self-centering damage-free seismic- resistant...

Self-Centering Damage-Free Seismic-

Resistant Structural Systems

Richard Sause

Professor of Structural Engineering, ATLSS Center Director

James M. Ricles

Professor of Structural Engineering, RTMD Facility Director

Ying-Cheng Lin, Dr. David Roke, and Brent Chancellor

ATLSS Center, Lehigh University

The Fourth Kwang-Hua Forum

and Opening Symposium of Tongji Shaking Table Array

Tongji University, Shanghai

December 11, 2011

Introduction: Conventional Earthquake

Design Practice in United States

• Design for “Life Safety” (LS) for “Design Basis Earthquake” (DBE) with ~500yr return period (10% in 50 years).

• We expect (but do not explicitly design for):

– “Immediate Occupancy” (IO) for “Frequently Occurring Earthquake” (FOE) with ~80yr return period.

– “Collapse Prevention” (CP) for the “Maximum Considered Earthquake” (MCE) with ~2500yr return period.

• Results:

– Expect modest to serious damage to a building from earthquake ground motions with relatively short return periods (in the range of ~100yr to ~500yr).

– Costs to repair damage or to demolish and replace damaged building can be significant life-cycle costs.

Introduction: Expected Damage for

Conventional Steel Moment Resisting

Frame after DBE (~500yr return period)

(b)

(a)

Reduced

beam section

steel moment-

resisting

frame

subassembly

at 3% rad

(0.03 rad)

lateral drift

• Damage leads to residual lateral drift.

• Costs to repair damage and residual drift or to demolish damaged buildings can be significant life-cycle costs

Self Centering (SC) Seismic-Resistant

Structural Systems

Discrete structural members are

post-tensioned (PT) to pre-

compress joints.

Gap opening at joints provides

softening of lateral force-drift

behavior without damage to

members.

PT forces close joints and

permanent lateral drift is avoided.

M

Steel SC moment resisting frame (MRF) subassembly at 3% rad drift

Self-Centering (SC) Steel Moment

Resisting Frames (1997-2004)

Garlock, Ricles, Sause (2008) Engineering Structures

Garlock, Sause, Ricles (2007) ASCE Journal of Structural Engineering

Rojas, Ricles, Sause (2005) ASCE Journal of Structural Engineering

Garlock, Ricles, Sause (2005) ASCE Journal of Structural Engineering

Ricles, Sause, Peng, Lu (2002) ASCE Journal of Structural Engineering

Ricles, Sause, Garlock, Zhao (2001) ASCE Journal of Structural Engineering

Little damage with potential for Immediate Occupancy (IO) under DBE

Comparison of Lateral Force-Drift Behavior

• Conventional system softens by inelastic damage to structural members.

• SC system softens by gap opening and reduced contact at joints.

• SC system energy dissipation is designed feature of SC system.

• Two systems have similar initial stiffness.

-600

-400

-200

0

200

400

600

-8 -6 -4 -2 0 2 4 6 8

Displacement, (in)

La

tera

l L

oa

d,

H (

kip

s)

SC System

Conventional System

Self Centering (SC) Precast Concrete Walls

and Moment Resisting Frames (1994-2004)

PRESSS Program:

Perez, Sause, Pessiki (2007) ASCE Journal of Structural Engineering

Perez, Pessiki, Sause (2004) PCI Journal

Kurama, Sause, Pessiki, Lu (2002) ACI Structural Journal

El-Sheikh, Pessiki, Sause, Lu (2000) ACI Structural Journal


Self Centering (SC) Precast Concrete Walls

and Moment Resisting Frames (1994-2004)

Gap opening behavior at 3% rad

drift

Little damage with potential for

Immediate Occupancy (IO)

under DBE

PRESSS Program:

Perez, Sause, Pessiki (2007) ASCE Journal of Structural Engineering

Perez, Pessiki, Sause (2004) PCI Journal


El-Sheikh, Pessiki, Sause, Lu (2000) ACI Structural Journal


-200

-150

-100

-50

0

50

100

150

200

-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7

Lateral Drift (%)

Base S

hear

(kip

s)

T3 (Ap = 7.50 in.2)

T5 (Ap = 3.75 in.2)

fpi/fpu = const. Deformation

capacity

controlled by

post-tensioning

and structural

geometry as

well as material

ductility

SC Precast Walls: Deformation Capacity for

Collapse Prevention (CP) under MCE

(~2500yr return period)

3 cycles to 6% rad drift

SC Damage-Free Seismic-Resistant Steel

Frame Systems Project (NEES 2004-2010)

PT Bars

Moment-resisting frame (SC-MRF) systems

Concentrically-braced frame (SC-CBF) systems


Frame Systems Project: SC-MRFs

Performance Objectives:

• Damage free with potential for Immediate

Occupancy (IO) under Design Basis

Earthquake (DBE) with ~500yr return period.

