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Strengthening of Concrete Structures Using Fiber Reinforced Polymers (FRP)

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Contents

Preface

1 Introduction

1.1 Overview

1.2 FRP strengthening systems

1.3 Composite interfacial debonding

1.4 FRP design standards and guides

1.5 Designing with FRP reinforcement

1.5.1 Flexural strengthening

1.5.2 Shear strengthening

1.6 Numerical modeling

1.7 Installation of EB FRP systems

2 Fiber-reinforced polymer composites

2.1 FRP constituents

2.1.1 Fibers

2.1.2 Matrix

2.1.3 Interface

2.2 Composite interfacial adhesion and debonding

2.3 FRP durability

3 Composite mechanics

3.1 Introduction

3.2 Laminate

3.2.1 Unidirectional ply

3.2.2 Classical laminate theory

3.3 Textile fabric

3.3.1 Mechanics

3.4 Durability and failure modes

3.4.1 Failure modes and strength prediction

3.4.1.1 First-ply failure

3.4.1.2 Shear failure

3.4.1.3 Local buckling

3.5 Finite Element Analysis (FEA)

3.5.1 Finite element simulation

3.5.2 Numerical modeling of FRP-strengthened concrete beams

4 Design provisions

4.1 Introduction

4.2 Flexural FRP strengthening of RC/PC bridge members

4.2.1 Introduction

4.2.2 Strengthening limits

4.2.2.1 AASHTO

4.2.2.2 ACI 440.2R-08

4.2.2.3 ISIS

4.2.2.4 Other codes

4.2.2.5 Summary

4.2.3 Environmental reduction factors

4.2.3.1 ACI

4.2.3.2 CNR

4.2.3.3 ISIS

4.2.3.4 TR55

4.2.3.5 JSCE

4.2.3.6 AASHTO

4.2.3.7 Summary

4.2.4 FRP strain limits

4.2.4.1 ACI

4.2.4.2 ISIS

4.2.4.3 AASHTO

4.2.4.4 TR55

4.2.4.5 CNR

4.2.4.6 JSCE

4.2.4.7 Summary

4.2.5 Strength reduction factors

4.2.5.1 ACI

4.2.5.2 ISIS

4.2.5.3 AASHTO

4.2.5.4 TR55

4.2.5.5 CNR

4.2.5.6 Summary

4.2.6 Serviceability and service load limits

4.2.6.1 ACI

4.2.6.2 AASHTO

4.2.6.3 ISIS

4.2.6.4 TR55

4.2.6.5 CNR

4.2.6.6 JSCE

4.2.6.7 Summary

4.2.7 Creep rupture and fatigue stress limits

4.2.7.1 ACI

4.2.7.2 ISIS

4.2.7.3 AASHTO

4.2.7.4 CNR

4.2.7.5 TR55

4.2.7.6 JSCE

4.2.7.7 Summary

4.2.8 End peeling

4.2.8.1 ACI

4.2.8.2 AASHTO

4.2.8.3 TR55

4.2.8.4 JSCE

4.2.8.5 CNR

4.2.8.6 Anchorage methods for FRP

4.2.8.7 Summary

4.2.9 Development length

4.2.9.1 AASHTO

4.2.9.2 ACI

4.2.9.3 ISIS

4.2.9.4 CNR

4.2.9.5 TR55

4.2.9.6 Summary

4.2.10 Flexural design approach and assumptions

4.2.10.1 AASHTO

4.2.10.2 JSCE

4.2.10.3 CNR

4.2.10.4 ACI

4.2.10.5 ISIS

4.2.10.6 TR55

4.2.10.7 Summary

4.3 Shear FRP strengthening of RC/PC bridge members

4.3.1 Introduction

4.3.2 Wrapping schemes

4.3.2.1 ACI

4.3.2.2 AASHTO

4.3.2.3 ISIS

4.3.2.4 CNR

4.3.2.5 TR55

4.3.2.6 Wrapping schemes—summary

4.3.3 Strength reduction factors

4.3.4 Reinforcement limits and spacing limits

4.3.4.1 ACI

Shear strengthening limits

Spacing of FRP strips

4.3.4.2 AASHTO

Maximum FRP shear reinforcement

4.3.4.3 Summary

4.3.5 FRP design strain limits

4.3.5.1 ACI

4.3.5.2 AASHTO

4.3.5.3 ISIS

4.3.5.4 Summary

4.3.6 Shear design approach and assumptions

4.3.6.1 ACI

4.3.6.2 ISIS

4.3.6.3 AASHTO

AASHTO GFRP

4.3.6.4 CNR

4.3.6.5 JSCE

4.3.6.6 UK

4.3.6.7 Summary

4.4 FRP-confinement strengthening of RC/PC bridge members

4.4.1 Introduction

4.4.2 Design considerations

4.4.2.1 Strength reduction factors

4.4.2.2 Maximum FRP strain due to confinement

CNR

AASHTO

ACI

ISIS

TR55

Summary—maximum FRP strain due to confinement

4.4.2.3 FRP stress limits

4.4.3 Analysis and design procedures

4.4.3.1 AASHTO

Axial capacity of confined columns in compression

Evaluation of confined compressive strength, f′cc

4.4.3.2 ACI

Axial capacity of confined columns in compression

Stress–strain model for confined reinforced concrete columns

Evaluation of confined compressive strength f′cc

Serviceability considerations

4.4.3.3 ISIS

Axial capacity of confined columns in compression

Evaluation of the confined compressive strength, f′cc

4.4.3.4 CNR

Axial capacity of FRP-confined members under concentric or slightly eccentric force

