B C l C tiBeam-Column Connections

Jack MoehleUniversity of California, Berkeley

with contributions from

Dawn Lehman and Laura LowesUniversity of Washington, Seattle

OutlineOutlinedesign of new jointsexisting joint detailsfailure of existing joints in earthquakesgeneral response characteristicsimportance of including joint deformationsimportance of including joint deformationsstiffnessstrengthstrengthdeformation capacityaxial failureaxial failure

Special Moment-Resisting Frames - Design intent -g

Vcol For seismic design, beam yieldingbeam yielding defines demands

wMpr

MprMpr

Beam

lVpVp

lc

lnbVp

Beam SectionMpr

Vcol

Joint demands T =

Vcol

Joint demandsC2 = Ts2

Ts1 = 1.25Asfy

Vb1 Vb2

Ts2 =C1 = Ts2

(b) internal stress resultants

1.25AsfyVcol

Vcol

acting on joint

(a) moments, shears, axial loads acting on joint

Ts1 C2

(c) joint shear

Vu =Vj = Ts1 + C1 - Vcol

Joint geometry(ACI Committee 352)(ACI Committee 352)

a) Interior A 1

c) Corner A 3

b) Exterior A 2A.1 A.3A.2

d) RoofI t i B 1

e) Roof E t i B 2

f) RoofC B 3Interior B.1 Exterior B.2 Corner B.3

ACI 352

Joint shear strength- code-conforming joints -- code-conforming joints -

hbfVV jcnu'φγφ ==

φ 0 85Values of γ (ACI 352)

φ = 0.85

Classification/type

interior exterior corner

Values of γ (ACI 352)

yp

cont. column 20 15 12

Roof 15 12 8

ACI 352

Joint Details - InteriorJoint Details Interior

h l ≥ 20dbhcol ≥ 20db

ACI 352

Joint Details - CornerJoint Details Corner≥ ldh

ACI 352

Code-conforming jointsCode conforming joints

Older-type beam-column connectionsOlder type beam column connections

Survey of existing buildingsSurvey of existing buildings

Mosier

Joint failuresJoint failures

Studies of older-type jointsStudies of older type joints

Lehman

Damage progressioninterior connectionsinterior connections

60

80

Yield of Beam Longitudinal R i f t

Spalling of Concrete Cover Longitudinal

Column Bar Exposed

Measurable residual cracks

20

40

hear

(K)

Reinforcement

-20

0

Col

umn

Sh

20% Reduction in Envelope

80

-60

-40

-80-6 -4 -2 0 2 4 6

Drift %Lehman

Effect of load historyinterior connectionsinterior connections

I l i l di hi t

k)

Envelope for standard cyclic history

Impulsive loading history

mn

Shea

r (k

Column Bar

y y

Col

um

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

Lehman

Damage at 5% driftStandard Loading Impulsive Loading

Damage at 5% drift

Lehman

Contributions to driftinterior connections

120

interior connections

100

on Beam

Column

60

80

Con

trib

utio

Bar Slip

Beam

40

Perc

ent C

Joint Shear

“J i h ll b d l d

0

20

Specimen CD15-14

“Joints shall be modeled as either stiff or rigid components.” (FEMA 356)

01 4 7 10 13 16 19 22 25 28 31 34

Cycle NumberLehman

Evaluation of FEMA-356 Modelinterior connectionsinterior connections

18

12

14

16

acto

r

8

10

12

hear

Fa

FEMA

4

6

8

Join

t S PEER-14CD15-14CD30-14PADH-14

0

2

4PEER-22CD30-22PADH-22

0 0.005 0.01 0.015 0.02 0.025 0.03

Joint Shear StrainLehman

Joint panel deformationsJoint panel deformations

Joint DeformationJoint Deformation

Joint shear stiffnessinterior connectionsinterior connections

12

Gc /5Gc

(MPa

)

10psifc ,20 '

Gc /8

psif20 '

stre

ss ( 10

8

6 psif10 '

0

psifc ,20

nt s

hear

4

2

psifc ,10

0.0000

0.005 0.010 0.015 0.020 0.025 0.030

Joint shear strain

Join

Lehman

Joint strengtheffect of beam yieldingeffect of beam yielding

1600

ss (p

si)

1200

1600

Yield

int S

tres

800

Joi

0

400Yield

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

Joint strength interior connections - lower/upper boundsinterior connections - lower/upper bounds

0 4Joint failure without i ldi

0.3

0.4 yielding near 25.5√f ’c

/fc’ 0.2vj

Failure forced into beams between 8 5√f ’ and 11√f ’

Joint Shear fc

0.1

j

Beam Hinging/

8.5√f c and 11√f cFailure

00 10 20 30 40 50 60

g gBeam Bar Slip

Λ

Lehman

Joint strengthinterior connectionsinterior connections

2500

3000

3500

psi) Joint Failures

1500

2000

2500

Stre

ss (p

500

1000

1500

Join

t S

psifc ,10 '

