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7/31/2019 Park Japan Presentation Final
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Analytical and Experimental Study onAnalytical and Experimental Study onAnalytical and Experimental Study onAnalytical and Experimental Study onAnalytical and Experimental Study onAnalytical and Experimental Study onAnalytical and Experimental Study onAnalytical and Experimental Study on
R/C Exterior BeamR/C Exterior BeamR/C Exterior BeamR/C Exterior BeamR/C Exterior BeamR/C Exterior BeamR/C Exterior BeamR/C Exterior Beam--------Column JointsColumn JointsColumn JointsColumn JointsColumn JointsColumn JointsColumn JointsColumn Joints
without Transverse Reinforcementwithout Transverse Reinforcementwithout Transverse Reinforcementwithout Transverse Reinforcementwithout Transverse Reinforcementwithout Transverse Reinforcementwithout Transverse Reinforcementwithout Transverse Reinforcement
Sangjoon Park, Ph.D Candidate
Khalid Mosalam, Prof. & Vice Chair
UC Berkeley
5th ICEE, Tokyo, Japan, March 3-5, 2010
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MotivationMotivation
Seismic performance of old existing RC building joints
- No seismic design code prior to 1970s
- No transverse reinforcement in the joint region
Brittle failure and collapse
Lateral displacement
Lateralf
orce
Beam flexural failure
Joint shear failure
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MotivationMotivation
Existing joint strength models and suggestions
- Inappropriate application from reinforcedjoints to unreinforcedjoints
- Overly simplified failure mechanism
- Underestimation of shear strength (ASCE41)
'
c
proposed,j
f
v
'
c
test,j
f
v
0
2
4
6
8
10
12
14
16
0 2 4 6 8 10 12 14 16
)psi('
ccjjj fhbVv ==
joint
geometry
4
6
8
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Unreinforced exterior joint tests w/o or w/ one lateral beam
Anchorage details of selected specimens
Column width (bc) beam width (b
b)
62 test data are collected
Failure mode: J (joint shear failure without beam yielding)
BJ (joint shear failure with beam yielding)
Database of Previous TestsDatabase of Previous Tests
Type A Type B Type C Type D
(a) (b) (c)
or
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Developed SemiDeveloped Semi--Empirical ModelEmpirical Model
0
0.2
0.4
0.6
0.8
1
1.2
0.8 1 1.2 1.4 1.6 1.8 2 2.2
H
h
f
f
hb
A b
c
y
cj
s 85.01'
low aspect ratio,
high aspect ratio,
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Joint aspect ratio, hb/hc
c
b'
ccj
jh
h
h
a
fhbV
085.031.1
cos2+
=
Beam reinforcement index
H
h
fhb
fAb
ccj
ys85.01
'
=
H
hfA
fhb
Vb
ys
ccj
jh85.01
'
25.11.0factorthoverstreng:
'
ccj
jh
fhb
V
Ymax=X2
Ymin=1.25X1
X1
X2
Proposed
Model
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Developed Analytical ModelDeveloped Analytical Model
21 STjh,STjh,jh VVV += ( )==h
l
ssjhjh,ST1 dxfnfAVV0
bs
( )c
l
sjhjh,ST2 VdxfnVVh
== 0b)1(
)( sf
ST1ST2
Asfs
1jh,STV
fy fpfs : tensile stress of beam reinforcement
: Bond strength
E
Y
R
Lehman & Moehle (2000)
CEB-FIP (1990)
]psi[12'
cf
]psi[6'
cf
]psi[8.1'
cf
Vc
( )
=
s
l
s
b f
df
h.H
Hh
0
b
x41
850
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Developed Analytical ModelDeveloped Analytical Model
No
Input:
hsbc
cbbyc
lAHh
bhbff
,,,,
,,,,,'
Calculate: fo ,fp ,fr,
1 , 2 , Vjh,ST1,max
Assume:fs,i
Determine: i
Calculate: Vjh,i , Vjh,ST1,i
Check: Vjh,ST1,iVjh,ST1,maxCheck: fs,i < foYes
Define: Vjh,i =Asfo(1-0.85hb/H)
Yes
NoDefine: Vjh = Vjh,i
End
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Predictions by Proposed ModelsPredictions by Proposed Models
