new frontiers in the design and strengthening of … · new frontiers in the design and...

NEW FRONTIERS IN THE DESIGN AND

STRENGTHENING OF RC/PC STRUCTURES

USING FRP COMPOSITES

Advances in Construction Technology

Dbayeh/Beirut, Lebanon

June 11, 2015

Abdeldjelil “DJ” Belarbi, PhD, PE, FACI, FASCE

Distinguished Professor of Civil Engineering

1. Introduction

2. Fiber-ReinforcedPolymers (FRP)

3. StrengtheningUsing FRP

4. ShearStrengtheningCase

5. Softened Membrane Model –On-GoingResearch Project

6. PrestressingUsing FRP –On-GoingResearch Project

7. ConcludingRemarks

2

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OUTLINE OF THE PRESENTATION

Man constructs,Man destructs,Man constructs…

Source: http://whateverhappensny.bandcamp.com/releases

1- Introduction

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WW II – Mass destruction of built environment and infrastructure of cities all around the world.

Hiroshima – Japan, 1945

Warsaw, Poland

1935 1945 2009

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1- Introduction

Reconstruction of the cities and boost of infrastructure started after

WWII era in 1950s.

Majority of structures today are reaching to their design life time.

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1- Introduction

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• Boost in urbanization and accompanied infrastructure

development. (Roads, bridges, sewers, buildings etc.)

• High demands, poor maintenance and aging bring accelerated

deterioration.

1- Introduction

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2000’s

1950’s

A great number of US bridges have become structurally

deficient or functionally obsolete due to:

Changing traffic demands

1- Introduction

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• Changing traffic demands

• Improvements in design standards

1- Introduction

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• Long-term deterioration

1- Introduction

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• Long-term deterioration

• Man-made structural damage

1- Introduction

0

10,000

20,000

30,000

40,000

50,000

60,000

Nu

mb

er

of

Bri

dge

s

Year

Bridge construction in the USA

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About 1,000,000 bridges

1- Introduction

• ASCE 2013 Report Card for Bridges:

C+• Need to invest $20.5 billion annually till 2028

75%

Concrete, 41.6%

Steel, 30.1%

Prestressed Concrete,

24.0%

Wood, 3.7%Other, 0.6%

Source: www.FHWA.DOT.GOV

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1- Introduction

75%

Structurally

Deficient

11%

Functionally

Obsolete

14%75%

ASCE 2013 Report Card for Bridges:

C+Need to invest $20.5 billion annually till 2028

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1- Introduction

Problem should be addressed and solutions should be

proposed in the light of former experience and foresight :

- Traditional vs. new materials

- Economical solutions

- Immediate actions

ADVANCE COMPOSITE MATERIALS

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1- Introduction

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Flexural Strengthening Confinement Shear Strengthening

Since 1970s FRP has been used in civil engineering application

Among all the research about FRP, the study of the shear

behavior still remains as a challenging debate.

2- Fiber-ReinforcedPolymers (FRP)

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FRPs are advanced composite materials

consisting of high strength fibers such as aramid,

carbon or glass embedded in a polymer resin.

Commercially available forms

Reinforcing Bar and Prestressing Tendons

Pre-cured laminate shells

Grids

Fiber sheets


• What is FRP?

Fibers

Provide strength

and stiffness

Carbon, glass, aramid

Matrix

Protects and transfers load

between fibres

Epoxy, polyester, vinylester

Composite

Creates a material with attributes superior to either

component alone!7/27/2015

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Light weight

High Strength

Corrosion Resistant

High Versatility

Advanced Composite Materials – FRP

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FRP properties (compared to steel reinforcement):

• Linear elastic

• No yielding

• Higher ultimate strength

• Lower strain at failure

1 ksi = 6.89 MPa

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Limitations :Higher Cost

Anisotropy

Brittle Behavior

Complex Characterization

Lack of Comprehensive

Standard Design Codes (emerging)

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Primary advantage of FRPs

Will not corrode electrochemically.

Some durability concerns do exist...

