Evaluation and Advancement of a Reinforced Concrete Beam- Column Joint Model

shootperchUrban and Civil

Nov 26, 2013 (3 years and 11 months ago)

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Evaluation and Advancement of
a Reinforced Concrete Beam-
Column Joint Model
Nilanjan Mitra
Laura N. Lowes
University of Washington, Seattle, USA
Research Sponsored by the
Pacific Earthquake Engineering Research Center
Need for modeling joint regions
Beam
Beam
-
-
column joint response to earthquake loading may determine
column joint response to earthquake loading may determine
structural performance
structural performance
Kaiser Office Building, Northridge CA
following Northridge Earthquake in 1994
(images courtesy of NISEE, UC Berkeley)
I-280 Freeway, San Francisco, CA
following Loma Prieta Earthquake in 1989
(images courtesy of NISEE, UC Berkeley)
Joint Behavior –
Previous models –
UW model –
Modification –
Evaluation
Joint loading
tension resultant (steel)
compression resultant
(concrete and steel)
shear resultant
(concrete)
Earthquake Loading of Beam-Column Joint
Joint Behavior

Previous models –
UW model –
Modification –
Evaluation
Joint internal load distribution
anchorage bond stress
acting on joint core concrete
compression force carried by
joint core concrete
Joint Behavior

Previous models –
UW model –
Modification –
Evaluation
Previously proposed RC joint models
Kunnath et al. (1995)
Otani
(1974),
Anderson et al. (1977)
El-Metwally
et al.
(1988)
Biddah
et al. (1999)
Fleury
et al. (2000)
Elmorsi
et al. (1998)
Joint Behavior

Previous models –
UW model –
Modification –
Evaluation
UW model (Lowes et al. 2003)
Zero length
interface-shear
springs
column
column
beam
beam
shear
panel
Zero length
bar-slip
springs
External nodes
Internal nodes
Joint Behavior –
Previous models

UW model –
Modification –
Evaluation
Bar-slip material model (Lowes et al. 2003)
Observed (Viwathanatepa
et al. 1979)
Simulated
BAR SLIP SPRINGS
Joint Behavior –
Previous models

UW model –
Modification –
Evaluation
Material model for shear panel
SHEAR PANEL REGION
shear strain (radians)
shear stress (MPa
)
Modified Compression-Field Theory
Monotonic Envelope for Joint Element
0
0.003
0.006
0.009
0.012
0.015
0
2
4
6
8
ρ
= 0.005
ρ
= 0.025
MCFT (Vecchio and Collins 1986)
Joint Behavior –
Previous models

UW model –
Modification –
Evaluation
Hysteretic one-dimensional material model
deformation
load
(ePd1,ePf1)
(ePd4,ePf4)
(ePd
3,ePf3)
(ePd2,ePf2)
(eNd3,eNf3)
(eNd2,eNf
2)
(*,uForceP.ePf
3)
(dmin,f
(dmin))
(dmax,f(dmax))
(rDispP.dmax,rForceP.f(dmax))
(rDispN.dmin,rForceN.f(dmin))
(*,uForceN.eNf3)
(eNd1,eNf1)
1D response is defined by:

Response envelope

Unload reload path

Damage rules
Joint Behavior –
Previous models

UW model –
Modification –
Evaluation
Damage simulation in material model
Joint Behavior –
Previous models

UW model –
Modification –
Evaluation
(
)
()
cycles
load
of
No
or
E
E
d
monotonic
i
i
.
.
2
~
.
1
4
3
max
=
+
=
χ
χ
α
α
δ
α
α
Hysteretic Damage Index:
Evaluation of model through comparison of
simulated and observed response
Development of experimental dataset (4 test progs., 22 spc.)
Two-dimensional joint specimens with no slab,
no beam eccentricity and no out-of-plane beams.
Joints with at least minimal volume of transverse reinf.
Availability of sufficient exp. data for modeling and
evaluation.
Simulation of observed response
Using OpenSees
(http://opensees.berkeley.edu)
and revised model.
Comparison of simulated and observed response
strength (yield & ultimate)
stiffness (initial & unloading @ ultimate)
drift capacity
post peak strength loss
Joint Behavior –
Previous models –
UW model –
Modification

Evaluation
Design parameter variation for dataset
top
bot
PR1
0.41
0.43
0.43
1.15
45.86
PR2
0.64
0.90
0.62
1.07
35.97
PR3
0.46
0.48
0.48
0.60
36.17
PR4
0.58
0.85
0.58
0.59
40.06
DW
X1
1.03
0.87
0.77
0.16
34.31
DW
X2
1.13
0.91
0.82
0.24
30.87
DW
X3
0.91
0.91
0.81
0.19
31.01
NKOKJ1
1.25
0.93
0.93
0.14
69.94
NKOKJ3
1.19
0.75
0.75
0.12
106.90
NKOKJ4
1.20
0.93
0.93
0.14
69.94
NKOKJ5
1.13
0.93
0.93
0.15
69.94
NKOKJ6
1.20
1.06
1.06
0.16
53.45
OKAJ1
0.80
0.84
0.84
0.07
25.70
OKAJ2
0.83
0.86
0.86
0.14
24.03
OKAJ3
0.90
0.86
0.86
0.29
24.03
OKAJ4
0.74
0.84
0.84
0.07
25.70
OKAJ5
0.70
0.79
0.79
0.07
28.74
OKAS1
0.45
0.69
0.69
0.62
27.76
OKAS2
0.48
0.69
0.69
0.58
27.76
OKAS3
0.58
0.63
0.63
0.49
27.76
OKAS4
0.56
0.98
0.98
0.53
25.11
OKAS6
0.51
0.73
0.73
0.18
25.11
fc
(M
p
a)
Joint
Spcmn.
(Mpa)
Park and
Ruitong
(1988)
Durrani and
Wight

