Beam

Column Connections
Jack Moehle
University of California, Berkeley
with contributions from
Dawn Lehman and Laura Lowes
University of Washington, Seattle
Outline
design of new joints
existing joint details
failure of existing joints in earthquakes
general response characteristics
importance of including joint deformations
stiffness
strength
deformation capacity
axial failure
Special Moment

Resisting Frames

Design intent

Beam
Beam Section
l
nb
V
p
w
M
pr
M
pr
V
p
M
pr
V
p
M
pr
l
c
V
col
V
col
For seismic design,
beam yielding
defines demands
Joint demands
(a) moments, shears, axial
loads acting on joint
(c) joint shear
V
col
T
s1
C
2
V
u
=V
j
=
Ts1 + C
1

V
col
(b) internal stress resultants
acting on joint
T
s2
=
1.25
A
s
f
y
C
2
=
T
s2
T
s1
=
1.25
A
s
f
y
C
1
=
T
s2
V
col
V
col
V
b1
V
b2
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
Classification
/type
interior
exterior
corner
cont. column
20
15
12
Roof
15
12
8
Values of
g
(ACI 352)
Joint shear strength

code

conforming joints

h
b
f
V
V
j
c
n
u
'
g
= 0.85
ACI 352
Joint Details

Interior
h
col
20
d
b
ACI 352
Joint Details

Corner
l
dh
ACI 352
Code

conforming joints
Older

type beam

column connections
Survey of existing buildings
Mosier
Joint failures
Studies of older

type joints
Lehman
80
60
40
20
0
20
40
60
80
6
4
2
0
2
4
6
Drift %
Column Shear (K)
Yield of Beam
Longitudinal
Reinforcement
Spalling of
Concrete Cover
Longitudinal
Column Bar
Exposed
Measurable
residual cracks
20% Reduction
in Envelope
Damage progression
interior connections
Lehman
Effect of load history
interior connections

6

4

2
0
2
4
6
Story Drift
Column Shear (k)
Column Bar
Envelope for standard
cyclic history
Impulsive loading history
Lehman
Standard Loading
Impulsive Loading
Damage at 5% drift
Lehman
0
20
40
60
80
100
120
1
4
7
10
13
16
19
22
25
28
31
34
Cycle Number
Percent Contribution
Jo
int Shear
Bar Slip
Beam
Flexur
e
Column
Specimen CD15

14
Contributions to drift
interior connections
“Joints shall be modeled
as either stiff or rigid
components.” (FEMA 356)
Lehman
Evaluation of FEMA

356 Model
interior connections
0
2
4
6
8
10
12
14
16
18
0
0.005
0.01
0.015
0.02
0.025
0.03
Joint Shear Strain
Joint Shear Factor
FEMA
PEER

14
CD15

14
CD30

14
PADH

14
PEER

22
CD30

22
PADH

22
Lehman
Joint panel deformations
Joint Deformation
0.000
0
12
G
c
/5
G
c
Joint shear stiffness
interior connections
psi
f
c
,
20
'
0.005
0.010
0.015
0.020
0.025
0.030
Joint shear strain
Joint shear stress (MPa)
10
8
6
4
2
psi
f
c
,
20
'
psi
f
c
,
10
'
G
c
/8
Lehman
Joint strength
effect of beam yielding
Joint Stress (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
Joint strength
interior connections

