1. Charles A. Kircher, Ph.D., P.E.
2007 PEER Annual Meeting
Overview of ATC-63 Project “Quantification of Building System and Response Parameters”
Charles A. Kircher, Ph.D., P.E.
Kircher & Associates
Palo Alto, California
January 19, 2007

2. ATC -63 Project Objectives
Primary – Create a methodology for determining Seismic Performance Factors (SPF’s) “that, when properly implemented in the design process, will result in the equivalent earthquake performance of buildings having different structural systems” (i.e., different lateral-force-resisting systems)
Secondary – Evaluate a sufficient number of different lateral-force-resisting systems to provide a basis for Seismic Code committees (e.g., BSSC PUC) to develop a simpler set of lateral-force-resisting systems and more rational SPF’s (and related design criteria) that would more reliably achieve the inherent earthquake safety performance objectives of building codes

3. Project Organization FEMA Michael Mahoney Robert Hanson (Adv.)
TOP Management
Chris Rojahn (PED)
Jon Heintz (PTM)
William Holmes (PQC)
PRP Members
Phipps (Chair)
Elnashai - MAE
Ghosh - SKGA
Gilsanz- GMS
Hamburger - SGH
Hayes - NIST
Holmes – R&C
Klingner - UT
Line - AFPA
Manley - AISI
Reinhorn - UB
Rojahn - ATC
Sabelli - DASSE
PMC Members
Charels Kircher (Chair)
Greg Deierlein – Stanford
M. Constantinou – Buffalo
John Hooper - MKA
James Harris – HA
Allan Porush - URS
Working Groups
Stanford – NDA
SUNY – NSA/NCA
Filiatrault – Wood
Krawinkler - AAC

4. Project Tasks and Schedule

5. Seismic-Force-Resisting Systems (Tasks 5 and 6)
Reinforced-Concrete Structures
4-Story SMF, IMF and OMF
12-Story IMF/OMF and Shear Wall (Core Wall)
Parametric Study of RC Frames
1, 2, 4, 8, 12 and 20 stories
Space vs. perimeter configurations
Drift Limits (1% - 4%)
Weak story irregularities (Code limits: 80%, 65%)
Concrete – Stanford
Gregory Deierlein
Curt Haselton
Abbie Liel
Brian Dean
Jason Chou
Ashpica Chhabra
John Hooper (MKA)
Brian Morgan (MKA)

6. Seismic-Force-Resisting Systems (Tasks 5 and 6)
Wood Structures (CUREE):
Townhouse – Superior, typical, poor quality
Apartment – Superior, typical and poor quality
Other (Japanese Home, Templeton Hospital)
Autoclaved Aerated Concrete (AAC) Test Structures
Steel Structures:
4-Story (RBS) SMF (IMF, OMF)
Wood - Buffalo
Andre Filiatrault
Ioannis Christovasilis
Hiroshi Isoda
Michael Constantino
AAC - Stanford
Helmut Krawinkler
Farzin Zareian
Kevin Haas
Dimitiros Lignos
Steel - Stanford
Greg Deierlein
Abbie Liel
Helmut Krawinkler
Dimitiros Lignos
Curt Haselton

7. Elements of the Methodology

8. Guiding Principals
New Buildings – Methodology applies to the seismic-force-resisting system of new buildings and may not be appropriate for non-building structures and does not apply to nonstructural systems.
NEHRP Provisions – Methodology is based on design criteria, detailing requirements, etc. of the NEHRP Provisions (i.e., ASCE 7-05 as adopted by the BSSC for future NEHRP Provisions development) and, by reference, applicable design standards
Life Safety – Methodology is based on life safety performance (only) and does not address damage protection and functionality issues (e.g., I = 1.0 will be assumed)
Structure Collapse – Life safety performance is achieved by providing uniform protection against local or global collapse of the seismic-force-resisting system for MCE ground motions
Ground Motions – MCE ground motions are based on the spectral response parameters of the NEHRP Provisions, including site class effects

9. Methodology Overview
Conceptual Framework – Methodology adopts the concepts and definitions of seismic performance factors (SPF’s) of the NEHRP Provisions (e.g., global pushover concept as described in the Commentary of FEMA 450 )
Failure Modes – Methodology evaluates structural collapse defined by system-dependent local and global modes of failure
Collapse Probability – Methodology evaluates structural collapse probability considering response and capacity variability (and epistemic and aleatory uncertainty)
Archetypical Systems – Methodology defines “archetypical” structural systems that have configurations typical of a given type or class of lateral-force-resisting system
Analytical Models – Methodology incorporates models (of archetypical systems) that have sufficient complexity to realistically represent global performance of actual building systems considering nonlinear inelastic behavior of seismic-force-resisting components
Analytical Methods – Methodology utilizes nonlinear analysis methods (i.e., pushover and incremental dynamic analysis)

10. Design Earthquake Ground Motions
Definition of Seismic Performance Factors (SPF’s) (from FEMA 450 Commentary)
R = Response Modification Coefficient = VE/V R VE V DE
Roof Displacement
Base Shear
Pushover Curve
Design Earthquake Ground Motions Cd
Cd = Deflection Amplification Factor = d/de d de 0 Rd
WO = System Over-strength Factor = VY/V = DY/de DY VY

11. SPF’s and MCE Collapse Margin
Spectral Displacement
Spectral Acceleration (g)
SY1
SDe Cs
SDM1
MCE Ground Motions
SM1
1.5Cd WO
1.5R
Margin
SA-Based
Collapse Fragility
Median
10th Percentile
SC1
SDC1
Collapse Level Ground Motions T
Margin
SD-Based Collapse Fragility
Median
10th Percentile

