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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. ATC -63 Project Objectives.

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Overview of atc 63 project quantification of building system and response parameters

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


Atc 63 project objectives
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


Project organization

FEMA

Michael Mahoney

Robert Hanson (Adv.)

Project Organization

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



Seismic force resisting systems tasks 5 and 6
Seismic-Force-Resisting Systems (Tasks 5 and 6)

Concrete – Stanford

Gregory Deierlein

Curt Haselton

Abbie Liel

Brian Dean

Jason Chou

Ashpica Chhabra

John Hooper (MKA)

Brian Morgan (MKA)

  • 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%)


Seismic force resisting systems tasks 5 and 61
Seismic-Force-Resisting Systems (Tasks 5 and 6)

Wood - Buffalo

Andre Filiatrault

Ioannis Christovasilis

Hiroshi Isoda

Michael Constantino

  • 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)

AAC - Stanford

Helmut Krawinkler

Farzin Zareian

Kevin Haas

Dimitiros Lignos

Steel - Stanford

Greg Deierlein

Abbie Liel

Helmut Krawinkler

Dimitiros Lignos

Curt Haselton



Guiding principals
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 7-05as 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


Methodology overview
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)


Definition of seismic performance factors spf s from fema 450 commentary

R = Response Modification Coefficient = VE/V

Design Earthquake Ground Motions

Cd = Deflection Amplification Factor = d/de

Cd

WO = System Over-strength Factor = VY/V = DY/de

Base Shear

VE

Pushover Curve

Rd

R

VY

0

V

DY

de

d

DE

Roof Displacement

Definition of Seismic Performance Factors (SPF’s)(from FEMA 450 Commentary)


Spf s and mce collapse margin

SA-Based

Collapse Fragility

Collapse Level Ground Motions

Median

10th Percentile

T

SC1

MCE Ground Motions

Margin

SM1

Spectral Acceleration (g)

SD-Based Collapse Fragility

1.5R

1.5Cd

Margin

SY1

Median

WO

Cs

10th Percentile

SDe

SDM1

SDC1

Spectral Displacement

SPF’s and MCE Collapse Margin


Example collapse fragility one data point

Building (Joe’s Bar)

Incipient Collapse

Scaled Ground Motion Record

=

+

Example Collapse Fragility – One Data Point

Evaluation of a single structure (one configuration/set of performance properties) to failure using one ground motion record scaled to effect incipient collapse


Example collapse fragility comprehensive and representative collapse data

Comprehensive and representative collapse data

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Incipient Collapse

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Building (Joe’s Bar)

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

Ground Motion

=

=

=

=

=

=

=

=

=

=

=

=

=

=

=

=

=

=

+

+

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Comprehensive models of building configuration/performance properties evaluated with representative earthquake records

Example Collapse Fragility – Comprehensive and Representative Collapse Data


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

Notional Collapse Fragility Curve


Collapse fragility with modeling uncertainty

Margin

Collapse Fragility with Modeling Uncertainty


Atc 63 ground motion record sets objectives
ATC-63 Ground Motion Record Sets - Objectives

  • Code (ASCE 7-05) Consistent – Pairs of horizontal components “selected and scaled from individual recorded events.” Section 16.1.3.1 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


Ground motion record sets peer nga database
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)

    • 14 Events

    • 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)




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)

Comparison of Median Response Spectra at Collapse – 4-Story R/C SMF Model Building


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)

Comparison of Collapse Fragility Curves – 4-Story R/C SMF Model Building


Spectral shape factor
Spectral Shape Factor to 1.1)

  • 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 = 1.6 (e.g., R = 8)

    • Moderate ductility Systems SSF = 1.2 (e.g., R = 4)

    • Low Systems SSF = 1.0 (e.g., R = 2)


Reinforced concrete rc special moment frame smf system example
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)


Notional flowchart of process
Notional Flowchart of Process Example

Develop System

Characterize Behavior

Establish Design Provisions

Develop Archetype Models

Evaluate Collapse Performance

No

P[C] < Limit

Yes

Peer Review


Archetype design configurations 18
Archetype Design Configurations (18) Example

  • 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

  • Basic Set - High Seismic (SDC D) designs (6)

    • High gravity (space frame) configuration

    • 1, 2, 4, 8, 12 and 20-story archetypes

    • 20-foot bay size

  • 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)




Example ida results and margin 4 story sdc d space frame with 30 foot bays

2.5 Margin (2.77/1.11) Example

Median Collapse Sa = 2.77g

MCE Sa = 1.11g

Example IDA Results and Margin(4-story, SDC D, space frame with 30-foot bays)


Acceptable collapse margin based on composite uncertainty and collapse goal
Acceptable Collapse Margin Example(based on composite uncertainty and collapse goal)


Initial results rc smf asce 7 05
Initial Results – RC SMF ( ExampleASCE 7-05)


Re design to improve collapse margin of tall buildings 12 and 20 story heights
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. 9.5.5.2.1-3):

    Cs 0.044 SDS I (I = 1.0)

1. Effective value of R due to limits on the seismic coefficient, Cs.


Revised results rc smf asce 7 02
Revised Results – RC SMF ( and 20-story heights)ASCE 7-02)


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