Fatigue and Serviceability of GFRP Reinforced Bridge Decks

1

Bridge Deck Research at Villanova University

Fatigue and Serviceability of

GFRP Reinforced Bridge

Decks Designed by Traditional

and Empirical Methodologies

Presented at the 2015 AASHTO SCOBS T6 Committee Meeting,

Saratoga Springs, NY

Villanova Faculty

Joseph Robert Yost (corresponding: [email protected]),

David Dinehart, Shawn Gross

2

Two full scale bridge decks, each -

• 33 ft. – 6 in. by 8 ft.

• AASHTO TYPE II support

• Girder spacing = 9 ft. x 3

• Fascia overhang = 3 ft. 3 in.

• 8 in. thick deck

• 3 in. haunch with shear reinforcement

• Fatigue loaded for critical M+ and M- load cases with 2,000,000 load cycles/load case

South half (TDM)

North half (EDM)

33 ft. - 6 in.

Deck thickness = 8 in.

AASHTO Type II support (typ.) 3 ft. - 3 in. (typ.)

Full parapet (typ.)

3 equal spaces at 9 ft. = 27 ft.

Research Scope

South North

GFRP

Reinforced

AASHTO

TraditionalCSA Empirical

Steel

Reinforced

AASHTO

Traditional

AASHTO

Empirical

DeckDesign Method

3

1. Research Scope

2. Sample Fabrication and Material Properties

3. Load Cases and Design Methodology

4. Experimental Details

5. Test Results

6. Conclusions and Findings

Presentation Overview

4

Sample Fabrication

Supporting Beams Poured First

Parapets poured last Finished samples

Deck poured next (GFRP reinforced deck shown)

5

Str

ess

Strain

Steel: Elatic-plastic

GFRP: Elastic-brittle

Material Properties

• GFRP supplier – Hughes Brothers

• Epoxy coated steel rebar

• Concrete

• Supplier – JDM Materials

• PennDOT Class AAA

• 1 truck per deck

• Poured on same day

Steel GFRP Concrete

Fy or Fu (ksi)

Es or Ef (ksi)

f'c (ksi)

Steel

Reinforced60 29,000 7.6

GFRP

Reinforced105 6,700 5.8

Deck Sample

6

• Tensile strengths 1.5 to 2 times as great as Grade 60 steel • 25% the weight of steel • Modulus about 25% of steel • Impervious to Chlorides and low pH chemicals

Nominal Area Tensile Strength Modulus of Elasticity

(in2) (ksi) (ksi)

Steel #5 0.307 60 29,000

GFRP #5 0.307 105 6,700

Bar SizeMaterial

Hughes Brothers Aslan 100 FRP

• Manufactured through a pultrusion process

• Sand-coated and helically wrapped to increase bond

• Brittle behavior leads to over-reinforced design

• Design guides published by : o American Concrete Institute (ACI)

o American Association of State Highway and Transportation Officials (AASHTO)

o Canadian Standards Association (CSA)

Properties of Glass Fiber Reinforced Polymer (GFRP) Rebar

7

1. Research Scope




5. Test Results


7. Future Research


8

Pservice = PLL {m} {IM} where, PLL = HS25 Truck Load = 20 kips/wheel or 40 kips/axle m = multiple presence factor = 1.2 for 1 lane loaded IM = impact factor = 1.33 Pservice = 64 kips/axle

The service load used for testing was based on HS25 loading and calculated as follows:

32 k 32 k

Service Limit State

9

Positive bending (MP-TR)

Negative bending (MN-TR)

Positive bending (MP-EM)

Negative bending (MN-EM)

Each for

GFRP Reinforced Deck

Steel Reinforced Deck

Traditional Design

(South half)

Empirical Design

North half)

Load Case Summary

Traditional Design Empirical Design

Negative Traditional

Positive Empirical

Negative Empirical

Positive Traditional

3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 1.5 ft 1.5 ft

South North

MP-EM

MN-EM

MP-TR

MN-TR

The deck was subjected to four (4) load cases

10

GFRP Reinforced Deck Design

AASHTO Traditional Design

• LRFD Bridge Design Guide Specifications for GFRP-Reinforced Concrete Bridge Decks and Railings (AASHTO 2009)

• Based on strength fMn > Mu using Equivalent Strip (ES)

