VIRGINIA CONCRETE
CONFERENCE
March 3

4, 2011
Presented by:
Teddy Theryo, P.E.
Parsons Brinckerhoff
SEGMENTAL BRIDGE GROUP
1.
Introduction
2.
Understanding of Creep & Shrinkage
3.
Code Development of Creep & Shrinkage
4.
Impact of Creep & Shrinkage on Post

Tensioned
Bridges
5.
Conclusions
Definitions
Creep
is time dependent deformations of concrete
under permanent loads (self weight), PT forces and
permanent displacement
Shrinkage
is shortening of concrete due to drying and
is independent of applied loads
Factors Affecting Creep
Concrete mix proportion
Cement properties
Curing conditions
Size and shape of members
Environment
Age at loading
Stress level
Factors Affecting Shrinkage
Concrete mix proportion
Cement properties
Aggregate properties
Curing conditions
Size and shape of members
Environment
In structural concrete creep and shrinkage strains are
coexist and occur together.
The rate of both creep and shrinkage decrease with time.
Theoretically the creep and shrinkage are considered
diminished at 10,000 days (27 years) after construction.
For practical purposes the ending time of 4,000 days (11
years) is also commonly used in creep and shrinkage
calculations .
Mathematically the non linear shape of creep and
shrinkage has been assumed as hyperbolic, exponential or
logarithmic.
S
t
r
a
i
n
S
t
r
a
i
n
Time
Time
Creep strain
Instantaneous
strain
TYPICAL CREEP
–
TIMECURVE
TYPICAL SHRINKAGE
–
TIMECURVE
Drying
creep
Basic
creep
Total
creep
Shrinkage
Nominal
elastic strain
Time (t
–
t )
0
t
0
S
t
r
a
i
n
0
50
100
150
200
Instantaneous
recovery
Creep recovery
Residual
deformation
500
1000
1500
Strain on application
of load
Time since application of load

days
S
t
r
a
i
n

1
0

6
1.
Introduction
2.
Understanding of Creep & Shrinkage
3.
Code Development of Creep & Shrinkage
4.
Impact of Creep & Shrinkage on Post

Tensioned
Bridges
5.
Conclusions
Relationship between creep and elastic deformations
cr
=
el
=
E
28
where:
cr
= creep strain
el
= elastic strain
= stress
E
28
= elastic modules of concrete at age 28 days
= creep factor
4.0
3.5
3.0
2.5
2.0
1.5
3.72
3.03
2.57
2.22
2.00
1.70
1.44
1.0
0.5
0
3
7
14
21
28
42
56
3
4
5
6
9
1
1.5
2
3
5
Days
Months
Years
1
.
2
0
1
.
0
7
1
.
0
0
0
.
9
6
0
.
9
1
0
.
9
4
0
.
9
0
0
.
8
8
t
DURATION OF LOADING
T
O
T
A
L
E
L
A
S
T
I
C
A
N
D
C
R
E
E
P
S
T
R
A
I
N
M
cr
(t)
=
(1
–
e

(t)
) (M
II
–
M
I
)
M
Final
(t)
= M
II
+ (M
I
–
M
II
) e

(t)
where: (t) = creep factor at time t
e = Base of
Napierian
logarithms
= 2.7182
M
I
= Movement due to permanent loads before
change of
statical
system
M
II
= Movement due to the same loads applied on
changed
statical
system (build on
false

work)
Free Cantilever Statical System
Changed Statical System (Midspan Continuous)
M
Final (t)
½L
½L
M
I
M =
I
Fixed
Fixed
q
qL
2
8
M
II
M =
II
qL
2
12
qL
2
24
M
II
M
I
M
cr (t)
el
(t )
0
cr
(t )
P
P
P
ef
P
ef
Cantilever Beam
Simple Beam
el
(
)
t
0
cr
(t )
P
Post

Tensioned Beam
P
P
P
P
ef
P
ef
el
(t )
0
el
(t )
0
el
(t )
PT Tendon
1.
Introduction
2.
Understanding of Creep & Shrinkage
3.
Code Development of Creep & Shrinkage
4.
Impact of Creep & Shrinkage on Post