0
50
100
150
200
250
300
0 50 100 150 200 250 300
(a) Semi-Empirical
Vjh,test
[kip]
MEAN = 0.98
COV = 0.15
0
50
100
150
200
250
300
0 50 100 150 200 250 300
(b) Analytical
Vjh,test
[kip]
MEAN = 0.97
COV = 0.16
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For More DetailsFor More Details
PEER Report 2009/106
http://peer.berkeley.edu/publications/peer_reports/reports_2009/web_PEER9106_PARK_Mosalam.pdf
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Experimental ProgramExperimental Program
For All Specimens:
Target concrete strength: f'c = 24 MPa (3.5 ksi)
Reinforcing bars nominal yield strength: fy = 414 MPa (Grade 60)
1. Test matrix Beam Section (A-A)
Column Section (B-B)
SP1&2 SP3&4
18"
18"
8-#8
hoop #3@3''
8-D25
D10@76mm457
457
18"
18"
8-#8
hoop #3@3''
8-D32
D10@76mm457
457
AspectRatio
SP1 SP2
SP3
18"
16"
4-#8
4-#7
stirrup
#3@3''
18"
16"
4-#6
4-#6
stirrup
#3@3''
4-D19
4-D19D10@76mm
4-D25
4-D22D10@76mm
457 457
406 406
Reinforcement Ratio
30"
16"
4-#6
4-#6#3
stirrup
#3@3''30"
16"
4-#8
4-#7#3
stirrup
#3@3''
4-D19
4-D19
D10@76mm
4-D25
4-D22
D10@76mm762
406 406
762
top and bottom slab reinforcement : D10@305mm
B B
A
A
L=2.44m
H=3.6
8m
SP4 (in progress)
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Experimental ProgramExperimental Program
2. Construction
EW direction
76.2mm
38.1mm
NS direction
50.8mm
63.5mm
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Experimental ProgramExperimental Program
3. Loading Control beam tip displacementControl beam tip displacement
+
-EW
+
-NS
+
-
+
-
40
y=
y
y 5.1
y 25.2
Papplied
SP1&2 : Papplied=-95 + 4Vb,x + 4Vb,y
SP3&4 : Papplied=-95 + 2Vb,x + 2Vb,y
- Simulate variation of column axial loading
previouse3
1
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6Group 7
P/(f'cA
g)
Testing time (sec)0 0.5 1 1.5 2 2.5 3 3.5
x 104
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
SP1SP2
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Test ResultsTest Results
-8 -6 -4 -2 0 2 4 6 8-150
-100
-50
0
50
100
150
Drift (%)
-8 -6 -4 -2 0 2 4 6 8-150
-100
-50
0
50
100
150
Drift (%)
Beam
shear(kN) EW direction NS direction
Yielding
Peak
Yielding
Peak
SP1
SP1- Load vs. Drift
8
7
6 54
4
56
7
84
5 6
7
7
65
4
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Test ResultsTest Results
Drift (%)-8 -6 -4 -2 0 2 4 6 8
-200
-150
-100
-50
0
50
100
150
-8 -6 -4 -2 0 2 4 6 8-200
-150
-100
-50
0
50
100
150
Drift (%)
Yielding
Peak
Yielding
Peak
Beam
shear(kN) EW direction NS direction
SP2
SP2- Load vs. Drift
8
7
65
4
8
7
65 4
4
56
7
84
5 6
7
8
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Test ResultsTest Results
-8 -6 -4 -2 0 2 4 6 8-200
-150
-100
-50
0
50
100
150
200
-8 -6 -4 -2 0 2 4 6 8-200
-150
-100
-50
0
50
100
150
200
Drift (%) Drift (%)
Yielding
Peak
Beam
shear(kN) EW direction NS direction
Beam
shear(kN)
SP3- Load vs. Drift
Yielding
Peak
8
7
65
4
4
56
7
8
4
56
7
8
8
7
6
54
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-0.02-0.015-0.01-0.005 0 0.005 0.01 0.015 0.02
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Test ResultsTest Results
Normalized joint shear vs. Joint distortion
-0.01 -0.005 0 0.005 0.01
-1
-0.8
-0.6
-0.4-0.2
0
0.2
0.4
0.6
0.8
Joint shear strain
(
MPa)
-0.01 -0.005 0 0.005 0.01
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Joint shear strain
EW direction
NS direction
Joint distortion (rad)
Joint distortion (rad)
-0.01 -0.005 0 0.005 0.01
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.60.8
Joint shear strain
-0.01 -0.005 0 0.005 0.01
-1
-0.8
-0.6
-0.4-0.2
0
0.2
0.4
0.6
0.8
Joint shear strain
(
MPa)