• Overreinforced for flexure

• Cracking width: w ≤ 0.02 in. (Art. 2.9.3.4)

• Concrete stress: fc ≤ 0.45 f’c (Art. 2.9.3.6)

• Deflection: D ≤ L/1000 (Art. 2.7.2)

CSA Empirical Design

• Design recognizes arching action

• Canadian Standards Association (CSA) Empirical Design Published in Clause 16.8.8.1 of Canadian Highway Bridge Design Code (CSA, 2006)

11

AASHTO Strength (Traditional) Design

• Based on flexural strength fMn > Mu

• Underreinforced for flexure

• Designing using Equivalent Strip (ES)

• PennDOT modifications

AASHTO Empirical Design

• Design recognizes arching action

• Failure punching shear

• Composite, cast-in-place, other

• 0.27in2/ft. in bottom layers (#5@12”)

• 0.18 in2/ft. in top layers (#4@12”)

Steel Reinforced Deck Design

12

Reinforcement Summary

Traditional Design Empirical Design

Transverse bars

Longitudinal bars

bottom bars

top bars

Top clear cover 2.5" steel

1.0" GFRP

Bottom cover 1.0" steel

1.0" GFRP

Negative Traditional

Positive Empirical

Negative Empirical

Positive Traditional

3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 3 ft 1.5 ft 1.5 ft

(# at in.) (in2 / ft) (# at in.) (in

2 / ft) (# at in.) (in

2 / ft) (# at in.) (in

2 / ft) (in

2 / ft

2)

Strength#5 at

5.5"0.67 #5 at 6" 0.61 #4 at 12" 0.20 #5 at 9" 0.41 1.89

Empirical #4 at 12" 0.20 #5 at 12" 0.31 #4 at 12" 0.20 #5 at 12" 0.31 1.01

Ratio (E/S) 0.29 0.50 1.00 0.75 0.53

Strength #5 at 4" 0.92 #5 at 4" 0.92 #5 at 10" 0.37 #5 at 5" 0.74 2.95

Empirical #5 at 12" 0.31 #5 at 4" 0.92 #5 at 12" 0.31 #5 at 12" 0.31 1.84

Ratio (E/S) 0.33 1.00 0.83 0.42 0.63

Steel

GFRP

Design

Transverse Longitudinal

Total

Top BottomTop BottomMaterial

South North

MP-EM

MN-EM

MP-TR

MN-TR

13

1. Research Scope




5. Test Results


7. Future Research


14

Instrumentation Plan

15

Pretest Phase - Crack deck

Overload Phase - Stabilize deck

Fatigue Phase 1 - 1,000,000 cycles/load-case at fatigue limit state

Fatigue Phase 2 - 1,000,000 cycles/load-case at service limit state

Load Schedule

For each load phase, four load cases were applied and sequenced as:

1) Negative Bending Traditional (MN-TR)

2) Negative Bending Empirical (MN-EM)

3) Positive Bending Traditional (MP-TR)

4) Positive Bending Empirical (MP-EM)

Conclusion – each deck loaded in total by 8 million cycles

64 k

Pretest phase

(PTP)

Lo

ad

Time

80 k

36 k

60 k

2 C

ycl

es

100

Cycl

es

1 k

1 Million

Cycles

Overload phase

(OLP)

Fatigue Phase 1 (FP1)

Fatigue Phase 2 (FP2)

1 Million

Cycles

16

Pretest and Overload Phases Signal Stabilization

Crack Width on GFRP Deck MN-TR

0

10

20

30

40

50

60

70

80

90

0 0.01 0.02 0.03 0.04

Ap

pli

ed

Lo

ad (

kip

s)

Deflection (in) - LVDT 5

Pretest Phase (PTP)

Overload Phase (OLP)

Last 10 Cycles OLP0

10

20

30

40

50

60

70

80

90

-0.006 -0.005 -0.004 -0.003 -0.002 -0.001 0.000

Ap

pli

ed

Lo

ad (

kip

s)

Crack Width (in) - Pi Gage 2

Pretest Phase (PTP)

Overload Phase (OLP)

Last 10 Cycles OLP

Continued Crack Opening

Initial Crack OpeningStable

Crack Stable Deflection

Results for Crack Width on GFRP Deck; Negative Bending - Traditional Design

Negative Bending

Traditional Design

crack

measurement

17

1. Research Scope




5. Test Results


7. Future Research


18

Serviceability Limits

Deflection (2)

