1

Advanced Composite Material Applications in Structural Engineering

Advances and Challenges

Advanced Composite Material Advanced Composite Material

Applications in Structural EngineeringApplications in Structural Engineering

Advances and ChallengesAdvances and Challenges

By

Amjad J. Aref

Structural Engineering Lecture Series - October 18, 2007

2

OUTLINE

Introduction: What are Composite Materials?

Bridge Applications

Final Remarks

3

What are Composite Materials?

Composite structures are often called fiber reinforced polymer (FRP) structures, and polymer matrix composites (PMC).

Composite materials are man-made, and must contain at least two constituents that are distinct chemically and physically.

Intended to achieve an increase in certain properties such as stiffness, strength, fracture toughness among others, or decrease certain properties such as weight and corrosion. Composites in general can be categorized in two groups as follows:

4

Composites Architecture

Reinforcement

Interface

Matrix

5

ReinforcementLong continuous bundles

l/d > 10 by definition, (typical dia for a fiber ~ 6-15 µm)unidirectionalmultidirectionalwoven or braided Continuous fibers

Short chopped fibersrandomly oriented

Whiskerslong thin crystals d< 1 micron length in the order of 100 microns used in ceramic matrix composites (CMC) and metal matrix composites (MMC)

ParticulatesNear sphericalnot usually used for strengthincrease the toughness of the material

Flakesmetallic, electrical/heating applications2-D in nature, not usually used for strength

6

Reinforcement (cont’d)Glass (E-, S-, C-glass fibers)E-glass: Young’s modulus ~ 72 GPa, σu=3450 MPa (500 ksi ), Strain to failure 1-2%

Carbon EL:250-517 GPa, ET=12-20 GPaσu=2000-2900 MPa (290-435 ksi), strain to failure 0.5-1%

Kevlar, Spectra (organic)E: 62-131GPaσu=2500-3790 MPa (360-550 ksi), strain to failure 2-5%

Ceramic fibers: high strength, stiffness and temperature stabilityAlumina (Al2O3)E: 370 GPaσu=1380 MPa (200 ksi)SiC

Boron (toxic material), typically large diameter

7

Matrix

Metallic

Ceramic

Polymeric– Thermoplastic– Thermoset

8

Polymer Matrix

Linear Branched

Cross-linked

Network

Poly mer

9

Composites Categories

Reinforced Plastics

Low strength and stiffness

Inexpensive

Glass fibers is primary reinforcement

Applications:o Boat Hullso Corrugated sheetso Pipingo Automotive panelso Sporting goods

Advanced Composites

High strength and stiffness

Expensive

High performance reinforcement such as: graphite, aramid, kevlar

Applications:Aerospace industry

10

Typical Applications in Structural Engineering

Retrofitting of beams and columns

Seismic Retrofitting

New applicationsBridge DeckBridge Superstructure

11

FRP COMPOSITES IN STRUCTURAL APPLICATIONS

Advantages– High specific strength

and stiffness– Corrosion resistance– Tailored properties– Enhanced fatigue life– Lightweight– Ease of installation– Lower life-cycle costs

Factors preventing FRP from being widely accepted– High initial costs– No specifications– No widely accepted

structural components and systems

– Insufficient data on long-term environmental durability

12

CONDITIONS OF U.S. HIGHWAY BRIDGES

28% of 590,000 public bridges are classified as “deficient”.

The annual cost to improve bridge conditions is estimated to be $10.6 billion.

24

18

23

17

21

14

20

14

19

14

18

14

17

14

17

13

16

14

15

14

15

14

14

14

0

5

10

15

20

25

30

35

40

45

Perc

enta

ge o

f Def

icie

nt B

ridge

s (%

)

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001Year

Functionally ObsoleteStructurally Deficient

Need for bridge systems thathave long-term durability andrequire less maintenance (Source: National Bridge Inventory)

13

Demand for FRP in Bridge Applications

Is it necessary to use expensive FRP materials for bridge renewal?

Given the massive investment to renew deficient bridges (28% of all bridges are deficient), repeating the same designs, materials, etc. may not be a prudent approach.

Consider the fact that the average life span of a bridge in the U.S. is less than 50 years.

FRP materials, if designed properly, could provide new bridges that last over 100 years.

14

GLASS FIBER REINFORCED POLYMER (GFRP) BOX SECTIONS

The compressive flange is weaker than the tensile flange.

A failure of a GFRP box section usually occurs in a catastrophic manner.

The design of a GFRP box section is usually governed by stiffness instead of strength.

