Massachusetts Institute of TechnologyCambridge, MA, USA
High-Rise Buildings: Evolution and Innovations
Keynote LectureCIB2004 World Building Congress
Toronto, Ontario CANADAMay 2-7, 2004
Dr. Oral BuyukozturkProfessor of Civil and Environmental Engineering
Oguz GunesPh.D. Candidate
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
OUTLINE
• INTRODUCTION
• LOADS
• EVOLUTION
• INNOVATIONS
• CONCLUSION
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Introduction
What is a high-rise building?
“A building whose height creates different conditions in the design, construction, and use than those that exist in common buildings of a
certain region and period.”
The Council of Tall Buildings and Urban Habitat
IntroductionIntroduction
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Demand for High-Rise Buildings
• Scarcity of land in urban areas• Increasing demand for business and residential
space• Economic growth• Technological advancements• Innovations in Structural Systems• Desire for aesthetics in urban settings• Concept of city skyline• Cultural significance and prestige• Human aspiration to build higher
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
(Tables source: Emporis Corporation April 2004)
Geographical Distribution of High-Rise Buildings
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Economy vs. Demand for High-Rise BuildingsEconomic growth and resulting demand for office space is a good indication of demand for high-rise buildings
U.S. Asking Office Rents, Class A$ Per Sq. Ft. Per Year Full Service
$20
$30
$40
$50
Jan-98Jan-99Jan-00Jan-01Jan-02Jan-03Jan-04
CBD Suburban
U.S. Office Vacancy Rates
5.0%7.0%9.0%
11.0%13.0%15.0%17.0%19.0%
86 88 90 92 94 96 98 00 02 04
U.S. Office Supply vs. DemandSq. Ft. in Millions
-100-50
050
100150
86 88 90 92 94 96 98 00 02 04
Completed Absorbed
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
U.S. Gross Domestic Product
-2%0%2%4%6%8%
10%
2001 2002 2003 2004
(Grubb & Ellis Company, 2004)
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Structural Loads
• Gravity loads – Dead loads – Live loads– Snow loads
• Lateral loads– Wind loads– Seismic loads
• Special load cases– Impact loads– Blast loads
Earthquake Load
Snow Load
Wind Load
Dead Loads
Live Loads
Blast Load
ImpactLoad
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Gravity Loads
• Floor systems account for a major portion of the gravity loads• Selection of the floor system may influence structural behavior
and resistance• Structural use plays a major role in selection of the floor system
– Office buildings • large simply supported spans
– Residential and hotel buildings • short continuous spans
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Types of floor systems• Concrete• Prestressed concrete• Steel• Composite
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Wind Loads
Plan view
Wind
zQ hQzQ
hQ
hQ hQ
2zQ KV I=
z
h z z HQ Q
==
H
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
(Schueller, 1977)
(Taranath, 1998)
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Seismic Loads
Spe
ctra
l res
pons
e ac
cele
ratio
n (g
)
Period (sec)
0 2 4 6 8
Response with increasing damping
Decreasing V/W
sV C W= ×
V
W
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Design for Increased Height• Building weight and cost increase nonlinearly with increasing
height due to lateral loads• Efficient structural and material systems are needed to reduce
weight and cost• Wind loads generally govern design for lateral loads for heights
• > 150 m for steel buildings• > 250 m for concrete buildings
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
(Ali, M., 2001)
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Evolution of Structural Systems
Structural Systems• Moment resisting frame systems• Braced frame, shear wall systems• Core and outrigger systems• Tubular systems
– Framed tubes– Trussed tubes– Bundled tubes
• Hybrid systems
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
A clear classification of high-rise buildings with respect to their structural system is difficult
A rough classification can be made with respect to effectivenessin resisting lateral loads
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Evolution of Structural Systems
10
2030
40
5060
70
80
90
100
110
Type I Shear FramesType II Interacting SystemsType III Partial Tubular SystemsType IV Tubular Systems
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Type II Type III
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Type IV
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Sem
i-Rig
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ame
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ram
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e w
ith S
hear
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ss
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ith S
hear
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es
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nnel
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ith
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rior S
hear
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sses
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Cha
nnel
and
Mid
dle
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amed
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es
Exte
rior F
ram
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ube
Bun
dled
Fra
med
Tub
e
Exte
rior D
iago
naliz
edTu
be
# of Floors
EvolutionEvolution
(CTBUH, 1980)
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Shear Frame System
• Resists lateral deformation by joint rotation• Requires high bending stiffness of columns and beams• Rigid joints are essential for stability• Not effective for heights over 30 stories
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Braced Frame System
• Lateral forces are resisted by axial actions of bracing and columns
• Steel bracing members or filled-in bays• More efficient than a rigid frame
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Cantilever Shear Combined
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Core Structure System
• Lateral and gravity loads supported by central core
• Eliminates columns and bracing elements
• Core is inefficient because it is not deep in respect to bending
• Moment supported floors are inefficient
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Cantilever supports
Individually cantilevered
floors
Core
Group cantilevered
floors
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Outrigger Braced Structure System
• 1- or 2-story deep truss connects core to perimeter columns
• Increases the bending rigidity
• Dependent of rigid core for shear resistance
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Outriggers Braced core
Tension
Compression
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Tubular System
• Majority of structural elements around the perimeter• Sides normal to lateral load resist bending• Sides parallel to lateral load resist shear• Minimize number of interior columns• Closely spaced exterior columns
Increased stress at corners created by shear lag effect
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Closely spaced columns
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Hybrid Systems
• Combine advantages of different structural and material systems
• Composite material system
• Concrete super columns
• Steel encased concrete columns
• Composite floor system
• Steel truss and outrigger systems
• High strength concrete super columns reduce deflections and weight
• Steel encased HS concrete combines
• easy erectability of steel,
• axial load capacity of HS concrete,
• efficient confinement and reinforcement.
