Effect of Gravity Framing on Earthquake-Induced …users.ntua.gr/divamva/docs/42RHUW/Lignos_42RHUW_Hydra.pdfl (DV) = G (DV DM) dG (DM EDP) dG (EDP I M) dl (I M) all DMs ò all EDPs

1 D. G. Lignos – Effect of Gravity Framing on Earthquake-Induced Losses & Collapse Risk of

Steel Frame Buildings Designed in Seismic Regions

Effect of Gravity Framing on Earthquake-Induced

Losses and Collapse Risk of Steel Frame

Buildings in Seismic Regions

June 23-24 2016, Hydra, Greece

DIMITRIOS G. LIGNOS

SWISS FEDERAL INSTITUTE OF TECHNOLOGY, LAUSANNE (EPFL)



Motivation

The next generation of performance-based earthquake

engineering (PBEE) has formalized a framework for assessing the

seismic performance of frame buildings.

The same framework can be employed to assess the earthquake-

induced losses in frame buildings (FEMA P-58).

Important for stakeholders, building owners:

Informed decisions for effective designs (new buildings)

Effective seismic retrofits (existing buildings)

Evaluation of repair actions in the aftermath of earthquakes



Overview of PBEE Methodology

l DV( ) = G DV DM( )dG DM EDP( )dG EDP IM( )dl IM( )allDMs

òallEDPs

òallIMs

ò

Image adopted by Zareian (2006)



Overview of PBEE Methodology (2) -Impact of Analytical Model Representation on EDPs (and losses)

Perimeter SMF

Equivalent

gravity frameRigid

link

4.6 m

4.0 m

4.0 m

4.0 m

6.1m 6.1m 6.1m

(a)

3 bays @ 6.10 m

I I I I

I

I

I

I

I

I

I

I

30.5

0 m

42.70 m

I

I

I

I

I

I

I

I

I

I

I

I

I I I I

I

I

I

I

Interior gravity

framingPerimeter SMF

Historically, “bare frame” models have been utilized for nonlinear response

history analysis of frame buildings (e.g., Composite action, gravity framing is

ignored).



Motivation (2) -Examples from Christchurch Earthquakes 2010, 2011

Total cost to insurers of rebuilding was approximately NZ$40Billion.

Significant portion of the estimated dollar loss is from damage to non-

structural components.

New Zealand: developed country with long tradition in earthquake

engineering research and practice!

Source: Bruneau et al. (2011)



Northridge 1994 Hyogoken-Nanbu 1995 Tohoku 2011

Motivation (3) -Collapse Risk During Extreme Earthquakes

Hyogoken-Nanbu 1995 Loma Prieta 1989 Loma Prieta 1989

Images Source: NISEE, E-Library



Motivation (4) -Residual Deformations and Demolition Actions

With the evolution of design provisions, code-conforming frame

buildings may not collapse (easily) but it is likely to experience large

residual deformations after a large earthquake.

Examples of steel and RC buildings with residual displacements leading to demolition (San

Fernando and Tohoku earthquakes)



Utilize loss metrics in order to quantify the seismic-induced

losses in steel frame buildings designed in urban California.

Assess the effect of analytical model representation of a

steel frame building on earthquake-induced losses under

various seismic intensities.

Quantify the effect of residual deformations on the loss

assessment of steel frame buildings with steel SMFs or

SCBFs.

Assess the effect of seismic design parameters (e.g., SCWB

ratio) on the earthquake-induced losses of steel frame

buildings in highly seismic regions.

Objectives and Scope



Overview of Loss Estimation Methodology

: Expected total repair costs conditioned on seismic intensity IM.

: Probability of having no-collapse given IM

: Probability of having no-collapse given IM but the building

will be demolished.

: Probability of having collapse given IM.

