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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.