joints - moehle c

8/3/2019 Joints - Moehle c

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Beam-Column Connections

Jack MoehleUniversity of California, Berkeley

with contributions from

Dawn Lehman and Laura LowesUniversity of Washington, Seattle


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Outline

design of new joints

existing joint details

failure of existing joints in earthquakes

general response characteristics

importance of including joint deformations

stiffness

strengthdeformation capacity

axial failure


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Special Moment-Resisting Frames- Design intent -

Beam

Beam Section

lnbVp

w

MprMpr

Vp

Mpr

Vp

Mpr

lc

Vcol

Vcol

For seismic design,beam yieldingdefines demands


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Joint demands

(a) moments, shears, axialloads acting on joint

(c) joint shear

Vcol

Ts1 C2

Vu =Vj = Ts1 + C1 - Vcol

(b) internal stress resultantsacting on joint

Ts2 =

1.25Asfy

C2 = Ts2

Ts1 =1.25Asfy

C1 = Ts2

Vcol

Vcol

Vb1 Vb2


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Joint geometry(ACI Committee 352)

a) Interior

A.1

c) Corner

A.3

b) Exterior

A.2

d) Roof

Interior B.1

e) Roof

Exterior B.2

f) Roof

Corner B.3

ACI 352


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Classification

/typeinterior exterior corner

cont. column 20 15 12

Roof 15 12 8

Values ofK (ACI 352)

Joint shear strength- code-conforming joints -

hbfVV jcnu'JKJ !!

J = 0.85

ACI 352


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Joint Details - Interior

hcol u 20db

ACI 352


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Joint Details - Corneru ldh

ACI 352


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Code-conforming joints


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Older-type beam-column connections


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Survey of existing buildings

Mosier


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Joint failures


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Studies of older-type joints

Lehman


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-80

-60

-40

-20

0

20

40

60

80

-6 -4 -2 0 2 4 6

Drift %

ColumnShear(K)

Yield of Beam

Longitudinal

Reinforcement

Spalling of

Concrete Cover Longitudinal

Column Bar

Exposed

Measurable

residual cracks

20% Reduction

in Envelope

Damage progressioninterior connections

Lehman


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Effect of load historyinterior connections

-6 -4 -2 0 2 4 6Story Drift

ColumnShear

(k)

Column Bar

Envelope for standardcyclic history

Impulsive loading history

Lehman


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Standard Loading Impulsive Loading

Damage at 5% drift

Lehman


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0

20

40

60

80

100

120

1 4 7 10 13 16 19 22 25 28 31 34

Cycle Number

P

ercentContribution

Joint Shear

Bar Slip

Beam

Column

Specimen CD15-14

Contributions to driftinterior connections

Joints shall be modeledas either stiff or rigidcomponents. (FEMA 356)

Lehman


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Evaluation of FEMA-356 Modelinterior connections

0

2

4

6

8

1012

14

16

18

0 0.005 0.01 0.015 0.02 0.025 0.03

Joint Shear Strain

J

ointShearF

actor

FEMA

PEER-14

CD15-14

CD30-14

PADH-14PEER-22

CD30-22

PADH-22

Lehman


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Joint panel deformations

Joint Deformation


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0.0000

12

Gc/5Gc

Joint shear stiffnessinterior connections

psifc,20 '

0.005 0.010 0.015 0.020 0.025 0.030

Joint shear strainJoint

shearstress

(MPa)

108

6

4

2

psifc,20 '

psifc,10 '

Gc/8

Lehman


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Joint strengtheffect of beam yielding

JointStre

ss(psi)

0

400

800

1200

1600

0 1 2 3 4 5 6

Drift (%)

Joint strength closely linked to beam flexural strength Plastic deformation capacity higher for lower joint shear

Lehman

Yield

Yield


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Joint strengthinterior connections - lower/upper bounds

/fc

0

0.1

0.3

0.4

0 10 20 30 40 50 60

0

0.2vj

Beam Hinging/Beam Bar Slip

Failure forced intobeams between8.5f

cand 11f

c

JointShearFailure

Joint failure withoutyielding near25.5f

c

Lehman


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Joint strengthinteriorconnections

0

500

1000

1500

2000

2500

3000

3500

0 4000 8000 12000 16000

Concrete Strength (psi)

JointStress

(psi) Joint Failures

Beam Failurespsifc

,

10

'

Lehman


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Joint deformability

JointStress

(psi)

