strengthening of beams for flexure using frp

:Table of Contents

1) Introduction : ( What is FRP ? ) .

2) Fiber Material Behavior .

3) FRP STRENGTHENING SYSTEMS .

4) Analysis and design .

5) Application requirements for repair and

strengthening works .

Introduction:

What is FRP ?

FRP ( Fiber reinforced polymer ) is a

composite made of high-strength fibers and a

matrix for binding these fibers to fabricate

structural shapes .

Fiber Types

Carbon

Glass

Aramid

Matrix Tyepes :

Epoxies

Esters

FRP systems have significant advantages

over classical structural materials

including:

High – tensile strength .

low weight .

Corrosion resistance .

Ease of application .

Taylor – made capability .

High – life service limit .

:Disadvantages of FRP systems

low – resistance to fire .

No yield plateau .

High – initial cost .

Repair of reinforced and prestressed

concrete elements .

Retrofitting of beams, columns, slabs,

and walls

Carbon

Aramid

Glass

0.000 0.010 0.020 0.030 0.040 0.050 0.060

Steel

FRP STRENGTHENING SYSTEMS

•Loading Specification

•Design Errors Material Specification

•Change of Code

•Drafting Errors

•Assumption Errors

ERRORS IN DESIGN STAGE

•Poor Insufficient compaction

•Construction Inadequate curing time

•Practices

• Poor Workmanship

• Lack of proper supervision

CONSTRUCTION ERRORS

• Overloading -Change of use

• Environmental factors - Concrete deterioration Earthquake/Seismic forces

SERVICE STAGE

Flexural Strengthening

with FRP

Shear Strengthening

with FRP

Axial Strengthening

with FRP

Load versus deflection curves for both control and

strengthened beams.

Part 3

Design For Flexure

Part 2STRENGTHENING

MATERIALS AND SYSTEMSCLASSIFICATION OF

STRENGTHENING WORKS

Part 1

TECHNICAL TERMSPROBABLE CAUSES OF STRUCTURAL DEFECTS

Probable Structural Defects

Overall structural defects

partial or total

collapse of the main structural elements

structural instability,

sliding

differential settlements , and concrete

cracking

Structuralelements defects

cracking, corrosion, excessive deformations,

bucking of columns, loss of concrete cover

Soil problems

Lack of proper structural detailing

The use of defective materials

Construction errors

Lack of maintenance

Modification of configurations, and elements of

the structure

Steel plate bonding .

Section enlargement and external

posttensioning .

Fiber reinforced composites .

Simply supported beam; 35% upgrade in live load

Bonded Steel Plate

0.5 cm bolted plate

110 kg dead load

Placed by lift truck

Member Enlargement

2 #20 rebar, 10 cm grout

1,125 kg dead load

Formed and cured

FRP Sheet

1 layer resin bonded

2.7 kg dead load

Placed by hand

Bond-critical

flexure

tension

torsion

shear

Contact-critical

column

strengthening

DESIGN VARIABLES FOR COMPOSITES TYPE OF FIBER

FIBER VOLUME

ORIENTATION OF FIBER

• 0o, 90o, +45o, -45o

TYPE OF POLYMER (RESIN)

COST

VOLUME OF PRODUCT - MANUFACTURING

METHOD

DESIGN VARIABLES FOR COMPOSITES

PHYSICAL:

• tensile strength

• Compressive strength

• stiffness

• weight, etc.

ENVIRONMENTAL:

• Fire

• UV ( Ultraviolet )

• Corrosion Resistance

1. Design calculations shall be based on the actual

dimensions .

2. Strains are linearly distributed over the cross-

section.

3. The maximum usable compressive strain in the

concrete is 0.003.

4. The tensile strength of concrete is neglected and all

the tensile stresses are resisted by the reinforcing

steel and the FRP.

5. There is no relative slip between external

FRP reinforcement and the concrete.

6. The FRP reinforcement has a linear elastic

stress-strain relationship to failure

d

b

As

Af = n tf wf

cd

-c

h-c

𝜺𝒔

𝜺𝒃𝒊𝜺𝒇𝒆

𝒇𝒔 𝒇𝒔

𝒇𝒇𝒆 = 𝑬𝒇. 𝜺𝒇𝒆/𝜸𝒇

𝟎. 𝟔𝟕𝒇𝒄𝒖 /𝜸𝒄

𝒇𝒇𝒆 = 𝑬𝒇. 𝜺𝒇𝒆/𝜸𝒇

𝜺𝒄𝟎. 𝟔𝟕𝒇𝒄𝒖 /𝜸𝒄

a = 0.8 c

Reinforced

concrete

section

Strain

distribution

Stress

distribution

(non linear for

concrete

stress)

Stress

distribution

(equivalent stress

concrete block )

(1)

(2)

(3)

(4)

Manual application

Strengthened surface

(substrate)

Resin / Adhesive

Fiber

Reinforced

Polymers

(FRP)

Plane and free of any forms of defects.

Free of moisture, chlorides and sulfate ions.

satisfy the necessary requirements that insure the effectiveness of FRP strengthening works.

free of carbonation and the steel reinforcement shall be free of rust.

The resin shall be a suitable material

capable of adhering the FRP laminates to

the concrete surface and satisfying the

specifications and requirements of the

project .

The type of resin depends on the type of

FRP laminates and surface condition.

The two main types of FRP reinforcement

are determined according to the type of

application .

Good quality control should be insured.

Incorrect or bad application will lead to

debonding between FRP and concrete .

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