E LT IMéë ùû

P NCÇR IM( )

P C IM( )

P NCÇD IM( )

Source: Ramirez and Miranda (2013)

P D NC, IM( ) = P D RSDR( )dP RSDR NC, IM( )0

¥

ò

Probability of demolition given IM but no collapse (Assumed μ=1.5% and σ=0.30) :



Archetype office steel buildings (2- to 20-stories) with perimeter steel

special moment frames designed in Urban California (IBC 2009, AISC-

2010)

(Sources: Elkady and Lignos 2014*)

Example: Steel Frame Buildings with Special Moment

Frames

*Elkady, A. and Lignos, D.G. (2014). "Modeling of the Composite Action in Fully Restrained Beam-to-Column Connections:

Implications in the Seismic Design and Collapse Capacity of Steel Special Moment Frames". Earthquake Engineering and

Structural Dynamics (EESD). Vol. 43(13), pp. 1935-1954, DOI: 10.1002/eqe.2430.



Source: National Seismic Hazard Map (USGS 2008)

Seismic Hazard in Design Location of Interest



Fragility and Cost Distribution Functions

To compute realistic loss estimations for steel frame

buildings architectural layouts were developed.

Steel frame buildings with SMFs: rectangular footprint of

14,000ft2

Cost estimates were developed based on the RS Means

Cost Estimating Manuals.

Non-structural components (both drift- and acceleration-

sensitive) were considered to compute the replacement cost

estimates per building.

Structural components (e.g., beam-to-column connections,

columns, slabs, base plates, etc) were also considered.

Base case replacement cost was estimated to be $250/ft2.



Steel Frame Buildings with Moment Resisting Frames -Modeling of Composite Action and Interior Gravity Framing




Source: Elkady and Lignos (2014)*

Perimeter SMF

Equivalent

gravity frameRigid

link

4.6 m

4.0 m

4.0 m

4.0 m

6.1m 6.1m 6.1m

-0.08 -0.04 0 0.04 0.08

Mom

ent

(kN

-m)

-2000

-1000

0

1000

2000

3000

Chord Rotation θ (rad)

(b)

Exp. DataSimulation

-0.1 0 0.1

-450

0

450

Chord Rotation θ (rad)

(c) M

om

ent

(kN

-m)

Exp. DataSimulation

θbind

bindM

maxM

maxM

θu

θu

Joint panel zone model

Lumped plasticity model

Elastic beam-column element

Equivalent gravity beam & column

Composite shear-tab connection model

(a)



Experimental Data

Simulation

Experimental Data

Simulation

Steel Frame Buildings with Special Moment Frames

-Modeling of steel columns

Source: Suzuki and Lignos (2015)*

*Suzuki, Y., Lignos, D.G. (2015). ”Large Scale Collapse Experiments of Wide Flange Steel Beam-Columns”, Proceedings 8th

International Conference on Behavior of Steel Structures in Seismic Areas, Shanghai, China, July 1-3, 2015.



0.5 1 1.5 20

0.5

1

1.5

2

2.5

Sa[g

]

Period T [sec]

Design Spectrum

Mean Spectrum

Individual GM

0 0.05 0.1 0.150

0.5

1

1.5

2

2.5

Maximum Story Drift Ratio [rad]

Sa (

T1, 5%

) [

g]

Median Collapse Capacity ŜCT

Collapse

Collapse Risk of Steel Frame Buildings with SMFs

-Ground Motion Sets and Process to Trace Collapse


Ground Motion Set from FEMA P695

Far-Field Set of 44 Ground Motions

Incremental Dynamic Analysis

to Trace Dynamic Instability






Collapse Risk of Steel Frame Buildings with SMFs

*Elkady, A. and Lignos, D.G. (2015). ”Effect of Gravity Framing on the Overstrength and Collapse Capacity of Steel Frame

Buildings with Perimeter Special Moment Frames”, Earthquake Engineering and Structural Dynamics (EESD), Vol. 44(8),

1289-1307, DOI: 10.1002/eqe.2519.