(in) (mm) (in) fc (ksi) ec (me) (4)

GFRP 0.02 0.51 0.108 1.8 (3) 600

(2) L/1000 and L = 9 x 12 in

(3) AASHTO GFRP Art. 2.9.3.6 (2009) f c < .45(f'c = 5.8 ksi) = 2.6 ksi

(4) ec = fc / Ec where Ec = 57 {f'c = 5800 psi}

1/2 ksi

(1) AASHTO GFRP Art 2.9.3.4 (2009)

Material

Allowable Limit

Crack width (1) CC Stress & Strain

19

Sequence

Hysteresis at 1 and 2 million cycles with % Allowable at 2M

• Crack width (negative and positive bending)

• Deflection (negative and positive bending)

• Concrete Strain (negative and positive bending)

% Allowable at 2 million - GFRP vs. Steel

• Crack width

• Deflection

• Concrete Strain

Profile Plots

• Deflection

• Concrete strain

20

GFRP results at 1 and 2 million cycles Crack Width - Negative Bending

Traditional Design Empirical Design MN-EM MN-TR

crack measurement crack measurement

0

64

-0.02 0.00

Load

(k

)

Crack width (in)

MN-TR 1 million

MN-TR 2 million

MN-EM 1 million

MN-EM 2 million

AASHTO Limit (0.02 in.)

Traditional Empirical

0.3

7

0.7

7

0.0

0.2

0.4

0.6

0.8

1.0

MN-TR MN-EM

Rat

io:

Mea

sure

d/A

llow

able

at

2M

(-)

Load Case

21

GFRP results at 1 and 2 million cycles Crack Width - Positive Bending

Top B ottom Top B ottom

(# atin.) (# atin.) (# atin.) (# atin.)

S treng th # 5at4in. # 5at4in. # 5at10in. # 5at4in.

Empirical # 5at12in. # 5at12in. # 5at12in. # 5at12in.

S treng th # 5at5.5in. # 5at6in. # 4at12in. # 5at9in.


Lo ng itudinalB ars

G FR P

S teel

M aterial Desig n

TransverseB ars

Traditional

Design

Empirical

Design MP-EM MP-TR

crack measurement crack measurement

0

64

-0.02 0.00

Load

(k

)

Crack width (in)

MP-TR 1 million

MP-TR 2 million

MP-EM 1 million

MP-EM 2 million


Traditional

Empirical

0.3

1 0.4

1

0.0

0.2

0.4

0.6

0.8

1.0

MP-TR MP-EM

Rat

io:

Mea

sure

d/A

llow

able

at

2M

(-)

Load Case

22

GFRP results at 1 and 2 million cycles Deflection - Negative Bending


0

64

0.00 0.12

Lo

ad (

k)

Deflection (in)

MN-TR 1 million

MN-TR 2 million

MN-EM 1 million

MN-EM 2 million


Traditional

Empirical

0.4

7 0

.62

0.0

0.2

0.4

0.6

0.8

1.0

MN-TR MN-EM

Rat

io:

Mea

sure

d/A

llow

able

at

2M

(-)

Load Case

23

GFRP results at 1 and 2 million cycles Deflection - Positive Bending







Lo ng itudinalB ars

G FR P

S teel

M aterial Desig n

TransverseB ars

Traditional

Design

Empirical

Design MP-EM MP-TR

0

64

0.00 0.12

Lo

ad (

k)

Deflection (in)

MP-TR 1 million

MP-TR 2 million

MP-EM 1 million

MP-EM 2 million


Traditional

Empirical

0.5

0

0.7

3

0.0

0.2

0.4

0.6

0.8

1.0

MP-TR MP-EM

Rat

io:

Mea

sure

d/A

llow

able

at

2M

(-)

Load Case

24

GFRP results at 1 and 2 million cycles Concrete Strain - Negative Bending


0

64

-600 0

Lo

ad (

k)

Critical concrete strain (me)

MN-TR 1 million

MN-TR 2 million

MN-EM 1 million

MN-EM 2 million

Traditional Empirical

AASHTO Limit (600 me)

0.5

0

0.7

4

0.0

0.2

0.4

0.6

0.8

1.0

MN-TR MN-EM

Rat

io:

Mea

sure

d/A

llow

able

at

2M

(-)