Evaluation of the confined compressive strength, fccd

Evaluation of the confined lateral pressure

Evaluation of kH, kV, and ka

4.4.4 Summary

4.5 Witness panels

5 Provisions for installation, quality control, and maintenance

5.1 Introduction

5.2 Installation of FRP strengthening systems

5.2.1 Shipping, storage, and handling

5.2.1.1 ACI

Shipping

Storage

Handling

5.2.1.2 ISIS

Shipping

Storage

Handling

5.2.1.3 AASHTO

Shipping and storage

Handling

5.2.1.4 JSCE

Shipping

Storage and handling

5.2.1.5 TR55

5.2.1.6 CNR

Shipping and storage

Handling

5.2.1.7 Summary of shipping, storage, and handling

5.2.2 Contractor qualifications

5.2.2.1 ACI

5.2.2.2 ISIS

5.2.2.3 AASHTO

5.2.2.4 JSCE

5.2.2.5 TR55

5.2.2.6 CNR

5.2.2.7 Summary of contractor qualifications

5.2.3 Installation procedures

5.2.3.1 ACI

Temperature, humidity, and moisture considerations

Equipment

Surface preparation

Mixing of resins

Application

Alignment of FRP materials

Multiple plies and lap splices

Curing

5.2.3.2 ISIS

Temperature, humidity, and moisture considerations

Equipment

Surface preparation

Mixing of resins

Application

Alignment of FRP materials

Multiple plies and lap splices

Curing

Protective coating

5.2.3.3 AASHTO

Temperature, humidity, and moisture considerations

Surface preparation

5.2.3.4 JSCE

Temperature, humidity, and moisture considerations

Surface preparation

Application

Lap splices

Curing

Anchorage length

5.2.3.5 TR55

Temperature, humidity, and moisture considerations

Surface preparation

Mixing of resins

Application

5.2.3.6 CNR

Temperature, humidity, and moisture considerations

Surface preparation

Application

Witness areas

Protective coating

5.2.3.7 Summary of installation procedures

5.3 Inspection, evaluation, and acceptance

5.3.1 Introduction

5.3.2 Inspection

5.3.2.1 ACI

5.3.2.2 ISIS

Contractor’s quality control responsibilities

Inspection of concrete substrate

Inspection before installation

Inspection during installation and at completion

Inspection at completion

5.3.2.3 AASHTO

5.3.2.4 JSCE

Materials and storage inspection

Inspection of the existing structure

Inspection before, during, and after installation

5.3.2.5 TR55

Material QC requirements

Inspection before installation

Inspection during installation

5.3.2.6 CNR

5.3.3 Evaluation and acceptance

5.3.3.1 ACI

Evaluation and acceptance before starting the project

Evaluation and acceptance at project completion

5.3.3.2 ISIS

Evaluation and acceptance before starting the project

Evaluation and acceptance at project completion

5.3.3.3 AASHTO

Contractor submittals

Moisture content and epoxy requirements

Environmental conditioning

Epoxy physical and adhesive properties testing

5.3.3.4 JSCE

Fire safety

Collision resistance

Finishing work

5.3.3.5 TR55

5.3.3.6 CNR

Evaluation and acceptance before starting the project

Responsibilities of the construction manager

Evaluation and acceptance at project completion

5.3.3.7 Summary of evaluation and acceptance

5.4 Maintenance and repair

5.4.1 Introduction

5.4.1.1 ACI

Inspection and assessment