Collapse Risk of Steel Frame Buildings with Special

Concentrically Braced Frames (SCBFs)



Expected Losses Conditioned on Seismic Intensity

-Utilization of Bare Frame Analytical Models

Due to P-Delta

effects

Hazards: Service Level, Design Basis (DLE) & Maximum Considered Event (MCE)

Minimum monetary loss due to business interruption is not considered

Due to P-Delta

effects



8-story SMF: B-Model

Bare Frame Only 8-story SMF: CG-Model

Composite Action & Gravity Framing


-Effect of Analytical Model Representation: Steel SMFs

Earthquake-induced loss assessment at discrete levels of intensity may be over-

conservative when it is based on “bare frame” model representations of the building.




-Effect of Analytical Model Representation: Steel SCBFs

Earthquake-induced loss assessment at discrete levels of seismic intensity may be

over-conservative when it is based on “bare frame” model representations of the

building.

B CG B CG B CG B CG B CG B CG

Illustration: 6-story Steel Frame Building with SCBFs

E[L

T/IM

]




Effect of Strong-Column-Weak-Beam Ratio on Expected Losses





Expected Annual Losses (EAL) as a Loss Metric

E LT( ) = E LT IM( )dl IM( ) =0

¥

ò E LT IM( )dl IM( )

dIMdIM

0

¥

ò

Sa(T

1, 5%) [g]

10-2

10-1

100

101

6S

a [

1/y

ear]

10-5

10-4

10-3

10-2

10-1

100

3-Story SCBF12-Story SCBF4-Story SMF12-Story SMF

EAL weights all possible levels of the seismic hazard by taking into

account their probability of occurrence.



Expected Annual Losses (EALs)



Concluding Remarks At seismic intensities associated with service and design-basis

earthquakes damage to non-structural content dominates steel frame

building earthquake induced losses regardless of the selected numerical

model and loss metric.

Earthquake induced loss estimates at discrete seismic intensities:

overestimated when building EDPs are based on “bare-frame”

models.

Composite action and the interior gravity framing reduce the

earthquake-induced loss estimates due to demolition by more than

50%. Loss estimates due to collapse risk reduce by 75%.

EALs: practical not affected by the choice of the numerical model

representation (Bare model or Composite-Gravity included).

Actions to reduce losses due to collapse risk (i.e., employed SCWB)

should be based on “better” building model representations as well as

discrete seismic intensities.



Thank you for your kind attention!

For more information visit: resslab.epfl.ch

http://resslab.epfl.ch/



Acknowledgements-Research Sponsors



Backup Slides



Archetype office steel buildings (2- to 12-stories) with perimeter steel

special concentrically braced frames designed in Urban California (IBC

2009, AISC-2010)

(Sources: NIST 2010)

Steel Frame Buildings with Special Concentrically

Braced Frames



Fragility and Cost Distribution Functions (2)

-Examples of Damageable Components and Damage States

Story Drift Ratio, SDR [rad]0 0.01 0.02 0.03 0.04

Pro

bab

ility

of

Exce

ed

en

ce

0

0.2

0.4

0.6

0.8

1

Flexural BucklingLocal BucklingFracture

(Source: Lignos and Karamanci 2013*)

*Lignos, D.G., and Karamanci, E. (2013). “Drift-based and Dual-Parameter Fragility Curves for Concentrically Braced Frames in

Seismic Regions". Journal of Construnctional Steel Research, Vol. 90, pp. 209-220.



