Tall Buildings
Performance-based guidelines and
regulations
Joe Maffei
Rutherford & Chekene
Jack Moehle
UC Berkeley
Outline
• Today’s tall buildings
• Applicability of PBEE to tall
buildings
• PBEE practice needs
• PEER Tall Building Initiative
Buildings over 240 ft
(proposed, approved, or under construction)
San Francisco – 38; Los Angeles – 53; Seattle …
Types of
Occupancy
CONDO
HOTEL
$
RETAIL
PARKING
$
STEEL GRAVITY
FRAMING
$
Washington Mutual /
Seattle Art Museum
Bucklingrestrained
braces
What’s different about these
buildings?
• High-performance materials
• Framing systems not satisfying code
prescriptive limits
• Non-prescriptive designs are accepted
in the code by demonstrating at least
equivalent seismic performance.
UBC 1629.10.1, 1605.2, 104.2.8
after MKA
What is “Equivalent” Performance?
• Consider both the intended performance of
the code and the performance of a typical
good prescriptive design.
• Equivalence to poorly-performing but codeprescriptive buildings should not be
acceptable.
• Use Seismic Peer Review.
Two-Stage Design
• Determine the strengths at nonlinear locations
using the building code requirements
– Code (DBE) level earthquake  R factor
– Minimum base shear
• All other actions are designed to remain elastic
under MCE level ground motions:
– Wall shear, shear friction, wall flexure outside of
intended yield locations, floor and roof diaphragms and
collectors and connections, foundation perimeter walls,
etc.
Example PBEE
Practice Needs
Acceptability of yielding
outside base hinge zone.
Protection
against shear
failure
Protection
against sliding
shear
Linear and nonlinear
modeling assumptions
UCSD
Wall
Elastic
ETABS
Model
Z
Y
X
RUTHERFORD & CHEKENE
EQ3
Wall: Eeff = 0.2Ec
Slab: Eeff = 0.1Ec
8
Roof Displacement [in]
6
4
2
0
40
45
50
55
60
-2
-4
-6
UCSD Test
ETABS
-8
Time [s]
RUTHERFORD & CHEKENE
PBEE Practice Needs
Structural Design (Joe’s top 15)
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•
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•
•
•
•
•
•
•
•
•
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Minimum base shear
Capacity design factors
Inherent slab-outrigger effect
Story mechanism protection
Wall shear strength
Effective damping in NLRH analysis
Other NLRH assumptions
Effective elastic stiffness
Podium force transfer
Rational drift limits
P-delta modeling
Concrete slab to core wall connections
Steel framing to core wall connections
Deep mat slab behavior
Dual system requirements
• Applicable ground motions
– (e.g., T = 9 sec)
• Ground motion scaling
• Input motions for
subterranean levels
• Performance objectives
Tall Buildings Initiative
• 24 month initiative to advance design of tall
buildings
• Main participants
– PEER, SCEC, USGS, SFDBI, LADBS, FEMA
– ATC, LATBSDC, SEAOC, SEAONC
– Project Management Committee (T-PAC)
•
•
•
•
J. Moehle, Y. Bozorgnia
N. Abrahamson, M. Lew, P. Somerville
R. Hamburger, H. Krawinkler, M. Moore, F. Naeim
R. Lui
– Kickoff meeting – 11 August 2006
Scope
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•
•
Tall buildings
Seismic design of structural system
Coastal California
Concrete and steel
Residential focus, but not excluding other
occupancies
Tasks
• Establish and operate Project Advisory Committee (T-PAC)
• Research tasks
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–
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–
–
–
–
–
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Consensus performance objectives
Assessment of ground motion selection and scaling procedures
Synthetically generated ground motions
Review of synthetically generated ground motions
Guidelines on ground motion selection and modification
Guidelines on modeling and acceptance criteria
Input ground motions for tall buildings with subterranean levels
Other tasks to be defined….
Guidelines for seismic design of tall buildings
• Workshops, presentations, etc.
• Final report to sponsoring organizations
Performance Objectives
• Core group: W. Holmes, C. Kircher, L. Kornfield, B. Petak, N. Yousef
• Approach: Obtain input from stakeholders, formulate strawman
performance objective, workshop, …
What do you think of this performance scenario?
Rare earthquake scenario damage,
(one in ten chance of occurring during the 50-yr life of condominium towers)
Expected No. of Bldgs in each Structural Damage State
Hypothetical
Performance
None/Slight
Moderate
Extensive
Complete
Collapse
Level A
20
15
4
1
0
Level B
19
9
7
4
1
Level C
12
6
9
9
4
Selection and scaling of ground
motion
• Core group: J. Moehle, S. Mahin, J. Hooper, T. Yang, C. McQuiod
• Approach: Select ground motion bins, analyze building models to
develop response statistics, and test various ground motion selection and
scaling methods against the “true” result.
L42
L37
Floor number [-]
Story level
L32
L27
L22
L17
L11
L6
L1
B5
0
0.5
1
1.5
Maximum story moment in Y direction [kip-in.]
Story Moment
2
2.5
7
x 10
Ground motion simulation, review,
and selection and scaling guidelines
• Core group: P. Somerville, B. Aagaard,
N. Collins, R. Graves
• Approach: Develop waveforms for
large-magnitudes, small distances in SF
and LA, constrained by PSHA
• Review: F. Naeim, Y. Bozorgnia, N.
Abrahamson, B. Chiou, CB Crouse, D.
Dreger, Y. Moriwaki, Y. Zeng
• Guidelines: Y. Bozorgnia, N. Luco, F.
Naeim, J. Hooper, N. Abrahamson, J.
Maffei
Guidelines for Modeling and
Acceptance Criteria
• Core group – J. Malley, G. Deierlein, H. Krawinkler, J. Maffei, M.
Pourzanjani and J. Wallace
• Approach: Workshop to identify key issues, assignments to experts to
develop principles, procedures, and values.
• Key issues:
–
–
–
–
Basic principles, including capacity design
General modeling issues (e.g., effective damping)
Podium force transfer
Modeling of various systems and elements (core walls, frames,
coupling beams, etc.)
– Foundation modeling (with Task 8)
Input ground motions for tall buildings
with subterranean levels
• Core Group: J. Stewart, C.B. Crouse, M. Lew, A. Mikami, F. Ostadan, E.
Taciroglu
• Approach: Report on the state of practice and “art,” and recommend future
studies.
• Key issues:
– Quantifying ground motions in basements relative to free-field
• Reductions of horizontal motions
• Introduction of rotation
– Are these effects significant at the EDP level (and beyond)?
– Importance of flexibility of embedded sub-structure
qf
uf
ug
Final product
Guidelines for
performance-based
seismic design of
tall buildings
December 2008
PBEE practice needs
ROOF
13th
BASE
(a) Building elevation
Minimum
Maximum
Mean (m)
m+s
c.o.v.
Nonlinear
static
Roof
drift, ft
Wall
base
shear, k
Wall
moment at
13th floor,
1000 x k-ft
2.1
6.7
4.2
5.4
0.23
7600
29700
15500
22200
0.43
513
1080
900
1090
0.21
5500
760
(b) Summary of results