• Avoid significant yielding limit states.

• Collapse Prevention (CP) under the Maximum

Considered Earthquake (MCE) with ~2500yr

return period .

• Avoid local buckling and PT strand yielding.

Performance-Based Seismic Design of

Damage-Free SC-MRFs

Perimeter SC-MRF as

Experimental Substructure

Tributary Gravity Frames,

Seismic Mass, and

Inherent Damping as

Analytical Substructure

Large-Scale Hybrid Simulations on SC-MRF

Earthquake Loading Direction

• Based on 4-story office building on stiff soil site in California

at 0.6 scale

• Numerical integration of equations of motion for coupled

analytical and experimental (laboratory) substructures.

0.6-Scale 2-bay 4-story SC-MRF Experimental Substructure


Floor displacements

at each time step

imposed by

actuators. Restoring

forces feed back to

equations of motion.

Matrix of Simulations

Slow

Hybrid


DBE (~500yr return period) MCE (~2500yr return period)

DBE-3 Simulation Results

Level qs max (% rad.)

Residual Drift

(% rad.)

RF 3.9 0.008

3F 3.5 0.023

2F 3.5 0.063

1F 2.1 0.074

Experimental Response • No damage in beams and

columns, except for yielding at column base.

• No residual drift: self-centering

0 5 10 15 20-8

-4

0

4

8

12

Time(sec.)

Flr

. D

isl. (

in.)

1F

2F

3F

RF

DBE-3 Floor Displacements and Story Drifts


Findings from Large-Scale Hybrid

Simulations on Damage-Free SC-MRF

• Validated the performance-based seismic design procedure.

• SC-WFD beam-to-column connections dissipated energy (friction) while maintaining self-centering.

• Demonstrated that SC-MRF system can be damage free with potential for Immediate Occupancy (IO) performance under DBE (~500 yr return period).

• Showed that damage of SC-MRF system is minimal under MCE (~2500 yr return period) achieving Collapse Prevention (CP) performance .


Frame Systems Project: SC-CBFs

SC-CBF Configurations Studied by

Numerical Simulations

Frame A

PT bars

Frame B

Fg Fg Fg

Fg

Frame C

PT bars

Frame B

Fg Fg

Typical column uplift and

SC-CBF rocking behavior



Frame D

Energy dissipation

through relative

motion between

uplifting SC-CBF

column and gravity

column

Gravity column

(does not uplift)

SC-CBF column

(uplifts as frame rocks)

ED

element



Frame B

Fg Fg

Gravity columns (no uplift)

CBF

column

Optional

ED

element

Lateral load

bearing with

friction

Frame DDF Configuration DDF

Selected for

Experimental Study

Lateral load bearing

with friction



Performance Objectives:

• Damage free with potential for Immediate

Occupancy (IO) under Design Basis

Earthquake (DBE) with ~500yr return period.

• Prevent significant yielding limit states.

• Collapse Prevention (CP) under the Maximum

Considered Earthquake (MCE) with ~2500yr

return period .

• Prevent member failure (buckling and

subsequent fracture).

Probabilistic Performance-Based Seismic

Design of SC-CBFs

Lateral Force

Roof Drift

1

2 3 4

CP Performance

IO Performance

Limit states:

1: Column

decompression

2: PT bar yielding

3: Member yielding

4: Member failure

Median DBE-

level response

Probabilistic Performance-Based

Design (PBD) of SC-CBFs: Criteria

Δgap

• Based on 4-story office building on stiff soil site in California

at 0.6 scale 3 @ 7’-6”

2 @ 9’

Large-Scale Hybrid Simulations on SC-CBF 6

@ 1

8’ =

10

8’

6 @ 18’ = 108’

Tributary Gravity Frames, Seismic Mass, and Inherent Damping as Analytical Substructure

