This presentation discusses the evolution and benefits of expressed and exposed bracing systems in architecture. It traces the development of bracing from early examples in high-tech architecture to more modern applications as architecturally exposed structural steel (AESS) and diagrid structures. Exposed bracing provides seismic benefits as it allows for easier inspection and repair. Diagrid designs integrate bracing and structure for efficiency. However, further research is needed to expand the use of exposed bracing systems through code changes, new connection details, and addressing issues like thermal bridging.

1. EMBRACE THE BRACE
Terri Meyer Boake
Professor
School of Architecture University
of Waterloo Canada
PDH: N43a-89385 N43b-86676

2. Nature of the Presentation
A look at the benefits of expressed and exposed
bracing systems
• Their evolution as AESS elements
• Their use in seismic applications
• Their basis in diagrid structural systems

3. EMBRACE THE BRACE
The Evolution of the Brace
From High Tech to AESS

4. Sainsbury Centre for the Arts, England – Norman Foster
HIGH TECH ARCHITECTURE BEGINS TO CREATE AN AESTHETIC OF EXPOSED STEEL

5. Tubular members are first used for exposed bracing systems
HIGH TECH ARCHITECTURE BEGINS TO CREATE AN AESTHETIC OF EXPOSED STEEL

6. Tubular members are first used for exposed bracing systems
HIGH TECH ARCHITECTURE BEGINS TO CREATE AN AESTHETIC OF EXPOSED STEEL

7. Pompidou Centre, Paris – Renzo Piano and Richard Rogers
HIGH TECH ARCHITECTURE BEGINS TO CREATE AN AESTHETIC OF EXPOSED STEEL

8. Expressed cross bracing as a distinct system
HIGH TECH ARCHITECTURE BEGINS TO CREATE AN AESTHETIC OF EXPOSED STEEL

9. Expressive connections that are not hidden
HIGH TECH ARCHITECTURE BEGINS TO CREATE AN AESTHETIC OF EXPOSED STEEL

10. Murphy/Jahn Architects
THE BIRTH OF AESS IN CHICAGO O’HARE AIRPORT

11. Expressed bracing systems continue to create a connection language
THE BIRTH OF AESS IN CHICAGO O’HARE AIRPORT

12. NEO Bankside, London – Rogers, Stirk, Harbour + Partners
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

13. NEO Bankside, London – Rogers, Stirk, Harbour + Partners
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

14. Office Building, Berlin, Germany
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

15. Munich International Airport
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

16. Architectural Office, Las Vegas, Nevada
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

17. New Lynn Transit Terminal, Auckland, New Zealand
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

18. University Building, Waterloo – KPMB Architects
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

19. University Building, Waterloo – KPMB Architects
PURPOSEFULLY EXPOSED BRACING – Architecturally Exposed Structural Steel