Load Case

25

GFRP results at 1 and 2 million cycles Concrete Strain - Positive Bending







Lo ng itudinalB ars

G FR P

S teel

M aterial Desig n

TransverseB ars

Traditional

Design

Empirical

Design MP-EM MP-TR

0

64

-600 0

Lo

ad (

k)

Critical concrete strain (me)

MP-TR 1 million

MP-TR 2 million

MP-EM 1 million

MP-EM 2 million

Traditional

Empirical

AASHTO Limit (600 me)

0.3

7

0.5

8

0.0

0.2

0.4

0.6

0.8

1.0

MP-TR MP-EM

Rat

io:

Mea

sure

d/A

llow

able

at

2M

(-)

Load Case

26

% Allowable - Crack Width GFRP vs. Steel at 2 million cycles

0.5

3

0.4

2

0.5

3

2.0

0

0.3

1

0.4

1

0.3

7

0.7

7

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

MP-TR MP-EM MN-TR MN-EM

Cra

ck-w

idth

Rat

io:

Mea

sure

d/A

llo

wab

le (

-)

Load Case

Steel GFRP

27

% Allowable - Deflection GFRP vs. Steel at 2 million cycles

0.7

7

1.1

0

0.5

7

0.9

9

0.5

0

0.7

3

0.4

7

0.6

2

0.0

0.2

0.4

0.6

0.8

1.0

1.2


Def

lect

ion R

atio

: M

easu

red

/All

ow

able

(-)

Load Case

Steel GFRP

28

% Allowable - Concrete Strain GFRP vs. Steel at 2 million cycles

0.6

8

0.7

1

0.3

7

1.4

6

0.3

7

0.5

8

0.5

0

0.7

4

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4


CC

Str

ess

Rat

io:

Mea

sure

d/A

llo

wab

le (

-)

Load Casee

Steel GFRP

29

Profiles at 2 Million Cycles Deflection

-0.0341

-0.0411

0.0038

-0.0342

0.0011

-0.0426 -0.050

-0.040

-0.030

-0.020

-0.010

0.000

0.010

0 9 18 27

Def

lect

ion

(in

)

Deck Width (ft)

Traditional Design: Before

Traditional Design: After

Empirical Design: Before

Empirical Design: After

G1

G2 G3 G4

-0.0249

-0.0233

0.0019

-0.0221

-0.0288

0.0068

-0.0287

-0.0383 -0.045

-0.040

-0.035

-0.030

-0.025

-0.020

-0.015

-0.010

-0.005

0.000

0.005

0.010

0 9 18 27

Def

lect

ion

(in

)

Deck Width (ft)





G1 G2 G3

G4

Negative Bending

(MN-TR and MN-EM)

Positive Bending

(MP-TR and MP-EM)

30

Negative Bending

(MN-TR and MN-EM)

Positive Bending

(MP-TR and MP-EM)

Profiles at 2 Million Cycles Concrete Strain

-108

-179 -189

-173

-240 -246

-300

-250

-200

-150

-100

-50

0

50

100

0 9 18 27

Co

ncr

ete

Str

ain

(µε)

Deck Width (ft)

Taditional Design: Before




G1

G2 G3 G4

-140

-186 -177

-242

-300

-250

-200

-150

-100

-50

0

50

100

150

0 9 18 27

Con

cret

e S

trai

n (µε)

Deck Width (ft)





G1

G2 G3 G4

31

Conclusions and Findings

• For GFRP Traditional Design, Maximum % Allowable After 2 M Cycles

Crack Width = 37%

Deflection = 50%

CC Strain = 50%

• For GFRP Empirical Design, Maximum % Allowable After 2 M Cycles

Crack Width = 77%

Deflection = 73%

CC Strain = 74%

• Signal magnitude and stiffness stable after 2 million load cycles

• In many cases % Allowable for GFRP better than steel for like design (Traditional & Empirical) and like load case (Positive & Negative)

32

Questions?

• For further information please contact

Joseph Robert Yost, Ph.D., PE

Professor, Structural Engineering

Department of Civil and Environmental Engineering

Villanova University

800 Lancaster Avenue, Villanova, PA 19085-1681

Email: [email protected]

Phone/Fax: 610-519-4955/6754

Documents

Fatigue and Serviceability of GFRP Reinforced Bridge Decks