EvolutionEvolution
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
High-Efficiency Mega-Braced Frame System
• Very large columns and bracing
• Small number of columns
• Bracing extends over multiple floors
• Stiff transfer floors allow for internal flexiblity
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Mega braces
Transfer zones
Mega columns
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Evolution of Materials
• High performance concrete (HPC)• High performance steel (HPS)• Composite construction
Steel42%
Concrete25%
Composite33%
02468
101214161820
1930 1940 1950 1960 1970 1980 1990 2000*
Decade
Num
ber o
f Bui
ldin
gs
Material systems of the tallest 200 Buildings
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Innovations
• Vulnerability and risk assessment
• Performance based design
• Materials
• Structural control
• Egress strategies
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Vulnerability and Risk Assessment
• Probabilistic risk assessment (PRA) and decision making have been effectively used in
• nuclear engineering, • manufacturing, • seismic loss estimation etc.
• Probabilistic, nonlinear, and coupled evaluation of building vulnerability is needed for identified hazards.
Hazard identification,
prioritization and evaluation
Vulnerability analysis
Risk assessment & Loss estimation
Optimum mitigation strategy
Decision & Implementation
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
MINORSHAKING
MODERATESHAKING
MAJORSHAKING
WEAKER CONSTRUCTION
STRONGER CONSTRUCTION
SPECTRAL DISPLACEMENT
SPEC
TRA
L A
CC
ELER
ATI
ON
NONE SLIGHT MODERATE EXTENSIVE COLLAPSE
Vulnerability Analysis
Structural model
Risk Assessment and Performance Based Design
InnovationsInnovations
Attenuation
Amplification
Seismic source
Hazard Analysis
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Design for Fire
• Old: Prescriptive-Based Design– Design based on fire rating of
materials used– Fire rating of material from tables– Compliance with a code specified
value
• New: Performance-Based Design– Evaluate the strength and stiffness for a particular
design fire– Coupled stress-thermal analysis– Specialized design for fire effects– Use of fire retardant materials, advanced coatings
and ceramics
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Performance Evaluation Under Fire
Coupled structural/fire analysis
Structural loads
Thermal analysis Stress analysis
Fire modeling
Deformations, damage, collapse
Elastic/strength properties
Thermalproperties
Structural Model Geometry
DemandTime: 20 min
Onset of fire
Time: 35 min
Time: 45 min
Weakest link
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Design for Impact Loading
• Modeling of impact• Assessment of impact damage• Evaluation of structural safety after impact• Modeling of potential fire after impact• Coupled evaluation of structural integrity and collapse
potential
InnovationsInnovations
Engineering problems related to impact loads:
(FEMA 403)
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Impact Modeling
220 m/sV ≈
212 3460 MJkE MV= = 3.0 MNcuttingP ≈
Velocity
Total kinetic energy Fuselage cutting force
MIT Impact and Crashworthiness Laboratory
Exteriorcolumns
Corecolumns
Boeing 767-200
Floor
Floor
Core area
Boeing 767-200
Boeing 767-200Max. takeoff weight: 395,000 lb (180 ton)Max. fuel capacity: 24,000 gal (91,000 liter)Cruise speed: 530 mph (237 m/s)
VV
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
The initial kinetic energy of the plane is dissipated through
• Permanent plastic deformation (crushing)• Generated Heat• Fracture and fragmentation
(creating new surfaces)• Friction• Residual velocity• Elastic vibrations
Energy Dissipation During Impact
Core columns
28%
Aircraft25%
Exterior columns3%
Floorstructure
53%
Estimated distribution of energy dissipation
May be used asa design tool
MIT Impact and Crashworthiness Laboratory
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Design for Blast LoadingSequence of damage due to a
blast outside the buildingIncident pressure waveform
(FEMA 427)
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Redundancy and Progressive Failure
Structural behavior Low redundancy High redundancy
REDUNDANCY: Presence of alternate load paths PROGRESSIVE FAILURE: Successive failure of critical elements• Redundancy is essential for structural safety and protection• Ductile structural elements and details• Design for load reversals• Avoid shear failures