20. Pavilion, Minneapolis – Frank Gehry Architect
BRACING GIVES FORM TO THE SHAPE OF THE BUILDING

21. Pavilion, Minneapolis – Frank Gehry Architect
BRACING GIVES FORM TO THE SHAPE OF THE BUILDING

22. Pavilion, Minneapolis – Frank Gehry Architect
BRACING GIVES FORM TO THE SHAPE OF THE BUILDING

23. Dubai, UAE
EXPOSED BRACING FOR LATERAL STABILITY IN TALL BUILDINGS

24. Intermodal Terminal, Milwaukee, Wisconsin
THE USE OF DIAGONAL STEEL FOR ARCHITECTURAL AESTHETIC

25. Intermodal Terminal, Milwaukee, Wisconsin
THE USE OF DIAGONAL STEEL FOR ARCHITECTURAL AESTHETIC

26. Intermodal Terminal, Milwaukee, Wisconsin
THE USE OF DIAGONAL STEEL FOR ARCHITECTURAL AESTHETIC

27. EMBRACE THE BRACE
Seismic Applications

28. Ai Weiwei Exhibit at the Art Gallery of Ontario
Sichuan Earthquake 2008

29. Sichuan Earthquake 2008 (Ai Weiwei blog)

30. Sichuan Earthquake 2008 = Major loss of life

31. Christchurch Earthquake, February 22, 2011

32. Chart prepared prior to the Christchurch earthquake of February 2011.
THE “COSTS” OF EARTHQUAKES

33. The cost of rebuilding Christchurch has been estimated at NZ$15
billion (£7.6 billion) or more.
Mr. John Key (Prime Minister of New Zealand) stressed how
significant the earthquakes had been to New Zealand's tiny
economy, saying the cost was equivalent to 8 per cent of GDP.
"Damage from the 1995 Kobe earthquake in Japan was just over
2 per cent of Japan's GDP, Hurricane Katrina in 2005 cost about 1
per cent of US GDP, and March's Japanese earthquake and
tsunami disaster was an estimated 3-5 per cent of Japan's GDP,"
he said.
http://www.telegraph.co.uk/news/worldnews/australiaandthepacific/newzealand/8593434/Christ
church-earthquake-government-wants-to-demolish-5000-homes.html

34. Christchurch Earthquake = Major loss of property
“Reinforced concrete, as customarily designed and detailed, and
in contrast to structural steel, is essentially a brittle construction
material. Brittleness can be a danger in regions prone to
earthquakes. However, with due care in design and
detailing, reinforced concrete structures can be made
adequately ductile for good performance in earthquakes.”
J. P. Hollings, researcher, 1968

35. Concrete structure being demolished

36. Earthquake damage to reinforced concrete residential structure

37. Earthquake damage at Theatre Royal

38. Seismic repair of historic stone church building in Christchurch
REPAIR BRACING

39. Seismic repair of 13th century monastery, Athens, Greece

40. Seismic repair of 13th century monastery, Athens, Greece

41. Seismic repair of 13th century monastery, Athens, Greece

42. Pacific Tower, 22 storeys - A Success Story

44. Cracked EBF link in parking garage
Cracked EBF link in Pacific Tower

45. Exposed steel bracing in Pacific Tower parking structure

46. Opening up walls and floors to inspect the EBF system
The concealed system
was difficult to inspect for
damage.

48. Cut out existing links and replace with removable/replaceable links

49. Major issue is access to the link to perform the work – and subsequent repair

50. Three 35, Addington, Christchurch by Jasmax Architects
FIRST EVER NEW APPLICATION OF REPLACEABLE LINK BRACING

59. “Exposed” seismic retrofit, Wellington, New Zealand
RETROFIT BRACING

60. Exposed seismic retrofit, Wellington, New Zealand
Not “designed” to be integrated into the architecture

61. Exposed seismic bracing, Athens, Greece
Integrated into the architecture

62. Retrofit for School of Architecture, Wellington, New Zealand

63. Exposed seismic bracing, Salt Lake City, Utah
Integrated into the architecture

64. If the economic impact of earthquake damaged buildings is so
great, why continue to design buildings that are:
• Constructed from substandard materials (noting the use of
bad quality concrete in both the Sichuan and Haiti
earthquakes)
• Prone to irreparable damage
• Difficult to inspect
• Difficult and expensive to repair
Earthquake design objectives need to ALSO focus
on the economic impact and recovery time in
addition to LOSS OF LIFE.

65. EMBRACE THE BRACE
Diagrid Structures

66. Diagrid structures
take bracing
systems to new
heights as the
expression of the
bracing system
becomes the
architectural
expression of the
building.

67.  originated in the work
of Vladimir Shukhov circa
1896
 creation of tall
hyperbolic paraboloid
structures to support
water towers
 structure had no need
of a core for lateral load
resistance

68.  Diagonals re-
appeared as
expressions of
bracing
 They provided
lateral support
for wind and
seismic loads
 Columns carried
the gravity loads
 Core was the
primary means of
lateral resistance

69. Expressed lateral high rise bracing
Scale issues with blockage of window views due to frequency/size of members

70. Image:VincentHui
Note: The core will be framed in steel or cast in concrete as a
function of local practices and construction
sequencing/erection priorities.
A pure steel diagrid tower does not require a core for lateral
resistance.

