extending the life of prestressed concrete bridge ... the life of... · extending the life of...

1

SWANSON school of engineering

civil and environmental engineering

structural engineering and mechanics

Watkins Haggart structural engineering laboratory

Extending the Life of Prestressed Concrete Bridge Infrastructure

Kent A. Harries, PhD, FACI, P.Eng University of Pittsburgh

Jarret Kasan, PhD HDR Inc., Pittsburgh

2

Two Stories…

Following the 2005 collapse of the Lake View Drive Bridge, Dr. Harries made a [bold] statement: This girder/bridge was repairable

The demonstration of this conclusion was developed through: • two PennDOT-funded projects • NCHRP Project 20-07/307 • two independent studies • one industry-funded investigation • and NCHRP Project 12-95

Resulting in: • seven refereed journal articles • three international conferences

presentations (Canada, Korea, UK) • four publically available technical

reports • one international research award

3

Motivation

Charlotte NC May 2000

Washington PA December 2005

Laval Qc October 2006

Unknown existing condition issues with precast concrete bridge girders…

… and impact damage…

4

Impact damage

Lake View Drive collapse onto I-70. Impact damage led to significant strand loss, subsequent corrosion and eventual collapse under girder self-weight.

Impact damage to facia beam of McIlvaine Road over I-70. Entire bridge was demolished within 24 hours.

Bridge over I-26 north of Columbia SC showing evidence of significant vehicle impact.

Crawford Lane over I-70 showing relatively minor impact damage

Subsequent damage from corrosion of exposed strand…

5

Damage Assessment: Cracking and Strand Loss

Typical damage from vehicle impact

Splitting-like cracks from a variety of sources

125% Rule

When considering strand loss, consider adjacent strands:

125% of observable strand loss when extent of corrosion is explored

150% when extent is not explored.

x x x x x

6

ltr

ld

fpe

fps

bondingcommences

sound concretesevered

strand

distance along strand

stra

nd s

tres

s

Damage Assessment: Strand ‘Redevelopment’

Typically, the contribution of severed and corroded strands will be neglected in load rating along the entire span.

However, the strand transfer length is ‘redeveloped’ through the Hoyer effect and strand-to-concrete bond.

Away from the damage, the strand remains fully developed and may be relied upon for capacity.

The Hoyer effect enhances prestress transfer through the diametric expansion of the strand

nominal

diameter

stressed diameter

Kasan, J. and Harries, K.A., 2011. Redevelopment of Prestressing Force in Severed Prestressing Strand, ASCE Journal of Bridge Engineering 16 (3)

7

Damage Assessment: Adjacent Box Girder Bridges

Loss of or absence of shear key and/or transverse tie rods result in individual girders acting independently

Increase in loads on girders:

Barrier wall loads not distributed to interior girders resulting in eccentric loading conditions on exterior girders

Live load increases approximately 66% based on AASHTO distribution factors.

Shear key details are presently the subject of newly awarded NCHRP Project 12-95 (PI: Dr. Brent Phares at Iowa State).

8

Damage Assessment: Adjacent Box Girder Bridges

Curb slab/barrier wall construction ultimately results in a composite asymmetric section having an eccentric load

Impact damage typically affects the exterior soffit corner resulting in additional asymmetry

Asymmetric damage to asymmetric sections loaded eccentrically results in significant biaxial flexural effects which reduce the actual and apparent capacity of the exterior girders.

Despite this, typical engineering assessment is 1D analysis K

asan

, J a

nd

Har

ries

, K.A

., 2

01

3. A

nal

ysis

of

Ecc

entr

ical

ly L

oad

ed A

dja

cen

t B

ox

Gir

der

s, A

SCE

Jo

urn

al o

f B

rid

ge

En

gin

eeri

ng

18

(1

)

9

Analysis of eccentrically loaded box girders

Biaxial nonlinear fiber element section analysis program (XTRACT)

Determines Mx-My failure surface based on user selected failure strains:

εcu = 0.003

εpu = 0.010

εsu = 0.100

Kasan, J and Harries, K.A., 2013. Analysis of Eccentrically Loaded Adjacent Box Girders, ASCE Journal of Bridge Engineering 18 (1)

10

Test Girder from Lake View Drive Bridge

Harries, K.A. (2009) Structural Testing of Prestressed Concrete Girders from the Lake View Drive Bridge, ASCE Journal of Bridge Engineering 14(2)

