Seismic Fragility Assessment of SCED Brace System using Hybrid Simulation

Oh-Sung Kwon Assistant ProfessorViswanath Kammula MASc student

Constantin Christopoulos Associate ProfessorJeff Erochko PhD student

July 12, 2012

Outline Seismic Fragility Function Reference Structure Hybrid Simulation Configuration Experimental Results Summary

Seismic Risk/Loss Assessment

Hazard

Scio-eco.impact

Inventorydata

Damageprediction

IM

P

Fragilityfunctions

0.0

0.2

0.4

0.6

0.8

1.0

0 0.05 0.10 0.15 0.20 0.25

Seismic Intensity (PGA, g)

Pro

babili

ty

Seismic Fragility Functions Development of Seismic Fragility Functions

Empirical – post-earthquake survey Judgmental – experts’ opinion Analytical – numerical analysis of structures Hybrid (combination of above)

Most Common Methods in Industry Leading catastrophe modeling industries: EQECAT, AIR

Worldwide, RMS Methods: analysis, empirical, judgmental methods

Seismic Fragility Functions Analytical Derivation of Seismic Fragility Functions

Monte-Carlo simulation SAC-FEMA based approach Response surface method

ˆ bD aIM

ˆDD

ˆDD

log IM

logD

Identical dispersion

IM

logD

Median D at each IM are independent

2025

3035

4045

250

300

350

400

0.06

0.07

0.08

0.09

0.10

0.11

Concrete strength, fcSteel strength, fy

Fai

lure

pea

k ac

cele

ratio

n, g

2 20 1 2 3 4, , exp( )af c y c y c yS f F f F f F

Regardless of the method, analytical derivation highly

depends on the accuracy of analytical prediction.

Seismic Fragility Functions Analytical Prediction of Structural Response

Collapse test of a full-scale four story steel building , 2007

http://www.blind-analysis.jp/2008/2007/index_e.html

3D Analysis Blind Prediction Results

(measured and best 3 teams of each category)

Seismic Fragility Functions Analytical Prediction of Structural Response

Concrete column blind prediction contest, 2010

http://nisee2.berkeley.edu/peer/prediction_contest/

Prediction of structural behaviour using NLTH is still very challenging and depends on many assumptions in the

numerical model.

Hybrid (Analysis-Experiment) Simulation

MUST-SIM Facility, UIUC

UI-SIMCOR

FEDEASLab

Vector 2

MatlabExperiment

Critical component can be physically tested in hybrid simulation

Hybrid simulation can reduce the gap between analytical prediction and actual behavior by representing critical

component(s) experimentally.

Objective To develop seismic fragility functions of a structure

with Self-Centering Energy-Dissipative (SCED) Braces using hybrid simulation

Outline Seismic Fragility Function Reference Structure Hybrid Simulation Configuration Experimental Results Current Research and Development in University of

Toronto

Self-Centering Systems Characterized with ‘flag-shape’ hysteresis loop Minimal residual deformation with energy

dissipation capacity Damage-free structural system

Self-centering moment resisting steel frame (Christopoulos et al. 2002, Herning et al. 2009)

Controlled rocking steel frame (Eatherton et al. 2010)

Segmental bridge bents (ElGawady and Sha’lan 2011)

Self-centering braces (Christopoulos et al. 2008)

among many others.

SCED Brace System Christopoulos, C., Tremblay, R., Kim, H.-J., and Lacerte, M. (2008). “Self-

Centering Energy Dissipative Bracing System for the Seismic Resistance of Structures: Development and Validation.” Journal of Structural Engineering, 134(1), 96.