71. I.M. PEI w/
LESLIE ROBERTON ENG.
BANK OF CHINA 1989
Hong Kong
Diagonal geometry permitted unusual
massing of the tower.

72. I.M. PEI w/
LESLIE ROBERTON ENG.
BANK OF CHINA 1989
Hong Kong
Diagonals were constructed of steel
that was embedded in large masses of
concrete at the major nodes.
Images:LeslieE.Robertson

73. FOSTER+PARTNERS
w/ARUP
SWISS RE 2004
London, England
Photo: ARUP
Steel as the exclusive structural
system for exterior, floors and core.

74. FOSTER+PARTNERS w/
WSP GROUP
HEARST MAGAZINE TOWER 2006
New York, New York
 Used for a rectilinear building
 Expression of the diagrid on
the detailing of the corners
 Exclusive steel structure for
core, exterior diagrid support
and floor system

75.  Increased stability due to
triangulation
 diagrids combine the gravity and
lateral load bearing
systems, thereby providing more
efficiency
 provision of alternate load paths
in the event of a structural failure
 some buildings noting a 20%
reduction in the amount of
structural steel required
FOSTER+PARTNERS w/ ZEIDLER
HALCROW YOLLES
BOW ENCANA 2012
Calgary, Alberta

76.  reduced use of structural
materials which translates into
“carbon” or environmental savings
 reduced weight of the
superstructure translates into
reduced load on the foundations
 ability to provide structural
support for a myriad of shapes
 MOST APPLICATIONS ARE
ARCHITECTURALLY DRIVEN
ROGERS STIRK HARBOUR +
PARTNERS
w/ ARUP
THE LEADENHALL BUILDING 2013
London, England

77. KYOUNG SUN MOON
YALE UNIVERSITY
OPTIMIZATION WORK
2007 TO PRESENT
6 storeys 8 storeys 10 storeys

78. KYOUNG SUN MOON
OPTIMIZATION WORK
Bending moment at the base
Shear resistance at the top

79. WILKINSON + EYRE w/ARUP
GUANGZHOU IFC 2010
Guangzhou, China
12 storeys
(54m)
 400m
Supertall
tower
 Taper
towards
top
 Rounded
triangular
plan
 Large
scale for
large
building

80. 7 storey
“megaframe”
 exposed steel
 double façade
 sloped face
 module height linked to trapezoidal
shape/height of building
ROGERS STIRK HARBOUR+PARTNERS
w/ ARUP
LEADENHALL 2013 London, England

81. MZ ARCHITECTS w/ARUP
ALDAR HQ 2012
Abu Dhabi, UAE
4+4=
8 storeys
 Concealed steel
 Gently curved shape
 floor edge beams brace diagrid
along its length
Image:WilliamHare

82. RMJM ARCHITECTS
SELF ENGINEERED
CAPITAL GATE 2012
Abu Dhabi, UAE
2 storeys
 Eccentric
geometry
 18o
backwards lean
 Offset
concrete core
 Large
diagonals on
close spacing
for structural
reasons
Image:MiroslavMunka

83. SOM
Lotte Super Tower (visionary)
Seoul, Korea
 555m supertall tower
 Taper towards top
 Rounded plan at the
top
 Square plan at the
bottom
 steepness of the
diagrid shifts from
moment resisting
(steep) at the base to
shear resisting (shallow)
at the top
Image:SOM

84. SOM
Lotte Super Tower
(visionary)
Seoul, Korea
 plan changes from
square at the bottom to
round at the top
 module height changes
from 10 storeys at the
bottom to 2 storeys at
the top
 round open lattice at
the top good for vortex
shedding
Image:SOM

85. 8 storeys
 Concealed steel
 Fixed node
 No shoring
 Shop fabricated
 Bolted on site
FOSTER+PARTNERS w/ WSP GROUP
HEARST TOWER 2006
Images:Foster+Partners