Potentially damaging effects resulting from:

Temperature

Moisture

UV Radiation

Alkalinity

Fire

ENVIRONMENTAL

DURABILITY

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Global demand for CFRP in tonnes (2008 – 2020)

Civil Engineering = 6%

Estimated

Global Carbon Fiber

consumption per application (2012)

Source: “Composite Market Report, Market developments, trends, challenges and opportunities”, 2013, AVK, Federation of Reinforced Plastics

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General use of FRP in Transportation

Aircrafts Race Cars Trucks Cars

Concept CarsBusesSport CarsHelicopters

A380

Fiber Metal LaminateMcLaren – Formula 1

CFRP Thermoset

Car Body Structure

SMC Thermoset Parts

for Driver Cabin

GMT-Thermoplastic

Rotor Blade

Erosion ProtectionCFRP Thermoset Car

Body Structure

SMC Thermoset

PanelsInjection Moulded

Thermoplastic Car Body

Automotive/Railway and Aerospace7/27/2015

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• Bridge deck

• Abutment panel

• Rebar or prestressing

reinforcement

• Dowel bar

• Pole and post

• Signboard and signpost

• Guardrail system

FRP composites have various applications in bridge

construction:

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Fiber Orientation

Location

Type

FRP Strengthening

Flexural

On surface

(Tension side)

Parallel

to long. axis

Axial

On periphery

Circumferential

Shear

On surface (Web side)

Perpendicular to long. axis

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3-Strengtheningusing FRP

A number of experimental investigations have shown

externally bonded FRPs to be effective with increasing

the axial, flexural, and shear capacity of concrete

members


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Bonded Steel Plate Member Enlargement FRP Sheet

5 mm bolted plate

115 Kgs dead load

Place by lift truck

Two No.25 rebar

100 mm grout

1150 Kgs dead load Formed and cured

1 layer resin bonded

3 Kgs dead load

Placed by hand

FRP vs. Conventional Upgrade

Simply supported beam; 35% upgrade in live load


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Flexural StrengtheningFollows well established analysis procedures with additional consideration for bond-related issuesw


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Flexural Strengthening

Follows well established analysis procedures with additional consideration for bond-

related issues

w

Deflection

Load

Unstrengthened

RC Beam

Light FRP Reinf.

Moderate FRP Reinf.

Heavy FRP Reinf.

Ductility

Str

engt

h


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FRP STRENGTHENING – AXIAL

Confining the axially loaded members to increase their strength and ductility


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Stress-strain curve of confined concrete


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4-ShearStrengtheningCase

• Analysis procedures are more empirical as compared to flexural and

axial strengthening

• Limited experimental knowledge base

• Not all parameters affecting the shear behavior have been investigated

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Internal

reinforcement

FRP

laminates

Complete

WrappingU- Wrap

Side Bonding

(Contact critical)

(Bond critical)

Schemes

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Shear Mechanism Based on Truss Model

The shear contribution of each

component is derived separately.

However, a high level of

interaction exists between them.

General Form of Design Equations :

Vs

Vf

Vc

n c s f fV V V V

Adopted from

RC design

Considered

similar as

steel

Vn = Vu/f


Analytical Models – Use of Fixed Value of Effective Strain εfe

Chajes et al. (1995)

Hutchinson and Rizkalla (1999)

CSA S806-07 (2007)

(failure mode was not

0

d

.0

ef n )

05

i ed

fe

For other fail

0.004 for

ure mode,

peeling off of FRP o

Triantafillou (1998)

bserved especia

and Khalifa (2

ll

00

y in I girder

0) were referred

fe

FRP rupture

FRP debonding

due to the lack of effective bond length

FRP debonding

due to shear peeling

(a) when proper anchorage is provided

(e.g., complete wrapping)

(b) When proper anchorage is not provided

(e.g., U-wrap and one-side strip)

(c) When the outward force normal to FRP sheets exist

(e.g., I beams as shown)

