Beam column connections

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1. Beam-Column Connections
Jack Moehle
University of California, Berkeley
with contributions from
Dawn Lehman and Laura Lowes
University of Washington, Seattle

2. 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

3. 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

4. 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
=
1.25A
s
f
y
C
2
= T
s2
T
s1
=
1.25A
s
f
y
C
1
= T
s2
V
col
V
col
V
b1
V
b2

5. 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

6. 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 -
hbfVV
jcnu
'
fgf==
f = 0.85
ACI 352

7. Joint Details - Interior
h
col
³ 20d
b
ACI 352

8. Joint Details - Corner
³ l
dh
ACI 352

9. Code-conforming joints

10. Older-type beam-column
connections

11. Survey of existing buildings

Mosier

12. Joint failures

13. Studies of older-type joints
Lehman

14. -80
-60
-40
-20
0
20
40
60
80
-6 -4 -2 0 2 4 6
Drift %
C
o
l
u
m
n

S
h
e
a
r

(
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

15. Effect of load history
interior connections
-6 -4 -2 0 2 4 6
Story Drift
C
o
l
u
m
n

S
h
e
a
r

(
k
)
Column Bar
Envelope for standard
cyclic history
Impulsive loading history
Lehman

16. Standard Loading Impulsive Loading
Damage at 5% drift
Lehman

17. Specimen CD15-14
Contributions to drift
interior connections
“Joints shall be modeled
as either stiff or rigid
components.” (FEMA 356)
Lehman

18. 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
J
o
in
t

S
h
e
a
r

F
a
c
t
o
r
FEMA
PEER-14
CD15-14
CD30-14
PADH-14
PEER-22
CD30-22
PADH-22
Lehman

19. Joint panel deformations
Joint Deformation

20. 0.000
0
12
G
c
/5G
c
Joint shear stiffness
interior connections
psif
c
,20
'
0.005 0.010 0.015 0.020 0.025 0.030
Joint shear strain
J
o
in
t

s
h
e
a
r

s
t
r
e
s
s

(
M
P
a
)
10
8
6
4
2
psif
c
,20
'
psif
c
,10
'
G
c
/8
Lehman

21. Joint strength
effect of beam yielding
J
o
in
t

S
t
r
e
s
s

(
p
s
i)
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

22. 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

23. Joint strength
interior connections
0
500
1000
1500
2000
2500
3000
3500
0 4000 8000 12000 16000
Concrete Strength (psi)
J
o
in
t

S
t
r
e
s
s

(
p
s
i)
Joint Failures
Beam Failures
psif
c
,10
'
Lehman

24. Joint deformability
J
o
in
t

S
t
r
e
s
s

(
p
s
i)
0
400
800
1200
1600
0 1 2 3 4 5 6
v
max
Drift (%)
0.2v
max
plastic drift capacity
envelope

25. Plastic drift capacity
interior connections
0
5
10
15
20
25
30
0 0.010.020.030.040.050.06
plastic drift angle
psi
f
v
c
jo
,
'
int
Note: the plastic drift angle includes inelastic deformations of the beams

26. Damage progression
exterior connections
Pantelides, 2002

27. 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

28. Plastic drift capacity
0
5
10
15
20
25
30
0 0.010.020.030.040.050.06
plastic drift angle
psi
f
v
c
jo
,
'
int
Note: the plastic drift angle includes inelastic deformations of the beams
Interior
Exterior

29. Exterior joint
hook detail
hook bent into joint
hook bent out of joint

30. Interior joints with
discontinuous bars
Column
shear,
kips
40
30
20
10
0
0 1 2 3 4 5
Drift ratio, %
Beres, 1992

31. •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
bhfV
cj
'
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.

32. Joint failure?
s
y
t
cr
t
cr
'
'
6
16
c
y
ccr
f
f
s
t -=
, psi

33. Joint failure?
Drift at “tensile failure”
Drift at “axial failure”
L
a
t
e
r
a
l
L
o
a
d
Lateral Deflection, mm
Drift at “lateral failure”
Priestley, 1994

34. 0
0.02
0.04
0.06
0.08
0.1
0 0.050.10.150.20.250.3
Axial load ratio
D
r
i
f
t

r
a
t
i
o }
Interior
0
.
0
3

-

0
.
0
7
0
.
1
0

-

0
.
1
8
0
.
2
0

-

0
.
2
2
Range of g values
Joint test summary
axial failures identified
Tests with axial load failure
0
.
3
6
Exterior, hooks bent in
Exterior, hooks bent out
Corner
'
cj
fvg=

35. 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
psif
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

36. 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
0.020.01
strength = beam strength
but not to exceed psif
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
cf
Note: the plastic drift angle includes inelastic deformations of the beams

37. Joint panel deformations
Joint Deformation

38. Methods of Repair (MOR)
Method of
Repair
Activities
Damage
States
0. Cosmetic
Repair
Replace and repair finishes 0-2
1. Epoxy InjectionInject 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 jointReplace damaged reinforcing
steel, remove and replace
concrete, and replace finishes
12
Pagni

39. Interior joint fragility relations
0.01.02.03.04.05.06.0
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
0.01.02.03.04.05.06.0
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
P
r
o
b
a
b
i
l
i
t
y
o
f

R
e
q
u
i
r
i
n
g

a
M
O
R"$%)
)',%
-%
)%%%
)%,
Cosmetic repair
Epoxy injection
Patching
Replace concrete
Replace joint

40. Beam-Column Connections
Jack Moehle
University of California, Berkeley
with contributions from
Dawn Lehman and Laura Lowes
University of Washington, Seattle

41. 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.

42. 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.