11


PLAN

A

84'-2" test span

rock anchorsELEVATION

Load Apparatus

Load Apparatus

48”

SECTION A-A

1 1/2” thread rodtension ties

double channelstrong back

double channelstrong back

4 - 60 kip hydraulichollow-core rams

rock anchors

support block

footing

steelstub

column

Har

ries

, K.A

. (2

00

9)

Stru

ctu

ral T

esti

ng

of

Pre

stre

ssed

Co

ncr

ete

Gir

der

s fr

om

th

e L

ake

Vie

w D

rive

Bri

dge

, ASC

E J

ou

rna

l of

Bri

dg

e E

ng

inee

rin

g 1

4(2

)

12


0

10

20

30

40

50

60

70

80

0 1 2 3 4

Applie

d L

oad, P

(kip

s)

Lateral Deflection at Midspan (in.)

top flange

bottom flange

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10

Applie

d L

oad, P

(kip

s)

Deflection , (inches)

P P

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2 4 6 8 10

Late

ral D

efle

ction (

in)

Midspan Deflection, (in)

P P

Harries, K.A. (2009) Structural Testing of Prestressed Concrete Girders from the Lake View Drive Bridge,

ASCE Journal of Bridge Engineering 14(2)

13

Analysis of Lake View Drive Exterior Girder

WEST EAST

0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 m

A B C D E F G H J

impact damage at D damage at E impact damage at F damage at G spalling at J

Locate and identify nature and extent of damage along length of beam

Harries, K.A. and Kasan, J.L. 2012. Assessment of Damaged Prestressed Adjacent Box Girder Bridges: A Case Study, Proceedings of 14th International Conference on Structural Faults and Repair Edinburgh

14


Perform multiple 2D sections analyses, stitching these together considering ‘redevelopment’ of severed strands.

0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 250

2000

4000

6000

5000

3000

1000

8000

7000

distance along beam, west to east (m)

mom

ent,

kNm


15

0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 250

2000

4000

6000

5000

3000

1000

8000

7000


mom

ent,

kNm

moment due to girder self weight

moment due to self weightplus 326.5 kN applied load

326.5 kN applied axle load

111.2 kN applied axle load


Applied moment


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0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 250

2000

4000

6000

5000

3000

1000

8000

7000


mom

ent,

kNm

barrier wall

NORTH web

Observed Failure and Damage


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0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 250

2000

4000

6000

5000

3000

1000

8000

7000


mom

ent,

kNm

100% strand removed 125% strand removed1D analysis:

2 100% strand removed 125% strand removedD analysis:

Significant over estimation of capacity using conventional 1D analysis.

Underestimation of capacity if only critical section is considered.

In this case, 125% rule accounted for additional unseen damage.


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Field testing of Prestressed Box Girder

Damaged exterior girder recovered from decommissioned bridge in SW PA

Harries, K.A., Holford, A. and Kasan, J. 2013. Demonstration of Fiber Optic Instrumentation System for Prestressed Concrete Bridge Elements, ASCE Journal of Performance of Constructed Facilities

Girder at test site prior to recasting top slab

Applied loading using same set-up as Lake View Drive study Impact and subsequent

deterioration damage documented

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Girder capacity predictions made accounting for eccentricity and

strand redevelopment

Harries, K.A., Holford, A. and Kasan, J. 2013. Demonstration of Fiber Optic Instrumentation System for Prestressed Concrete Bridge Elements, ASCE Journal of Performance of Constructed Facilities

Instrumentation using innovative fiber optic system based on the principle of microbending and the measurement of intensity modulation.

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High precision data that tracked girder behaviour even at low stress levels.

Outstanding correlation with predictions including measurements not otherwise possible to obtain in situ.

Har

ries

, K.A

., H

olf

ord

, A. a

nd

Kas

an, J

. 20

13

. Dem

on

stra

tio

n o

f F

iber

Op

tic

Inst

rum

enta

tio

n S

yste

m fo

r P

rest

ress

ed C

on

cret

e B

rid

ge E

lem

ents

, ASC

E

Jou

rna

l of

Per

form

an

ce o

f C

on

stru

cted

Fa

cili

ties

21

So…where are we?


Improved understanding and execution of in situ assessment.

Integration of beneficial effects of strand redevelopment.

Analytic tools that better capture anticipated eccentric behavior of exterior box girders.

Tools for improved SHM of in situ structures.

Now we need to establish which girders can be repaired and by which means.

