This document summarizes a presentation on creep and shrinkage in concrete structures. It discusses factors affecting creep and shrinkage, typical creep and shrinkage curves over time, code developments, and impacts on post-tensioned bridges. Specifically, it notes that creep and shrinkage can cause deformations in simply supported and indeterminate structures as well as redistribution of stresses. It also provides examples showing how creep and shrinkage can impact bridge deck profiles, expansion joints, bearings, and girder rotations over time. The conclusion recommends understanding creep/shrinkage behaviors, accurately estimating their effects, implementing countermeasures, and using simple structural details to avoid negative long-term impacts.

1. VIRGINIA CONCRETE
CONFERENCE
March 3-4, 2011
Presented by:
Teddy Theryo, P.E.
Parsons Brinckerhoff
SEGMENTAL BRIDGE GROUP

2. 1. Introduction
2. Understanding of Creep & Shrinkage
3. Code Development of Creep & Shrinkage
4. Impact of Creep & Shrinkage on Post-Tensioned
Bridges
5. Conclusions

3. 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

4. Factors Affecting Creep
 Concrete mix proportion
 Cement properties
 Curing conditions
 Size and shape of members
 Environment
 Age at loading
 Stress level

5. Factors Affecting Shrinkage
 Concrete mix proportion
 Cement properties
 Aggregate properties
 Curing conditions
 Size and shape of members
 Environment

6.  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.

7. Strain
Strain
Time Time
Creep strain
Instantaneous
strain
TYPICAL CREEP – TIMECURVE TYPICAL SHRINKAGE – TIMECURVE

8. Drying
creep
Basic
creep
Total
creep
Shrinkage
Nominal
elastic strain
Time (t – t )
0
t0
Strain

9. 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
Strain
-
10
-
6

10. 1. Introduction
2. Understanding of Creep & Shrinkage
3. Code Development of Creep & Shrinkage
4. Impact of Creep & Shrinkage on Post-Tensioned
Bridges
5. Conclusions

11. Relationship between creep and elastic deformations
cr = el =
E28
where: cr = creep strain
el = elastic strain
= stress
E28 = elastic modules of concrete at age 28 days
= creep factor

12. 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
1.20
1.07
1.00
0.96
0.91
0.94
0.90
0.88
t
DURATION OF LOADING
TOTAL
ELASTIC
AND
CREEP
STRAIN

13. Mcr(t) = (1 – e - (t)) (MII – MI)
MFinal(t) = MII + (MI – MII) e- (t)
where: (t) = creep factor at time t
e = Base of Napierian logarithms
= 2.7182
MI = Movement due to permanent loads before
change of statical system
MII = Movement due to the same loads applied on
changed statical system (build on
false-work)

15. Free Cantilever Statical System
Changed Statical System (Midspan Continuous)
MFinal (t)
½L ½L
MI M =
I
Fixed Fixed
q
qL
2
8
MII
M =
II
qL
2
12
qL
2
24
MII
MI
Mcr (t)

16. el (t )
0
cr (t )
P P
Pef Pef
Cantilever Beam
Simple Beam
el ( )
t0
cr (t )

17. P
Post-Tensioned Beam
P
P P
P
ef P
ef
el (t )
0
el (t )
0
el (t )
PT Tendon

20. 1. Introduction
2. Understanding of Creep & Shrinkage
3. Code Development of Creep & Shrinkage
4. Impact of Creep & Shrinkage on Post-Tensioned
Bridges
5. Conclusions

21. CEB-FIP 1970 Model Code
CEB-FIP 1978 Model Code
CEB-FIP 1990 Model Code
FIB 2010 Draft Model Code
ACI-209
BP3

22. 1. Introduction
2. Understanding of Creep & Shrinkage
3. Code Development of Creep & Shrinkage
4. Impact of Creep & Shrinkage on Post-Tensioned
Bridges
5. Conclusions

23. 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

24. C
L
C
L
In-span Hinge
In-span Hinge
Mid-span Hinge
Bearing &
Expansion Joint Bearing

25. Expansion Joint
Bearing
Old Generation of Midspan Hinge
(not recommended)

26. Mid-Span
Hinge
In-Span
Hinge
5.1%
S
1.8%
2.5
5.0
7.5
Deformation
(cm)
Span Length: 79m (260 feet)

27. 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’
0.82’

28. 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’
0.84’
Reference

29. Active Hinge
(proposed by Jean M. Muller)
Active hinge member
Midspan expansion joint
Typical internal
diaphragm
Hydraulic jack

30. Sliding
Expansion Joint
C
L Mid-Span
Steel Strong Back
Fixed
Elastomeric Bearing
Teflon Surface (typ)
Mid-span Hinge with Strong Back

31. -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)
Vertical
Displacement
(in)
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

32. Expansion Joint at Abutment
Abutment
Span 1

33. 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

34. Over Extended of Bearing Top Plate

35. Torsional Creep Deformation in Horizontally Curved Bridge
A
A
GOOD
BAD
Roadway Axis
Girder Axis
Support
Axis
SECTION A-A
BAD STRATEGY GOOD STRATEGY
Top Abutment
Elevation

36.  Introduction
 Understanding of Creep & Shrinkage
 Code Development of Creep & Shrinkage
 Impact of Creep & Shrinkage on Post-Tensioned
Bridges
 Conclusions

37. 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