1. Performance-based guidelines and regulations
Tall Buildings
Performance-based guidelines and regulations
Joe Maffei
Rutherford & Chekene
Jack Moehle
UC Berkeley

2. Outline Today’s tall buildings Applicability of PBEE to tall buildings
PBEE practice needs
PEER Tall Building Initiative

3. Buildings over 240 ft (proposed, approved, or under construction)
San Francisco – 38; Los Angeles – 53; Seattle …

4. Types of Occupancy
CONDO
HOTEL
RETAIL $
PARKING $

5. STEEL GRAVITY FRAMING $

6. Washington Mutual / Seattle Art Museum

12. Buckling-restrained braces

13. 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 , ,
after MKA

14. 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 code-prescriptive buildings should not be acceptable.
Use Seismic Peer Review.

15. 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.

16. Example PBEE Practice Needs
Acceptability of yielding outside base hinge zone.

17. Protection against shear failure

18. Protection against sliding shear

19. Linear and nonlinear modeling assumptions
Elastic ETABS Model
UCSD Wall
RUTHERFORD & CHEKENE

20. Wall: Eeff = 0.2Ec
Slab: Eeff = 0.1Ec
RUTHERFORD & CHEKENE

21. PBEE Practice Needs Structural Design (Joe’s top 15)
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

22. 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

23. Scope Tall buildings Seismic design of structural system
Coastal California
Concrete and steel
Residential focus, but not excluding other occupancies

24. Tasks Establish and operate Project Advisory Committee (T-PAC)
Research tasks
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

25. 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)

26. 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.
Story Moment
Story level

27. 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
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

28. 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)

29. 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 uf ug qf

30. Guidelines for performance-based seismic design of
Final product
Guidelines for performance-based seismic design of
tall buildings
December 2008

31. Wall moment at 13th floor, 1000 x k-ft
PBEE practice needs
BASE
13th
ROOF
Roof drift, ft
Wall base shear, k
Wall moment at 13th floor, 1000 x k-ft
Minimum
Maximum
Mean (m)
m + s
c.o.v.
Nonlinear
static
2.1
6.7
4.2
5.4
0.23
7600
29700
15500
22200
0.43
5500
513
1080
900
1090
0.21
760
(a) Building elevation
(b) Summary of results