bond -sp01: bond -slip model to capture strain penetration
TRANSCRIPT
BondBond--SP01: BondSP01: Bond--slip model slip model
to Capture Strain Penetration to Capture Strain Penetration
Effects in OpenSeesEffects in OpenSees
Sri SritharanSri Sritharan
Associate professorAssociate professor
Iowa State UniversityIowa State University
Jian ZhaoJian Zhao
Assistant professorAssistant professor
University of Wisconsin University of Wisconsin --MilwaukeeMilwaukee
PrePre--NEESR ProjectNEESR Project
Design and
Practitioner
input/feedback
Remote participation,
Education/Outreach
Design,
Instrumentation
and Testing
Simulation
and Remote
control of
test
�� 3 T3 T--wallswalls
2 at 50% scale2 at 50% scale
1 at 75% scale1 at 75% scale
�� Specimen Specimen
under under
constructionconstruction
�� Testing Testing ––
October 2005October 2005
Test PlanTest Plan
OpenSees AnalysesOpenSees Analyses
�� Examine capabilities using existing test dataExamine capabilities using existing test data
-100
-50
0
50
-4 -2 0 2 4
Top Displacement (in,)
Late
ral L
oad (kip
s)
Experimental Data
openSEES 90
openSEES 270
�� Make improvements as neededMake improvements as needed
�� Modeling of bond slip resulting from strain Modeling of bond slip resulting from strain
penetration into the footingpenetration into the footing
Flange in
compression
Flange in
tension
Plot by Jon Waugh at ISUPlot by Jon Waugh at ISU
Strain PenetrationStrain Penetration
Building frame Bridge bentStructural wall
1
1
11
22
Existing Models of Bond SlipExisting Models of Bond Slip
Rotational
spring 1D springs Special interface element
ZeroZero--length Section Elementlength Section Element
Element Section
ZeroLength
Structure
σ
s
Fibers
Bar stress vs.
bar slip
relationship
Strain Penetration ModelStrain Penetration Model
yf
sy
bar @ yield
sy
slip (s) bond stress (τ)
Anchorage
length
la
α
τ
1
1s
s
Previous means:
•Assume effective
anchorage length
• Assume constant
bond stress
distribution
•Assume material
model for steel
•Integrate bar
strain over la
Bar Stress vs. Slip ModelBar Stress vs. Slip Model
σ
σy
σu
ssy
su
K
bK
Ks=σ
( )yyu σσσσσ +−×= ~
( )yy ssss −=~
ReReRe
s
s
b
s
s
1
~
~1
~
~
~
−+
⋅
−=
µµ
µσ
Bar stress
Bar slip
Bridge b
1
Slip at Bar Yield (Slip at Bar Yield (ssyy))
0 0.1 0.2 0.3 0.4 0.5
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07L
oad
ed-e
nd s
lip a
t b
ar y
ield
ing (
s y)
( )α
α
1
12'4
+
c
yb
f
fd
( ) 013.012'4
1.0
1
+
+=
α
α
c
yby
f
fds
db: bar diameter
fy: yield strength in ksi
fc': concrete strenght in psi
a : parameter in local bond model (0.4 from MC9018,23)
Model ValidationModel Validation
0 0.2 0.4 0.6 0.8 1Loaded-End Slip (s)
0
20
40
60
80
100B
ar S
tres
s (σ
)
Experiment
Prediction
model parameters:
s y = 0.0264in. f y = 68ksi
s u = 0.98in. f u = 100ksi
b = 0.45 R c = 1.01
Cyclic ModelCyclic Model
(maxrs, maxrl)
(minrs, minrl)
minrl×= *σσ
( ) ysrsvgss '* −=
RcRc
uy
Rc
uy
uy
ss
s
s
ss
s
1
*
*1
*
*
*
−+
−=σ
σ
s
: (rsvg, 0)K
KK
s'y
s'ys'
y
maxrl×= *σσ
Simulation of a Short ColumnSimulation of a Short Column
(a) F @ Dy (b) F @ 4Dy
0 0.50
10
20
30
40
Co
lum
n H
eig
ht
(in
.)
0 1 2 3Column Deflection (in.)
Measured deflection (no shear)
Analysis w/ strain penetration
Analysis w/o strain penetration
Simulation of a Circular ColumnSimulation of a Circular Column
(a) at Dy (b) at 1.6Dy
gaged bar
loading
1000 2000 3000 4000 50000
20
40
60
Co
lum
n H
eig
ht
(in
.)
2000 4000 6000 8000Bar Strain x 106 (in/in)
Measured strain
w/ strain pene.
w/o strain pene.
Simulation of a Bridge JointSimulation of a Bridge Joint
-4 -2 0 2 4Column Displacement (in.)
-100
-50
0
50
100
Ap
pli
ed F
orc
e (k
ips)
Measured response
Analysis w/o strain penetration
Analysis w/ strain penetration
cap beamcolumn
Simulation of a Bridge Joint (con.)Simulation of a Bridge Joint (con.)
-0.004 -0.002 0 0.002 0.004Curvature at Column End (1/in.)
-600
-400
-200
0
200
400
600
Mom
ent
at
Colu
mn
En
d (
kip
s-ft
)
Measured response
Analysis w/o strain penetration
Analysis w/ strain penetration
critical
section
ConclusionsConclusions�� Strain penetration has impact on the behavior of RC Strain penetration has impact on the behavior of RC
membersmembers
�� Strain penetration effects can be modeled in fiberStrain penetration effects can be modeled in fiber--based based analysis using a zeroanalysis using a zero--length section element length section element
�� Proposed bar stress vs. slip model can represent the Proposed bar stress vs. slip model can represent the behavior of bars with ample anchorage behavior of bars with ample anchorage
�� With the proposed model, strain penetration effects on With the proposed model, strain penetration effects on RC member behavior can be capturedRC member behavior can be captured
�� Source code and user manual for BondSource code and user manual for Bond--SP01:SP01:
Email Email [email protected]@uwm.edu
Will be uploaded to OpenSees RepositoryWill be uploaded to OpenSees Repository