86.  AESS (intumescent coating)
 Concrete filled tubes
 No shoring
 Shop fabricated
 Welded on site (temp bolts)
Images:ARUP
WILKINSON + EYRE w/ARUP
GUANGZHOU IFC 2010

87.  Concealed
 Fixed node
 No shoring
 Shop fabricated
 Bolted on site
4 storeys
Images:ARUP
FOSTER+PARTNERS w/ARUP
SWISS RE 2004
Tension
rings

88.  AESS
 Tensioned connection
 Adjusted during construction to
correct lean of building
 Node types vary per location
 Bolted on site
ROGERS STIRK HARBOUR+PARTNERS
w/ ARUP
LEADENHALL 2013

89. LIBESKIND w/
ARUP CANADA/HALSALL
ROM CRYSTAL 2006
Toronto, Canada
GENERAL ISSUES:
 Eliminate shoring
 Quick (bolted) site
connections
 Staging area
 Highly skilled labour
ROM SPECIFIC ISSUES:
 Geometrical challenges due to lack of
uniformity
 Gravity working against erection
(eccentric pieces)
 Abundance of unique situations

90. RMJM ARCHITECTS
CAPITAL GATE 2011
Abu Dhabi, UAE
ISSUES:
 eccentric geometry
 no two nodes alike (822 unique)
 all welded – welding access
 tensioned core to offset lean
Images:ADNEC/JeffSchofield

91.  Fire engineering a must (codes)
 Member selection criteria
 Function of space/aesthetic
 Impact of scale of members/nodes
RMJM ARCHITECTS
CAPITAL GATE 2012

92. WILKINSON + EYRE w/ARUP
GUANGZHOU IFC 2010
 Fire engineering a must (codes)
 Concrete-filled steel tubes +
Intumescent
Function of space/aesthetic
 Impact of scale of members/nodes

93. FITZPATRICK+PARTNERS w/ARUP
MCQUARIE BANK 2011
Sydney, Australia
 Climate restricted (hot or temperate)
 Thermal bridging issues
 Corrosion protection

94. FITZPATRICK+PARTNERS w/ARUP
MCQUARIE BANK 2011
Sydney, Australia
 Hot dip galvanized exterior structure
 standard structural steel interior
 bolted site connections

95. WARREN + MAHONEY ARCHITECTS
w/MJH ENGINEERING
Manukau Institute of Technology
Auckland, New Zealand
 Climate restricted
 Thermal bridging
 Corrosion protection
 Module 5 storeys
 Middle node at mid floor height
 Use of steel cable to tie mid height
nodes together

96. ARCHITECT
ENGINEER
FABRICATOR
Images:ARUP
* New code issues!
Diagrids not in current
seismic codes

97. If we can create an architectural language
of expressed diagonal steel (diagrids)
The next step is to adapt this to a new
aesthetic based upon expressed seismic
bracing, including replaceable links.ROGERS STIRK HARBOUR+PARTNERS
w/ ARUP
LEADENHALL 2013 London, England
WARREN + MAHONEY ARCHITECTS
w/MJH ENGINEERING
Manukau Institute of Technology
Auckland, New Zealand

98. WHAT ARE THE BARRIERS?

99. • Overcome any aesthetic stigma associated with exposed bracing
• Additional research and testing on current replaceable link EBF
systems
• New research on the requirements for different steel shapes as
the diagonal bracing members (hot rolled shapes –
round, rectangular and elliptical)
• Understanding that exterior bracing systems are limited to
warmer climates due to thermal expansion and thermal bridging
issues
• Grow an acceptance of exposed bracing systems for interior
applications
• Fire resistance ratings for interior exposed systems (is
intumescent enough?)
• Incorporate replaceable link systems into current seismic codes
• RESEARCH FUNDING $$$$$$$$

100. Terri Meyer Boake
Professor
School of Architecture
University of Waterloo
tboake@uwaterloo.ca
www.tboake.com
2012
2014 20152011 2014
PDH: N43a-89385 N43b-86676