Hybrid designor

Special structural

system

15

BRIDGE APPLICATIONS – 1(TOM’S CREEK BRIDGE)

Virginia Tech and Strongwell

Pultruded composite beam (hybrid design of glass and carbon fibers and vinyl ester matrix)

Span : 5.33 m , Width : 7.32 m

203mm

152 mm

16

BRIDGE APPLICATIONS – 2(TECH 21 BRIDGE)

LJB Engineers & Architects, Inc. and Martin Marietta Materials

Length : 10.1 m, Width : 7.3 m

E-glass fiber reinforcement and polyester matrix

Deck : pultruded trapezoidal tubes between two face sheets (tubes run parallel with the traffic direction)

Stringer : three U-shaped structural beams

838mm

17

BRIDGE APPLICATIONS – 3(KINGS STORMWATER CHANNEL BRIDGE)

UC San Diego, Alliant TechSystems, Inc., and Martin Marietta

Span: 2 x 10 m, Width: 13 mSix longitudinal concrete filled carbon tube girders (carbon/epoxy system)GFRP deck panel (pultruded trapezoidal E-glass/epoxy tubes with a top skin layer

Filament wound CFRP tube GFRP deck

18

BRIDGE APPLICATIONS – 4(TOOWOOMBA BRIDGE)

University of Southern Queensland, Wagners Composite FibreTechnologies, and Huntsman CompositesSpan : 10 m, Width : 5.0 mHybrid box beams : prefabricated concrete, GFRP, and CFRP

350

450

100

(dimensions in mm)

concrete

GFRP

CFRP

19

MARKET SHARE (FRP COMPOSITES)

Consumer7%

Corrosion12%

Marine10%

Transportation31%

Construction20%

Appliance6%

Aerospace1%

Other3%

Electrical10%

20

FRP COMPOSITE SHIPMENTS

U.S. Composite Shipments

0

100

200

300

400

500

600

60 65 70 75 80 85 90 95 00

Year

Ship

men

ts (T

hous

ands

of M

etric

Ton

s)

AerospaceApplianceConstructionConsumerCorrosionElectricalMarineTransportationOther

21

Recent Development of FRP Bridge Recent Development of FRP Bridge Deck and Superstructure SystemsDeck and Superstructure Systems

22

Hybrid-FRP-Concrete Bridge Deck and Superstructure System

The system is developed at UB by an optimum selection of concrete and FRP.

The system is validated analytically and experimentally to assess the feasibility of the proposed hybrid bridge superstructure and deck.

Simple methods of analysis for the proposed hybrid bridge superstructure were developed.

23

BASIC CONCEPT OF PROPOSED HYBRID FRP-CONCRETE BRIDGE

Single span with a span length of 18.3 m

AASHTO LRFD Bridge Specifications– Live load deflection check

dLL<L/800 under (1+IM)Truck

– Service I limit

DC+DW+Lane+(1+IM)Truck

– Strength I limit

1.25DC+1.5DW+1.75[Lane+(1+IM)Truck]

Concrete should fail first in flexure.

A strength reduction factor for GFRP was taken as 0.4.

18288 mm

99mm

1160mm

3785 mm

Simple-span one-lane hybrid bridge

24

PROPOSED HYBRID BRIDGE SUPERSTRUCTURE

Advantages include:– Increase in stiffness– Corrosion resistance– Cost-effectiveness– Lightweight– Local deformation reduction– High torsional rigidity– Pre-fabrication– Short construction period

25

DISPLACEMENT AND STRENGTH CHECKS

Deflection check: 0.61 x L/800Max. failure index : 0.107 (safety factor=3.1)

(a) Live load deflection check (b) Tsai-Hill Failure index under Strength I limit

26

TSAI-HILL FAILURE INDEX

2

26

2

22

221

2

21

SYXXITH

σσσσσ++−=

Failure condition : 0.1=THI

where} {}{ 122211621 τσσσσσ =

SYX and , , : Strengths in the principal 1 and 2 directions and in-plane shear

: Tensile and compressive directions

⎩⎨⎧ >

= otherwise 0for 1

C

T

XX

Xσ

⎩⎨⎧ >

= otherwise 0for 2

C

T

YY

Yσ

CT and

27

EXPERIMENTAL PROGRAM

Materials– GFRP– Concrete

Non-destructive tests– Flexure– Off-axis flexure

Fatigue testDestructive tests– Flexure– Shear– Bearing

28

TEST SPECIMEN

One-fifth scale modelSpan length = 3658 mm

19.9R12.5

R12.5

R12.5

R12.5

5.28

3.962.31

193212

220188

232

142307142591

307142307750757

(dimensions in mm)