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Establishing a ‘Spectra of Repair’

Kasan, J.L., Harries, K.A., Miller, R.A. and Brinkman, R. 2013. Limits of Application of Externally-Bonded CFRP Repairs for Prestressed Concrete Girders, ASCE Journal of Composites for Construction 17 (6)

Extensive study involving the design of 541 repairs of 3 prototype girders subject to damage ranging from minor to severe.

Each repair was assessed based on practicality, constructability and LRFR rating and compared to its original ‘as built’ capacity.

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Prototype girders (3):

Adjacent and Spread Box Girders and AASHTO I-girders

Impact damage resulting in :

1.8% to over 40% strand loss; residual capacity as low as 40% of as built

Repair techniques (10):

strand splicing EB-CFRP strip EB-CFRP fabric bPT-CFRP uPT-CFRP P-CFRP NSM-CFRP PT-steel steel jacket hybrid replace girder

Normalized rating factors:

for which,

CD ≥ 1.1DC + 1.1DW + 0.75(LL+IM) ±γPP

Undamaged girder: RF0 =1.0

Damaged girder: RFD < 1.0

Repaired girder: RFR > RFD

Objective is to determine whether RFR is adequate for continued operation.

PDWDCC

PDWDCCRF

PDWDC

PDWDCD

D

0

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Example: Exterior AB girder repaired with EB-CFRP

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

rep

aire

d r

atin

g f

acto

r, R

FR

damaged rating factor, RFD

AB 3-2-0 example (see text)

AB 2-1-0 with 2-50mm CFRP strips (see text)

AB

3-2

-0

as-b

uil

t R

F0

= 1

.0

most

damaged

least

damaged

AB

6-5

-2-2

-2

AB

2-1

-0

AB

1-0

-0

maximum feasible repair

(24-50 mm CFRP strips)

unrepaired RFR

18- 50mm CFRP strips

6-50mm CFRP strips

12-50mm CFRP strips

objective RFR = 1.0

range of

damage


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Example: Exterior AB girder repaired with EB-CFRP

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

rep

aire

d r

atin

g f

acto

r, R

FR


AB 3-2-0 example (see text)

AB 2-1-0 with 2-50mm CFRP strips (see text)

AB

3-2

-0

as-b

uil

t R

F0

= 1

.0

most

damaged

least

damaged

AB

6-5

-2-2

-2

AB

2-1

-0

AB

1-0

-0

maximum feasible repair

(24-50 mm CFRP strips)

unrepaired RFR

18- 50mm CFRP strips

6-50mm CFRP strips

12-50mm CFRP strips

objective RFR = 1.0

range of

damage

15 – 50 mm EB CFRP strips

Damaged girder: RFD = 0.88

Repaired girder:

RFR = 1.05


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Limitations of Repair Techniques

all external

techniques CD ≥ 1.1DC + 1.1DW + 0.75(LL+IM) ±γPP

Repair

Technique

Limitation of Repair Techniques

Geometric

Constraint CFRP Bond

Maximum number of strands

replaced

EB-CFRP

soffit:

bf ≤ b

bPT-CFRP can also restore lost

prestress force:

bPT-CFRP

soffit:

bf ≤ ≈0.5b

NSM-CFRP

soffit:

bf ≤≈0.5b εfd = 0.7εfu

strand

splices

limited to developing 0.85fpu in stands 12.7 mm diameter or less; therefore

effective number of strands restored by strand splices = 0.85nspliced

limited to splicing 15% of strands in a girder regardless of staggering

fu

ff

cfd 9.0

tnE

'f083.0

fufu

ff

cfd 9.0

tnE

'f083.0

HAf

HbntEn

ppu

fdfffmax

ppe

fufffPTmax

Af

bntEn


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Hybrid Repair – Strand Splices and EB-CFRP

Kasan, J.L., Harries, K.A., Miller, R.A. and Brinkman, R. 2013. Repair of Prestressed Concrete Girders Combining Internal Strand Splicing and Externally-Bonded CFRP Techniques, ASCE Journal of Bridge Engineering

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

repair

ed r

ati

ng f

acto

r, R

FR


as-

bu

ilt

RF

0=

1.0

damaged

prototype girder

RFD = 0.59

objective RFR = 1.0

installation of 5

strand splices

RFR = 0.79 see Figure 4

additonal installation

of 4 plies EB-CFRP

RFR = 0.95

560 mm

178

mm

Example: Exterior IB girder (25% strand loss):