0

400

800

1200

1600

0 1 2 3 4 5 6

vmax

Drift (%)

0.2vmax

plastic drift capacity

envelope


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Plastic drift capacityinterior connections

0

5

10

1520

25

30

0 0.01 0.02 0.03 0.04 0.05 0.06

plastic drift angle

psif

v

c

jo,

'

int

Note: the plastic drift angle includes inelastic deformations of the beams


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Damage progressionexterior connections

Pantelides, 2002


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Joint behaviorexteriorconnections

2 Clyde6 Clyde4 Clyde

5 Clyde5 Pantelides6 Pantelides6 HakutoPriestley longitudinalPriestley transverse

psif

v

c

jo,

'

int

15

0 1 2 3 4 5 6 7

10

5

0

Drift, %

bidirectional

loading


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Plastic drift capacity

0

5

10

1520

25

30

0 0.01 0.02 0.03 0.04 0.05 0.06

plastic drift angle

psif

v

c

jo,

'

int


InteriorExterior


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Exterior jointhook detail

hook bent into joint

hook bent out of joint


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Interior joints withdiscontinuous bars

Columnshear,kips

40

30

20

10

00 1 2 3 4 5

Drift ratio, %Beres, 1992


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Assuming bars are anchored injoint, strength limited by strength offraming members, with upperbound ofK } 25. For 25 K 8,joint failure may occur afterinelastic response. ForK 8, joint

unlikely to fail.

Unreinforced Joint Strength

bhfVcj

'K!

Kjoint

geometry

4

6

10

8

12

FEMA 356 specifies the following:

No new data. Probably still valid.

Assuming bars are anchored injoint, strength limited by strength offraming members, with upper-bound ofK } 15. For 15 K 4,joint failure may occur afterinelastic response. ForK 4, jointunlikely to fail.


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Joint failure?

WyXcr

Xcr

'

'

6

16

c

y

ccr

ff

W

X ! , psi


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Joint failure?

Drift at tensile failure

Drift at axial failure

LateralLoad

Lateral Deflection, mm

Drift at lateral failure

Priestley, 1994


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0

0.02

0.04

0.06

0.08

0.1

0 0.05 0.1 0.15 0.2 0.25 0.3

Axial load ratio

Driftratio }

Interior

0.0

3-0.0

7

0.1

0-0.1

8

0.2

0-0.2

2

Range ofK values

Joint test summaryaxial failures identified

Tests with axial load failure

0.3

6

Exterior, hooks bent in

Exterior, hooks bent out

Corner

'

cj fv K!


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Suggested envelope relationinterior connections with continuous beam bars

psif

v

c

jo,

'

int 25

20

15

10

5

0

0.015

0.04 0.02

8

psifc

,25'

strength = beam strengthbut not to exceed

stiffness based on effectivestiffness to yield



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axial-load stability unknown,especially under high axial loads

Suggested envelope relationexterior connections with hooked beam bars

psif

v

c

jo,

'

int 25

20

15

10

5

0

0.010

0.02 0.01

strength = beam strength

but not to exceed psifc ,12'

stiffness based on effectivestiffness to yield

connections with demand lessthan have beam-yieldmechanisms and do not follow

this model

'4c

f



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Joint panel deformations

Joint Deformation


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Methods of Repair (MOR)

Method ofRepair

ActivitiesDamageStates

0. CosmeticRepair

Replace and repair finishes 0-2

1. Epoxy Injection Inject cracks with epoxy andreplace finishes

3-5

2. Patching Patch spalled concrete, epoxyinject cracks and replace

finishes

6-8

3. Replaceconcrete

Remove and replace damagedconcrete, replace finishes

9-11

4. Replace joint Replace damaged reinforcingsteel, remove and replace

concrete, and replace finishes

12

Pagni


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Interior joint fragility relations

0.0 1.0 2.0 3.0 4.0 5.0 6.00

0.1

0.20.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Drift (%)

MOR 0

MOR 1MOR 2MOR 3MOR 4

0.0 1.0 2.0 3.0 4.0 5.0 6.00

0.1

0.20.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Drift (%)

MOR 0


MOR 0


MOR 0


ProbabilityofRequiringaMOR

Cosmetic repairEpoxy injection

PatchingReplace concreteReplace joint


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Beam-Column Connections

Jack MoehleUniversity of California, Berkeley

with contributions from

Dawn Lehman and Laura LowesUniversity of Washington, Seattle


41/42

References Clyde, C., C. Pantelides, and L. Reaveley (2000), Performance-based evaluation of exterior reinforced

concrete building joints for seismic excitation, ReportNo.PEER-2000/05, Pacific EarthquakeEngineering Research Center, University ofCalifornia, Berkeley, 61 pp.

