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Use of PBEE in the Design Practice

Marko Schotanus

RUTHERFORD & CHEKENE

Marko SchotanusJuly 2009

Outline When is PBEE used in design practice?

PBD of Tall Buildings

Elastic analysis

Effective stiffness properties

Damping


Damping

Nonlinear Modeling

Component models and acceptance criteria

Capacity Design

Dynamic amplification and system effects

PBEE in Practice

Existing Structures

- Standardized in ASCE 41-06 (supplement 1)

- Incorporated in Chapter 34 of 2006 IBC

- Innovative materials/systems

- More specific performance objectives


- More specific performance objectives

New Structures

- Justification of lower demands/higher capacities

- Innovative materials/systems

…use fancy analysis to do something the code won’t allow…

Advantages

Fast adoption of new materials and systems

Immediate incorporation of state-of-the-art modeling


Expert review

Tailor made structures

Disadvantages

Increases design time and cost

Analysis intensive

Inconsistent design criteria for similar buildings


buildings

Convincing local autorities

Mediation with(in) Peer review teams

Designers are working against a “moving target”


Beyond ASCE-41

Incremental Dynamic Response

1.5

2.0

2.5

Sa

(g

)

Static PO

IDA-16%

IDA-50%

IDA-84%

capacity1.5

2.0

2.5

Sa

(g

)

Static PO

IDA-16%

IDA-50%

IDA-84%

capacity


Existing Retrofitted

0.0

0.5

1.0

0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5%

Roof Drift

Sa

(g

)

0.0

0.5

1.0

0.0% 0.5% 1.0% 1.5% 2.0% 2.5% 3.0% 3.5%

Roof DriftS

a (

g)

Advanced Seismic Assessment Method


Advanced Seismic Assessment Method

R&C has applied the method to a range of different building types:

• Electrical


• Electrical substations, office buildings, parking and maintenance facilities

• 1-story –8-stories

•

Acknowledgements

Karl Telleen

Joe Maffei


PBD of Tall Buildings


What’s Different about these Buildings?

High-performance materials

Framing systems not satisfying code prescriptive limits

Non-prescriptive designs are


Non-prescriptive designs are accepted in the code by demonstrating at least equivalent seismic performance.

CBC 1629.10.1, 1605.2, 104.2.8after MKA

Technical Basis for Height Limits

Limit height for systems that can develop story mechanisms

Favor systems that distribute inelastic energy dissipation over


inelastic energy dissipation over the height of the building.

What is “Equivalent” Performance?

Consider both the intended performance of

the code and the performance of a

typical good prescriptive design.

Equivalence to poorly-performing but code-


Equivalence to poorly-performing but code-

prescriptive buildings should not be

acceptable.

Use Seismic Peer Review.

Washington Mutual / Seattle Art Museum


SEOR: Magnusson Klemencic Associates Seattle

Limitations of the Building Code

High-performance materials

Building systems with height limits or not addressed

Higher mode effects


Higher mode effects

Preclude a story mechanism in moment frames

Shear amplification

Damping

Explicit Performance Objectives

How Consistent are Design Criteria?

SEAONC PBD of Tall Buildings committee

compared design criteria for tall

buildings.

10 tall buildings on West Coast of USA,



designed by 6 firms.

SEAONC Committee

Brian Dean, Rafael Sabelli (Walter P. Moore)

Jason Krolicki (chair), Michael Willford, Ibbi Al-Mufti, Damian Grant (ARUP)

Derrick Roorda, Nic Rodrigues (DeSimone Consulting Eng.)

Ron Klemencic


Ron Klemencic (Magnusson Klemencic Associates)

Neville Mathias, Mahmoud Hachem (Skidmore, Owings & Merrill)

Michael Gemmill (Nabih Youssef Associates)

Mark Moore (ZFA Structural Engineers)

Saeed Fathali (Rutherford & Chekene)

How Consistent are Design Criteria?


designed by 6 firms.

San Francisco, Seattle, Los Angeles


>240ft, five well over 500ft

Ductile, coupled reinforced concrete shear

walls (combined with moment frames,

outriggers, and megabraces)

Areas of Consensus

Wind tunnel testingProvisions for nonstructural componentsPerformance objectivesAnalysis proceduresExtent of three-dimensional modeling


Extent of three-dimensional modelingDesign seismic hazard levelsNumber of ground motion pairs used for NLRH analysis

Ground motion orientation relative to building

Inter-story drift limits

Items with Highest ScatterDamping specificationFlipping of ground motion pairsBackstay effectElastic stiffness modifiersComponent models for NLRH analysis


Component models for NLRH analysisAcceptance criteriaForce levels used to evaluate acceptance criteria

Two-Step DesignDetermine the strengths at nonlinear locations

using the building code requirements

• Code (DBE) level earthquake ÷ R factor

• Minimum base shear

All other actions are designed to remain elastic


All other actions are designed to remain elastic

under MCE level ground motions:

• Wall shear, shear friction, wall flexure outside of intended yield locations, floor and roof diaphragms and collectors and connections, foundation perimeter walls, etc.