Reference Structure Six-storey Steel Frame

Designed with ASCE 7-05 Assumed R-factor of 7 (brace system) Los Angeles, CA Design Sa = 1.4g, MCE Sa = 2.1g

Reference Structure Six-storey Steel Frame

Designed with ASCE 7-05 Assumed R-factor of 7 (brace system) Los Angeles, CA Design Sa = 1.4g, MCE Sa = 2.1g

Gravity column

SCED braces

Input Ground Motions SAC-FEMA Method for fragility analysis Ground motions

Far-field motions from PEER-NGA Database Wide range of Sa at fundamental period of the structure Total thirty ground motions for hybrid simulation Scale factors of 0.65 ~ 1.1 are used to ensure that Sa are widely distributed Ground motions are truncated to reduce simulation time

ˆ bD aIM

ˆDD

ˆDD

log IM

logD

Identical dispersion

Outline Seismic Fragility Function Reference Structure Hybrid Simulation Configuration Experimental Results Current Research and Development in University of

Toronto

Hybrid Simulation Configuration

a) Whole Model c) Specimen d) OpenSeesb) UI-SimCor

Note: Gravity columns are included but not illustrated in the above figure.

SCED brace is a main lateral load resisting system.

NE

T W

OR

K

Hybrid Simulation ConfigurationU

I-S

imC

or

Command

MeasurementNICON

NI

ComactDAQUS

B MTS

FlexTest ControllerV

olta

ge MTS

Actuator

Act

ion

Specimen

PID Control Loop

Displacement feedback

NICA

PIP

E

OpenSeesCommand

Analysis Result

ACTIA

US

BCommand

Force feedback

Hybrid Simulation Configuration

Ph.D. research of J. Erochko, Advisor: Prof. C. Christopoulos

Hybrid Simulation Configuration

Ph.D. research of J. Erochko, Advisor: Prof. C. Christopoulos

Static Cyclic Test

-600

-400

-200

0

200

400

600

-40 -30 -20 -10 0 10 20 30 40

Forc

e, k

N

Displacement, mm

Brace Hysteresis

Frame Hysteresis

Challenges Slackness in loading frame Implemented control algorithm based on external feedback

Outline Seismic Fragility Function Reference Structure Hybrid Simulation Configuration Experimental Results Current Research and Development in University of

Toronto

Simulation Results

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

-15-10-505

10152025 Node 23 - Analyitcal HST

Node 23 - Experimental HST

Time (Sec)

Dis

pla

cem

ent

(mm

)

Whittier Narrows-01, 1987, Brea Dam

3 4 5 6 7 8 9 10

-40-30-20-10

010203040 Node 23 - Analyitcal HST

Node 23 - Experimental HST

Time (Sec)

Dis

pla

cem

en

t (m

m)

Loma Prieta, 1989, Gilroy Array#2

Simulation Results

-40 -30 -20 -10 0 10 20 30 40 50 60

-400

-300

-200

-100

0

100

200

300

400

Analytical HST

Experimental HST

Displacement (mm)

Fo

rce

(K

N)

-5 -4 -3 -2 -1 0 1 2 3 4 5

-300

-200

-100

0

100

200

300

400

Analytical HST

Experimental HST

Displacement (mm)

Fo

rce

(K

N)

Difference in response was due to idealization of brace behavior with flag shape.

Simulation Results Seismic Demand

0.0 0.5 1.0 1.5 2.0 2.50.0

0.5

1.0

1.5

2.0 Analytical HST

Experimental HST

Spectral Acceleration (g)

Inte

rsto

rey

Dri

ft (

%)

Collapse prevention limit (ASCE 41-06)

Life safety limit (ASCE 41-06)

De

sig

n E

Q

Ma

xim

um

Cre

dib

le E

Q

Simulation Results Seismic Fragility Curves

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.2

0.4

0.6

0.8

1.0

Spectral Acceleration (g)

Pro

ba

bil

ity

of

fail

ure LS = 0.5%

LS = 1.0%

LS = 1.5%

LS = 2.0%

Analysis

Hybrid

Max

imum

Cre

dibl

e E

Q

Des

ign

EQ

Summary Seismic fragility functions of a structure with SCED

braces are developed using hybrid simulations. The structure, designed with ASCE 7-05, satisfied

inter-story drift limits in ASCE 41. This conclusion is preliminary, though, as the R

factor in ASCE 7 and performance limit in ASCE 41 are not calibrated for SCED braces.

Research is in progress to develop strategy for element selection and model updating.

Thank you!