(1982)
Noguchi and
Kashiwazaki
(1992)
Otani,
Kobaya
shi and
Aoyama

(1984)
(% )
c
j
f

υ
j
ty
ts
V
f
A
=
ϕ
c
d
b
y
f
l
d
f

=
4
τ
Joint Behavior –
Previous models –
UW model –
Modification

Evaluation
Model simulation
Concrete Stres
s-Strain
(Compressive only,
no tensile strength)
Reinforcing Steel Stress-Strain
Beam-Column Elements:
Force based lumped plasticity element
Plastic Hinge region
Elastic region
Fiber discretization
Joint Behavior –
Previous models –
UW model –
Modification –
Evaluation
Modifications to the UW RC-BC joint model
Height of the tension-compression couple.
Post-peak response of bond-slip springs.
Anchorage length.
Joint Behavior –
Previous models –
UW model –
Modification

Evaluation
PR specimen details
Joint
Specimen
NO.
top
bot
top
bot
top
bot
PARK & RUITONG
P
R1
42630
42630
0.63
0.63
5
2
PR2
45530
43500
1.102
0.787
2
2
PR3
42630
42630
0.63
0.63
5
2
PR4
45530
43500
1.102
0.787
2
2
Beam Reinf. fy (psi)
Beam bar di
a. db (in
)
Beam rein
f. no.
f
c
(psi
)
6655.5
5220
5249
5814.5
ρ
_ar(%)
ρ
_
vol
(%
)
As (in
2
)f
y (psi)
1.30
1.43
2.52
43688.5
1.72
1.00
3.5
41035
0.56
0.62
1.21
47154
0.88
0.93
1.65
45298
Tra
nsverse/
Hoop S
teel (Joi
nt)
Axial Loa
d
Sc
ale
(lb)
(
α
fcAg)
12364.5
0.0097
15062.2
0.0151
12364.5
0.0123
15062.2
0.0135
Joint Behavior –
Previous models –
UW model –
Modification –
Evaluation
Simulated and observed response
(a) Observed response
Joint Behavior –
Previous models –
UW model –
Modification –
Evaluation
(b) Simulated response
Comparison of observed and simulated response
Exp.
Model
Exp.
Model
Exp.
M
odel
E
xp.
Model
Exp.
Model
(kN/mm)
Exp.
(kN)
Exp.
(kN)
Exp.
(kN/mm)
Exp.
(kN)
Exp.
PR1
2.33
1.00
70.0
1.00
80.3
0.
98
1.15
0.83
NA
NA
PR2
3.50
0.97
105.0
0.97
111.7
0.
99
2.23
1.00
92.5
0.58
PR3
2.40
0.91
72.0
0.91
79.4
0.
94
1.59
0.79
NA
NA
PR4
3.30
1.01
99.0
1.01
106.5
0.9
7
1.77
0.84
79.7
1.05
DWX1
4.89
0.94
186.8
0.94
191.2
0.
94
6.26
0.74
171.2
0.85
DWX2
5.25
0.95
186.8
0.94
197.9
0.
93
6.49
0.56
182.4
0.57
DWX3
4.57
0.89
151.2
0.89
151.2
0.
90
3.96
0.75
137.9
0.65
NKOKJ1
8.00
1.02
250.0
0.51
250.0
0.5
1
13.89
0.46
200.0
0.51
NKOKJ3
8.33
0.90
295.0
0.54
295.0
0.4
8
29.50
0.32
250.0
0.46
NKOKJ4
7.33
1.22
245.0
0.61
245.0
0.5
9
14.41
0.30
200.0
0.35
NKOKJ5
8.00
1.04
250.0
0.52
250.0
0.5
1
12.50
0.30
150.0
0.30
NKOKJ6
6.83
0.90
220.0
0.89
220.0
0.5
6
11.00
0.20
150.0
0.20
OKA
J1
5.63
1.48
90.1
0.74
117.7
0.5
7
1.10
0.20
96.1
0.20
OKA
J2
3.68
1.90
117.6
0.95
127.4
0.
88
1.02
0.20
97.5
0.25
OKA
J3
3.90
0.98
125.0
0.98
132.3
1.
00
3.15
0.83
NA
NA
OKA
J4
3.67
0.68
117.7
0.68
117.7
0.
68
4.71
0.78
68.6
0.20
OKA
J5
3.67
0.68
117.7
0.68
117.7
0.
68
2.35
0.90
83.3
0.20
OKA
S1
4.17
0.95
66.7
0.95
70.6
0.
98
1.24
1.00
NA
NA
OKA
S2
4.17
0.97
66.7
0.97
74.5
0.
96
1.43
0.94
NA
NA
OKA
S3
4.48
0.94
71.6
0.94
79.4
0.
95
3.31
0.90
77.4
0.90
OKA
S4
4.90
0.95
78.3
0.95
80.9
0.
95
1.37
0.91
76.4
0.87
OKA
S6
4.10
0.98
64.0
0.98
70.6
0.
99
1.19
1.00
NA
NA
avg.
0.96
0.92
0.90
0.77
0.6
6
std. dev.
0.04
0.12
0.15
0.24
0.2
8
coeff. Var.
0.04
0.13
0.17
0.31
0.4
3
Unloading Stiffness
@ Max. Strength
Failure
Stren
gth
Initial Stiffness
Nominal
Strength
Maximum
Strength
Sp
ec
imen
Joint Behavior –
Previous models –
UW model –
Modification –
Evaluation
Conclusions and future direction
Using the revised model for joints with φ>0.15, observed response
predicted well including anchorage failure and stiffness strength loss.
For joints with φ<0.15, which could be expected to fail by shear, MCFT
does not predict observed response. This is currently being addressed.
Questions ?