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A Comparative Study on Long Term Deformation of High

Performance Prestressed Concrete Bridges

1/23/2012

Under the Guidance of:

Dr. J. Karthikeyan

Assistant Professor Department of Civil Engineering

National Institute of Technology Tiruchirappalli -620

015

Presented by:

Naresh Prasad Keshari203210021

Structural Engineering



Presentation Flow Introduction

Literature Review

Objectives

Methodology

Model Validation Twin cell box girder bridge

I section Girder Bridge

Comparison of Results Conclusion

Recommendations

References1/23/2012 2



Introduction

Bridges with precast, prestressed concrete girders andreinforced concrete decks are common in new bridge

construction

± Lower initial cost relative to other bridges system

± Relatively low maintenance cost through the life of thestructures

In recent years the Federal Highway Administration (FWHA)

has stimulated the development and implementation of High

Performance concrete (HPC) ± Utilization of higher compressive strength

± Enhances the long term durability

± Increased span length and fewer structural components1/23/2012 3



Contd«.

HPC as concrete that has been designed to be more durable

and, if necessary, stronger than conventional concrete (FHWA)

HPC as concrete meeting special combinations of performance

and uniformity requirements that cannot always be achieved

routinely with conventional constituents and normal mixing,

placing, and curing practices.(ACI)

Increased durability and strength of HPC are generally achieved

through the use of chemical and mineral admixtures.

1/23/2012 4



Contd«.

Accurate prediction of long term prestress losses is essentialpart of the design process:

± Over prediction could mean limitation in span length and

considerable increase in the prestress force

± Under prediction could translate into undesired deflectionsand cracking under service condition.

Prestress losses can be defined as a decrease in the initial

prestressing force

± Instantaneous elastic shortening loss

± long term losses

Relaxation of strands

Creep and shrinkage of concrete

1/23/2012 5



1/23/2012

Contd«.

Prestress losses are also influenced by other time dependent

properties of concrete

± Compressive strength

± Modulus of elasticity

The prediction of deflection requires more emphasis

± Camber

± Due to creep and shrinkage of concrete

Camber may increase

Leads to invasion of road profile and irregular surface

6



1/23/2012 7

F ig. Components of time dependent camber and deflectionSource:-Center for Transportation Research, Bureau of

Engineering Research, The university of Texas at Austin (Oct. 1997)



1/23/2012 8

1. Alex Aswad et al.(1991). ³Rational prediction of Bridge

Girder reinforcing and Strength.´ PCI Journal

± Simple mathematical formulas to predict required number of strands with small error.

± Predict the required concrete strength for concrete bridge

girders of different types.

Literature Review



Contd«.

2. J. Michael Stallings et al. (2003). ³Camber and Prestress Lossesin Alabama HPC Bridge Girders.´ PCI Journal

± Overestimation of camber and prestress losses for HPPC

girders may discourage the efficient use of design and longer spans.

± Comparison of field values and calculated values

± Accurate prediction of camber are possible using the

incremental -time step method and the approximate time stepmethod

± AASHTO bridge design specification may overestimateprestressed losses due to creep and shrinkage in HPC girders.

1/23/2012 9



3. Young-Ha Park et al. ³Development of Long Span PrestressedConcrete I Girder Bridge by Optimal Design.´, Expressway and

Transportation Research Institute 08-06,Korea Expressway

Corporation

± Optimal design of standard type PSC I girder bridge. ± I girder section for varying top flange , bottom flange and

web thickness based on span of the bridge

± Optimal girders have consistent safety with respect to

flexural and shear failure

± Serviceability for both the live load deflection and long term

deflection after deck slab placing.

1/23/2012 10

Contd«.



1/23/2012 11

T he optimal girder sections shapes designed in this study



Contd«.