0

500

0 4000 8000 12000 16000

Beam Failures

Concrete Strength (psi)

Lehman

Joint deformabilityJoint deformability(p

si)

1200

1600

plastic drift capacity

t Stre

ss

800

1200vmax

plastic drift capacity

Join

t

4000.2vmaxenvelope

00 1 2 3 4 5 6

Drift (%)( )

Plastic drift capacityinterior connectionsinterior connections

25

30psif

v

c

jo ,'

int

10

15

20

0

5

10

0 0.01 0.02 0.03 0.04 0.05 0.060 0.01 0.02 0.03 0.04 0.05 0.06

plastic drift angle

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

Damage progressionexterior connectionsexterior connections

Pantelides, 2002

Joint behaviorexterior connectionsexterior connections

2 Clyde6 Clyde4 Clyde

psif

v jo ,'

int

15

10 4 Clyde5 Clyde5 Pantelides6 Pantelides6 HakutoPriestley longitudinal

fc 10

5Priestley longitudinalPriestley transverse

0 1 2 3 4 5 6 70

bidirectional loadingDrift, % loading

Plastic drift capacityPlastic drift capacity

25

30psif

v

c

jo ,'

intInteriorExterior

10

15

20

0

5

10

0 0.01 0.02 0.03 0.04 0.05 0.060 0.01 0.02 0.03 0.04 0.05 0.06

plastic drift angle

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

Exterior jointhook detailhook detail

hook bent into joint

hook bent out of joint

Interior joints with discontinuous barsdiscontinuous bars

C l40

Column shear, kips

30p

20

10

00 1 2 3 4 5

Drift ratio, %Beres, 1992

Unreinforced Joint StrengthUnreinforced Joint Strength

bhfV '

FEMA 356 specifies the following:

bhfV cj γ=

γjointgeometry

• No new data. Probably still valid.

• Assuming bars are anchored in j i t t th li it d b t th f

4

6

joint, strength limited by strength of framing members, with upper-bound of γ ≈ 15. For 15 ≥ γ ≥ 4, joint failure may occur after

A i b h d i

6

8

j yinelastic response. For γ ≤ 4, joint unlikely to fail.

• Assuming bars are anchored in joint, strength limited by strength of framing members, with upper bound of γ ≈ 25. For 25 ≥ γ ≥ 8,

10γ γ ,

joint failure may occur after inelastic response. For γ ≤ 8, joint unlikely to fail.

12

Joint failure?Joint failure?

σyττcr

ττcr

' 16 yccr f

στ −= psi'6 c

ccrf

f , psi

Joint failure?Joint failure?

L t l D fl tiLateral Deflection, mm

Loa

dLa

tera

l

Drift at “tensile failure”Drift at “tensile failure”

Drift at “axial failure”Drift at “lateral failure”

Priestley, 1994

Joint test summaryaxial failures identifiedaxial failures identified

Tests with axial load failure

0.08

0.1

}7 8 2

'cj fv γ=

0.06

0 08

ift ra

tio }Interior

0.03

-0.

0

0.10

-0.

1

0.20

-0.

2

Range of γ values

0.36

j

0.02

0.04Dr Interior

Exterior, hooks bent in

Exterior, hooks bent out

Corner

00 0.05 0.1 0.15 0.2 0.25 0.3

Corner

Axial load ratio

Suggested envelope relationinterior connections with continuous beam barsinterior connections with continuous beam bars

stiffness based on effective

psif

v jo ,'

int 25

20

0.015

f '

strength = beam strength b t t t d

stiffness to yield

fc 20

15

psifc ,25 'but not to exceed

10

58

00.04 0.02

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

Suggested envelope relationexterior connections with hooked beam barsexterior connections with hooked beam bars

tiff b d ff ti

psif

v jo ,'

int 25

20 strength = beam strength

stiffness based on effective stiffness to yield

fc 20

15 0.010

strength = beam strength but not to exceed psifc ,12 '

connections with demand less10

5

connections with demand less than have beam-yield mechanisms and do not follow this model

'4 cf

axial-load stability unknown, especially under high axial loads

00.02 0.01

p y g

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

Joint panel deformationsJoint panel deformations

Joint DeformationJoint Deformation

Methods of Repair (MOR)Methods of Repair (MOR)Method of Activities Damage

Repair Activities States0. Cosmetic Repair

Replace and repair finishes 0-2Repair1. Epoxy Injection Inject cracks with epoxy and

replace finishes3-5

2. Patching Patch spalled concrete, epoxy inject cracks and replace finishes

6-8

3. Replace concrete

Remove and replace damaged concrete, replace finishes

9-11

R l d d i f i4. Replace joint Replace damaged reinforcing steel, remove and replace concrete, and replace finishes