29

STACKING SEQUENCES

Inner TubeLaminate

Outer-Most Laminate

Outer Tube Laminate

]0[ 7°

]0)45[( 48 °°±

]0[ 16°

Thickness of one layer = 0.33-0.40 mm

30

FABRICATION – 1

31

FABRICATION – 2

32

SHEAR KEYS

Shear keys

610

305

51 4.8

Longitudinal direction

(dimensions in mm)

33

MATERIALS – GFRP

E-glass woven fabric reinforcement– Cheaper than carbon

fiber reinforcement– Impact resistance

Vinyl ester– High durability– Extremely high

corrosion resistance– Thermal stability

63.8--2.45Warp

56.1--2.72FillShear

-2650.25422.5Warp

-2410.09915.9FillComp

3350.13117.9Warp

2850.12916.6FillTens

Strength(MPa)

νE or G (GPa)

Dir.Test

Material Properties

Fill

Warp

34

GFRP – TENSION

0

50

100

150

200

250

300

350

0 0.005 0.01 0.015 0.02 0.025Strain

Stre

ss (M

Pa)

T0-1T0-2T0-3

35

GFRP – COMPRESSION

-300

-250

-200

-150

-100

-50

0

-0.02 -0.015 -0.01 -0.005 0 0.005Strain

Stre

ss (M

Pa)

C0-1C0-2C0-3

36

GFRP – SHEAR

0

10

20

30

40

50

60

0 0.05 0.1 0.15

Shear Strain

Shea

r Str

ess

(MPa

)

S0-1S0-2S0-3

37

MATERIALS - CONCRETE

0

5

10

15

20

25

30

35

40

45

0 0.001 0.002 0.003 0.004 0.005 0.006Strain (m/m)

Stre

ss (M

Pa)

B-1B-2B-3B-4

No coarse aggregateswater : cement : aggregate = 0.46 : 1.0 : 3.4 by weight

37.98.38

Strength (MPa)

Young’s Modulus

(GPa)

Compressive Properties

38

TEST SETUP

39

FLEXURAL LOADING CONFIGURATION

(dimensions in mm)

(b) Cross section(flexure)

(a) Elevation

(c) Cross section(off-axis flexure)

40

NONDESTRUCTIVE FLEXURE (TEST PROTOCOL)

0.0

1.0

2.0

3.0

4.0

5.0

0 270 540 810 1080 1350

Time (sec)

App

lied

Dis

plac

emen

t(X

Spa

n/24

00)

0.0

1.5

3.0

4.5

6.0

7.5

(mm

)

To examine elastic behavior of the bridge under the flexural loading

Displacement control

Max applied displ. = L/480 (L: span length)

41

NONDESTRUCTIVE FLEXURE (FORCE-DISPLACEMENT)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4Vertical Displacement (X Span/800)

App

lied

Load

(X T

ande

m L

oad)

0

5

10

15

20

25

30

0.0 1.0 2.0 3.0 4.0 5.0 6.0

(mm)

(kN

)

HybridFRP Only

G-BOT-C

G

19% increase

40% for the prototype

42

NONDESTRUCTIVE FLEXURE (TOP SURFACE DEFORMATION)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

Location (m)

Vert

ical

Dis

plac

emen

t (X

Span

/800

)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

(mm

)

0.5 x Tandem 1.0 x Tandem1.5 x Tandem 2.0 x Tandem2.5 x Tandem

HybridFRP OnlyLoading point

H

43

NONDESTRUCTIVE FLEXURE (STRAIN RESULTS)

(a) Bottom surfacealong the center-line

(b) Exterior web over height

0

100

200

300

400

500

600

0.000 0.125 0.250 0.375 0.500

Location / Span Length

Long

itudi

nal S

trai

n ( μ

)

0.5 x Tandem1.0 x Tandem1.5 x Tandem2.0 x Tandem2.5 x Tandem

Section C

Section A

Section ESection F

Section G

F GECA

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-300 -200 -100 0 100 200 300 400 500

Longitudinal Strain (μ)

Hei

ght /

Brid

ge H

eigh

t

0.5 x Tandem1.0 x Tandem1.5 x Tandem2.0 x Tandem2.5 x Tandem

GBoundaries of the concrete layer

44

FATIGUE LOADING (TEST PROTOCOL)

To examine fatigue characteristics

Flexural loading

Force control

2 x 106 cycles

Freq.= 3.0 Hz

Max. load = 2.0 x Tandem

Stiffness evaluation every 0.2 million cycles

0.0

0.4

0.8

1.2

1.6

2.0

0.00 0.25 0.50 0.75 1.00

Time (sec)

App

lied

Load

(X T

ande

m L

oad)

0

2

4

6

8

10

12

14

16

(kN

)