4. Hema Jayaseelan, Bruce W. Russell (2007). ³Prestress lossesand the Estimation of long term deflection and camber for

Prestressed Concrete Bridge.´ Final Report, Oklahoma state

University

± Add top prestressed strands to lower long term deformation and

camber by 69%

± AASHTO time step method is adequate for the estimation of long

term deflection and camber

± 20% increase in Elastic modulus of concrete lowers the long term

prestress losses by 6% and long term camber by 12%

1/23/2012 12



Cont.«

5. Karthikeyan. J (2008). ³Long Term Deformation of High

Performance Prestressed Concrete Bridges.´ Ph.D

Thesis,IIT, Roorkee (India)

± Creep and shrinkage strains have been measured for a

period of 850 days of two different test specimen sizes

No much size effect

±

Long term deformation prediction using RM2004

bridgeengineering software and Incremental time step method

1/23/2012 13



Contd«.

6. S.Rana et al . (2010). ³Design of prestressed concrete I- girder bridge superstructure using optimization algorithum.´ IABSE-

JSCE joint conference on Advances in Bridge Engineering ± II

,Dhaka Bangladesh

± Demonstrate the real life project named Teesta Bridge I - girder prestressed bridge (post-tensioned)

Medium span (50 m)

Existing spacing of girder 2.4 m

Optimum Design spacing 3.0 m

± 35% economical than the existing design

1/23/2012 14



Objectives

To identify long term deformation of two different type of HPPCbridge girders using RM2004 & Incremental time step method

± I section Girder (Pre ±tensioned)

± Twin cell Box Girder(Post ±tensioned)

To compare the long term deformation for the girders

mentioned above.

1/23/2012 15



1/23/2012 16

Methodology

Literature Review

Objectives

Modeling & Analysis of I-

section girder of 40 m span

(pre - tensioned) in RM2004

Modeling & Analysis of Twin cell box

girder bridge of 40 m span

(post-tensioned) in RM2004

Comparison of Long term deformation



AASTHO LRFD Model for Creep and Shrinkage

Low Relaxation Formula (PCI )

Incremental Time step method

Finite difference technique

1/23/2012 17

Methodology for Prediction of Long Term Behavior



1/23/2012 18

AASHTO-LRFD Model for Creep and

Shrinkage



1/23/2012 19

Cont.«



1/23/2012 20

Cont.«



1/23/2012 21

Cont.«



1/23/2012 22

Cont.«



1/23/2012 23

Cont.«



Incremental Time step Method

1/23/2012 24



1/23/2012 25

Cont.«



1/23/2012 26

Cont.«



1/23/2012 27

Cont.«



Alabama bridge modeling and Analysis using

RM2004 and long term deformation calculation

using Incremental time step method

Comparison of result with calculated result by J .

Michael Stallings et al.

The long term response of the bridge has been

monitored for 295 days.

1/23/2012 28

Validation of Model



Detail of the Alabama Bridge

1/23/2012 29



1/23/2012 30

Cont.«

F ig. Cross section of the bridge



Design parameters of Alabama Bridge

1/23/2012 31

Prestressing steel:

15.2 mm Low-relaxation strands

Number 42

Strand Area 1.42 x 10

-4

m2

Ultimate tensile strength, f pu 1860 MPa

Modulus of elasticity, Eps 189.6 GPa

Jacking stress, f pj 0.75 f pu

Girder characteristics

Span length, L 34.21 m

Hold-down location, a 14.06 m

Concrete properties

Release strength, f ci¶ 55.16 MPa

28-day strength, f c¶ 68.95 MPa

Unit weight 2399 Kg/m3

Modulus of elasticity, Ec

39.58 GPa

Sectional Properties

Cross-Sectional Area 0.4252 m2

Second moment of Inertia 0.1116 m4

Ytop 0.669 m

Ybottom 0.702 m



1/23/2012 32

Cont.«



1/23/2012 33

Cont.«

F ig. Mid span and end cross sections of HPPC girder showing the cable points.