Repair techniques

5.4.1.2 ISIS

5.4.1.3 AASHTO

5.4.1.4 JSCE

Inspection and assessment

Repair techniques

5.4.1.5 TR55

Inspection and assessment

Repair techniques

5.4.1.6 CNR

5.4.1.7 Summary of maintenance and repair

6 Laboratory testing

6.1 Durability testing overview

6.2 Bond durability

6.2.1 Sample preparation

6.2.2 Test plan and procedures

6.2.3 Pull-off testing

6.2.4 Test results

6.2.4.1 Pull-off testing

6.2.4.2 Evaluation of acceleration factor

6.3 FRP durability

6.3.1 Test environment

6.3.2 Test methods

6.3.2.1 Destructive flexural strength testing

6.3.2.2 Nondestructive modal testing for storage modulus and loss factor

6.3.3 Test materials and specimens

6.3.3.1 Test sequence

6.3.4 Test results

7 Field testing

7.1 Introduction

7.2 Field pull-off testing

7.3 Load distribution testing

7.3.1 Introduction

7.3.2 Installation plan

7.3.3 Test plan

7.3.4 Interpreting results

7.4 Proof load testing

8 Recommendations

8.1 Analysis and design recommendations

8.1.1 Criteria for recommendations

8.1.2 General recommendation and discussion

8.1.3 Recommended modifications to AASHTO provisions

8.1.3.1 Environmental reduction factors

8.1.3.2 Flexural design when considering compression failures

8.1.3.3 Initial strain for prestressed sections

8.1.3.4 Strength reduction factors and ductility provisions considering prestressed sections

8.2 Installation, quality control, and maintenance recommendations

8.2.1 Shipping, storage, and handling

8.2.1.1 Shipping

8.2.1.2 Storage

8.2.1.3 Handling

8.2.2 Manufacturer and contractor qualification

8.2.3 Installation

8.2.3.1 Temperature, humidity, and moisture considerations

8.2.3.2 Equipment

8.2.3.3 Substrate repair

8.2.3.4 Surface smoothness

8.2.3.5 Surface cleanliness

8.2.3.6 Resin mixing

8.2.3.7 Application of FRP systems

8.2.3.8 Alignment

8.2.3.9 Multiple plies and lap splices

8.2.3.10 Curing

8.2.4 Inspection

8.2.4.1 Quality assurance and control program

8.2.4.2 Material inspection

8.2.4.3 Inspection of concrete substrate

8.2.4.4 Inspections during installation

8.2.4.5 Project completion

8.2.5 Evaluation and acceptance

8.2.5.1 Materials

8.2.5.2 Cure

8.2.5.3 Orientation, placement, and thickness

8.2.5.4 Delamination

8.2.6 Maintenance and repair

8.2.6.1 Maintenance inspections

8.2.6.2 Repair

9 Design examples

9.1 Introduction

9.1.1 Flexural strengthening of a simply supported cast in-place reinforced concrete girder

9.1.2 Flexural strengthening of a simply supported prestressed concrete girder

9.1.3 Shear strengthening of a prestressed concrete beam using two-sided wrap

9.1.4 Shear strengthening of a T-beam using U-wrap

9.1.5 Axial strengthening of a confined circular column

9.1.6 Axial strengthening of a square column

9.1.7 Axial strengthening of a confined circular column (ACI procedure)

9.1.8 Axial strengthening of a confined square column (ACI procedure)

Appendix A: Nomenclature

A.1 AASHTO

A.2 ACI 440.2R 08

A.3 ISIS

A.4 CNR-DT 200/2004

A.5 TR-55

Appendix B: Inspection checklist

References

Index

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