Linear-Elastic Analysis


Effective Stiffness

Reduction by Reff

475y NL

475y linear response

RUTHERFORD & CHEKENERoof Displacement

2475y NL response

by Reff

Vmin

475y NL response

Effective Stiffness


Distribution of Effective Stiffness Values Used for Concrete Core Shear Walls

EFFECTIVE STIFFNESS

UCSD wall Elastic ETABS model

RUTHERFORD & CHEKENERUTHERFORD & CHEKENE

2000

4000

6000

8000

10000

Base M

om

en

t [k

ip-f

t]Experimental results

EQ3:

Essentially

linear


-10000

-8000

-6000

-4000

-2000

0

-17.5 -12.5 -7.5 -2.5 2.5 7.5 12.5 17.5

Roof Displacement [in]

Base M

om

en

t [k

ip-f

t]

EQ4: Non-linear

EQ3

2

4

6

8

Ro

of

Dis

pla

cem

en

t [i

n]

Wall: Eeff = 0.2Ec

Slab: Eeff = 0.1Ec


-8

-6

-4

-2

0

40 45 50 55 60

Time [s]

Ro

of

Dis

pla

cem

en

t [i

n]

UCSD Test

ETABS

EQ3

Wall: Eeff = 0.2Ec

Slab: Eeff = 0.1Ec

700

800

700

800

Experiment

ETABS

Mwall

700

800

Experiment

ETABS


0

100

200

300

400

500

600

0 5 10 15 20

Lateral Displacement [in]

Bu

ild

ing

He

igh

t [i

n]

Experiment

ETABS

0

100

200

300

400

500

600

0 2000 4000 6000 8000 10000

System Moment [kip-ft]

Bu

ild

ing

He

igh

t [i

n]

Mwall

Mn,exp

0

100

200

300

400

500

600

0 100 200 300

System Shear Force [kip]

Bu

ild

ing

He

igh

t [i

n]

2

4

6

8

Ro

of

Dis

pla

ce

me

nt

[in

]EQ3

Wall: Eeff = 0.8Ec

Slab: Eeff = 0.5Ec


-8

-6

-4

-2

0

2

40 45 50 55 60

Time [s]

Ro

of

Dis

pla

ce

me

nt

[in

]

UCSD Test

ETABS


Effective Stiffness


Effective Stiffness Values Used for Coupling Beams Together with Related Core Wall Values

Damping

Measured damping ratio vs building height

6

7

8

9

10

Dam

pin

g r

ati

o (

%)

Buildings, Steel

Buildings, SRC

Buildings, RC

Chimneys, RC


0

1

2

3

4

5

0 50 100 150 200 250 300 350 400 450

Height [m]

Dam

pin

g r

ati

o (

%)

Measured Damping Ratio vs Building Height (Satake et al.)

Nonlinear Modeling


Effective Stiffness

Element Effective Stiffness Value


Element

Core Walls 0.3 0.8 0.5 0.25 0.8 0.9

Basement Walls 0.2 / 0.5 1.0 0.3 / 1.0 0.5 / 1.0 1.0 0.5

Diaphragms* 0.2 / 0.5 0.25 0.3 / 1.0 0.1 / 0.7 0.5 0.5

2

4

6

8

10

Sh

ear

Fo

rce,

kip

s

Coupling Beam C8(0.50Ig, 0.15 EnergyFactor, Nominal Strength with ΩΩΩΩ0, FEMA strength

degradation)Test-…

Component Models


-10

-8

-6

-4

-2

0

2

-3 -2 -1 0 1 2 3

Sh

ear

Fo

rce,

kip

s

Deflection, in.

2

4

6

8

10

Sh

ear

Fo

rce,

kip

sCoupling Beam C8

(0.22Ig, LinearEnergyFactor, Expected strength)

Test-…

Component Models


-10

-8

-6

-4

-2

0

2

-3 -2 -1 0 1 2 3

Sh

ear

Fo

rce,

kip

s

Deflection, in.

Acceptance Criteria


Conventional Coupling Beam Rotation Limits

Diagonally Reinforced Coupling Beam Rotation Limits

Blind Prediction Results - EQ3 - Shear Force Envelope

First 4 teams of each category

5

6

7

Measured

UCSD test blind prediction


0

1

2

3

4

0 50 100 150 200 250 300 350

Shear Force (kips)

Flo

or

200

250

300

350

Bu

ild

ing

Heig

ht

[ft]

R&C_MAX_X

R&C_MAX_Y

EOR_MAX_X

EOR_MAX_Y

Effect of Modeling on Results

0

50

100

150

0.00% 0.20% 0.40% 0.60% 0.80% 1.00% 1.20% 1.40% 1.60% 1.80% 2.00%

Inter-Story Drift Ratio [%]