Outward force resulting from

the tensile forces in the

vertical and diagonal legs of the

shear reinforcement

0.004 for for U-wrap

0.002 for Side-bonding

fe

ACI 440.2R-08 (2008)

for full wrapped FRP

For two-side bonding and U wraped FRP, differened equati

0.004

ons a

0.75

re provided

fe fu

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Review Of Shear

Strengthening With FRP

0

100

200

300

400

500

600

0 0.005 0.01 0.015 0.02 0.025

Strain (in/in)

Str

ess (

ksi)

0

100

200

300

400

500

600

0 0.005 0.01 0.015 0.02 0.025

Strain (in/in)

Str

ess (

ksi)

Carbon

Aramid

E-Glass

Most of strain limits fall into this range Most of strain limits fall into this range


•Debonding of FRP sheet from substrate

Possible Shear Failure Modes

Debonding/Delamination

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•Loss of aggregate interlock (i.e., loss of Vc)

* Photo taken from the work of George C. Manos and Kostas V. Katakalos 2013 ” The Use of Fiber Reinforced Plastic for The Repair and Strengthening of Existing Reinforced ConcreteStructural Elements Damaged by Earthquakes”

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•Loss of web width/area

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•Loss of web width/area

•FRP rupture due to stress concentration

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Analytical Models for Shear Resistance of FRP-Strengthened

Specimens

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 25 50 75 100 125 150 175 200 225 250 275

Vf / (b

w d

f)(k

si)

ρf Ef (ksi)

U-Wrapping

Chaallal et al., 2002

Hutchinson and Rizkalla, 1999

Carolin and Taljsten, 2005b

Chajes et al., 1995

Khalifa et al., 1998

ACI 440, 2008

Pellegrino and Modena, 2002

Cao et al., 2005

Triantafillou and Antonopoulos, 2000 Chen & Teng, 2003a,b

fib-TG9.3, 2001

CSA S806, 2002

Zhang and Hsu,

2005

vfnr

vf r

JSCE, 2001

Monti and Liotta, 2005

43 cm

18 cm

50 cm

SIGNIFICANT

DIFFERENCES IN

PREDICTIONS

NCHRP Report 678 (2011)

1 ksi = 6.89 MPa


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Element Behavior as Part of a Complete Structure

5-Softened Membrane Model

High-Rise Building Core(Shanghai Tower, 2,073 ft)

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Universal Panel Tester

Unique facility to test full scale panel elements under various

combination of in-plane and out-of-plane stress conditions.


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Unique in US and only two in the world

Equipped with 40 in-plane and 20 out-of-plane hydraulic actuators (1100

kN/each) and a robust servo-control system

Test specimen is 140 cm x 140 cm with a thickness up to 40 cm Specimen

can be reinforced with full size rebar

Have been used to test specimen of reinforced concrete, fiber reinforced

concrete, prestressed concrete, and masonry.

Universal Panel Tester


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Softened Membrane Model (2002)

SMM-FRP


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Softened Membrane Model (2002) Governing Equations of SMM

• Stress equilibrium equations

Applied

Stress

Principal

StressContribution

of Steel

Rebar

Contribution

of FRP


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• Strain transformation equations

Smeared

Strains

Principal

Strain



• Material laws

-Smeared Stress-Strain Curves of Concrete in Tension

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Smeared

StressSmeared

Strain

Poisson’s

Ratio

experimental tests by Zhu

and Hsu (2002)

Av

erag

e st

ress

in

Co

ncr

ete

Average strain in Concrete

RC

Plain Concrete

Av

erag

e st

ress

in

Co

ncr

ete


RC

Plain Concrete

FRP RC

Due to the extra bond created by the FRP and the

smaller crack distribution, the tension stiffening is

expected to be increased


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softening coefficient

Av

erag

e st

ress

in

Co

ncr

ete


Under Compression

Under Tension-Compression

Av

erag

e st

ress

in

Co

ncr

ete


Under Compression

Under Tension-Compression

FRP RC

Due to the confinement effect of FRP,

concrete should be less “softened”


• Material laws

-Concrete Softening under Biaxial Load

Smeared

StressSmeared

Strain

Poisson’s

Ratio


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• Material laws

-Smeared Stress-Strain Curves of Steel in Tension

Av

erag

e st

ress

in

ste

elAverage strain in steel

Bare Rebar

Rebar in RC

Rebar in FRP RC

The apparent yielding point will increase

due to the decrease in crack width because

of FRP.

