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
lnb
Vp
w
Mpr
Mpr
Vp
Mpr
Vp
Mpr
lc
Vcol
Vcol
For seismic design,
beam yielding
defines demands
15. Effect of load history
interior connections
-6 -4 -2 0 2 4 6
Story Drift
ColumnShear(k)
Column Bar
Envelope for standard
cyclic history
Impulsive loading history
Lehman
25. 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
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 0.01 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
31. • Assuming bars are anchored in
joint, strength limited by strength of
framing members, with upper
bound of γ ≈ 25. For 25 ≥ γ ≥ 8,
joint failure may occur after inelastic
response. For γ ≤ 8, joint unlikely to
fail.
Unreinforced Joint Strength
bhfV cj
'
γ=
γjoint
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 γ ≈ 15. For 15 ≥ γ ≥ 4,
joint failure may occur after inelastic
response. For γ ≤ 4, joint unlikely to
fail.
33. Joint failure?
Drift at “tensile failure”
Drift at “axial failure”
LateralLoad
Lateral Deflection, mm
Drift at “lateral failure”
Priestley, 1994
34. 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
0.03-0.07
0.10-0.18
0.20-0.22
Range of γ values
Joint test summary
axial failures identified
Tests with axial load failure
0.36
Exterior, hooks bent in
Exterior, hooks bent out
Corner
'
cj fv γ=
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
psifc ,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
0.02 0.01
strength = beam strength
but not to exceed psifc ,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
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.
Editor's Notes
<number>
Describe how the joint demands are obtained. Sketch in the beam Mp values, then the corresponding beam shears. Note that the newer 352 document, under ballot, uses the slab effective width in tension as we talked about previously. The vertical line through the joint is to represent the column, use statics to estimate the column shear. Show actions on the joint.
<number>
Never really covered this one, though we have talked about how the boundary conditions around a joint affect strength.
<number>
Self explanatory. I would show this transparency, then sketch in the geometries.
<number>
Define the values of joint shear strength
<number>
The figure show the reference specimen. Approximately 2/3 of full scale. An interior joint in an exterior frame. And was constructed without transverse beams. The longitudinal bars in the columns and beams have been grooved to permit placing the strain guages and minimize distrubance ot bond capacity.
This photograph shows the specimen in the laboratory. The specimen was tested by loading the beams. The dipslacement history is indicated. We subjected the specimen to increasing levels of drift including drifts of 0.5%, 1%, 1.5%, 2%, 3%, 4%, and 5%.
The specimen was not expected to loose axial load carrying capacity unless the bars buckled. However, the tests would be carried out until loss of the majority of the lateral load carrying capacity
<number>
The column force-drift response of the specimen is indicated. We note a significant decrease in strength from cycle 1 to cycle 2 at a drift of 3%. In additon, we see that the energy dissipation capacity of the subassemblage is reduced relative to a “ductile” response.
It is instructive to consider the damage at various drift levels.
At 0.5% drift (yield of the longitudinal bars occurred between drift of 0.5% and 0.75%), we not cracking in the joint region. After the first cycle to 3% drift, we see significant damage to the joint region. And at 5% drift we see more extensive damage to the joint region as well as damage to the beams and the columns.
Therefore, although the performance of the joint may not meet the expectation for a new joint, for an existing joint, we would expect the joint to sustain the lateral load carrying capacity until a drift of 3% and it axial load carrying capacity was sustained throughout, even cycling to 5% drift 5 times. These results have significant implications for the need to retrofit or not retrofit the joints.
<number>
Note that the tension force is 1.25 fy, for seismic. The compression force balances the tension force. On the right, show the joint shear.