Braced Frame Collapse Specifics



-0.04 -0.02 0 0.02 0.04-2000

0

2000

Rotation, [rad]

Eq

. S

hea

r F

orc

e, V

[k

N]

2

yV

p

Vy

Kp

Ksh

Vcol

Vcol

deff-

V

V V

V

Mb-Mb

+deff

+

ts

drib

Steel Frame Buildings with Special Moment Frames

-Modeling of panel zone shear distortion

W27x94

W24x84

W2

4x

13

1

W2

4x

13

1

W2

4x

13

1

W2

4x

13

1W24x84

W21x68

W2

4x

94

W2

4x

94

W2

4x

94

W2

4x

94

W30x108

W30x116

W30x116

W27x94

W2

4x

14

6

W2

4x

19

2

W2

4x

19

2

W2

4x

14

6

H =

32

.60

m

W2

4x

13

1

W2

4x

17

6

W2

4x

17

6

W2

4x

13

1

3 bays @ 6.10m

4.6

m4

.0m

4.0

m4

.0m

4.0

m4

.0m

4.0

m4

.0m

Perimeter

SMF

Rigid links

Equivalent

gravity frame







Steel Frame Buildings with Special Concentrically Braced Frames -Modeling of Steel Braces: Flexural Buckling and Fracture due to Low-Cycle Fatigue

*Karamanci, E., and Lignos, D.G. (2014). ”Computational Approach for Collapse Assessment of Concentrically Braced Frames

in Seismic Regions.” ASCE, Journal of Structural Engineering, Vol. 15(A401419), pp. 1-15.

Source: Karamanci and Lignos (2014)*

e0 = 0.748kL

r

æ

èç

ö

ø÷

-0.399D

t

æ

èç

ö

ø÷

-0.628E

Fy

æ

èçç

ö

ø÷÷

0.2

D

t

Calibrated with over 270 tests from steel braces


Steel Frame Buildings Designed in Seismic Regions *Karamanci, E., and Lignos, D.G. (2014). ”Computational Approach for Collapse Assessment of Concentrically Braced Frames

in Seismic Regions.” ASCE, Journal of Structural Engineering, Vol. 15(A401419), pp. 1-15.

Source: Karamanci and Lignos (2014)*

Steel Frame Buildings with Special Concentrically Braced Frames -Modeling of Steel Braces: Flexural Buckling and Fracture due to Low-Cycle Fatigue



-0.1 0 0.1

-450

0

450

Rotation [rad]

Mom

ent

[kN

.m]

Exp. Data

Simulation

Mmax

+

u

bind

Mmax

-

u

Mbind

-

W27x94

W24x84

W2

4x

13

1

W2

4x

13

1

W2

4x

13

1

W2

4x

13

1W24x84

W21x68

W2

4x

94

W2

4x

94

W2

4x

94

W2

4x

94

W30x108

W30x116

W30x116

W27x94

W2

4x

14

6

W2

4x

19

2

W2

4x

19

2

W2

4x

14

6

H =

32

.60

m

W2

4x

13

1

W2

4x

17

6

W2

4x

17

6

W2

4x

13

1

3 bays @ 6.10m

4.6

m4

.0m

4.0

m4

.0m

4.0

m4

.0m

4.0

m4

.0m

Perimeter

SMF

Rigid links

Equivalent

gravity frame

Steel Frame Buildings with SMFs or SCBFs

-Modeling of gravity framing system and its connections

Image source: Liu and Astaneh (2002)


*Elkady, A. and Lignos, D.G. (2015). ”Effect of Gravity Framing on the Overstrength and Collapse Capacity of Steel Frame

Buildings with Perimeter Special Moment Frames”, Earthquake Engineering and Structural Dynamics (EESD), Vol. 44(8), pp.

1289-1307, DOI: 10.1002/eqe.2519.



Tracing Sidesway Collapse of Frame Buildings -Example of definition of dynamic collapse due to earthquake shaking




-Effect of Analytical Model Representation: Steel SCBFs

12-story SCBF: B Model

Brace Frame Only 12-story SCBF: CG Model

Composite Action + Gravity Framing





EDPs for 12-story steel SMF

Documents

Effect of Gravity Framing on Earthquake-Induced …users.ntua.gr/divamva/docs/42RHUW/Lignos_42RHUW_Hydra.pdfl (DV) = G (DV DM) dG (DM EDP) dG (EDP I M) dl (I M) all DMs ò all EDPs