Single SC-CBF with Adjacent Gravity Columns as Experimental Substructure

Elevation of column line with SC-CBF

Plan of Building

PT Anchorage

PT Anchorage

SC-CBF Experimental

Substructure

Ground Motion Selection

# of θr,max θs,max Vb,max θr,max θs,max Vb,max

Hazard Motion Tests (% rad) (% rad) (kN) * * *

DBE Mean 0.880 0.981 1812

MCE Mean 1.467 1.582 2201

DBE cls000 3 0.641 0.720 1240 -0.81 -0.80 -1.04

DBE 5108-090 14 0.827 0.909 1972 -0.18 -0.22 0.29

DBE h-shp270 1 0.912 1.023 2087 0.11 0.13 0.50

DBE arl090 2 1.393 1.513 2023 1.74 1.62 0.38

DBE nr-pel360 1 0.940 1.147 2483 0.20 0.51 1.22

MCE stn110 2 1.622 1.746 2013 0.31 0.32 -0.32

MCE a-tmz270 1 1.120 1.246 2407 -0.69 -0.66 0.35

MCE lp-hda255 3 1.477 1.588 2341 0.02 0.01 0.24

MCE cap000 1 2.068 2.221 2292 1.19 1.26 0.16

MCE h-cpe237 1 1.742 1.832 2556 0.55 0.49 0.61

tak090 2 4.333 4.460 2711 5.68 5.66 0.87

* - Given as a multiplier of the standard deviation above (+) or below (-) the mean

31 intense EQs used in hybrid simulations

For tak90 the maximum roof drift qr,max = 0.0433rads

is 5.68 larger than the mean qr,max = 0.0147rads for the MCE.

Numerical response statistics for 30 ground motions each input level

Simulation: DBE_arl090_01-04-2010

DBE_arl090_01-04-2010: Roof Drift

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

0 5 10 15 20 25

Ro

of D

rift

(%)

Time (s)

TEST

MODEL

DBE_arl090_01-04-2010: OM vs Roof Drift

-15000

-10000

-5000

0

5000

10000

-2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50

Ove

rtu

rnin

g M

om

en

t (kN

-m)

Roof Drift (%)

TEST

MODEL

Simulation: MCE_tak090_01-13-2010

MCE_tak090_01-13-2010: Roof Drift

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

0 2 4 6 8 10 12 14 16 18 20

Ro

of D

rift

(% r

ad)

Time (s)

TEST

MODEL

μ = 0.65

MCE_tak090: PT Bar Yielding

0 5 10 15 200

300

600

900

1200

So

uth

PT

Bar

Fo

rce

PT

S (

kN

)

0 5 10 15 200

300

600

900

1200

Cen

ter

PT

Bar

Fo

rce

PT

C (

kN

)

0 5 10 15 200

300

600

900

1200

No

rth

PT

Bar

Fo

rce

PT

N (

kN

)

Time (sec)

North PT Bars

Time (sec)

PT

Ba

r F

orc

e (

kN

)

Post-MCE Aftershock with Small PT Bar

Force from Yielding during MCE

- 1.5%

- 1.0%

- 0.5%

0.0%

0.5%

1.0%

1.5%

0 2 4 6 8 10

Ro

of

Dri

ft (

% r

ad

)

Time (s)

Original: Response of undamaged frame to 5108-090

Aftershock: Response of frame to 5108-090 with reduced PT bar force due to yielding

SC-CBF after 31 DBE-Level and MCE-

Level Hybrid Simulations

Findings from Large-Scale Hybrid

Simulations on Damage Free SC-CBF

• No damage under any DBE (~500yr.

return period) ground motions.

• No damage under most MCE (~2500yr.

return period) ground motions.

• Some damage to lateral load bearings

under largest MCE.

• PT bars yielded under largest MCE:

– SC-CBF performed well under post-MCE

aftershock.

– SC-CBF self-centers after all initial PT force is

lost due to yielding.

– Re-stressing PT bars can return the SC-CBF

to its initial state.

Lateral load bearing

with friction

Conclusions from SC Damage-Free Seismic-

Resistant Steel Frame Systems Project

• Selected SC-MRF and SC-CBF configurations

performed well.

• Essentially damage free under DBE (~500yr.

return period ) with modest damage under

extreme MCE (~2500yr. return period)

response.

• SC steel systems self-centered under all

earthquake conditions that were studied.

• Seismic performance objectives were met.

Acknowledgement

Project: NEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems

This material is based on work supported by the

National Science Foundation, Award No. CMS-

0420974, in the George E. Brown, Jr. Network for

Earthquake Engineering Simulation Research

(NEESR) program, and Award No. CMS-0402490

NEES Consortium Operation.

Current Work on Medium-Rise Steel SC-CBFs

4 Story

6 Story

9 Story

12 Story

15 Story

18 Story

Thank you

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