12. Example Collapse Fragility – One Data Point
Building (Joe’s Bar)
Incipient Collapse =
Scaled Ground Motion Record +
Evaluation of a single structure (one configuration/set of performance properties) to failure using one ground motion record scaled to effect incipient collapse

13. Example Collapse Fragility – Comprehensive and Representative Collapse Data
Ground Motion +
Building (Joe’s Bar)
Incipient Collapse =
Comprehensive models of building configuration/performance properties evaluated with representative earthquake records
Comprehensive and representative collapse data

14. Notional Collapse Fragility Curve
Margin
50% probability (median) of collapse at SC1 = 1.6 g
Acceptably low probability of collapse (TBD) given MCE spectral demand
10% probability of collapse at SM1 = 0.9 g

15. Collapse Fragility with Modeling Uncertainty
Margin

16. ATC-63 Ground Motion Record Sets - Objectives
Code (ASCE 7-05) Consistent – Pairs of horizontal components “selected and scaled from individual recorded events.” Section of ASCE 7-05
Very Strong Ground motions – Ground motions strong enough to collapse new buildings
Large Number of Records – Enough records in set to estimate median and RTR variability (collapse fragility)
Structure-Type Independent – Appropriate for NDA (IDA) of variety structures with different dynamic characteristics and performance properties
Site/Hazard Independent – Appropriate for evaluation of structures located at different sites/hazard levels

17. Ground Motion Record Sets (PEER NGA database)
Far-field Record Set (Basic Set):
22 records (2 components each)
14 Events
Mechanisms: 9 strike-slip, 5 thrust
Near-field Record Set:
28 records (2 components each)
Half of records with a pulse, half without a pulse
Scale records (consistent with ASCE 7-05):
Normalize individual records by PGV
Anchor record set median spectral demand to MCE demand (at period of structure)

18. Response Spectra - Far-Field Record Set

19. Spectral Shape – Far-Field Record Set

20. Comparison of Median Response Spectra at Collapse – 4-Story R/C SMF Model Building
60% increase in margin due to increase in mean epsilon (0.36 to 1.1)

21. Comparison of Collapse Fragility Curves – 4-Story R/C SMF Model Building
60% increase in margin due to increase in mean epsilon (0.36 to 1.1)
10-fold decrease in margin due to increase in mean epsilon (0.36 to 1.1)

22. Spectral Shape Factor
The Need - Incorporation of spectral shape effect is essential to accurate estimation of collapse margin required to achieve acceptably low probability of collapse
The Problem - Currently available maps of epsilon (from hazard de-aggregation) are not directly applicable and development of applicable maps/methods is not feasible near term
The Solution - Alternatively, generically applicable site-independent spectral shape factors (SSF’s) can be used to approximate “typical” epsilon effect on spectral shape (i.e., factors used to bias margin calculated using “epsilon-neutral” records)
Trial Values (SSF) - Generic spectral shape factor would be a function of system ductile capacity:
High ductility Systems SSF = (e.g., R = 8)
Moderate ductility Systems SSF = (e.g., R = 4)
Low Systems SSF = (e.g., R = 2)

23. Reinforced-Concrete (RC) Special Moment Frame (SMF) System Example
Purpose
Illustrate methodology for an existing seismic-force-resisting (RC SMF) system (as if it were a new system being proposed for the Code)
Demonstrate validity of the methodology (show R = 8 is reasonable for RC SMF)
Approach
Develop comprehensive set of archetypical systems (e.g., 18 designs) based on ASCE 7-05 (and ACI 318)
Determine over-strength factors (WO) from push over
Determine margins from IDA’s
Adjust margins for spectrum shape factor (epsilon)
Evaluate margin acceptability (considering total uncertainty (RTR + modeling + design + testing)

24. Notional Flowchart of Process
Develop System
Characterize Behavior
Establish Design Provisions
Develop Archetype Models
Evaluate Collapse Performance No
P[C] < Limit
Yes
Peer Review

25. Archetype Design Configurations (18)
Basic Set - High Seismic (SDC D) designs (6)
Low gravity (perimeter frame) configuration
1, 2, 4, 8, 12 and 20-story heights
20-foot bay size
High gravity (space frame) configuration
1, 2, 4, 8, 12 and 20-story archetypes
Check Low Seismic - Low Seismic (B/C) designs (4)
8, 12, and 20-story heights – Low gravity (perimeter)
20-story height – high gravity (space frame)
Check Bay Size - 30-foot bay designs (2)
High Seismic (SDC D) designs
4-story – low gravity (perimeter frame)
4-story – high gravity (space frame)

26. Index Archetype Configuration (4-Story)

27. Summary of Archetype Design Properties Initial Design ASCE 7-05)

28. Example IDA Results and Margin (4-story, SDC D, space frame with 30-foot bays)
Median Collapse Sa = 2.77g
MCE Sa = 1.11g
2.5 Margin (2.77/1.11)

29. Acceptable Collapse Margin (based on composite uncertainty and collapse goal)

30. Initial Results – RC SMF (ASCE 7-05)

31. Re-design to Improve Collapse Margin of Tall Buildings (12 and 20-story heights)
Restore minimum base shear provision removed from ASCE 7-02 (Eq ):
Cs  SDS I (I = 1.0)
1. Effective value of R due to limits on the seismic coefficient, Cs.

32. Revised Results – RC SMF (ASCE 7-02)