lower/upper bounds
/f
c
’
0
0.1
0.3
0.4
0
10
20
30
40
50
60
L
0.2
v
j
Beam Hinging/
Beam Bar Slip
Failure forced into
beams between
8.5
√
f’
c
and
11
√
f’
c
Joint
Shear
Failure
Joint failure without
yielding near
25.5
√
f’
c
Lehman
Joint strength
interior connections
0
500
1000
1500
2000
2500
3000
3500
0
4000
8000
12000
16000
Concrete Strength (psi)
Joint Stress (psi)
Joint Failures
Beam Failures
psi
f
c
,
10
'
Lehman
Joint deformability
Joint Stress (psi)
0
400
800
1200
1600
0
1
2
3
4
5
6
v
max
Drift (%)
0.2
v
max
plastic drift capacity
envelope
Plastic drift capacity
interior connections
0
5
10
15
20
25
30
0
0.01
0.02
0.03
0.04
0.05
0.06
plastic drift angle
psi
f
v
c
jo
,
'
int
Note: the plastic drift angle includes inelastic deformations of the beams
Damage progression
exterior connections
Pantelides, 2002
Joint behavior
exterior connections
2 Clyde
6 Clyde
4 Clyde
5 Clyde
5 Pantelides
6 Pantelides
6 Hakuto
Priestley longitudinal
Priestley transverse
psi
f
v
c
jo
,
'
int
15
0
1
2
3
4
5
6
7
10
5
0
Drift, %
bidirectional
loading
Plastic drift capacity
0
5
10
15
20
25
30
0
0.01
0.02
0.03
0.04
0.05
0.06
plastic drift angle
psi
f
v
c
jo
,
'
int
Note: the plastic drift angle includes inelastic deformations of the beams
Interior
Exterior
Exterior joint
hook detail
hook bent into joint
hook bent out of joint
Interior joints with
discontinuous bars
Column
shear,
kips
40
30
20
10
0
0
1
2
3
4
5
Drift ratio, %
Beres, 1992
•
Assuming bars are anchored in
joint, strength limited by strength of
framing members, with upper
bound of
g
25. For 25 ≥
g
≥ 8,
joint failure may occur after
inelastic response. For
g
≤ 8, joint
unlikely to fail.
Unreinforced Joint Strength
bh
f
V
c
j
'
g
g
joint
geometry
4
6
10
8
12
FEMA 356 specifies the following:
•
No new data. Probably still valid.
•
Assuming bars are anchored in
joint, strength limited by strength of
framing members, with upper

bound of
g
15. For 15
≥
g
≥ 4,
joint failure may occur after
inelastic response. For
g
≤ 4, joint
unlikely to fail.
Joint failure?
s
y
t
cr
t
cr
'
'
6
1
6
c
y
c
cr
f
f
s
t
, psi
Joint failure?
Drift at “tensile failure”
Drift at “axial failure”
Lateral Load
Lateral Deflection, mm
Drift at “lateral failure”
Priestley, 1994
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
Drift ratio
}
Interior
0.03

0.07
0.10

0.18
0.20

0.22
Range of
g
values
Joint test summary
axial failures identified
Tests with axial load failure
0.36
Exterior, hooks bent in
Exterior, hooks bent out
Corner
'
c
j
f
v
g
Suggested envelope relation
interior connections with continuous beam bars
psi
f
v
c
jo
,
'
int
25
20
15
10
5
0
0.015
0.04
0.02
8
psi
f
c
,
25
'
strength = beam strength
but not to exceed
stiffness based on effective
stiffness to yield
Note: the plastic drift angle includes inelastic deformations of the beams
axial

load stability unknown,
especially under high axial loads
Suggested envelope relation
exterior connections with hooked beam bars
psi
f
v
c
jo
,
'
int
25
20
15
10
5
0
0.010
0.02
0.01
strength = beam strength
but not to exceed
psi
f
c
,
12
'
stiffness based on effective
stiffness to yield
connections with demand less
than have beam

yield
mechanisms and do not follow
this model
'
4
c
f
Note: the plastic drift angle includes inelastic deformations of the beams
Joint panel deformations
Joint Deformation
Methods of Repair (MOR)
Method of
Repair
Activities
Damage
States
0. Cosmetic
Repair
Replace and repair finishes
0

2
1. Epoxy Injection
Inject cracks with epoxy and
replace finishes
3

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
4. Replace joint
Replace damaged reinforcing
steel, remove and replace
concrete, and replace finishes
12
Pagni
Interior joint fragility relations
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Drift (%)
MOR 0
MOR 1
MOR 2
MOR 3
MOR 4
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Drift (%)
MOR 0
MOR 1
MOR 2
MOR 3
MOR 4
MOR 0
MOR 1
MOR 2
MOR 3
MOR 4
MOR 0
MOR 1
MOR 2
MOR 3
MOR 4
Probability of Requiring a MOR
Cosmetic repair
Epoxy injection
Patching
Replace concrete
Replace joint
Beam

Column Connections
Jack Moehle
University of California, Berkeley
with contributions from
Dawn Lehman and Laura Lowes
University of Washington, Seattle
References
•
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 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 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 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)
•
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 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 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”.
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.
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