Screenshot from RM2004

1/23/2012 34

F ig. Cable Profile

F ig. 3D view



Results

1/23/2012 35

Girder Age (Days)

Long-term Deformation at Mid-span (mm)

AbsoluteDifference

(mm)

Percentage

differenceMeasured

(Stallings)

Calculated

(Stallings )Validated

G11

295

84.83

115.57

76.70

109.47

74.43

107.318

-2.28

-2.156

-2.97

-1.97

G21

295

92.20

124.46

76.70

109.47

74.43

107.318

-2.28

-2.156

-2.97

-1.97

G31

242

81.02

103.88

76.70

107.69

74.43

106.612

-2.27

-1.084

-2.97

-1.01

G41

242

83.31

106.68

76.70

107.69

74.43

106.612

-2.27

-1.084

-2.97

-1.01

G51

234

84.83

105.91

76.70

107.44

74.43

106.238

-2.27

-1.254

-2.97

-1.17



1/23/2012 36

0

10

20

30

40

50

60

70

80

90

100

Measured [Stallings et al.] Calculated [Stalings et al.] Validated

C a m b e r

( m m )

Comparision of Initial Camber

G1 G2 G3 G4 G5



1/23/2012 37

0

20

40

60

80

100

120

140

Measured [Stallings et al.] Calculated [Stalings et al.] Validated

C a m b e r

( m m )

Comparision of Long Term Deformation

G1 G2 G3 G4 G5



1/23/2012 38

F ig. General arrangement drawing of the bridge

Detail of Twin cell Box Girder Bridge



1/23/2012 39

Design parameters of Twin cell Box Girder Bridge

24 Prestressing tendons:

Each tendon consists of 19

numbers of 12

.7

mm diameter,low relaxation tendons have been

used

Jacking force, F2618 kN simultaneously stressed

at both the ends

Frictional coefficient 0.2

Deviation angle () 0.86 deg/m

Wedge/slip 0.006 m

Area of one tendon 1.875 x 10-3 m2

Area of the duct 6. 36 x 10-3 m2

Modulus of elasticity, Ep 195 x 103 MPa

Ultimate tensile strength (UTS) 1862 MPa

Jacking stress (0.75

UTS

)139

6 MPaC.G distance of the girder Ytop Ybot (m)

At supports 1.498 1.502

At quarter-span 1.222 1.778

At mid-span 1.222 1.778



1/23/2012 40

F ig. Section Elevation of the bridge



1/23/2012 41

F ig. T win ± cell box section at the mid span



1/23/2012 42

F ig. T win ± cell box section at the Support end



1/23/2012 43

F ig. Cable arrangement at support



1/23/2012 44

F ig. Cable arrangement at mid section




1/23/2012 45

F ig. Cable Profile

F ig. 3D view




1/23/2012 46

F ig. IRC Class A Loading

F ig. IRC Class 70R Loading

R lt



1/23/2012 47

Results

AgeCamber (mm)

At quarter span At mid span

Initial 8.78 12.13

7 Days 9.57 12.75

168 Days 11.83 15.63

365 Days 12.06 15.91

1825 Days 12.30 16.16

10800 Days 12.34 16.18



1/23/2012 48

8.78

9.58

11.84 12.07 12.30 12.35

0

2

4

6

8

10

12

14

Initial 7 Days 168 Days 365 Days 1825 Days 10800 Days

D e f o r m a t i o n ( m m )

Quarter Span Camber



1/23/2012 49

12.1312.76

15.63 15.91 16.16 16.19

0

2

4

6

8

10

12

14

16

18


D e f o r m a t i o n ( m m )

Mid Span Camber



1/23/2012 50

0

4

8

12

16

20

0 15 30 45

C a m b

e r ( m m )

Span (m)

Long-Term Deformation




1/23/2012 51

F ig. Cross section of bridge (I- section)

Detail of I-Section Girders Bridge



1/23/2012 52

Design parameters of I section Girders Bridge

Prestressing steel:

15.2 mm Low-relaxation strands

Number 49

Strand Area 1.42 x 10-4 m2

Ultimate tensile strength, f pu 1860 MPa

Modulus of elasticity, Eps 189.6 GPa

Jacking stress, f pj 0.75 f pu

Girder characteristicsSpan length, L 40 m

Hold-down location, a 16 m

Concrete properties

Release strength, f ci¶ 55.16 MPa

28-day strength, f c¶ 68.95 MPa

Unit weight 2399 Kg/m3

Modulus of elasticity, Ec 39.58 GPa

Girder Cross sectional Properties

Cross sectional Area 0.7156 m2

Second moment of Inertia , I 0.2773 m4

Ytop 0.8659 m

Ybottom 0.8541 m



1/23/2012 53

F ig. Cross section I- section girder



1/23/2012 54

F ig. T endon scheme near to support F ig. T endon scheme at Middle of span




1/23/2012 55

F ig. Cable Profile

F ig. 3D view



1/23/2012 56

Results for Prior to construction of Deck slab

Age of StructureDeformation (mm)