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Hybrid Repair – Strand Splices and EB-CFRP

Kasan, J.L., Harries, K.A., Miller, R.A. and Brinkman, R. 2013. Repair of Prestressed Concrete Girders Combining Internal Strand Splicing and Externally-Bonded CFRP Techniques, ASCE Journal of Bridge Engineering

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

repair

ed r

ati

ng f

acto

r, R

FR


as-

bu

ilt

RF

0=

1.0

damaged

prototype girder

RFD = 0.59

objective RFR = 1.0

installation of 5

strand splices

RFR = 0.79 see Figure 4

additonal installation

of 4 plies EB-CFRP

RFR = 0.95

560 mm

178

mm

Example: Exterior IB girder (25% strand loss):

undamaged strandrepaired with strand splice

not repaired

4 plies EB-CFRP

1 ply CFRP U-wrap

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So…was Harries right or just a braggard?


First, some history:

The BIV-48 girder had 60 – 3/8” 250 ksi strands. From inspections:

1994: 14 of 60 (23%) strands reported severed RFD ≈ 0.77

2004: 20 of 60 (33%) strands reported severed RFD ≈ 0.66

post collapse: 32 of 60 (53%) strands reported severed RFD ≈ 0.47

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Residual capacity of girder was inadequate – the girder collapsed under its own self weight!

CD < 1.1DC + 1.1DW + 0.75(LL+IM)

Although this could have been remediated by:

• removing wearing surface; replacing with composite deck

• replacing 700 lb/ft barrier wall with steel barrier rail (girder was no behaving compositely with bridge therefore 100% of barrier load carried by exterior girder)

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RFD ≈ 0.47

Maximum available repairs:

EB-CFRP RFR ≈ 0.75

bPT-CFRP RFR ≈ 1.08

Strand splicing and NSM-CFRP is not recommended for box girders

So… technically, the girder was repairable and, being an exterior girder, was perhaps adequate with a rating factor of about 0.75.

32

Bibliography

Kasan, J.L., Harries, K.A., Miller, R.A. and Brinkman, R. 2013. Repair of Prestressed Concrete Girders Combining

Internal Strand Splicing and Externally-Bonded CFRP Techniques, ASCE Journal of Bridge Engineering

Kasan, J.L., Harries, K.A., Miller, R.A. and Brinkman, R. 2013. Limits of Application of Externally-Bonded CFRP

Repairs for Prestressed Concrete Girders, ASCE Journal of Composites for Construction

Harries, K.A., Holford, A. and Kasan, J. 2013. Demonstration of Fiber Optic Instrumentation System for

Prestressed Concrete Bridge Elements, ASCE Journal of Performance of Constructed Facilities

Kasan, J and Harries, K.A., 2013. Analysis of Eccentrically Loaded Adjacent Box Girders, ASCE Journal of Bridge

Engineering

Briere, V., Harries, K.A., Kasan, J. and Hager, C. 2013. Dilation Behavior of Seven-Wire Prestressing Strand – The

Hoyer Effect, Journal of Construction and Building Materials

Harries, K.A. and Kasan, J.L. 2012. Assessment of Damaged Prestressed Adjacent Box Girder Bridges: A Case

Study, Proceedings of 14th International Conference on Structural Faults and Repair Edinburgh

Kasan, J. and Harries, K.A., 2011. Redevelopment of Prestressing Force in Severed Prestressing Strand, ASCE

Journal of Bridge Engineering

Kasan, J. and Harries, K.A. 2010. Repair of Prestressed Concrete Adjacent Box Girder Bridges, Proceedings of

the International Conference on Short and Medium Span Bridges, Niagara Falls, Canada

Kasan, J. and Harries, K.A. 2009. Repair of Impact-damaged Prestressed Concrete Bridge Girders with CFRP,

Proceedings of the Asia-Pacific Conference on FRP in Structures (APFIS 2009), Seoul.

Harries, K.A. 2009. Structural Testing of Prestressed Concrete Girders from the Lake View Drive Bridge ASCE

Journal of Bridge Engineering

33

SWANSON school of engineering

civil and environmental engineering

structural engineering and mechanics

Watkins Haggart structural engineering laboratory

Extending the Life of Prestressed Concrete Bridge Infrastructure

Kent A. Harries, PhD, FACI, P.Eng University of Pittsburgh

Jarret Kasan, PhD HDR Inc., Pittsburgh

extending the life of prestressed concrete bridge ... the life of... · extending the life of...

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