Joints - Moehle c
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Transcript of 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
Note: the plastic drift angle includes inelastic deformations of the beams
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
Note: the plastic drift angle includes inelastic deformations of the beams
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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
Note: the plastic drift angle includes inelastic deformations of the beams
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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 1MOR 2MOR 3MOR 4
MOR 0
MOR 1MOR 2MOR 3MOR 4
MOR 0
MOR 1MOR 2MOR 3MOR 4
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
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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.