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Redundancy and Progressive FailureRedundancy in column system
Redundancy in floor system
System Redundancy(Global frame)
Local Redundancy(Local joints)
FEMA403
InnovationsInnovations
Improved local
redundancy
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Design Against Progressive Failure
• Transfer trusses at upper floors allowing columns to hang
• Strong moment connections for cantilever action of floor frames
• Perimeter frames with sufficient capacity to span multi-bays
• Mega-brace systems capable of resisting partial collapse
Other possible design actions
High-capacity column-beam connections
(Houghton and Karns)
Catenary action of cablesCables in the floor
Before removal of the column
After removal of the column
Catenary action
(Astaneh-Asl, 2003)
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Materials Development
• High performance concrete and steel enable efficient and innovative design
• FRP composites may be effective in combination with conventional materials
• Fiber reinforced concrete shows promise in fire protection
0
0.2
0.4
0.6
0.8
1
0 200 400 600 800 1000
Temperature (C)
Rel
ativ
e M
OE
or C
omp.
Str
engt
h
Modulus of Elasticity
0
0.2
0.4
0.6
0.8
1
0 200 400 600 800 1000
CompressiveStrength
Effect of Heat on Reinforced Concrete(2 hours of exposure to 1000 C fire)
Ordinary RC Riber RC
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Structural Control
• Lateral motion problems can be resolved through various types of damping systems
• Controls systems can be implemented in initial design or as a retrofit
• Viscous Dampers– Piston forcing fluid through an orifice– Compact and easily installed
• Hysteretic Dampers– Dissipates energy by cyclic yielding in
tensions and compression– Easy to install, but may need to be
replaced after major event• Tuned Mass Dampers (TMD)
– Translation TMD– Pendulum TMD
Passive dampers are commonly used in new tall buildings
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Pall friction damper
Active mass damperTuned mass damper
Tuned liquid column damper Tuned liquid damper
Diagonal brace with viscous or viscoelastic damper
Chevron brace with viscous dampers
Chevron brace with viscoelastic damper
Hybrid mass damper
damper spring actuator
Structural Control Systems
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Passive Structural Control
m
dc
c
dmdk
k
udu u+
Governing equations of motion:
dmmm
=2(1 ) 2 dpm u u u mum
ξω ω+ + + = −&& & &&
22d d d d d du u u uξ ω ω+ + =−&& & &&
Building
Damper
John Hancock Building, BostonTuned Mass Dampers
p
2i i i ic mξ= w
2 ii
i
km
ω =
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Active Structural Control
m
dc
c
dk
k
u
du u+
Governing equation of motion for the AMD
Hybrid Mass Dampers
p d au u u+ +
d au u u+ +
F amak
2 ( )a a a da
Fu u u um
ω+ =− + +&& && &&
Nishikicho Building, Tokyo(Connor, 2003)
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Health Monitoring
Ambient vibrations
Accelerometer(s)
Data acquisition unit
Vibration techniques can be used to determine the vibration characteristics of high-rise buildings
Advantages• Rapid• Can be used for periodic or
continuous monitoring• Economically feasible• Provides a preliminary
assessment of the building stiffness
• Leads to more accurate seismic demand prediction
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Emergency Egress Strategies
• Elevated passages to neighboring buildings
• Refuge floors/rooms with fire escape elevators
• Perimeter wall rescue vehicles
• Fire resistant escape chutes
• Flying rescue platforms
• Individual fire resistant parachutes
InnovationsInnovations
IntroductionIntroduction LoadsLoads EvolutionEvolution InnovationsInnovations ConclusionConclusion
Conclusions• Highrise buildings enjoy rapid evolution and new
innovations
• Efficient composite hybrid structural systems for super-tall buildings
• Use of composite material systems
• Improved analysis and design tools for better fire, impact, blast resistance
• Redundancy against progressive failure
• Effective egress strategies
• Use of passive and active control systems
• Implementation of health and long-term performance monitoring
ConclusionConclusion