Pantelides, C., J. Hansen, J. Nadauld, L Reaveley (2002, Assessment of reinforced concrete buildingexterior joints with substandard details, ReportNo.PEER-2002/18, Pacific Earthquake EngineeringResearchCenter, University ofCalifornia, Berkeley, 103 pp.

Park, R. (2002), "A Summary of Results of Simulated Seismic Load Tests on Reinforced Concrete Beam-Column Joints, Beams and Columns with Substandard Reinforcing Details, JournalofEarthquakeEngineering, Vol. 6, No. 2, pp. 147-174.

Priestley, M., and G. Hart (1994), Seismic Behavior of As-Built and As-Designed Corner Joints,SEQAD Report to Hart Consultant Group, Report#94-09, 93 pp. plus appendices.

Walker, S., C. Yeargin, D. Lehman, and J. Stanton (2002), Influence of Joint Shear Stress Demand andDisplacement History on the Seismic Performance ofBeam-Column Joints, Proceedings, The Third US-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced ConcreteBuilding Structures, Seattle, USA, 16-18 August 2001, ReportNo.PEER-2002/02, Pacific EarthquakeEngineering Research Center, University ofCalifornia, Berkeley, pp. 349-362.

Hakuto, S., R. Park, and H. Tanaka, Seismic Load Tests on Interior and ExteriorBeam-Column Jointswith Substandard Reinforcing Details, ACI Structural Journal, Vol. 97, No. 1, January 2000, pp. 11-25.

Beres, A., R.White, and P. Gergely, Seismic Behavior of Reinforced Concrete Frame Structures withNonductile Details: Part I Summary of Experimental Findings of Full Scale Beam-Column Joint Tests,Report NCEER-92-0024, NCEER, State University ofNew York at Buffalo, 1992.

Pessiki, S., C. Conley, P. Gergely, and R. White, Seismic Behavior of Lightly-Reinforced ConcreteColumn and Beam Column Joint Details, Report NCEER-90-0014, NCEER, State University ofNewYork at Buffalo, 1990.

ACI-ASCE Committee 352, Recommendations for Design ofBeam-Column Connections in MonolithicReinforced Concrete Structures, American Concrete Institute, Farmington Hills, 2002.


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References (continued) D. Lehman, University ofWashington, personal communication, based on the following resources:

Fragilityfunctions:

Pagni, C.A. and L.N. Lowes (2006). Empirical Models for Predicting Earthquake Damage and RepairRequirements for Older Reinforced Concrete Beam-Column Joints. Earthquake Spectra. In press.Jointelement:

Lowes, L.N. and A. Altoontash. Modeling the Response of Reinforced Concrete Beam-Column Joints.JournalofStructuralEngineering,ASCE. 129(12) (2003):1686-1697.Mitra, N. and L.N. Lowes. Evaluation, Calibration and Verification of a Reinforced Concrete Beam-Column Joint Model. JournalofStructuralEngineering,ASCE. Submitted July 2005.Anderson, M.R. (2003). Analytical Modeling of Existing Reinforced Concrete Beam-Column JointsMSCE thesis, University ofWashington, Seattle, 308 p.Analysesusingjointmodel:

Theiss, A.G. Modeling the Response of Older Reinforced Concrete Building Joints. M.S. Thesis.Seattle: University ofWashington (2005): 209 p.ExperimentalResearch

Walker, S.*, Yeargin, C.*, Lehman, D.E., and Stanton, J. Seismic Performance ofNon-DuctileReinforced Concrete Beam-Column Joints, StructuralJournal,American Concrete Institute, acceptedfor publication.

Walker, S.G. (2001). Seismic Performance of Existing Reinforced Concrete Beam-Column Joints.MSCE Thesis, University ofWashington, Seattle. 308 p.Alire, D.A. (2002). "Seismic Evaluation of Existing Unconfined Reinforced Concrete Beam-ColumnJoints", MSCE thesis, University ofWashington, Seattle, 250 p.Infrastructure ReviewMosier, G. (2000). Seismic Assessment of Reinforced Concrete Beam-Column Joints. MSCE thesis,University ofWashington, Seattle. 218 p.

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