Tensioned
Bridges
5.
Conclusions
CEB

FIP 1970 Model Code
CEB

FIP 1978 Model Code
CEB

FIP 1990 Model Code
FIB 2010 Draft Model Code
ACI

209
BP3
1.
Introduction
2.
Understanding of Creep & Shrinkage
3.
Code Development of Creep & Shrinkage
4.
Impact of Creep & Shrinkage on Post

Tensioned
Bridges
5.
Conclusions
There are two major impacts of creep and shrinkage
on structural concrete
Deformations (simply supported and indeterminate
structures)
Redistribution of stresses / forces on indeterminate
structure, including support reactions
C
L
C
L
In

span Hinge
In

span Hinge
Mid

span Hinge
Bearing &
Expansion Joint
Bearing
Expansion Joint
Bearing
Old Generation of
Midspan
Hing
e
(not
recommended)
M
i
d

S
p
a
n
H
i
n
g
e
I
n

S
p
a
n
H
i
n
g
e
5.1%
S
1.8%
2.5
5.0
7.5
D
e
f
o
r
m
a
t
i
o
n
(
c
m
)
Span Length: 79m (260 feet)
Deck Profile based
on As

Built Dwgs
Existing
Deck Profile
Reference
Line
C EXP. JT. NO. 3
L
STA. 67+16.50
C PIER 9
L
STA. 68+16.59
BEGIN S.E. TRANSITION
STA. 68+18
C PIER 8
L
STA. 65+74
0.36’
0.46’
0
.
8
2
’
Deck Profile based
on As

Built
Dwgs
Existing
Deck Profile
Line
C EXP. JT. NO. 3
L
STA. 67+16.50
C PIER 9
L
STA. 68+16.59
C PIER 8
L
STA. 65+74
0.49’
0.35’
0
.
8
4
’
Reference
Active Hinge
(proposed by Jean M. Muller)
Active hinge member
Midspan expansion joint
Typical internal
diaphragm
Hydraulic jack
Sliding
Expansion Joint
C
L Mid

Span
Steel Strong Back
Fixed
Elastomeric Bearing
Teflon Surface (typ)
Mid

span Hinge with Strong Back

0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0
200
400
600
800
Distance Along the Bridge (ft)
V
e
r
t
i
c
a
l
D
i
s
p
l
a
c
e
m
e
n
t
(
i
n
)
L
L
@ TF
o
creep
0.079 Degree
8’

6”
3’

6”
12’

0”
L
creep = 0.079 x 3.5 x 12 = 3.31”
Assuming 50% of the creep had been corrected
camber during segment casting.
L
available gap at 60F in 2010
o
Abutment 1 = 3

3/4”

0.5 (3.31) = 2.09” vs 1.75”
Abutment 29 = 3

3/8”

0.5 (3.31) = 1.75” vs 1”
Point of rotation
creep
V
Abutment
Back Wall
Camber Diagram of Unit 1 at T =
End Span Girder Rotation at Abutment 1
(Varina

Enon Bridge Case Study)
Elastomeric Bearing
Expansion Joint at Abutment
Abutment
Span 1
X
C
L
Top Plate
Bottom Pot
>X
C
L
Top Plate
X min.
C
L
C
L
Bottom
Pot
C
L
Bottom
Pot
creep at T =
Top Plate
creep at T =
e =
Ideal/preferred
position at T=
Incorrect
position at T=
Correct bearing &
joint expansion
preset at construction
Expansion
Joint
Over Extended of Bearing Top Plate
Torsional
Creep Deformation
i
n Horizontally
Curved
Bridge
A
A
GOOD
BAD
Roadway Axis
Girder Axis
S
u
p
p
o
r
t
A
x
i
s
SECTION A

A
BAD STRATEGY
GOOD STRATEGY
Top Abutment
Elevation
Introduction
Understanding of Creep & Shrinkage
Code Development of Creep & Shrinkage
Impact of Creep & Shrinkage on Post

Tensioned
Bridges
Conclusions
In order to avoid the negative impacts of long

term
creep and shrinkage:
1.
Good understanding of creep and shrinkage behaviors
2.
Accurate estimation of creep and shrinkage on structural
concrete design
3.
Proper counter measures of long

term creep and
shrinkage effects
4.
Implement simple structural details
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