45

FATIGUE LOADING (TEST RESULTS)

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Millions

Applied Load Cycles

Stiff

ness

Rat

io

Average (top)Average (bottom)Average

5.9 % degradation

46

DESTRUCTIVE FLEXURE (TEST PROTOCOL)

(a) Displacement history #1

(b) Displacement history #2

Time

App

lied

Dis

plac

emen

t Step I

Time

App

lied

Dis

plac

emen

t Step II

To examine the strength of the bridge and failure modes

Flexural loading

Displacement control

Two stages– Step I (displacement history #1)– Step II (displacement history #2)

47

DESTRUCTIVE FLEXURE (TEST RESULTS – 1)

Failure load = 35 x Tandem load

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12 14 16 18 20 22

Vertical Displacement (X Span/800)

App

lied

Load

(X T

ande

m L

oad)

0

50

100

150

200

250

300

3500 10 20 30 40 50 60 70 80 90 100

(mm)

(kN

)

1st Cycle (Step I)2nd Cycle (Step I)3rd Cycle (Step I)Step IIFailure

G-BOT-C

Loud noise

Loud noise

G

localglobal

48

CHANGE OF A LOADING CONDITION

From four point loads to two line loads

contact

49

DESTRUCTIVE FLEXURE (TEST RESULTS – 2)

Failure modes– Concrete crushing– Failure of GFRP

in compression

50

DESTRUCTIVE FLEXURE(FAILURE MODES)

51

SHEAR TEST

0

5

10

15

20

25

30

35

40

0.0 1.0 2.0 3.0 4.0 5.0Vertical Displacement (X Span/800)

App

lied

Load

(X T

ande

m L

oad)

0

50

100

150

200

250

300

3500 2 4 6 8 10 12 14 16 18 20 22

(mm)

(kN

)

Actuator

Beams contacted the specimen

52

BEARING TEST

0

5

10

15

20

25

30

35

0.0 1.0 2.0 3.0 4.0 5.0

Vertical Displacement (x Span/800)

App

lied

Load

(x T

ande

m L

oad)

0

20

40

60

80

100

120

140

0 5 10 15 20

(mm)

(kN

)

Failure

53

BEARING TEST(FAILURE MODE)

54

FINITE ELEMENT ANALYSIS

ABAQUS

Four-noded general shell element, S4R, for GFRP laminates

Eight-noded general 3D solid element, C3D8, for concrete

Assumed a perfect bonding between concrete and GFRP

Linear analysis

Nonlinear analysis

55

FINITE ELEMENT DISCRITIZATION (LINEAR ANALYSIS)

Number of nodes: 31,857

Number of elements: 38,892 (22,764 for S4R and 16,128 for C3D8)

56

LINEAR FEA RESULTS(FLEXURE – 1)

Stiffness was predicted by FEA within 5% error.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4Vertical Displacement (X Span/800)

App

lied

Load

(X T

ande

m L

oad)

0

5

10

15

20

25

30

0.0 1.0 2.0 3.0 4.0 5.0 6.0

(mm)

(kN

)

ExperimentLinear FEA

G-BOT-CG

57

LINEAR FEA RESULTS (FLEXURE – 2)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

Location (m)

Vert

ical

Dis

plac

emen

t (X

Span

/800

)0.0

1.0

2.0

3.0

4.0

5.0

6.0

(mm

)

ExperimentLinear FEA

2.5 x Tandem

2.0 x Tandem

1.5 x Tandem

1.0 x Tandem

0.5 x Tandem

G

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40

Location (m)

Vert

ical

Dis

plac

emen

t (X

Span

/800

)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

(mm

)

ExperimentLinear FEA

2.5 x Tandem

2.0 x Tandem

1.5 x Tandem

1.0 x Tandem

0.5 x TandemLoading point

H

(a) Top surface (b) Bottom surface

58

LINEAR FEA RESULTS(FLEXURE – 3)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-300 -200 -100 0 100 200 300 400 500

Longitudinal Strain (μ)

Hei

ght /

Brid

ge H

eigh

t

0.5 x Tandem1.0 x Tandem1.5 x Tandem2.0 x Tandem2.5 x TandemLinear FEA

G

0.5 1.51.0 2.52.0

0

100

200

300

400

500

600

0.000 0.125 0.250 0.375 0.500

Location / Span Length

Long

itudi

nal S

trai

n ( μ

)

0.5 x Tandem1.0 x Tandem1.5 x Tandem2.0 x Tandem2.5 x TandemLinear FEA

Section C

Section

Section E

Section F

Section G

F GECA

0.5

1.5

1.0

2.5

2.0

(a) Bottom surfacealong the center-line

(b) Exterior web over height

59

FINITE ELEMENT DISCRETIZATION (NONLINEAR ANALYSIS)