12

Pagni

Interior joint fragility relationsInterior joint fragility relations11

OR

0 70.80.9

0 70.80.9

ng a

MO

0 50.60.7

0 50.60.7

Req

uirin

0.30.40.5

MOR 0MOR 10.3

0.40.5

MOR 0MOR 1MOR 0MOR 1MOR 0MOR 1ili

ty o

f R Cosmetic repairEpoxy injectionPatching

0.10.2

MOR 1MOR 2MOR 3MOR 40.1

0.2MOR 1MOR 2MOR 3MOR 4

MOR 1MOR 2MOR 3MOR 4

MOR 1MOR 2MOR 3MOR 4Pr

obab

i PatchingReplace concreteReplace joint

0.0 1.0 2.0 3.0 4.0 5.0 6.00Drift (%)

0.0 1.0 2.0 3.0 4.0 5.0 6.00Drift (%)

P

B C l C tiBeam-Column Connections

Jack MoehleUniversity of California, Berkeley

with contributions from

Dawn Lehman and Laura LowesUniversity of Washington, Seattle

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

concrete building joints for seismic excitation,” Report No. PEER-2000/05, Pacific Earthquake Engineering Research Center University of California Berkeley 61 ppEngineering Research Center, University of California, Berkeley, 61 pp.

• Pantelides, C., J. Hansen, J. Nadauld, L Reaveley (2002, “Assessment of reinforced concrete building exterior joints with substandard details,” Report No. PEER-2002/18, Pacific Earthquake Engineering Research Center, University of California, 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, Journal of Earthquake Engineering, 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 and Displacement History on the Seismic Performance of Beam-Column Joints,” Proceedings, The Third US-Japan Workshop on Performance Based Earthquake Engineering Methodology for Reinforced ConcreteJapan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures, Seattle, USA, 16-18 August 2001, Report No. PEER-2002/02, Pacific Earthquake Engineering Research Center, University of California, Berkeley, pp. 349-362.

• Hakuto, S., R. Park, and H. Tanaka, “Seismic Load Tests on Interior and Exterior Beam-Column Joints with 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 withBeres, A., R.White, and P. Gergely, Seismic Behavior of Reinforced Concrete Frame Structures with Nonductile Details: Part I – Summary of Experimental Findings of Full Scale Beam-Column Joint Tests,” Report NCEER-92-0024, NCEER, State University of New York at Buffalo, 1992.

• Pessiki, S., C. Conley, P. Gergely, and R. White, “Seismic Behavior of Lightly-Reinforced Concrete Column and Beam Column Joint Details,” Report NCEER-90-0014, NCEER, State University of New York at Buffalo, 1990.

• ACI-ASCE Committee 352, Recommendations for Design of Beam-Column Connections in Monolithic Reinforced Concrete Structures,” American Concrete Institute, Farmington Hills, 2002.

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

Fragility functions:•Pagni C A and L N Lowes (2006) “Empirical Models for Predicting Earthquake Damage and RepairPagni, C.A. and L.N. Lowes (2006). Empirical Models for Predicting Earthquake Damage and Repair Requirements for Older Reinforced Concrete Beam-Column Joints.” Earthquake Spectra. In press.Joint element:•Lowes, L.N. and A. Altoontash. “Modeling the Response of Reinforced Concrete Beam-Column Joints.” Journal of Structural Engineering, ASCE. 129(12) (2003):1686-1697.•Mitra, N. and L.N. Lowes. “Evaluation, Calibration and Verification of a Reinforced Concrete Beam-Column Joint Model.” Journal of Structural Engineering, ASCE. Submitted July 2005. •Anderson, M.R. (2003). “Analytical Modeling of Existing Reinforced Concrete Beam-Column Joints” MSCE thesis, University of Washington, Seattle, 308 p.Analyses using joint model:•Theiss, A.G. “Modeling the Response of Older Reinforced Concrete Building Joints.” M.S. Thesis. Seattle: University of Washington (2005): 209 pSeattle: University of Washington (2005): 209 p.Experimental Research•Walker, S.*, Yeargin, C.*, Lehman, D.E., and Stanton, J. Seismic Performance of Non-Ductile Reinforced Concrete Beam-Column Joints, Structural Journal, American Concrete Institute, accepted for publication.•Walker, S.G. (2001). “Seismic Performance of Existing Reinforced Concrete Beam-Column Joints”.Walker, S.G. (2001). Seismic Performance of Existing Reinforced Concrete Beam Column Joints . MSCE Thesis, University of Washington, Seattle. 308 p.•Alire, D.A. (2002). "Seismic Evaluation of Existing Unconfined Reinforced Concrete Beam-Column Joints", MSCE thesis, University of Washington, Seattle, 250 p.•Infrastructure Review•Mosier, G. (2000). “Seismic Assessment of Reinforced Concrete Beam-Column Joints”. MSCE thesis, University of Washington, Seattle. 218 p.