Initial 32.98 43.87

7 Days 38.76 56.10

168 Days 46.62 68.25

365 Days 47.19 69.30

1825 Days 48.46 71.26

10800 Days 48.47 71.02



1/23/2012 57

32.99

38.77

46.63 47.2048.46 48.47

0

10

20

30

40

50

60


C a m b e r

( m m )

Quarter Span Camber



1/23/2012 58

43.87

56.10

68.26 69.3071.27 71.02

0

20

40

60

80


C a m b e r ( m m )

Mid Span Camber



1/23/2012 59

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35 40 45

C a m b e

r ( m m )

Span (m)

Long-term camber Without Slab topping




1/23/2012 60

Results for after construction of Deck slab

Age of Structure

Deformation (mm) [with slab]


Initial (i.e 168 Days) 46.63 68.26

365 Days 52.84 76.82

1825 Days 54.63 79.50

10800 Days 54.53 79.62



1/23/2012 61

46.63

52.84

54.64 54.54

42

44

46

48

50

52

54

56

Initial 365 Days 1825 Days 10800 Days

C a m b e r ( m m )

Quarter Span Camber



1/23/2012 62

68.26

76.8279.50 79.62

0

20

40

60

80

100

Initial 365 Days 1825 Days 10800 Days

C a m b e r ( m m )

Mid Span Camber



1/23/2012 #



Comparison of Results

1/23/2012 64

11.84 12.07 12.30 12.35

46.63

52.8454.64 54.54

0

10

20

30

40

50

60

168 Days 365 Days 1825 Days 10800 Days

C a m b e r ( m m )

Comparision of Long Term Deformation atQuarter Span

Twin cell Box Girder HPPC Bridge I-Section HPPC Bridge



1/23/2012 65

15.63 15.91 16.16 16.19

68.26

76.8279.50 79.62

0

10

20

30

40

50

60

70

80

90

168 Days 365 Days 1825 Days 10800 Days

C a m b e r ( m m )

Comparision of Long Term Deformation at Mid

Sapn

Twin cell Box Girder HPPC Bridge I-Section HPPC Bridge

C l i



Conclusion

Determination of long term deformation using

proposed method shows good match with

calculated by stallings et al.[error -2.27 to -1.08]

In twin cell box girder bridge camber is increasinggradually and very controlled manner.

In I section girders bridge camber increases

gradually with respect to age of the structure .

1/23/2012 66



In I section girders bridge camber increases after

placing of the RCC deck slab.

Incremental time step method is flexible in time i.e.we can calculate the camber as our requirement

time elapsed.

In both type of bridges the camber is almostconstant after 365 days.

1/23/2012 67

Contd«.



Recommendations

For long span bridges it¶s not suitable for go for precast pre-

tensioned because of difficulties in erecting ,required more

grade of concrete compared to post-tensioned.

Standard design guidelines and those recommendations have

been made more refined prediction of prestress losses, camber

and deflection as follows;

±

Add top prestressing strands in prestressed concrete beams tolower the long term losses and camber by approximately 69%.

1/23/2012 68



± Add mild steel which increases stiffness to the concrete

beam as well as reduces the long term camber by

approximately 17.4%.

1/23/2012 69

Contd«.



References

1. AASHTO-LRFD (2004), AASHTO-LRFD bridge design specification,3rd edition, American Association of State Highway and

Transportation Officials, Washington, D.C., US A.

2. ACI Committee 209, (1992). Report on factors affecting shrinkage

and creep of hardened concrete, ACI Manual of Concrete Practice American Concrete Institute: Farmington Hills, MI, US A.

3. Aswad, A. and Gus G. Aswad (1991) Rational prediction of bridge

girder reinforcing and strength. PCI J ournal May-J une, 68-77.