A quarter model

x

y

Loadingpoint

60

NONLINEAR FEA RESULTS – 1

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25

Vertical Displacement (X Span/800)

App

lied

Load

(X T

ande

m L

oad)

0

50

100

150

200

250

300

3500 20 40 60 80 100

(mm)

(kN

)

Flexural TestFailureFRP only (Linear)Hybrid (Linear)FRP only (Nonlinear)Hybrid (Nonlinear)

G-BOT-C

G

61

NONLINEAR FEA RESULTS – 2 (DAMAGED AREA)

x

yy

xx

y

x

y

failure section

(a) FEA (b) Experiment

62

SIMPLE METHODS OF ANALYSISSimple methods– Beam analysis– Orthotropic plate analysis

Classical lamination theory

Use of effective engineering properties of laminates

Perfect bonding between concrete and GFRP was assumed.

Shear deformation was neglected

Primary objective is to obtain deflection under design loads.

63

BEAM ANALYSIS

The bridge is modeled as a beam with a span length, L, effective flexural rigidity, EIeff, and effective torsional rigidity, GJeff.

∫=Ay

yeff dAzEEI 2

∫ ∫

=ds

dzG

AGJ

xy

encleff 1

4 2

where

yE

zxyG

: Effective modulus

: Effective shear modulus

: Vertical coord. from the neutral axis

enclA

s

: Area enclosed by median lines of the top and bot. flanges and exterior webs

: Axis along the median line of a component

64

ORTHOTROPIC PLATE ANALYSIS

The bridge is modeled as an orthotropic plate with span length of L and width of W.

),(2 40

4

220

4

40

4

yxqywD

yxwH

xwD yx =

∂∂

+∂∂

∂+

∂∂

0wq

HDD yx and, ,

: Vertical displacement

: Distributed load on the plate

: Rigidities that can be obtained by using the classical lamination theory

where

65

REPRESENTATIVE UNITSFOR THE PLATE ANALYSIS

A

A

Section A-A

(a) Longitudinal direction (b) Transverse direction

66

SIMPLE METHODS OF ANALYSIS (UNDER TANDEM LOAD ONLY)

0.00

0.10

0.20

0.30

0.40

0.50

0.0 0.2 0.4 0.6 0.8 1.0

Y-coordinate (x Span)

Dis

plac

emen

t (x

Span

/800

)

FEABeamPlate

0.00

0.10

0.20

0.30

0.40

0.50

-2.0 -1.0 0.0 1.0 2.0

X-coordinate (m)

Dis

plac

emen

t (x

Span

/800

)

FEA (Top) FEA (Bot)Beam Plate

(a) Transverse direction (b) Longitudinal direction

67

SummaryComposite materials hold great promise for effective renewal of deficient bridges.

The hybrid FRP-concrete bridge superstructure is highly feasible from the structural engineering point of view.

GFRP used in this study has revealed that its stress-strain relationship is not perfectly linear-elastic. However, for design purposes, the equivalent linear model can be used.

68

Summary (CONT’D)

As is often the case with all-composite bridges, the design of the hybrid bridge superstructure is also stiffness driven.

Results from a series of quasi-static tests have shown an excellent performance of the proposed hybrid bridge under live loads.

The beam and orthotropic plate simplified analyses have proven to be effective to accurately predict the deflection of the hybrid bridge under design loads.

69

Challenges

A systematic way to determine design parameters should be developed. It is also important to propose and optimize the design based on life-cycle cost as well as performance.

Long-term performance of FRP bridges is not yet established and should be investigated:

creep, fatigue, and material degradation.

Thermal effects on FRP bridges is still unknown and should be investigated.

Quality control concerns— the material properties are highly dependent on the manufacturing process.

70

Challenges (CONT’D)

Several practical aspects of FRP applications in bridges need to be addressed by researchers. The following are some of the outstanding issues:– Methods to expand lanes– Methods to cast concrete– Considerations for negative moments– Concrete barrier or steel parapet– Support conditions

71

There are benefits in using light FRP deck or superstructure in bridges located in moderate and seismic regions.

Automated fabrication process must be used to fabricate the FRP parts of the superstructure or deck.

Challenges (CONT’D)

72

AUTOMATED FABRICATION PROCESSES

Pultrusion

RTM

VARTM

Use of braided fabrics

Filament Winding

73

Acknowledgment

Dr. Y. Kitane

Dr. W. Alnahhal

New York State Department of Transportation

74

THANK YOUTHANK YOU