Bu

ild

ing

Heig

ht

[ft]

Plastic analysis – SEAOC seismic design examples, Volume 3


Capacity Design


CANTILEVER WALL


Plastic hinge location


COUPLED WALL

Plastic hinge locations


locations


Runs scaled from 0.1x MCE to 4x MCE


IDA Demands

750000

1000000

1250000

1500000

1750000

2000000

Pe

ak

Co

re M

om

en

t a

bo

ut

H1

(k

ip-f

t) maximum base moment versus maximum lateral roof displacement in the H1 direction (Stronger core direction)


0

250000

500000

750000

1000000

1250000

1500000

1750000

2000000

0 5 10 15 20 25 30 35 40 45

Peak Roof Displacement (ft)

Pe

ak

Co

re M

om

en

t a

bo

ut

H2

(k

ip-f

t)

IDA H1@7th

IDA H1@1st

MCE level

0

250000

500000

0 5 10 15 20 25 30 35 40 45

Peak Roof Displacement (ft)

Pe

ak

Co

re M

om

en

t a

bo

ut

H1

(k

ip-f

t)

IDA H2@7th

IDA H2@1st

MCE

level

direction)

maximum base moment versus maximum roof displacement in the H2 direction (Weaker core direction)

0.4

0.5

0.6

0.7

0.8

0.9

1.0

No

rma

lize

d E

ffe

cti

ve

He

igh

t (M

/V)/

H

IDA H1@7th

IDA H1@1st

IDA H2@7th

MCE level

Moment to Shear Ratio2/3

1/2


0.0

0.1

0.2

0.3

0.4

0 1 2 3 4

Ground-Motion Scale Factor

No

rma

lize

d E

ffe

cti

ve

He

igh

t (M

/V)/

H

Variation of location of resultant lateral force with increasing intensity

0

50

100

150

200

250

300

350

400

450

500

0 5000 10000 15000 20000 25000 30000 35000

Core Shear Force H1 (kips)

Bu

ild

ing

He

igh

t (f

t)

1.00xCC067

1.25xCC067

1.50xCC067

1.75xCC067

2.00xCC067

Capacity

Full Capacity

Preventing Shear Failure



0

50

100

150

200

250

300

350

400

450

500

0 5000 10000 15000 20000 25000 30000 35000


Bu

ild

ing

He

igh

t (f

t)

1.00xCC067

1.25xCC067

1.50xCC067

1.75xCC067

2.00xCC067

Capacity

Full Capacity

Incrementally-scaled NLRH analyses results in terms of maximum story shear force in both H1 (left) and H2 (right) directions, together with shear capacity

250

300

350

400

450

500

Bu

ild

ing

Heig

ht

(ft)

Yielding Outside Hinge Zone


0

50

100

150

200

-0.01 0 0.01 0.02 0.03

Strain in Corner N

Bu

ild

ing

Heig

ht

(ft)

Strain Profile over the Building Height at Different Time Steps

Tall Buildings Initiative

Initiative to advance design of tall buildings

Main participants

• PEER, SCEC, USGS, SFDBI, LADBS, FEMA

• ATC, LATBSDC, SEAOC, SEAONC

• Project Management Committee (T-PAC)


• Project Management Committee (T-PAC)– J. Moehle, Y. Bozorgnia

– N. Abrahamson, M. Lew, P. Somerville

– R. Hamburger, H. Krawinkler, M. Moore, F. Naeim

– R. Lui

Practice Needs (from PEER)

Structural DesignMinimum base shearCapacity design factorsInherent slab-outrigger effectStory mechanism protectionWall shear strengthEffective damping in NLRH analysisOther NLRH assumptions

• Applicable ground motions– (e.g., T = 9 sec)

• Ground motion scaling

• Input motions for subterranean levels

• Performance objectives


Other NLRH assumptionsEffective elastic stiffnessPodium force transferRational drift limitsP-delta modelingConcrete slab to core wall connectionsSteel framing to core wall connectionsDeep mat slab behaviorDual system requirements

Guidelines for Modeling and Acceptance CriteriaCore group – J. Malley, G. Deierlein, H. Krawinkler, J. Maffei, M.

Pourzanjani and J. Wallace

Approach: Workshop to identify key issues, assignments to experts to develop principles, procedures, and values.

• Key issues:– Basic principles, including capacity design


– Basic principles, including capacity design– General modeling issues (e.g., effective damping)

– Podium force transfer– Modeling of various systems and elements (core walls, frames, coupling beams, etc.)

– Foundation modeling (with Task 8)

Closing Remarks

Little focus on risk in practical applications of PBEE

Need for better guidelines (… or better enforcement?)


enforcement?)

Focus on better understanding of relation between parameters on performance of final product

Verify performance of existing structures

use of pbee in the design practice - reluis · use of pbee in the design practice marko schotanus...

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