EW direction
NS direction
Joint distortion (rad)
Joint distortion (rad)
EW direction
NS direction
Joint distortion (rad)
Joint distortion (rad)
ASCE 41
ASCE 41
SP1 SP2 SP3
- Normalized joint shear stress ASCE41
- Joint distortion: upward loading, i.e. slab in compression > downward loading, i.e. slab in tension
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Test ResultsTest Results
Joint Shear Strength
Joint aspect ratio, hb/hc
0
0.2
0.4
0.6
0.8
1
1.2
0.8 1 1.2 1.4 1.6 1.8 2 2.2
SP2
SP1
SP3
LoadingTest
[MPa0.5]
Semi-
empirical
[MPa0.5]
SP1
EWUp 0.71 0.64 (0.90)*
Down 0.71 0.71 (1.00)
NSUp 0.67 0.64 (0.96)
Down 0.66 0.71 (1.08)
SP2
EWUp 0.80 0.79 (0.99)
Down 1.09 0.97 (0.89)
NS
Up 0.81 0.79 (0.98)
Down 1.10 0.97 (0.88)
SP3
EWUp 0.52 0.57(1.10)
Down 0.59 0.61(1.03)
NSUp 0.47 0.57(1.21)
Down 0.51 0.61(1.20)
( )*: vj_model/ vj_test
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Intermediate Column Bar
-1
-0.5
0
0.5
1
1.5
2
2.5
-5 -4 -3 -2 -1 0 1 2 3 4
Drift (%)
Strain(10-3)
top
middle
bottom
-1
-0.5
0
0.5
1
1.5
2
2.5
3
-5 -4 -3 -2 -1 0 1 2 3 4
Drift (%)
top
middle
bottom
topmiddle
bottom
topmiddle
bottom
(a) EW direction (b) NS direction
Test ResultsTest Results
Tension Tie ?
Not likely
SP2
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Test ResultsTest Results
Effect of Slab
Loading group
6543
1 2 3 41
2
3
4
1 2 3 4
Bottom gages only @1,2
Top gages @1 to 4
Stra
in(
)y
/
0
0.2
0.4
0.6
0.8
1
1 2
Bar number
0
1
2
3
4
5
1 2 3 4
Bar number
457
152 top
bot
slip
0
1
2
3
4
5
1 2 3 4
0
0.2
0.4
0.6
0.8
1
1 2
S
tra
in(
)y
/
Bar numberBar number
EW-Top EW-Bottom
slip
0
1
2
3
4
5
1 2 3 4
0
0.2
0.4
0.6
0.8
1
1 2
Bar number Bar number
SP1
NS-Top NS-Bottomslip
Stra
in
(
)y
/
SP2
0
1
2
3
4
5
1 2 3 4
0
0.2
0.4
0.6
0.8
1
1 2
Bar number Bar number
Strain
(
)y
/
NS-Bottomslip
EW-Top
NS-Top
EW-Bottom
Beam reinforcement
low high
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Test ResultsTest ResultsEffect of Slab
Loading group
6543
1 2 3 41
2
3
4
1 2 3 4
Bottom gages only @1,2
Top gages @1 to 4
457(SP1)
152
0
1
2
3
4
5
1 2 3 4
0
0.2
0.4
0.6
0.8
1
1 2
S
tra
in(
)y
/
Bar numberBar number
EW-Top EW-Bottom
slip
0
1
2
3
4
5
1 2 3 4
0
0.2
0.4
0.6
0.8
1
1 2
Bar number Bar number
SP1
NS-Top NS-Bottomslip
762(SP3)
0
1
2
3
4
5
1 2 3 4
0
1
2
3
4
5
1 2 3 4
0
0.2
0.4
0.6
0.8
1
1.2
1 2
0
0.2
0.4
0.6
0.8
1
1 2
EW-TopEW-Bottom
slip
NS-Top NS-Bottom
slip
SP3
S
tra
in(
)y
/
Strain(
)y
/
Strain
(
)y
/
Beam depth
small large
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SummarySummary
Joint aspect ratio (hb/ h
c)
Beam reinforcement index
1. Main parameters
= 0.5~1.1 from tests vs. = 0.5 from ASCE 41
Accurate prediction by proposed models
2. Shear strength of unreinforced exterior joints
3. Intermediate column bars
Contribution of slab reinforcement
Torsional effect
Different joint shear distortion when slab in tension or in compression
4. Effect of slab
No function as a tension tie
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Further verification of proposed models
Extension to unreinforced interior joints
Progressive collapse analysis using developed joint element
Collapse fragility curve of old existing R/C prototype buildings
Future ResearchFuture Research
Pro
ba
bilityo
fco
llapse
Hazard level (PGA)
Complete collapse
Partial collapse by column axial failure
Partial collapse by joint shear failure
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Thank You!
Test results are uploaded at
http://research.eerc.berkeley.edu/projects/cornerbeamcolumnjoints/
Thomas(Oct.,2009) Gordon(Dec.,2009) James(Jan.,2010) Percy(Next week)