Av

erag

e st

ress

in

ste

elAverage strain in steel

Bare Rebar

Rebar in RC

Apparent Yielding Point

Smeared

StressSmeared

Strain

Poisson’s

Ratio


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Shear Test Panels

= 40 MPa concrete strengths

= 420 MPa steel reinforcements

• Specimen preparation

- grinded

- Sandblasted

- Power washed

- Primer and putty

- Wet lay up FRP

application system

• Material tests

- Concrete: ASTM C39

- Steel: ASTM 8M-01

- FRP: ASTM D3039


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Experimental Results

0

1

2

3

4

5

6

0 0.01 0.02 0.03 0.04

Ap

pli

ed

Sh

ea

r S

tress

, τlt(M

Pa

)

Shear Strain, γlt (mm/mm)

P4_040_FAP4_040_SBP4_040_FW

0

1

2

3

4

5

6

0 0.01 0.02 0.03 0.04

App

lied

Sh

ea

r S

tress

, τlt

(MP

a)

Shear Strain, γlt (in./in.)

P4_025_FWREF_R4P4_040_FW

Application of FRP increased the shear capacity

of the RC panel by 30%

Wrapping scheme has a clear effect on the shear

capacity


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Leonhardt (1964) - in his “PrestressedConcrete - Design and Construction” stated that Freyssinet first mentioned the use of glass fibers or plastics for prestressing in 1938:

”Some day, glass fibres or plastics will be used as tendons for prestressing. This idea was first mentioned by Freyssinet in 1938. In the U.S.A., investigations are already in progress in this connection...

6- PrestressingUsing FRP

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FRP in Construction and

Infrastructure: It Was a Long

Journey

but there is no time

to rest and take a break

7-ConcludingRemarks

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Available Design

Guidelines Worldwide

ACI 440.2R-08

ISIS Canada Design Manual

European fib TG9.3 (2001)

CSA S806-12

7-ConcludingRemarks

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Emerging Technologies Accepted Technologies

7-ConcludingRemarks

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1925 1950 1975 20001825 1850 1875 1900 2025

1867

J. Monier

1957

Montaso

1933

E. Freyssinet

Reinforced

Concrete

RC vs PC vs FRP

FRP

Prestressed

ConcretePortland

Cement

1824

J. Aspdin

Close to two centuries full of technological breakthrough

But on time scale, all is new…….

7-ConcludingRemarks

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• Where do we stand in terms of level of knowledge regarding the

behavior of FRP strengthened reinforced concrete members ?

How much do we know and how we do not know?

7-ConcludingRemarks

92

Future: We cannot afford to be left behind….Let’s avoid such situations

7-ConcludingRemarks

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7-ConcludingRemarks

“Imagination is more important than knowledge. Knowledge is limited, whereas imagination embraces the entire world stimulating progress, giving birth toevolution.”

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7-ConcludingRemarks

Engineering is the art of modelling materials we do not wholly understand, into shapes we cannot precisely analyze so as to withstand forces we cannot properly assess, in such a way that the public has no reason to suspect the extent of our ignorance.

Dr. AR Dykes

We are blessed in so many ways but even

more to be engineers….

We build the quality of life

I leave you with this:

Acknowledgments:Many thanks to the funding agency, my collaborators, University

of Houston staff, CFRP suppliers, and precast plant staff

http://www.trb.org/

http://www.trb.org/

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Thank you!

UNIVERSITY of HOUSTONCivil & Environmental Engineering

NEW FRONTIERS IN THE DESIGN AND

STRENGTHENING OF RC/PC STRUCTURES USING

FRP COMPOSITES

Abdeldjelil “DJ” Belarbi, Ph.D., P.E.

Distinguished Professor of Civil Engineering

[email protected]

new frontiers in the design and strengthening of … · new frontiers in the design and...

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