerand-it-started-falling-apart.

Fenton, John H. The New York Times. “John Hancock to Build 60-Story Tower in Boston; Based in Boston.” November 28, 1967. https://www.nytimes.com/1967/11/28/archives/johnhancock-to-build-60story-tower-in-boston-based-in-boston.html.

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ABPL90085 Construction History

Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

Kifner, John. The New York Times. “Boston Tower’s Plywood Windows.” July 18, 1973. https://www.nytimes.com/1973/07/18/archives/boston-towers-plywood-windows.html.

Kifner, John, The New York Times, “Problems Still Plague Boston Tower.” April 15, 1976. https://www.nytimes.com/1976/04/15/archives/problems-still-plague-boston-tower.html.

Logan, Tim. The Boston Globe. “Why can’t Boston build taller.” April, 2018. https://apps.bostonglobe.com/business/graphics/2018/04/tallest-buildings/.

Myers, Marc. “A Cultural Conversation / With Henry Cobb: Mirror Over Copley Square.” Wall Street Journal.

September 29, 2011.

Eastern edition. https://search.proquest.com/docview/894597930?accountid=12372. __ The New York Times. “Hancock Sues Builders For Defects in Tower.” September 16, 1975. https://www.nytimes.com/1975/09/16/archives/hancock-sues-builders-for-defects-intower.html. __ The New York Times. “Renewal in Boston: Good and Bad.” April 19, 1964. https://www.nytimes.com/1964/04/19/archives/renewal-in-boston-good-and-bad.html.

Weingardt, Richard G. “William LeMessurier.” Structure Magazine. September 2012. 35 – 37. https://www.structuremag.org/wp-content/uploads/D-GreatAch-Weingardt-Sept121.pdf.

Report Madico. Case Study John Hancock Tower. n.p: Madico, 2019, https://madico.com/wpcontent/uploads/2019/05/M956005-Hancock-Tower-Case-Study-Clear-400.pdf.

Video Hill, Dominic and Gerber, Jane. “John Hancock Tower, Boston.” In Vertical City 5, Brighton, England: Electric Sky. 2008.

Video.

27:04. https://video-alexanderstreetcom.eu1.proxy.openathens.net/watch/john-hancock-tower-boston/clips?context=channel:artarchitecture.

Website Schwartz, Thomas A. “When Bad things Happen to Good Buildings.” ArchitectureWeek.

Published on April 25, 2001. http://www.architectureweek.com/2001/0425/building_3-2.html.

The Journal of The American institute of Architects. “John Hancock Tower.” Published on March 18, 2015. https://www.architectmagazine.com/project-gallery/john-hancock-tower.

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ABPL90085 Construction History

Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design List of Figures

Figure 1. John Hancock Tower. N.d.. Photograph. Pei Cobb Freed & Partners. https://www.pcfp.com/projects/john-hancock-tower/.

Figure 2. Four important features of Thermopane. 1946. Diagram and graphic. Libbey Owens Ford Glass Company Archive.

Figure 3. Cross section of Bondermetic insulating glass showing ¼ in. thick lites of glass and ½ in. wide lead-tape spacer with soldered connection to glass. N.d.. From Schwartz, Thomas A.. “The John Hancock Tower Glass Failure – Debunking the Myths.” In Advanced Technology in Structural Engineering. 7. Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. 10.1061/40492(2000)97.

Figure 4. Boston Reflections are seen in Vari-Tran glass now being installed in John Hancock Tower. 1972. Photograph. Libbey Owens Ford Glass Company Archive.

Figure 5. Reflective glass installation at the 60-story John Hancock Tower, now under construction in Boston, is accomplished from inside the structure. 1972. Photograph. Libbey Owens Ford Glass Company Archive.

Figure 6. Spencer, Grant. John Hancock Tower with plywood window fillers, Copley Square.

1974. Photograph. Digital Commonwealth Massachusetts Collections Online. https://www.digitalcommonwealth.org/search/commonwealth:h415pb046.

Figure 7. Spencer, Grant. John Hancock Tower with plywood window fillers, Copley Square.

1974. Photograph. Digital Commonwealth Massachusetts Collections Online. https://www.digitalcommonwealth.org/search/commonwealth:h415pb003.

Figure 8. John Hancock Tower – Tuned Mass Damper. N.d.. Photograph. LeMessurier. https://www.lemessurier.com/john_hancock_tower?cycle=allgrid.

Figure 9. Isometric Schematic of John Hancock Tower’s affected area after the storm in November 1972. N.d.. From Durgin, Frank H.. “Lessons from Studies of Cladding Pressures at the John Hancock Tower in Boston.” In Advanced Technology in Structural Engineering. 7.

Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)96.

Figure 10. Peak Negative Cps on Stuart Street Façade from the Wind Tunnel Test, from all wind directions. N.d.. From Durgin, Frank H.. “Lessons from Studies of Cladding Pressures at the John Hancock Tower in Boston.” In Advanced Technology in Structural Engineering. 8.

Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)96.

Figure 11. Peak Negative Cps on the Trinity Place Façade from the Wind Tunnel Test, from all wind directions. N.d.. From Durgin, Frank H.. “Lessons from Studies of Cladding Pressures at the John Hancock Tower in Boston.” In Advanced Technology in Structural Engineering. 8.

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Yeong Gyeong Son. The John Hancock Tower: Investigating The Cause of The Glass Failure And The Birth of Its design

Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)96.

Figure 12. Son, Yeong Gyeong. After Durgin’s Map of Area near the Hancock Tower. 2020.

From “Lessons from Studies of Cladding Pressures at the John Hancock Tower in Boston.” In Advanced Technology in Structural Engineering. 8. Proceedings of the 2000 Structures Congress & Exposition, Philadelphia, Pennsylvania, 08-10 May 2000. doi: 10.1061/40492(2000)96.

Figure 13. University of Western Ontario. Equivalent one-minute pressure experienced by glass from September 1971 to February 1973 base on UWO wind tunnel study. N.d.. From Figure 14. Another view of Trinity Church at Copley Square. c.a. 1909. Photograph. Library of Congress, Detroit Publishing Company Collection, Detroit. https://lostnewengland.com/2015/11/trinity-church-boston-2/.

Figure 15. Salazar, Matthew. Prudential Centre. N.d.. Photograph. Council on Tall Buildings and Urban Habitat. http://www.skyscrapercenter.com/building/prudential-tower/1127.

Figure 16. Boake, Terry Meyer. Cladding of the Prudential Centre. N.d.. Photograph. Council on Tall Buildings and Urban Habitat. http://www.skyscrapercenter.com/building/prudentialtower/1127.

Figure 17. Mies van der Rohe, Ludwig. Friedrichstrasse Competition entry. 1921. In Perspecta 27 (1992): 3.

Figure 18. Mies van der Rohe, Ludwig. Curvilinear glass skyscraper. 1922. In Perspecta 27 (1992): 3.

Figure 19. John Hancock Tower. N.d.. Photograph. Pei Cobb Freed & Partners. https://www.pcf-p.com/projects/john-hancock-tower/.

Figure 20. John Hancock Tower. N.d.. Photograph. Pei Cobb Freed & Partners. https://www.pcf-p.com/projects/john-hancock-tower/.

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