4. Barakat, S., Ali salem Al Harthy and Aouf R. Thamer (2002)

Design of prestressed concrete girder bridges using optimization

techniques. Pakistan J ournal of Information and Technology 1(2):

193-201

1/23/2012 70

C td



Contd.«

5. Barr, P. J., B. M. Kukay and M. W. Halling (2008) Comparison of

prestress losses for a prestress concrete bridge made with high

performance concrete. J ournal of Bridge Engineering © ASCE

6. Branson, D. E. and K. M. Kirpanarayanan (1970) Loss of

prestress, camber and deflection of non-composite and composite

prestressed concrete structures. The sixth congress of thefederation international de la precontrainite, Prague,

Czechoslovakia.

7. Debbarma, S. R. and S. Saha (2011) Behavior of pre-stressed

concrete bridge girders due to time dependent and temperatureeffects. First Middle East Conference on Smart Monitoring,

Assessment and Rehabilitation of Civil Structures, Dubai, U AE .

1/23/2012 71

C td



Contd.«

8. Glover, J. M. and James Michael Stallings High performance

bridge concrete, Highway Research Center, Harbert Engineering

Center, Alabama University, Alabama, US A, 2000.

9. Guo, T., Richard sause, Dan M. Frangopol and Aiqun Li (2011)

Time dependent reliability of PSC box-girder bridge considering

creep, shrinkage and corrosion. J ournal of Bridge Engineering © ASCE .

10. Hassanain, M. A. and Robert E. Loov (1999) Design of

prestressed girder bridges using high performance concrete- An

optimization approach. PCI journal March- A pril , 40-55.11. Hendy, C. R. and D. A. Smith Designers¶ guide to EN 1992-2

Eurocode 2: design of concrete structures Part 2: Concrete Bridges,

1st Edition, Thomas Telford Ltd., London , UK, 2007.

1/23/2012 72

C td



Contd.«

12. Hewson, Nigel R. Prestressed concrete bridges: design and

construction, 1st Edition, Thomas Telford Ltd., London, UK, 2003.

13. IRC: 18 (2000), Design Criteria for prestressed concrete road

bridges (post-tensioned concrete), 3rd revision, The Indian road

Congress, New Delhi, India.

14. IRC: 6 (2000), Standard specification and code of practice for road

bridges: Section-II, Loads and Stress, 4th Revision, The Indian Road

Congress, New Delhi, India.

15. Jayaseelan, H. and Bruce W. Russell Prestress losses and the

estimation of long-term deflection and camber for prestressed concrete bridges. Final Report August 2007, School of civil

Environmental Engineering Oklahoma State university.

1/23/2012 73

C td



Contd.«

16. Karthikeyan, J. (2008) Long term deformation of high performance

prestressed concrete bridges, Ph.D dissertation, Indian Institute of Technology, Roorkee.

17. Karthikeyan, J., Akhil Upadhyay and Navratan Mal Bhandari(2009) Incremental time-step method for predicting long termdeformation of a HPPC bridge, PCI/NBC .

18. Lounis, Z. and M.Z. Cohn (1993) Optimisation of precastprestressed concrete bridge girder systems. PCI J ournal J uly- August , 60-62.

19. Nilson, Arthur H. Design of prestressed concrete, 2nd Edition, JohnWiley and Sons, US A, 1978.

20. Park, Y. H, Chan-Min Park, Tae-Song Ahn, Hai-Moon Cheong,Bon-Sung Ku and Kyu-Chon Choi (2006) Development of longspan prestressed concrete I girder bridge by optimal design.Expressway & Transportation Research Institute, Korea.

1/23/2012 74

C td



Contd.«

21. PCI Design Handbook, Precast and prestressed concrete, 5th

Edition, Precast prestressed concrete Institute, Chicago, Illinois,

1999.

22. Rana, S. and R. Ahsan (2010) Design of prestressed concrete I-

girder bridge superstructure using optimization algorithm. I ABSE-

J SCE joint conference on Advances in Bridge Engineering-II, August 8-10 .

23. Stallings, J. M., Robert W. Barnes and Sam Eskildsen (2003)

Camber and prestress losses in Alabama HPC bridge girders. PCI

J ournal September-October , 2-16.

1/23/2012 75



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